[PATCH v3 00/20] SRSO fixes/cleanups

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* [PATCH v3 00/20] SRSO fixes/cleanups
@ 2023-09-05  5:04 Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 01/20] x86/srso: Fix srso_show_state() side effect Josh Poimboeuf
                   ` (20 more replies)
  0 siblings, 21 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

v3:
- drop kvm patches (to be picked up by Sean)
- fix "no microcode, no microcode" printk
- fix "Safe Ret" capitalization in documentation
- fix chopped line in commit log
- drop "x86/srso: Remove redundant X86_FEATURE_ENTRY_IBPB check" patch

Josh Poimboeuf (20):
  x86/srso: Fix srso_show_state() side effect
  x86/srso: Set CPUID feature bits independently of bug or mitigation
    status
  x86/srso: Don't probe microcode in a guest
  x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
  x86/srso: Fix SBPB enablement for (possible) future fixed HW
  x86/srso: Print actual mitigation if requested mitigation isn't
    possible
  x86/srso: Print mitigation for retbleed IBPB case
  x86/srso: Fix vulnerability reporting for missing microcode
  x86/srso: Fix unret validation dependencies
  x86/alternatives: Remove faulty optimization
  x86/srso: Improve i-cache locality for alias mitigation
  x86/srso: Unexport untraining functions
  x86/srso: Remove 'pred_cmd' label
  x86/bugs: Remove default case for fully switched enums
  x86/srso: Move retbleed IBPB check into existing 'has_microcode' code
    block
  x86/srso: Disentangle rethunk-dependent options
  x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
  x86/retpoline: Remove .text..__x86.return_thunk section
  x86/nospec: Refactor UNTRAIN_RET[_*]
  x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()

 Documentation/admin-guide/hw-vuln/srso.rst |  24 ++-
 arch/x86/include/asm/nospec-branch.h       |  69 ++++-----
 arch/x86/include/asm/processor.h           |   2 -
 arch/x86/kernel/alternative.c              |   8 -
 arch/x86/kernel/cpu/amd.c                  |  28 ++--
 arch/x86/kernel/cpu/bugs.c                 | 102 ++++++------
 arch/x86/kernel/vmlinux.lds.S              |  10 +-
 arch/x86/lib/retpoline.S                   | 171 +++++++++++----------
 include/linux/objtool.h                    |   3 +-
 scripts/Makefile.vmlinux_o                 |   3 +-
 10 files changed, 201 insertions(+), 219 deletions(-)

-- 
2.41.0


^ permalink raw reply	[flat|nested] 92+ messages in thread

* [PATCH v3 01/20] x86/srso: Fix srso_show_state() side effect
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 02/20] x86/srso: Set CPUID feature bits independently of bug or mitigation status Josh Poimboeuf
                   ` (19 subsequent siblings)
  20 siblings, 2 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

Reading the 'spec_rstack_overflow' sysfs file can trigger an unnecessary
MSR write, and possibly even a (handled) exception if the microcode
hasn't been updated.

Avoid all that by just checking X86_FEATURE_IBPB_BRTYPE instead, which
gets set by srso_select_mitigation() if the updated microcode exists.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f081d26616ac..bdd3e296f72b 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2717,7 +2717,7 @@ static ssize_t srso_show_state(char *buf)
 
 	return sysfs_emit(buf, "%s%s\n",
 			  srso_strings[srso_mitigation],
-			  (cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));
+			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
 }
 
 static ssize_t gds_show_state(char *buf)
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 02/20] x86/srso: Set CPUID feature bits independently of bug or mitigation status
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 01/20] x86/srso: Fix srso_show_state() side effect Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 03/20] x86/srso: Don't probe microcode in a guest Josh Poimboeuf
                   ` (18 subsequent siblings)
  20 siblings, 2 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

Booting with mitigations=off incorrectly prevents the
X86_FEATURE_{IBPB_BRTYPE,SBPB} CPUID bits from getting set.

Also, future CPUs without X86_BUG_SRSO might still have IBPB with branch
type prediction flushing, in which case SBPB should be used instead of
IBPB.  The current code doesn't allow for that.

Also, cpu_has_ibpb_brtype_microcode() has some surprising side effects
and the setting of these feature bits really doesn't belong in the
mitigation code anyway.  Move it to earlier.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/processor.h |  2 --
 arch/x86/kernel/cpu/amd.c        | 28 +++++++++-------------------
 arch/x86/kernel/cpu/bugs.c       | 13 +------------
 3 files changed, 10 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index fd750247ca89..9e26294e415c 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -676,12 +676,10 @@ extern u16 get_llc_id(unsigned int cpu);
 #ifdef CONFIG_CPU_SUP_AMD
 extern u32 amd_get_nodes_per_socket(void);
 extern u32 amd_get_highest_perf(void);
-extern bool cpu_has_ibpb_brtype_microcode(void);
 extern void amd_clear_divider(void);
 #else
 static inline u32 amd_get_nodes_per_socket(void)	{ return 0; }
 static inline u32 amd_get_highest_perf(void)		{ return 0; }
-static inline bool cpu_has_ibpb_brtype_microcode(void)	{ return false; }
 static inline void amd_clear_divider(void)		{ }
 #endif
 
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 7eca6a8abbb1..b08af929135d 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -766,6 +766,15 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 
 	if (cpu_has(c, X86_FEATURE_TOPOEXT))
 		smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1;
+
+	if (!cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
+		if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB))
+			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+		else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
+			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+			setup_force_cpu_cap(X86_FEATURE_SBPB);
+		}
+	}
 }
 
 static void init_amd_k8(struct cpuinfo_x86 *c)
@@ -1301,25 +1310,6 @@ void amd_check_microcode(void)
 	on_each_cpu(zenbleed_check_cpu, NULL, 1);
 }
 
-bool cpu_has_ibpb_brtype_microcode(void)
-{
-	switch (boot_cpu_data.x86) {
-	/* Zen1/2 IBPB flushes branch type predictions too. */
-	case 0x17:
-		return boot_cpu_has(X86_FEATURE_AMD_IBPB);
-	case 0x19:
-		/* Poke the MSR bit on Zen3/4 to check its presence. */
-		if (!wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
-			setup_force_cpu_cap(X86_FEATURE_SBPB);
-			return true;
-		} else {
-			return false;
-		}
-	default:
-		return false;
-	}
-}
-
 /*
  * Issue a DIV 0/1 insn to clear any division data from previous DIV
  * operations.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bdd3e296f72b..b0ae985aa6a4 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2404,26 +2404,15 @@ early_param("spec_rstack_overflow", srso_parse_cmdline);
 
 static void __init srso_select_mitigation(void)
 {
-	bool has_microcode;
+	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	/*
-	 * The first check is for the kernel running as a guest in order
-	 * for guests to verify whether IBPB is a viable mitigation.
-	 */
-	has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) || cpu_has_ibpb_brtype_microcode();
 	if (!has_microcode) {
 		pr_warn("IBPB-extending microcode not applied!\n");
 		pr_warn(SRSO_NOTICE);
 	} else {
-		/*
-		 * Enable the synthetic (even if in a real CPUID leaf)
-		 * flags for guests.
-		 */
-		setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
-
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 03/20] x86/srso: Don't probe microcode in a guest
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 01/20] x86/srso: Fix srso_show_state() side effect Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 02/20] x86/srso: Set CPUID feature bits independently of bug or mitigation status Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 04/20] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off Josh Poimboeuf
                   ` (17 subsequent siblings)
  20 siblings, 2 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

To support live migration, the hypervisor sets the "lowest common
denominator" of features.  Probing the microcode isn't allowed because
any detected features might go away after a migration.

As Andy Cooper states:

  "Linux must not probe microcode when virtualised.  What it may see
  instantaneously on boot (owing to MSR_PRED_CMD being fully passed
  through) is not accurate for the lifetime of the VM."

Rely on the hypervisor to set the needed IBPB_BRTYPE and SBPB bits.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index b08af929135d..28e77c5d6484 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -767,7 +767,7 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 	if (cpu_has(c, X86_FEATURE_TOPOEXT))
 		smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1;
 
-	if (!cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
+	if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
 		if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB))
 			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
 		else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 04/20] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (2 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 03/20] x86/srso: Don't probe microcode in a guest Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW Josh Poimboeuf
                   ` (16 subsequent siblings)
  20 siblings, 2 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

If the user has requested no SRSO mitigation, other mitigations can use
the lighter-weight SBPB instead of IBPB.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b0ae985aa6a4..10499bcd4e39 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2433,7 +2433,7 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		return;
+		goto pred_cmd;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (3 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 04/20] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
                   ` (15 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

Make the SBPB check more robust against the (possible) case where future
HW has SRSO fixed but doesn't have the SRSO_NO bit set.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 10499bcd4e39..2859a54660a2 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2496,7 +2496,7 @@ static void __init srso_select_mitigation(void)
 	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
 
 pred_cmd:
-	if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) &&
+	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
 	     boot_cpu_has(X86_FEATURE_SBPB))
 		x86_pred_cmd = PRED_CMD_SBPB;
 }
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (4 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
                   ` (14 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

If the kernel wasn't compiled to support the requested option, print the
actual option that ends up getting used.

Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2859a54660a2..235c0e00ae51 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2461,7 +2461,6 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2473,7 +2472,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2485,7 +2483,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
                 }
 		break;
 
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (5 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
                   ` (13 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

When overriding the requested mitigation with IBPB due to retbleed=ibpb,
print the mitigation in the usual format instead of a custom error
message.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 235c0e00ae51..6c47f37515b8 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2425,9 +2425,8 @@ static void __init srso_select_mitigation(void)
 
 	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 		if (has_microcode) {
-			pr_err("Retbleed IBPB mitigation enabled, using same for SRSO\n");
 			srso_mitigation = SRSO_MITIGATION_IBPB;
-			goto pred_cmd;
+			goto out;
 		}
 	}
 
@@ -2490,7 +2489,8 @@ static void __init srso_select_mitigation(void)
 		break;
 	}
 
-	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
+out:
+	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (6 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 09/20] x86/srso: Fix unret validation dependencies Josh Poimboeuf
                   ` (12 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

The SRSO default safe-ret mitigation is reported as "mitigated" even if
microcode hasn't been updated.  That's wrong because userspace may still
be vulnerable to SRSO attacks due to IBPB not flushing branch type
predictions.

Report the safe-ret + !microcode case as vulnerable.

Also report the microcode-only case as vulnerable as it leaves the
kernel open to attacks.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 Documentation/admin-guide/hw-vuln/srso.rst | 24 ++++++++++-----
 arch/x86/kernel/cpu/bugs.c                 | 36 +++++++++++++---------
 2 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index b6cfb51cb0b4..e715bfc09879 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -46,12 +46,22 @@ The possible values in this file are:
 
    The processor is not vulnerable
 
- * 'Vulnerable: no microcode':
+* 'Vulnerable':
+
+   The processor is vulnerable and no mitigations have been applied.
+
+ * 'Vulnerable: No microcode':
 
    The processor is vulnerable, no microcode extending IBPB
    functionality to address the vulnerability has been applied.
 
- * 'Mitigation: microcode':
+ * 'Vulnerable: Safe RET, no microcode':
+
+   The "Safe RET" mitigation (see below) has been applied to protect the
+   kernel, but the IBPB-extending microcode has not been applied.  User
+   space tasks may still be vulnerable.
+
+ * 'Vulnerable: Microcode, no safe RET':
 
    Extended IBPB functionality microcode patch has been applied. It does
    not address User->Kernel and Guest->Host transitions protection but it
@@ -72,11 +82,11 @@ The possible values in this file are:
 
    (spec_rstack_overflow=microcode)
 
- * 'Mitigation: safe RET':
+ * 'Mitigation: Safe RET':
 
-   Software-only mitigation. It complements the extended IBPB microcode
-   patch functionality by addressing User->Kernel and Guest->Host
-   transitions protection.
+   Combined microcode/software mitigation. It complements the
+   extended IBPB microcode patch functionality by addressing
+   User->Kernel and Guest->Host transitions protection.
 
    Selected by default or by spec_rstack_overflow=safe-ret
 
@@ -129,7 +139,7 @@ an indrect branch prediction barrier after having applied the required
 microcode patch for one's system. This mitigation comes also at
 a performance cost.
 
-Mitigation: safe RET
+Mitigation: Safe RET
 --------------------
 
 The mitigation works by ensuring all RET instructions speculate to
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6c47f37515b8..e45dd69aff7f 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2353,6 +2353,8 @@ early_param("l1tf", l1tf_cmdline);
 
 enum srso_mitigation {
 	SRSO_MITIGATION_NONE,
+	SRSO_MITIGATION_UCODE_NEEDED,
+	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,
 	SRSO_MITIGATION_MICROCODE,
 	SRSO_MITIGATION_SAFE_RET,
 	SRSO_MITIGATION_IBPB,
@@ -2368,11 +2370,13 @@ enum srso_mitigation_cmd {
 };
 
 static const char * const srso_strings[] = {
-	[SRSO_MITIGATION_NONE]           = "Vulnerable",
-	[SRSO_MITIGATION_MICROCODE]      = "Mitigation: microcode",
-	[SRSO_MITIGATION_SAFE_RET]	 = "Mitigation: safe RET",
-	[SRSO_MITIGATION_IBPB]		 = "Mitigation: IBPB",
-	[SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only"
+	[SRSO_MITIGATION_NONE]			= "Vulnerable",
+	[SRSO_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",
+	[SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED]	= "Vulnerable: Safe RET, no microcode",
+	[SRSO_MITIGATION_MICROCODE]		= "Vulnerable: Microcode, no safe RET",
+	[SRSO_MITIGATION_SAFE_RET]		= "Mitigation: Safe RET",
+	[SRSO_MITIGATION_IBPB]			= "Mitigation: IBPB",
+	[SRSO_MITIGATION_IBPB_ON_VMEXIT]	= "Mitigation: IBPB on VMEXIT only"
 };
 
 static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE;
@@ -2409,10 +2413,7 @@ static void __init srso_select_mitigation(void)
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	if (!has_microcode) {
-		pr_warn("IBPB-extending microcode not applied!\n");
-		pr_warn(SRSO_NOTICE);
-	} else {
+	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
@@ -2428,6 +2429,12 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}
+	} else {
+		pr_warn("IBPB-extending microcode not applied!\n");
+		pr_warn(SRSO_NOTICE);
+
+		/* may be overwritten by SRSO_CMD_SAFE_RET below */
+		srso_mitigation = SRSO_MITIGATION_UCODE_NEEDED;
 	}
 
 	switch (srso_cmd) {
@@ -2457,7 +2464,10 @@ static void __init srso_select_mitigation(void)
 				setup_force_cpu_cap(X86_FEATURE_SRSO);
 				x86_return_thunk = srso_return_thunk;
 			}
-			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			if (has_microcode)
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			else
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
 		}
@@ -2490,7 +2500,7 @@ static void __init srso_select_mitigation(void)
 	}
 
 out:
-	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
+	pr_info("%s\n", srso_strings[srso_mitigation]);
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
@@ -2701,9 +2711,7 @@ static ssize_t srso_show_state(char *buf)
 	if (boot_cpu_has(X86_FEATURE_SRSO_NO))
 		return sysfs_emit(buf, "Mitigation: SMT disabled\n");
 
-	return sysfs_emit(buf, "%s%s\n",
-			  srso_strings[srso_mitigation],
-			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
+	return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]);
 }
 
 static ssize_t gds_show_state(char *buf)
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 09/20] x86/srso: Fix unret validation dependencies
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (7 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 10/20] x86/alternatives: Remove faulty optimization Josh Poimboeuf
                   ` (11 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

CONFIG_CPU_SRSO isn't dependent on CONFIG_CPU_UNRET_ENTRY (AMD
Retbleed), so the two features are independently configurable.  Fix
several issues for the (presumably rare) case where CONFIG_CPU_SRSO is
enabled but CONFIG_CPU_UNRET_ENTRY isn't.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/nospec-branch.h | 4 ++--
 include/linux/objtool.h              | 3 ++-
 scripts/Makefile.vmlinux_o           | 3 ++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c55cc243592e..197ff4f4d1ce 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -271,7 +271,7 @@
 .Lskip_rsb_\@:
 .endm
 
-#ifdef CONFIG_CPU_UNRET_ENTRY
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 #define CALL_UNTRAIN_RET	"call entry_untrain_ret"
 #else
 #define CALL_UNTRAIN_RET	""
@@ -312,7 +312,7 @@
 
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING)
+	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 03f82c2c2ebf..b5440e7da55b 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -130,7 +130,8 @@
  * it will be ignored.
  */
 .macro VALIDATE_UNRET_BEGIN
-#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+#if defined(CONFIG_NOINSTR_VALIDATION) && \
+	(defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO))
 .Lhere_\@:
 	.pushsection .discard.validate_unret
 	.long	.Lhere_\@ - .
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 0edfdb40364b..25b3b587d37c 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -37,7 +37,8 @@ objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
 
 vmlinux-objtool-args-$(delay-objtool)			+= $(objtool-args-y)
 vmlinux-objtool-args-$(CONFIG_GCOV_KERNEL)		+= --no-unreachable
-vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr $(if $(CONFIG_CPU_UNRET_ENTRY), --unret)
+vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+							   $(if $(or $(CONFIG_CPU_UNRET_ENTRY),$(CONFIG_CPU_SRSO)), --unret)
 
 objtool-args = $(vmlinux-objtool-args-y) --link
 
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 10/20] x86/alternatives: Remove faulty optimization
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (8 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 09/20] x86/srso: Fix unret validation dependencies Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-05  5:04 ` [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
                   ` (10 subsequent siblings)
  20 siblings, 2 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

The following commit

  095b8303f383 ("x86/alternative: Make custom return thunk unconditional")

made '__x86_return_thunk' a placeholder value.  All code setting
X86_FEATURE_RETHUNK also changes the value of 'x86_return_thunk'.  So
the optimization at the beginning of apply_returns() is dead code.

Also, before the above-mentioned commit, the optimization actually had a
bug It bypassed __static_call_fixup(), causing some raw returns to
remain unpatched in static call trampolines.  Thus the 'Fixes' tag.

Fixes: d2408e043e72 ("x86/alternative: Optimize returns patching")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/alternative.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 099d58d02a26..34be5fbaf41e 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -720,14 +720,6 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end)
 {
 	s32 *s;
 
-	/*
-	 * Do not patch out the default return thunks if those needed are the
-	 * ones generated by the compiler.
-	 */
-	if (cpu_feature_enabled(X86_FEATURE_RETHUNK) &&
-	    (x86_return_thunk == __x86_return_thunk))
-		return;
-
 	for (s = start; s < end; s++) {
 		void *dest = NULL, *addr = (void *)s + *s;
 		struct insn insn;
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (9 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 10/20] x86/alternatives: Remove faulty optimization Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 12/20] x86/srso: Unexport untraining functions Josh Poimboeuf
                   ` (9 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

Move srso_alias_return_thunk() to the same section as
srso_alias_safe_ret() so they can share a cache line.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/lib/retpoline.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb5fdd3..9ab634f0b5d2 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -177,15 +177,14 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
 
-	.section .text..__x86.return_thunk
-
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
 
+	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 12/20] x86/srso: Unexport untraining functions
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (10 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label Josh Poimboeuf
                   ` (8 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

These functions aren't called outside of retpoline.S.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 arch/x86/lib/retpoline.S             | 7 ++-----
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 197ff4f4d1ce..6c14fd1f5912 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -352,10 +352,6 @@ extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
 
-extern void retbleed_untrain_ret(void);
-extern void srso_untrain_ret(void);
-extern void srso_alias_untrain_ret(void);
-
 extern void entry_untrain_ret(void);
 extern void entry_ibpb(void);
 
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 9ab634f0b5d2..a40ba18610d8 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -157,7 +157,6 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
-__EXPORT_THUNK(srso_alias_untrain_ret)
 
 	.section .text..__x86.rethunk_safe
 #else
@@ -215,7 +214,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:
@@ -263,7 +262,6 @@ SYM_CODE_END(retbleed_return_thunk)
 	jmp retbleed_return_thunk
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
-__EXPORT_THUNK(retbleed_untrain_ret)
 
 /*
  * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
@@ -277,7 +275,7 @@ __EXPORT_THUNK(retbleed_untrain_ret)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -298,7 +296,6 @@ SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
 	ud2
 SYM_CODE_END(srso_safe_ret)
 SYM_FUNC_END(srso_untrain_ret)
-__EXPORT_THUNK(srso_untrain_ret)
 
 SYM_CODE_START(srso_return_thunk)
 	UNWIND_HINT_FUNC
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (11 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 12/20] x86/srso: Unexport untraining functions Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums Josh Poimboeuf
                   ` (7 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

SBPB is only enabled in two distinct cases:

1) when SRSO has been disabled with srso=off

2) when SRSO has been fixed (in future HW)

Simplify the control flow by getting rid of the 'pred_cmd' label and
moving the SBPB enablement check to the two corresponding code sites.
This makes it more clear when exactly SBPB gets enabled.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e45dd69aff7f..4f1ad2350f49 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2410,13 +2410,21 @@ static void __init srso_select_mitigation(void)
 {
 	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
-		goto pred_cmd;
+	if (cpu_mitigations_off())
+		return;
+
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
+	}
 
 	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
+		 *
+		 * Zen1/2 don't have SBPB, no need to try to enable it here.
 		 */
 		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
@@ -2439,7 +2447,9 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		goto pred_cmd;
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {
@@ -2501,11 +2511,6 @@ static void __init srso_select_mitigation(void)
 
 out:
 	pr_info("%s\n", srso_strings[srso_mitigation]);
-
-pred_cmd:
-	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
-	     boot_cpu_has(X86_FEATURE_SBPB))
-		x86_pred_cmd = PRED_CMD_SBPB;
 }
 
 #undef pr_fmt
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (12 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:04 ` [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block Josh Poimboeuf
                   ` (6 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

For enum switch statements which handle all possible cases, remove the
default case so a compiler warning gets printed if one of the enums gets
accidentally omitted from the switch statement.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4f1ad2350f49..941ac94ad0d4 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1019,7 +1019,6 @@ static void __init retbleed_select_mitigation(void)
 
 do_cmd_auto:
 	case RETBLEED_CMD_AUTO:
-	default:
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
 		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 			if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
@@ -1290,6 +1289,8 @@ spectre_v2_user_select_mitigation(void)
 
 		spectre_v2_user_ibpb = mode;
 		switch (cmd) {
+		case SPECTRE_V2_USER_CMD_NONE:
+			break;
 		case SPECTRE_V2_USER_CMD_FORCE:
 		case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 		case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
@@ -1301,8 +1302,6 @@ spectre_v2_user_select_mitigation(void)
 		case SPECTRE_V2_USER_CMD_SECCOMP:
 			static_branch_enable(&switch_mm_cond_ibpb);
 			break;
-		default:
-			break;
 		}
 
 		pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
@@ -2160,6 +2159,10 @@ static int l1d_flush_prctl_get(struct task_struct *task)
 static int ssb_prctl_get(struct task_struct *task)
 {
 	switch (ssb_mode) {
+	case SPEC_STORE_BYPASS_NONE:
+		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+			return PR_SPEC_ENABLE;
+		return PR_SPEC_NOT_AFFECTED;
 	case SPEC_STORE_BYPASS_DISABLE:
 		return PR_SPEC_DISABLE;
 	case SPEC_STORE_BYPASS_SECCOMP:
@@ -2171,11 +2174,8 @@ static int ssb_prctl_get(struct task_struct *task)
 		if (task_spec_ssb_disable(task))
 			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
-	default:
-		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
-			return PR_SPEC_ENABLE;
-		return PR_SPEC_NOT_AFFECTED;
 	}
+	BUG();
 }
 
 static int ib_prctl_get(struct task_struct *task)
@@ -2504,9 +2504,6 @@ static void __init srso_select_mitigation(void)
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
                 }
 		break;
-
-	default:
-		break;
 	}
 
 out:
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (13 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums Josh Poimboeuf
@ 2023-09-05  5:04 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:05 ` [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
                   ` (5 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:04 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

Simplify the code flow a bit by moving the retbleed IBPB check into the
existing 'has_microcode' block.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/cpu/bugs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 941ac94ad0d4..6b443f0fde34 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2430,10 +2430,8 @@ static void __init srso_select_mitigation(void)
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
 			return;
 		}
-	}
 
-	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
-		if (has_microcode) {
+		if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (14 preceding siblings ...)
  2023-09-05  5:04 ` [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block Josh Poimboeuf
@ 2023-09-05  5:05 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:05 ` [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
                   ` (4 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:05 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

CONFIG_RETHUNK, CONFIG_CPU_UNRET_ENTRY and CONFIG_CPU_SRSO are all
tangled up.  De-spaghettify the code a bit.

Some of the rethunk-related code has been shuffled around within the
'.text..__x86.return_thunk' section, but otherwise there are no
functional changes.  srso_alias_untrain_ret() and srso_alias_safe_ret()
((which are very address-sensitive) haven't moved.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/nospec-branch.h |  25 +++--
 arch/x86/kernel/cpu/bugs.c           |   5 +-
 arch/x86/kernel/vmlinux.lds.S        |   7 +-
 arch/x86/lib/retpoline.S             | 157 +++++++++++++++------------
 4 files changed, 109 insertions(+), 85 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 6c14fd1f5912..51e3f1a287d2 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -289,19 +289,17 @@
  * where we have a stack but before any RET instruction.
  */
 .macro UNTRAIN_RET
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
 .macro UNTRAIN_RET_VM
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -311,8 +309,7 @@
 .endm
 
 .macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -348,6 +345,20 @@ extern void __x86_return_thunk(void);
 static inline void __x86_return_thunk(void) {}
 #endif
 
+#ifdef CONFIG_CPU_UNRET_ENTRY
+extern void retbleed_return_thunk(void);
+#else
+static inline void retbleed_return_thunk(void) {}
+#endif
+
+#ifdef CONFIG_CPU_SRSO
+extern void srso_return_thunk(void);
+extern void srso_alias_return_thunk(void);
+#else
+static inline void srso_return_thunk(void) {}
+static inline void srso_alias_return_thunk(void) {}
+#endif
+
 extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6b443f0fde34..9731e814dcb6 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -63,7 +63,7 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd);
 
 static DEFINE_MUTEX(spec_ctrl_mutex);
 
-void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
+void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;
 
 /* Update SPEC_CTRL MSR and its cached copy unconditionally */
 static void update_spec_ctrl(u64 val)
@@ -1041,8 +1041,7 @@ static void __init retbleed_select_mitigation(void)
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_UNRET);
 
-		if (IS_ENABLED(CONFIG_RETHUNK))
-			x86_return_thunk = retbleed_return_thunk;
+		x86_return_thunk = retbleed_return_thunk;
 
 		if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 		    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 83d41c2601d7..9188834e56c9 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -139,10 +139,7 @@ SECTIONS
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
-#ifdef CONFIG_CPU_SRSO
 		*(.text..__x86.rethunk_untrain)
-#endif
-
 		ENTRY_TEXT
 
 #ifdef CONFIG_CPU_SRSO
@@ -520,12 +517,12 @@ INIT_PER_CPU(irq_stack_backing_store);
            "fixed_percpu_data is not at start of per-cpu area");
 #endif
 
-#ifdef CONFIG_RETHUNK
+#ifdef CONFIG_CPU_UNRET_ENTRY
 . = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned");
-. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 #endif
 
 #ifdef CONFIG_CPU_SRSO
+. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 /*
  * GNU ld cannot do XOR until 2.41.
  * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index a40ba18610d8..8ba79d2b8997 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -126,12 +126,13 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 #include <asm/GEN-for-each-reg.h>
 #undef GEN
 #endif
-/*
- * This function name is magical and is used by -mfunction-return=thunk-extern
- * for the compiler to generate JMPs to it.
- */
+
 #ifdef CONFIG_RETHUNK
 
+	.section .text..__x86.return_thunk
+
+#ifdef CONFIG_CPU_SRSO
+
 /*
  * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at
  * special addresses:
@@ -147,9 +148,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  *
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
-#ifdef CONFIG_CPU_SRSO
-	.section .text..__x86.rethunk_untrain
-
+	.pushsection .text..__x86.rethunk_untrain
 SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
@@ -157,17 +156,9 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
+	.popsection
 
-	.section .text..__x86.rethunk_safe
-#else
-/* dummy definition for alternatives */
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_FUNC_END(srso_alias_untrain_ret)
-#endif
-
+	.pushsection .text..__x86.rethunk_safe
 SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
@@ -182,8 +173,58 @@ SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
+	.popsection
+
+/*
+ * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
+ * above. On kernel entry, srso_untrain_ret() is executed which is a
+ *
+ * movabs $0xccccc30824648d48,%rax
+ *
+ * and when the return thunk executes the inner label srso_safe_ret()
+ * later, it is a stack manipulation and a RET which is mispredicted and
+ * thus a "safe" one to use.
+ */
+	.align 64
+	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+	ANNOTATE_NOENDBR
+	.byte 0x48, 0xb8
+
+/*
+ * This forces the function return instruction to speculate into a trap
+ * (UD2 in srso_return_thunk() below).  This RET will then mispredict
+ * and execution will continue at the return site read from the top of
+ * the stack.
+ */
+SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
+	lea 8(%_ASM_SP), %_ASM_SP
+	ret
+	int3
+	int3
+	/* end of movabs */
+	lfence
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_safe_ret)
+SYM_FUNC_END(srso_untrain_ret)
+
+SYM_CODE_START(srso_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_return_thunk)
+
+#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret"
+#else /* !CONFIG_CPU_SRSO */
+#define JMP_SRSO_UNTRAIN_RET "ud2"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_SRSO */
+
+#ifdef CONFIG_CPU_UNRET_ENTRY
 
-	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *
@@ -263,64 +304,21 @@ SYM_CODE_END(retbleed_return_thunk)
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
 
-/*
- * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
- * above. On kernel entry, srso_untrain_ret() is executed which is a
- *
- * movabs $0xccccc30824648d48,%rax
- *
- * and when the return thunk executes the inner label srso_safe_ret()
- * later, it is a stack manipulation and a RET which is mispredicted and
- * thus a "safe" one to use.
- */
-	.align 64
-	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
-	ANNOTATE_NOENDBR
-	.byte 0x48, 0xb8
+#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret"
+#else /* !CONFIG_CPU_UNRET_ENTRY */
+#define JMP_RETBLEED_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_UNRET_ENTRY */
 
-/*
- * This forces the function return instruction to speculate into a trap
- * (UD2 in srso_return_thunk() below).  This RET will then mispredict
- * and execution will continue at the return site read from the top of
- * the stack.
- */
-SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
-	lea 8(%_ASM_SP), %_ASM_SP
-	ret
-	int3
-	int3
-	/* end of movabs */
-	lfence
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_safe_ret)
-SYM_FUNC_END(srso_untrain_ret)
-
-SYM_CODE_START(srso_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_return_thunk)
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 
 SYM_FUNC_START(entry_untrain_ret)
-	ALTERNATIVE_2 "jmp retbleed_untrain_ret", \
-		      "jmp srso_untrain_ret", X86_FEATURE_SRSO, \
-		      "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS
+	ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET,				\
+		      JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO,		\
+		      JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS
 SYM_FUNC_END(entry_untrain_ret)
 __EXPORT_THUNK(entry_untrain_ret)
 
-SYM_CODE_START(__x86_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_CODE_END(__x86_return_thunk)
-EXPORT_SYMBOL(__x86_return_thunk)
-
-#endif /* CONFIG_RETHUNK */
+#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
@@ -355,3 +353,22 @@ SYM_FUNC_START(__x86_return_skl)
 SYM_FUNC_END(__x86_return_skl)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
+
+/*
+ * This function name is magical and is used by -mfunction-return=thunk-extern
+ * for the compiler to generate JMPs to it.
+ *
+ * This code is only used during kernel boot or module init.  All
+ * 'JMP __x86_return_thunk' sites are changed to something else by
+ * apply_returns().
+ */
+SYM_CODE_START(__x86_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	ANNOTATE_UNRET_SAFE
+	ret
+	int3
+SYM_CODE_END(__x86_return_thunk)
+EXPORT_SYMBOL(__x86_return_thunk)
+
+#endif /* CONFIG_RETHUNK */
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (15 preceding siblings ...)
  2023-09-05  5:05 ` [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
@ 2023-09-05  5:05 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:05 ` [PATCH v3 18/20] x86/retpoline: Remove .text..__x86.return_thunk section Josh Poimboeuf
                   ` (3 subsequent siblings)
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:05 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

Macros already exist for unaligned code block symbols.  Use them.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/lib/retpoline.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 8ba79d2b8997..415521dbe15e 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -149,7 +149,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
 	.pushsection .text..__x86.rethunk_untrain
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_untrain_ret)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	ASM_NOP2
@@ -159,7 +159,7 @@ SYM_FUNC_END(srso_alias_untrain_ret)
 	.popsection
 
 	.pushsection .text..__x86.rethunk_safe
-SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_safe_ret)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
 	ANNOTATE_UNRET_SAFE
@@ -187,7 +187,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(srso_untrain_ret)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -255,7 +255,7 @@ SYM_CODE_END(srso_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(retbleed_untrain_ret)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 18/20] x86/retpoline: Remove .text..__x86.return_thunk section
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (16 preceding siblings ...)
  2023-09-05  5:05 ` [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
@ 2023-09-05  5:05 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (2 more replies)
  2023-09-05  5:05 ` [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
                   ` (2 subsequent siblings)
  20 siblings, 3 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:05 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

The '.text..__x86.return_thunk' section has no purpose.  Remove it and
let the return thunk code live in '.text..__x86.indirect_thunk'.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/kernel/vmlinux.lds.S | 3 ---
 arch/x86/lib/retpoline.S      | 2 --
 2 files changed, 5 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 9188834e56c9..f1c3516d356d 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -132,10 +132,7 @@ SECTIONS
 		LOCK_TEXT
 		KPROBES_TEXT
 		SOFTIRQENTRY_TEXT
-#ifdef CONFIG_RETPOLINE
 		*(.text..__x86.indirect_thunk)
-		*(.text..__x86.return_thunk)
-#endif
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 415521dbe15e..49f2be7c7b35 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -129,8 +129,6 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 
 #ifdef CONFIG_RETHUNK
 
-	.section .text..__x86.return_thunk
-
 #ifdef CONFIG_CPU_SRSO
 
 /*
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*]
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (17 preceding siblings ...)
  2023-09-05  5:05 ` [PATCH v3 18/20] x86/retpoline: Remove .text..__x86.return_thunk section Josh Poimboeuf
@ 2023-09-05  5:05 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  5:05 ` [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
  2023-09-05  6:35 ` [PATCH v3 00/20] SRSO fixes/cleanups Borislav Petkov
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:05 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

Factor out the UNTRAIN_RET[_*] common bits into a helper macro.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/nospec-branch.h | 31 +++++++++-------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 51e3f1a287d2..dcc78477a38d 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -288,35 +288,24 @@
  * As such, this must be placed after every *SWITCH_TO_KERNEL_CR3 at a point
  * where we have a stack but before any RET instruction.
  */
-.macro UNTRAIN_RET
+.macro __UNTRAIN_RET ibpb_feature, call_depth_insns
 #if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		      "call entry_ibpb", \ibpb_feature,			\
+		     __stringify(\call_depth_insns), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
-.macro UNTRAIN_RET_VM
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH)
 
-.macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET_VM \
+	__UNTRAIN_RET X86_FEATURE_IBPB_ON_VMEXIT, __stringify(RESET_CALL_DEPTH)
+
+#define UNTRAIN_RET_FROM_CALL \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH_FROM_CALL)
 
 
 .macro CALL_DEPTH_ACCOUNT
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (18 preceding siblings ...)
  2023-09-05  5:05 ` [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
@ 2023-09-05  5:05 ` Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
                     ` (3 more replies)
  2023-09-05  6:35 ` [PATCH v3 00/20] SRSO fixes/cleanups Borislav Petkov
  20 siblings, 4 replies; 92+ messages in thread
From: Josh Poimboeuf @ 2023-09-05  5:05 UTC (permalink / raw)
  To: x86
  Cc: linux-kernel, Borislav Petkov, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner

For consistency with the other return thunks, rename __x86_return_skl()
to call_depth_return_thunk().

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
---
 arch/x86/include/asm/nospec-branch.h | 13 ++++---------
 arch/x86/kernel/cpu/bugs.c           |  3 ++-
 arch/x86/lib/retpoline.S             |  4 ++--
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index dcc78477a38d..14cd3cd5f85a 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -358,12 +358,7 @@ extern void entry_ibpb(void);
 extern void (*x86_return_thunk)(void);
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
-extern void __x86_return_skl(void);
-
-static inline void x86_set_skl_return_thunk(void)
-{
-	x86_return_thunk = &__x86_return_skl;
-}
+extern void call_depth_return_thunk(void);
 
 #define CALL_DEPTH_ACCOUNT					\
 	ALTERNATIVE("",						\
@@ -376,12 +371,12 @@ DECLARE_PER_CPU(u64, __x86_ret_count);
 DECLARE_PER_CPU(u64, __x86_stuffs_count);
 DECLARE_PER_CPU(u64, __x86_ctxsw_count);
 #endif
-#else
-static inline void x86_set_skl_return_thunk(void) {}
+#else /* !CONFIG_CALL_DEPTH_TRACKING */
 
+static inline void call_depth_return_thunk(void) {}
 #define CALL_DEPTH_ACCOUNT ""
 
-#endif
+#endif /* CONFIG_CALL_DEPTH_TRACKING */
 
 #ifdef CONFIG_RETPOLINE
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9731e814dcb6..016a32613259 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1059,7 +1059,8 @@ static void __init retbleed_select_mitigation(void)
 	case RETBLEED_MITIGATION_STUFF:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
-		x86_set_skl_return_thunk();
+
+		x86_return_thunk = call_depth_return_thunk;
 		break;
 
 	default:
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 49f2be7c7b35..6376d0164395 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -321,7 +321,7 @@ __EXPORT_THUNK(entry_untrain_ret)
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
 	.align 64
-SYM_FUNC_START(__x86_return_skl)
+SYM_FUNC_START(call_depth_return_thunk)
 	ANNOTATE_NOENDBR
 	/*
 	 * Keep the hotpath in a 16byte I-fetch for the non-debug
@@ -348,7 +348,7 @@ SYM_FUNC_START(__x86_return_skl)
 	ANNOTATE_UNRET_SAFE
 	ret
 	int3
-SYM_FUNC_END(__x86_return_skl)
+SYM_FUNC_END(call_depth_return_thunk)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
 
-- 
2.41.0


^ permalink raw reply related	[flat|nested] 92+ messages in thread

* Re: [PATCH v3 00/20] SRSO fixes/cleanups
  2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
                   ` (19 preceding siblings ...)
  2023-09-05  5:05 ` [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
@ 2023-09-05  6:35 ` Borislav Petkov
  2023-09-05 10:02   ` Ingo Molnar
  20 siblings, 1 reply; 92+ messages in thread
From: Borislav Petkov @ 2023-09-05  6:35 UTC (permalink / raw)
  To: Josh Poimboeuf
  Cc: x86, linux-kernel, Peter Zijlstra, Babu Moger, Paolo Bonzini,
	Sean Christopherson, David.Kaplan, Andrew Cooper, Nikolay Borisov,
	gregkh, Thomas Gleixner

On Mon, Sep 04, 2023 at 10:04:44PM -0700, Josh Poimboeuf wrote:
> v3:
> - drop kvm patches (to be picked up by Sean)
> - fix "no microcode, no microcode" printk
> - fix "Safe Ret" capitalization in documentation
> - fix chopped line in commit log
> - drop "x86/srso: Remove redundant X86_FEATURE_ENTRY_IBPB check" patch
> 
> Josh Poimboeuf (20):
>   x86/srso: Fix srso_show_state() side effect
>   x86/srso: Set CPUID feature bits independently of bug or mitigation
>     status
>   x86/srso: Don't probe microcode in a guest
>   x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
>   x86/srso: Fix SBPB enablement for (possible) future fixed HW
>   x86/srso: Print actual mitigation if requested mitigation isn't
>     possible
>   x86/srso: Print mitigation for retbleed IBPB case
>   x86/srso: Fix vulnerability reporting for missing microcode
>   x86/srso: Fix unret validation dependencies
>   x86/alternatives: Remove faulty optimization
>   x86/srso: Improve i-cache locality for alias mitigation
>   x86/srso: Unexport untraining functions
>   x86/srso: Remove 'pred_cmd' label
>   x86/bugs: Remove default case for fully switched enums
>   x86/srso: Move retbleed IBPB check into existing 'has_microcode' code
>     block
>   x86/srso: Disentangle rethunk-dependent options
>   x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
>   x86/retpoline: Remove .text..__x86.return_thunk section
>   x86/nospec: Refactor UNTRAIN_RET[_*]
>   x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
> 
>  Documentation/admin-guide/hw-vuln/srso.rst |  24 ++-
>  arch/x86/include/asm/nospec-branch.h       |  69 ++++-----
>  arch/x86/include/asm/processor.h           |   2 -
>  arch/x86/kernel/alternative.c              |   8 -
>  arch/x86/kernel/cpu/amd.c                  |  28 ++--
>  arch/x86/kernel/cpu/bugs.c                 | 102 ++++++------
>  arch/x86/kernel/vmlinux.lds.S              |  10 +-
>  arch/x86/lib/retpoline.S                   | 171 +++++++++++----------
>  include/linux/objtool.h                    |   3 +-
>  scripts/Makefile.vmlinux_o                 |   3 +-
>  10 files changed, 201 insertions(+), 219 deletions(-)

They all look good to me, thanks!

Acked-by: Borislav Petkov (AMD) <bp@alien8.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

^ permalink raw reply	[flat|nested] 92+ messages in thread

* Re: [PATCH v3 00/20] SRSO fixes/cleanups
  2023-09-05  6:35 ` [PATCH v3 00/20] SRSO fixes/cleanups Borislav Petkov
@ 2023-09-05 10:02   ` Ingo Molnar
  0 siblings, 0 replies; 92+ messages in thread
From: Ingo Molnar @ 2023-09-05 10:02 UTC (permalink / raw)
  To: Borislav Petkov
  Cc: Josh Poimboeuf, x86, linux-kernel, Peter Zijlstra, Babu Moger,
	Paolo Bonzini, Sean Christopherson, David.Kaplan, Andrew Cooper,
	Nikolay Borisov, gregkh, Thomas Gleixner


* Borislav Petkov <bp@alien8.de> wrote:

> On Mon, Sep 04, 2023 at 10:04:44PM -0700, Josh Poimboeuf wrote:
> > v3:
> > - drop kvm patches (to be picked up by Sean)
> > - fix "no microcode, no microcode" printk
> > - fix "Safe Ret" capitalization in documentation
> > - fix chopped line in commit log
> > - drop "x86/srso: Remove redundant X86_FEATURE_ENTRY_IBPB check" patch
> > 
> > Josh Poimboeuf (20):
> >   x86/srso: Fix srso_show_state() side effect
> >   x86/srso: Set CPUID feature bits independently of bug or mitigation
> >     status
> >   x86/srso: Don't probe microcode in a guest
> >   x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
> >   x86/srso: Fix SBPB enablement for (possible) future fixed HW
> >   x86/srso: Print actual mitigation if requested mitigation isn't
> >     possible
> >   x86/srso: Print mitigation for retbleed IBPB case
> >   x86/srso: Fix vulnerability reporting for missing microcode
> >   x86/srso: Fix unret validation dependencies
> >   x86/alternatives: Remove faulty optimization
> >   x86/srso: Improve i-cache locality for alias mitigation
> >   x86/srso: Unexport untraining functions
> >   x86/srso: Remove 'pred_cmd' label
> >   x86/bugs: Remove default case for fully switched enums
> >   x86/srso: Move retbleed IBPB check into existing 'has_microcode' code
> >     block
> >   x86/srso: Disentangle rethunk-dependent options
> >   x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
> >   x86/retpoline: Remove .text..__x86.return_thunk section
> >   x86/nospec: Refactor UNTRAIN_RET[_*]
> >   x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
> > 
> >  Documentation/admin-guide/hw-vuln/srso.rst |  24 ++-
> >  arch/x86/include/asm/nospec-branch.h       |  69 ++++-----
> >  arch/x86/include/asm/processor.h           |   2 -
> >  arch/x86/kernel/alternative.c              |   8 -
> >  arch/x86/kernel/cpu/amd.c                  |  28 ++--
> >  arch/x86/kernel/cpu/bugs.c                 | 102 ++++++------
> >  arch/x86/kernel/vmlinux.lds.S              |  10 +-
> >  arch/x86/lib/retpoline.S                   | 171 +++++++++++----------
> >  include/linux/objtool.h                    |   3 +-
> >  scripts/Makefile.vmlinux_o                 |   3 +-
> >  10 files changed, 201 insertions(+), 219 deletions(-)
> 
> They all look good to me, thanks!
> 
> Acked-by: Borislav Petkov (AMD) <bp@alien8.de>

I've applied them to tip:x86/bugs, thanks guys!

Below is the delta diff from v2 to v3.

Thanks,

	Ingo

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index 4516719e00b5..e715bfc09879 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -57,7 +57,7 @@ The possible values in this file are:
 
  * 'Vulnerable: Safe RET, no microcode':
 
-   The "Safe Ret" mitigation (see below) has been applied to protect the
+   The "Safe RET" mitigation (see below) has been applied to protect the
    kernel, but the IBPB-extending microcode has not been applied.  User
    space tasks may still be vulnerable.
 
@@ -139,7 +139,7 @@ an indrect branch prediction barrier after having applied the required
 microcode patch for one's system. This mitigation comes also at
 a performance cost.
 
-Mitigation: safe RET
+Mitigation: Safe RET
 --------------------
 
 The mitigation works by ensuring all RET instructions speculate to
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d538043c776d..016a32613259 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2494,7 +2494,7 @@ static void __init srso_select_mitigation(void)
 
 	case SRSO_CMD_IBPB_ON_VMEXIT:
 		if (IS_ENABLED(CONFIG_CPU_SRSO)) {
-			if (has_microcode) {
+			if (!boot_cpu_has(X86_FEATURE_ENTRY_IBPB) && has_microcode) {
 				setup_force_cpu_cap(X86_FEATURE_IBPB_ON_VMEXIT);
 				srso_mitigation = SRSO_MITIGATION_IBPB_ON_VMEXIT;
 			}
@@ -2505,7 +2505,7 @@ static void __init srso_select_mitigation(void)
 	}
 
 out:
-	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
+	pr_info("%s\n", srso_strings[srso_mitigation]);
 }
 
 #undef pr_fmt

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
  2023-09-05  5:05 ` [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     423a4484b9235af31b1fd60d6049b820586e57d2
Gitweb:        https://git.kernel.org/tip/423a4484b9235af31b1fd60d6049b820586e57d2
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:04 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:08 +02:00

x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()

For consistency with the other return thunks, rename __x86_return_skl()
to call_depth_return_thunk().

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ae44e9f9976934e3b5b47a458d523ccb15867561.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 13 ++++---------
 arch/x86/kernel/cpu/bugs.c           |  3 ++-
 arch/x86/lib/retpoline.S             |  4 ++--
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index dcc7847..14cd3cd 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -358,12 +358,7 @@ extern void entry_ibpb(void);
 extern void (*x86_return_thunk)(void);
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
-extern void __x86_return_skl(void);
-
-static inline void x86_set_skl_return_thunk(void)
-{
-	x86_return_thunk = &__x86_return_skl;
-}
+extern void call_depth_return_thunk(void);
 
 #define CALL_DEPTH_ACCOUNT					\
 	ALTERNATIVE("",						\
@@ -376,12 +371,12 @@ DECLARE_PER_CPU(u64, __x86_ret_count);
 DECLARE_PER_CPU(u64, __x86_stuffs_count);
 DECLARE_PER_CPU(u64, __x86_ctxsw_count);
 #endif
-#else
-static inline void x86_set_skl_return_thunk(void) {}
+#else /* !CONFIG_CALL_DEPTH_TRACKING */
 
+static inline void call_depth_return_thunk(void) {}
 #define CALL_DEPTH_ACCOUNT ""
 
-#endif
+#endif /* CONFIG_CALL_DEPTH_TRACKING */
 
 #ifdef CONFIG_RETPOLINE
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9731e81..016a326 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1059,7 +1059,8 @@ do_cmd_auto:
 	case RETBLEED_MITIGATION_STUFF:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
-		x86_set_skl_return_thunk();
+
+		x86_return_thunk = call_depth_return_thunk;
 		break;
 
 	default:
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 49f2be7..6376d01 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -321,7 +321,7 @@ __EXPORT_THUNK(entry_untrain_ret)
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
 	.align 64
-SYM_FUNC_START(__x86_return_skl)
+SYM_FUNC_START(call_depth_return_thunk)
 	ANNOTATE_NOENDBR
 	/*
 	 * Keep the hotpath in a 16byte I-fetch for the non-debug
@@ -348,7 +348,7 @@ SYM_FUNC_START(__x86_return_skl)
 	ANNOTATE_UNRET_SAFE
 	ret
 	int3
-SYM_FUNC_END(__x86_return_skl)
+SYM_FUNC_END(call_depth_return_thunk)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/nospec: Refactor UNTRAIN_RET[_*]
  2023-09-05  5:05 ` [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     ef96daae49597e76a99f3db00dfc2c1559fe2443
Gitweb:        https://git.kernel.org/tip/ef96daae49597e76a99f3db00dfc2c1559fe2443
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:03 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:08 +02:00

x86/nospec: Refactor UNTRAIN_RET[_*]

Factor out the UNTRAIN_RET[_*] common bits into a helper macro.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/f06d45489778bd49623297af2a983eea09067a74.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 31 ++++++++-------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 51e3f1a..dcc7847 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -288,35 +288,24 @@
  * As such, this must be placed after every *SWITCH_TO_KERNEL_CR3 at a point
  * where we have a stack but before any RET instruction.
  */
-.macro UNTRAIN_RET
+.macro __UNTRAIN_RET ibpb_feature, call_depth_insns
 #if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		      "call entry_ibpb", \ibpb_feature,			\
+		     __stringify(\call_depth_insns), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
-.macro UNTRAIN_RET_VM
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH)
 
-.macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET_VM \
+	__UNTRAIN_RET X86_FEATURE_IBPB_ON_VMEXIT, __stringify(RESET_CALL_DEPTH)
+
+#define UNTRAIN_RET_FROM_CALL \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH_FROM_CALL)
 
 
 .macro CALL_DEPTH_ACCOUNT

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
  2023-09-05  5:05 ` [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     ba6ee6dfa046653621d57209873094962174ae6c
Gitweb:        https://git.kernel.org/tip/ba6ee6dfa046653621d57209873094962174ae6c
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:01 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros

Macros already exist for unaligned code block symbols.  Use them.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/26d461bd509cc840af24c94586561c06d39812b2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 8ba79d2..415521d 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -149,7 +149,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
 	.pushsection .text..__x86.rethunk_untrain
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_untrain_ret)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	ASM_NOP2
@@ -159,7 +159,7 @@ SYM_FUNC_END(srso_alias_untrain_ret)
 	.popsection
 
 	.pushsection .text..__x86.rethunk_safe
-SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_safe_ret)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
 	ANNOTATE_UNRET_SAFE
@@ -187,7 +187,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(srso_untrain_ret)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -255,7 +255,7 @@ SYM_CODE_END(srso_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(retbleed_untrain_ret)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/retpoline: Remove .text..__x86.return_thunk section
  2023-09-05  5:05 ` [PATCH v3 18/20] x86/retpoline: Remove .text..__x86.return_thunk section Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     6cb0ce310bad46ba9bc20ca906ff2ca40f170462
Gitweb:        https://git.kernel.org/tip/6cb0ce310bad46ba9bc20ca906ff2ca40f170462
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:02 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/retpoline: Remove .text..__x86.return_thunk section

The '.text..__x86.return_thunk' section has no purpose.  Remove it and
let the return thunk code live in '.text..__x86.indirect_thunk'.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/291aad1dcb2d27c6241fe3f182d66119857757fd.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/vmlinux.lds.S | 3 ---
 arch/x86/lib/retpoline.S      | 2 --
 2 files changed, 5 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 9188834..f1c3516 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -132,10 +132,7 @@ SECTIONS
 		LOCK_TEXT
 		KPROBES_TEXT
 		SOFTIRQENTRY_TEXT
-#ifdef CONFIG_RETPOLINE
 		*(.text..__x86.indirect_thunk)
-		*(.text..__x86.return_thunk)
-#endif
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 415521d..49f2be7 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -129,8 +129,6 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 
 #ifdef CONFIG_RETHUNK
 
-	.section .text..__x86.return_thunk
-
 #ifdef CONFIG_CPU_SRSO
 
 /*

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Disentangle rethunk-dependent options
  2023-09-05  5:05 ` [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     da5a1ae1877b9a455bab096869cec2d6bd33ddd6
Gitweb:        https://git.kernel.org/tip/da5a1ae1877b9a455bab096869cec2d6bd33ddd6
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:00 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/srso: Disentangle rethunk-dependent options

CONFIG_RETHUNK, CONFIG_CPU_UNRET_ENTRY and CONFIG_CPU_SRSO are all
tangled up.  De-spaghettify the code a bit.

Some of the rethunk-related code has been shuffled around within the
'.text..__x86.return_thunk' section, but otherwise there are no
functional changes.  srso_alias_untrain_ret() and srso_alias_safe_ret()
((which are very address-sensitive) haven't moved.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h |  25 ++--
 arch/x86/kernel/cpu/bugs.c           |   5 +-
 arch/x86/kernel/vmlinux.lds.S        |   7 +-
 arch/x86/lib/retpoline.S             | 157 ++++++++++++++------------
 4 files changed, 109 insertions(+), 85 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 6c14fd1..51e3f1a 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -289,19 +289,17 @@
  * where we have a stack but before any RET instruction.
  */
 .macro UNTRAIN_RET
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
 .macro UNTRAIN_RET_VM
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -311,8 +309,7 @@
 .endm
 
 .macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -348,6 +345,20 @@ extern void __x86_return_thunk(void);
 static inline void __x86_return_thunk(void) {}
 #endif
 
+#ifdef CONFIG_CPU_UNRET_ENTRY
+extern void retbleed_return_thunk(void);
+#else
+static inline void retbleed_return_thunk(void) {}
+#endif
+
+#ifdef CONFIG_CPU_SRSO
+extern void srso_return_thunk(void);
+extern void srso_alias_return_thunk(void);
+#else
+static inline void srso_return_thunk(void) {}
+static inline void srso_alias_return_thunk(void) {}
+#endif
+
 extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6b443f0..9731e81 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -63,7 +63,7 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd);
 
 static DEFINE_MUTEX(spec_ctrl_mutex);
 
-void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
+void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;
 
 /* Update SPEC_CTRL MSR and its cached copy unconditionally */
 static void update_spec_ctrl(u64 val)
@@ -1041,8 +1041,7 @@ do_cmd_auto:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_UNRET);
 
-		if (IS_ENABLED(CONFIG_RETHUNK))
-			x86_return_thunk = retbleed_return_thunk;
+		x86_return_thunk = retbleed_return_thunk;
 
 		if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 		    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 83d41c2..9188834 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -139,10 +139,7 @@ SECTIONS
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
-#ifdef CONFIG_CPU_SRSO
 		*(.text..__x86.rethunk_untrain)
-#endif
-
 		ENTRY_TEXT
 
 #ifdef CONFIG_CPU_SRSO
@@ -520,12 +517,12 @@ INIT_PER_CPU(irq_stack_backing_store);
            "fixed_percpu_data is not at start of per-cpu area");
 #endif
 
-#ifdef CONFIG_RETHUNK
+#ifdef CONFIG_CPU_UNRET_ENTRY
 . = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned");
-. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 #endif
 
 #ifdef CONFIG_CPU_SRSO
+. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 /*
  * GNU ld cannot do XOR until 2.41.
  * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index a40ba18..8ba79d2 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -126,12 +126,13 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 #include <asm/GEN-for-each-reg.h>
 #undef GEN
 #endif
-/*
- * This function name is magical and is used by -mfunction-return=thunk-extern
- * for the compiler to generate JMPs to it.
- */
+
 #ifdef CONFIG_RETHUNK
 
+	.section .text..__x86.return_thunk
+
+#ifdef CONFIG_CPU_SRSO
+
 /*
  * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at
  * special addresses:
@@ -147,9 +148,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  *
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
-#ifdef CONFIG_CPU_SRSO
-	.section .text..__x86.rethunk_untrain
-
+	.pushsection .text..__x86.rethunk_untrain
 SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
@@ -157,17 +156,9 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
+	.popsection
 
-	.section .text..__x86.rethunk_safe
-#else
-/* dummy definition for alternatives */
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_FUNC_END(srso_alias_untrain_ret)
-#endif
-
+	.pushsection .text..__x86.rethunk_safe
 SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
@@ -182,8 +173,58 @@ SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
+	.popsection
+
+/*
+ * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
+ * above. On kernel entry, srso_untrain_ret() is executed which is a
+ *
+ * movabs $0xccccc30824648d48,%rax
+ *
+ * and when the return thunk executes the inner label srso_safe_ret()
+ * later, it is a stack manipulation and a RET which is mispredicted and
+ * thus a "safe" one to use.
+ */
+	.align 64
+	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+	ANNOTATE_NOENDBR
+	.byte 0x48, 0xb8
+
+/*
+ * This forces the function return instruction to speculate into a trap
+ * (UD2 in srso_return_thunk() below).  This RET will then mispredict
+ * and execution will continue at the return site read from the top of
+ * the stack.
+ */
+SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
+	lea 8(%_ASM_SP), %_ASM_SP
+	ret
+	int3
+	int3
+	/* end of movabs */
+	lfence
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_safe_ret)
+SYM_FUNC_END(srso_untrain_ret)
+
+SYM_CODE_START(srso_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_return_thunk)
+
+#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret"
+#else /* !CONFIG_CPU_SRSO */
+#define JMP_SRSO_UNTRAIN_RET "ud2"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_SRSO */
+
+#ifdef CONFIG_CPU_UNRET_ENTRY
 
-	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *
@@ -263,64 +304,21 @@ SYM_CODE_END(retbleed_return_thunk)
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
 
-/*
- * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
- * above. On kernel entry, srso_untrain_ret() is executed which is a
- *
- * movabs $0xccccc30824648d48,%rax
- *
- * and when the return thunk executes the inner label srso_safe_ret()
- * later, it is a stack manipulation and a RET which is mispredicted and
- * thus a "safe" one to use.
- */
-	.align 64
-	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
-	ANNOTATE_NOENDBR
-	.byte 0x48, 0xb8
+#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret"
+#else /* !CONFIG_CPU_UNRET_ENTRY */
+#define JMP_RETBLEED_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_UNRET_ENTRY */
 
-/*
- * This forces the function return instruction to speculate into a trap
- * (UD2 in srso_return_thunk() below).  This RET will then mispredict
- * and execution will continue at the return site read from the top of
- * the stack.
- */
-SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
-	lea 8(%_ASM_SP), %_ASM_SP
-	ret
-	int3
-	int3
-	/* end of movabs */
-	lfence
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_safe_ret)
-SYM_FUNC_END(srso_untrain_ret)
-
-SYM_CODE_START(srso_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_return_thunk)
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 
 SYM_FUNC_START(entry_untrain_ret)
-	ALTERNATIVE_2 "jmp retbleed_untrain_ret", \
-		      "jmp srso_untrain_ret", X86_FEATURE_SRSO, \
-		      "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS
+	ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET,				\
+		      JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO,		\
+		      JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS
 SYM_FUNC_END(entry_untrain_ret)
 __EXPORT_THUNK(entry_untrain_ret)
 
-SYM_CODE_START(__x86_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_CODE_END(__x86_return_thunk)
-EXPORT_SYMBOL(__x86_return_thunk)
-
-#endif /* CONFIG_RETHUNK */
+#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
@@ -355,3 +353,22 @@ SYM_FUNC_START(__x86_return_skl)
 SYM_FUNC_END(__x86_return_skl)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
+
+/*
+ * This function name is magical and is used by -mfunction-return=thunk-extern
+ * for the compiler to generate JMPs to it.
+ *
+ * This code is only used during kernel boot or module init.  All
+ * 'JMP __x86_return_thunk' sites are changed to something else by
+ * apply_returns().
+ */
+SYM_CODE_START(__x86_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	ANNOTATE_UNRET_SAFE
+	ret
+	int3
+SYM_CODE_END(__x86_return_thunk)
+EXPORT_SYMBOL(__x86_return_thunk)
+
+#endif /* CONFIG_RETHUNK */

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block
  2023-09-05  5:04 ` [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     a94be9ae24d2e1580cf68fb58e14369ae6a4846b
Gitweb:        https://git.kernel.org/tip/a94be9ae24d2e1580cf68fb58e14369ae6a4846b
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:59 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block

Simplify the code flow a bit by moving the retbleed IBPB check into the
existing 'has_microcode' block.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/0a22b86b1f6b07f9046a9ab763fc0e0d1b7a91d4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 941ac94..6b443f0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2430,10 +2430,8 @@ static void __init srso_select_mitigation(void)
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
 			return;
 		}
-	}
 
-	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
-		if (has_microcode) {
+		if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Remove 'pred_cmd' label
  2023-09-05  5:04 ` [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     7a7b33e7a36b13e0032f77406461bd0fed68f55c
Gitweb:        https://git.kernel.org/tip/7a7b33e7a36b13e0032f77406461bd0fed68f55c
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:57 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/srso: Remove 'pred_cmd' label

SBPB is only enabled in two distinct cases:

1) when SRSO has been disabled with srso=off

2) when SRSO has been fixed (in future HW)

Simplify the control flow by getting rid of the 'pred_cmd' label and
moving the SBPB enablement check to the two corresponding code sites.
This makes it more clear when exactly SBPB gets enabled.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/bb20e8569cfa144def5e6f25e610804bc4974de2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e45dd69..4f1ad23 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2410,13 +2410,21 @@ static void __init srso_select_mitigation(void)
 {
 	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
-		goto pred_cmd;
+	if (cpu_mitigations_off())
+		return;
+
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
+	}
 
 	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
+		 *
+		 * Zen1/2 don't have SBPB, no need to try to enable it here.
 		 */
 		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
@@ -2439,7 +2447,9 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		goto pred_cmd;
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {
@@ -2501,11 +2511,6 @@ static void __init srso_select_mitigation(void)
 
 out:
 	pr_info("%s\n", srso_strings[srso_mitigation]);
-
-pred_cmd:
-	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
-	     boot_cpu_has(X86_FEATURE_SBPB))
-		x86_pred_cmd = PRED_CMD_SBPB;
 }
 
 #undef pr_fmt

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/bugs: Remove default case for fully switched enums
  2023-09-05  5:04 ` [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     3cd8bc46c3e4147551c89a38ca0ffc5ff7915e52
Gitweb:        https://git.kernel.org/tip/3cd8bc46c3e4147551c89a38ca0ffc5ff7915e52
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:58 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/bugs: Remove default case for fully switched enums

For enum switch statements which handle all possible cases, remove the
default case so a compiler warning gets printed if one of the enums gets
accidentally omitted from the switch statement.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/fcf6feefab991b72e411c2aed688b18e65e06aed.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4f1ad23..941ac94 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1019,7 +1019,6 @@ static void __init retbleed_select_mitigation(void)
 
 do_cmd_auto:
 	case RETBLEED_CMD_AUTO:
-	default:
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
 		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 			if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
@@ -1290,6 +1289,8 @@ spectre_v2_user_select_mitigation(void)
 
 		spectre_v2_user_ibpb = mode;
 		switch (cmd) {
+		case SPECTRE_V2_USER_CMD_NONE:
+			break;
 		case SPECTRE_V2_USER_CMD_FORCE:
 		case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 		case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
@@ -1301,8 +1302,6 @@ spectre_v2_user_select_mitigation(void)
 		case SPECTRE_V2_USER_CMD_SECCOMP:
 			static_branch_enable(&switch_mm_cond_ibpb);
 			break;
-		default:
-			break;
 		}
 
 		pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
@@ -2160,6 +2159,10 @@ static int l1d_flush_prctl_get(struct task_struct *task)
 static int ssb_prctl_get(struct task_struct *task)
 {
 	switch (ssb_mode) {
+	case SPEC_STORE_BYPASS_NONE:
+		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+			return PR_SPEC_ENABLE;
+		return PR_SPEC_NOT_AFFECTED;
 	case SPEC_STORE_BYPASS_DISABLE:
 		return PR_SPEC_DISABLE;
 	case SPEC_STORE_BYPASS_SECCOMP:
@@ -2171,11 +2174,8 @@ static int ssb_prctl_get(struct task_struct *task)
 		if (task_spec_ssb_disable(task))
 			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
-	default:
-		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
-			return PR_SPEC_ENABLE;
-		return PR_SPEC_NOT_AFFECTED;
 	}
+	BUG();
 }
 
 static int ib_prctl_get(struct task_struct *task)
@@ -2504,9 +2504,6 @@ static void __init srso_select_mitigation(void)
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
                 }
 		break;
-
-	default:
-		break;
 	}
 
 out:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Unexport untraining functions
  2023-09-05  5:04 ` [PATCH v3 12/20] x86/srso: Unexport untraining functions Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     253553c3364c20d4ff8f61ae53456a7429c5261b
Gitweb:        https://git.kernel.org/tip/253553c3364c20d4ff8f61ae53456a7429c5261b
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:56 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/srso: Unexport untraining functions

These functions aren't called outside of retpoline.S.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/1ae080f95ce7266c82cba6d2adde82349b832654.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 arch/x86/lib/retpoline.S             | 7 ++-----
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 197ff4f..6c14fd1 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -352,10 +352,6 @@ extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
 
-extern void retbleed_untrain_ret(void);
-extern void srso_untrain_ret(void);
-extern void srso_alias_untrain_ret(void);
-
 extern void entry_untrain_ret(void);
 extern void entry_ibpb(void);
 
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 9ab634f..a40ba18 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -157,7 +157,6 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
-__EXPORT_THUNK(srso_alias_untrain_ret)
 
 	.section .text..__x86.rethunk_safe
 #else
@@ -215,7 +214,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:
@@ -263,7 +262,6 @@ SYM_CODE_END(retbleed_return_thunk)
 	jmp retbleed_return_thunk
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
-__EXPORT_THUNK(retbleed_untrain_ret)
 
 /*
  * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
@@ -277,7 +275,7 @@ __EXPORT_THUNK(retbleed_untrain_ret)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -298,7 +296,6 @@ SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
 	ud2
 SYM_CODE_END(srso_safe_ret)
 SYM_FUNC_END(srso_untrain_ret)
-__EXPORT_THUNK(srso_untrain_ret)
 
 SYM_CODE_START(srso_return_thunk)
 	UNWIND_HINT_FUNC

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/alternatives: Remove faulty optimization
  2023-09-05  5:04 ` [PATCH v3 10/20] x86/alternatives: Remove faulty optimization Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     85d5fbfb7deaf3a5b4666e741bb72a68866439e6
Gitweb:        https://git.kernel.org/tip/85d5fbfb7deaf3a5b4666e741bb72a68866439e6
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:54 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/alternatives: Remove faulty optimization

The following commit

  095b8303f383 ("x86/alternative: Make custom return thunk unconditional")

made '__x86_return_thunk' a placeholder value.  All code setting
X86_FEATURE_RETHUNK also changes the value of 'x86_return_thunk'.  So
the optimization at the beginning of apply_returns() is dead code.

Also, before the above-mentioned commit, the optimization actually had a
bug It bypassed __static_call_fixup(), causing some raw returns to
remain unpatched in static call trampolines.  Thus the 'Fixes' tag.

Fixes: d2408e043e72 ("x86/alternative: Optimize returns patching")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/16d19d2249d4485d8380fb215ffaae81e6b8119e.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/alternative.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index a5ead6a..c850f5a 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -720,14 +720,6 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end)
 {
 	s32 *s;
 
-	/*
-	 * Do not patch out the default return thunks if those needed are the
-	 * ones generated by the compiler.
-	 */
-	if (cpu_feature_enabled(X86_FEATURE_RETHUNK) &&
-	    (x86_return_thunk == __x86_return_thunk))
-		return;
-
 	for (s = start; s < end; s++) {
 		void *dest = NULL, *addr = (void *)s + *s;
 		struct insn insn;

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Improve i-cache locality for alias mitigation
  2023-09-05  5:04 ` [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     001c04b48252282f3045acbdc4e91fb6f4142085
Gitweb:        https://git.kernel.org/tip/001c04b48252282f3045acbdc4e91fb6f4142085
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:55 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/srso: Improve i-cache locality for alias mitigation

Move srso_alias_return_thunk() to the same section as
srso_alias_safe_ret() so they can share a cache line.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/eadaf5530b46a7ae8b936522da45ae555d2b3393.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb..9ab634f 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -177,15 +177,14 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
 
-	.section .text..__x86.return_thunk
-
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
 
+	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix vulnerability reporting for missing microcode
  2023-09-05  5:04 ` [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     534be1d0ecfa327cda06fd9e556b2f56062da3d7
Gitweb:        https://git.kernel.org/tip/534be1d0ecfa327cda06fd9e556b2f56062da3d7
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:52 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/srso: Fix vulnerability reporting for missing microcode

The SRSO default safe-ret mitigation is reported as "mitigated" even if
microcode hasn't been updated.  That's wrong because userspace may still
be vulnerable to SRSO attacks due to IBPB not flushing branch type
predictions.

Report the safe-ret + !microcode case as vulnerable.

Also report the microcode-only case as vulnerable as it leaves the
kernel open to attacks.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/a8a14f97d1b0e03ec255c81637afdf4cf0ae9c99.1693889988.git.jpoimboe@kernel.org
---
 Documentation/admin-guide/hw-vuln/srso.rst | 24 +++++++++-----
 arch/x86/kernel/cpu/bugs.c                 | 36 ++++++++++++---------
 2 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index b6cfb51..e715bfc 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -46,12 +46,22 @@ The possible values in this file are:
 
    The processor is not vulnerable
 
- * 'Vulnerable: no microcode':
+* 'Vulnerable':
+
+   The processor is vulnerable and no mitigations have been applied.
+
+ * 'Vulnerable: No microcode':
 
    The processor is vulnerable, no microcode extending IBPB
    functionality to address the vulnerability has been applied.
 
- * 'Mitigation: microcode':
+ * 'Vulnerable: Safe RET, no microcode':
+
+   The "Safe RET" mitigation (see below) has been applied to protect the
+   kernel, but the IBPB-extending microcode has not been applied.  User
+   space tasks may still be vulnerable.
+
+ * 'Vulnerable: Microcode, no safe RET':
 
    Extended IBPB functionality microcode patch has been applied. It does
    not address User->Kernel and Guest->Host transitions protection but it
@@ -72,11 +82,11 @@ The possible values in this file are:
 
    (spec_rstack_overflow=microcode)
 
- * 'Mitigation: safe RET':
+ * 'Mitigation: Safe RET':
 
-   Software-only mitigation. It complements the extended IBPB microcode
-   patch functionality by addressing User->Kernel and Guest->Host
-   transitions protection.
+   Combined microcode/software mitigation. It complements the
+   extended IBPB microcode patch functionality by addressing
+   User->Kernel and Guest->Host transitions protection.
 
    Selected by default or by spec_rstack_overflow=safe-ret
 
@@ -129,7 +139,7 @@ an indrect branch prediction barrier after having applied the required
 microcode patch for one's system. This mitigation comes also at
 a performance cost.
 
-Mitigation: safe RET
+Mitigation: Safe RET
 --------------------
 
 The mitigation works by ensuring all RET instructions speculate to
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6c47f37..e45dd69 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2353,6 +2353,8 @@ early_param("l1tf", l1tf_cmdline);
 
 enum srso_mitigation {
 	SRSO_MITIGATION_NONE,
+	SRSO_MITIGATION_UCODE_NEEDED,
+	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,
 	SRSO_MITIGATION_MICROCODE,
 	SRSO_MITIGATION_SAFE_RET,
 	SRSO_MITIGATION_IBPB,
@@ -2368,11 +2370,13 @@ enum srso_mitigation_cmd {
 };
 
 static const char * const srso_strings[] = {
-	[SRSO_MITIGATION_NONE]           = "Vulnerable",
-	[SRSO_MITIGATION_MICROCODE]      = "Mitigation: microcode",
-	[SRSO_MITIGATION_SAFE_RET]	 = "Mitigation: safe RET",
-	[SRSO_MITIGATION_IBPB]		 = "Mitigation: IBPB",
-	[SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only"
+	[SRSO_MITIGATION_NONE]			= "Vulnerable",
+	[SRSO_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",
+	[SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED]	= "Vulnerable: Safe RET, no microcode",
+	[SRSO_MITIGATION_MICROCODE]		= "Vulnerable: Microcode, no safe RET",
+	[SRSO_MITIGATION_SAFE_RET]		= "Mitigation: Safe RET",
+	[SRSO_MITIGATION_IBPB]			= "Mitigation: IBPB",
+	[SRSO_MITIGATION_IBPB_ON_VMEXIT]	= "Mitigation: IBPB on VMEXIT only"
 };
 
 static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE;
@@ -2409,10 +2413,7 @@ static void __init srso_select_mitigation(void)
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	if (!has_microcode) {
-		pr_warn("IBPB-extending microcode not applied!\n");
-		pr_warn(SRSO_NOTICE);
-	} else {
+	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
@@ -2428,6 +2429,12 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}
+	} else {
+		pr_warn("IBPB-extending microcode not applied!\n");
+		pr_warn(SRSO_NOTICE);
+
+		/* may be overwritten by SRSO_CMD_SAFE_RET below */
+		srso_mitigation = SRSO_MITIGATION_UCODE_NEEDED;
 	}
 
 	switch (srso_cmd) {
@@ -2457,7 +2464,10 @@ static void __init srso_select_mitigation(void)
 				setup_force_cpu_cap(X86_FEATURE_SRSO);
 				x86_return_thunk = srso_return_thunk;
 			}
-			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			if (has_microcode)
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			else
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
 		}
@@ -2490,7 +2500,7 @@ static void __init srso_select_mitigation(void)
 	}
 
 out:
-	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
+	pr_info("%s\n", srso_strings[srso_mitigation]);
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
@@ -2701,9 +2711,7 @@ static ssize_t srso_show_state(char *buf)
 	if (boot_cpu_has(X86_FEATURE_SRSO_NO))
 		return sysfs_emit(buf, "Mitigation: SMT disabled\n");
 
-	return sysfs_emit(buf, "%s%s\n",
-			  srso_strings[srso_mitigation],
-			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
+	return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]);
 }
 
 static ssize_t gds_show_state(char *buf)

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix unret validation dependencies
  2023-09-05  5:04 ` [PATCH v3 09/20] x86/srso: Fix unret validation dependencies Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     96d660f35790646f15b69010f767b6b7948fb723
Gitweb:        https://git.kernel.org/tip/96d660f35790646f15b69010f767b6b7948fb723
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:53 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:07 +02:00

x86/srso: Fix unret validation dependencies

CONFIG_CPU_SRSO isn't dependent on CONFIG_CPU_UNRET_ENTRY (AMD
Retbleed), so the two features are independently configurable.  Fix
several issues for the (presumably rare) case where CONFIG_CPU_SRSO is
enabled but CONFIG_CPU_UNRET_ENTRY isn't.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/299fb7740174d0f2335e91c58af0e9c242b4bac1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ++--
 include/linux/objtool.h              | 3 ++-
 scripts/Makefile.vmlinux_o           | 3 ++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c55cc24..197ff4f 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -271,7 +271,7 @@
 .Lskip_rsb_\@:
 .endm
 
-#ifdef CONFIG_CPU_UNRET_ENTRY
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 #define CALL_UNTRAIN_RET	"call entry_untrain_ret"
 #else
 #define CALL_UNTRAIN_RET	""
@@ -312,7 +312,7 @@
 
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING)
+	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 03f82c2..b5440e7 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -130,7 +130,8 @@
  * it will be ignored.
  */
 .macro VALIDATE_UNRET_BEGIN
-#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+#if defined(CONFIG_NOINSTR_VALIDATION) && \
+	(defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO))
 .Lhere_\@:
 	.pushsection .discard.validate_unret
 	.long	.Lhere_\@ - .
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 0edfdb4..25b3b58 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -37,7 +37,8 @@ objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
 
 vmlinux-objtool-args-$(delay-objtool)			+= $(objtool-args-y)
 vmlinux-objtool-args-$(CONFIG_GCOV_KERNEL)		+= --no-unreachable
-vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr $(if $(CONFIG_CPU_UNRET_ENTRY), --unret)
+vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+							   $(if $(or $(CONFIG_CPU_UNRET_ENTRY),$(CONFIG_CPU_SRSO)), --unret)
 
 objtool-args = $(vmlinux-objtool-args-y) --link
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print actual mitigation if requested mitigation isn't possible
  2023-09-05  5:04 ` [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     777145d26c8b1ca57b5ec031cab352439b3a081a
Gitweb:        https://git.kernel.org/tip/777145d26c8b1ca57b5ec031cab352439b3a081a
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:50 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:06 +02:00

x86/srso: Print actual mitigation if requested mitigation isn't possible

If the kernel wasn't compiled to support the requested option, print the
actual option that ends up getting used.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/7e7a12ea9d85a9f76ca16a3efb71f262dee46ab1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2859a54..235c0e0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2461,7 +2461,6 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2473,7 +2472,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2485,7 +2483,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
                 }
 		break;
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print mitigation for retbleed IBPB case
  2023-09-05  5:04 ` [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     2294b77c2483ebc7a6c1cca2becf6b0164564a5b
Gitweb:        https://git.kernel.org/tip/2294b77c2483ebc7a6c1cca2becf6b0164564a5b
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:51 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:06 +02:00

x86/srso: Print mitigation for retbleed IBPB case

When overriding the requested mitigation with IBPB due to retbleed=ibpb,
print the mitigation in the usual format instead of a custom error
message.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ec3af919e267773d896c240faf30bfc6a1fd6304.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 235c0e0..6c47f37 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2425,9 +2425,8 @@ static void __init srso_select_mitigation(void)
 
 	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 		if (has_microcode) {
-			pr_err("Retbleed IBPB mitigation enabled, using same for SRSO\n");
 			srso_mitigation = SRSO_MITIGATION_IBPB;
-			goto pred_cmd;
+			goto out;
 		}
 	}
 
@@ -2490,7 +2489,8 @@ static void __init srso_select_mitigation(void)
 		break;
 	}
 
-	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
+out:
+	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix SBPB enablement for (possible) future fixed HW
  2023-09-05  5:04 ` [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
                     ` (2 subsequent siblings)
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     94e07e94c7ea53757995b8702171f4cd1936fb8c
Gitweb:        https://git.kernel.org/tip/94e07e94c7ea53757995b8702171f4cd1936fb8c
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:49 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:06 +02:00

x86/srso: Fix SBPB enablement for (possible) future fixed HW

Make the SBPB check more robust against the (possible) case where future
HW has SRSO fixed but doesn't have the SRSO_NO bit set.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/cee5050db750b391c9f35f5334f8ff40e66c01b9.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 10499bc..2859a54 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2496,7 +2496,7 @@ static void __init srso_select_mitigation(void)
 	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
 
 pred_cmd:
-	if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) &&
+	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
 	     boot_cpu_has(X86_FEATURE_SBPB))
 		x86_pred_cmd = PRED_CMD_SBPB;
 }

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
  2023-09-05  5:04 ` [PATCH v3 04/20] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     a9c7b944ff32243c248fb4a801ffac21635d7042
Gitweb:        https://git.kernel.org/tip/a9c7b944ff32243c248fb4a801ffac21635d7042
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:48 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:06 +02:00

x86/srso: Fix SBPB enablement for spec_rstack_overflow=off

If the user has requested no SRSO mitigation, other mitigations can use
the lighter-weight SBPB instead of IBPB.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/b20820c3cfd1003171135ec8d762a0b957348497.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b0ae985..10499bc 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2433,7 +2433,7 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		return;
+		goto pred_cmd;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Set CPUID feature bits independently of bug or mitigation status
  2023-09-05  5:04 ` [PATCH v3 02/20] x86/srso: Set CPUID feature bits independently of bug or mitigation status Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Nikolay Borisov,
	Borislav Petkov (AMD), x86, linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     2ab15814d800b8c4526eda2750bf33b58555b86b
Gitweb:        https://git.kernel.org/tip/2ab15814d800b8c4526eda2750bf33b58555b86b
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:46 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:06 +02:00

x86/srso: Set CPUID feature bits independently of bug or mitigation status

Booting with mitigations=off incorrectly prevents the
X86_FEATURE_{IBPB_BRTYPE,SBPB} CPUID bits from getting set.

Also, future CPUs without X86_BUG_SRSO might still have IBPB with branch
type prediction flushing, in which case SBPB should be used instead of
IBPB.  The current code doesn't allow for that.

Also, cpu_has_ibpb_brtype_microcode() has some surprising side effects
and the setting of these feature bits really doesn't belong in the
mitigation code anyway.  Move it to earlier.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/869a1709abfe13b673bdd10c2f4332ca253a40bc.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/processor.h |  2 --
 arch/x86/kernel/cpu/amd.c        | 28 +++++++++-------------------
 arch/x86/kernel/cpu/bugs.c       | 13 +------------
 3 files changed, 10 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0086920..a3669a7 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -683,13 +683,11 @@ extern u16 get_llc_id(unsigned int cpu);
 #ifdef CONFIG_CPU_SUP_AMD
 extern u32 amd_get_nodes_per_socket(void);
 extern u32 amd_get_highest_perf(void);
-extern bool cpu_has_ibpb_brtype_microcode(void);
 extern void amd_clear_divider(void);
 extern void amd_check_microcode(void);
 #else
 static inline u32 amd_get_nodes_per_socket(void)	{ return 0; }
 static inline u32 amd_get_highest_perf(void)		{ return 0; }
-static inline bool cpu_has_ibpb_brtype_microcode(void)	{ return false; }
 static inline void amd_clear_divider(void)		{ }
 static inline void amd_check_microcode(void)		{ }
 #endif
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index dd8379d..afacc48 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -766,6 +766,15 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 
 	if (cpu_has(c, X86_FEATURE_TOPOEXT))
 		smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1;
+
+	if (!cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
+		if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB))
+			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+		else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
+			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+			setup_force_cpu_cap(X86_FEATURE_SBPB);
+		}
+	}
 }
 
 static void init_amd_k8(struct cpuinfo_x86 *c)
@@ -1301,25 +1310,6 @@ void amd_check_microcode(void)
 	on_each_cpu(zenbleed_check_cpu, NULL, 1);
 }
 
-bool cpu_has_ibpb_brtype_microcode(void)
-{
-	switch (boot_cpu_data.x86) {
-	/* Zen1/2 IBPB flushes branch type predictions too. */
-	case 0x17:
-		return boot_cpu_has(X86_FEATURE_AMD_IBPB);
-	case 0x19:
-		/* Poke the MSR bit on Zen3/4 to check its presence. */
-		if (!wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
-			setup_force_cpu_cap(X86_FEATURE_SBPB);
-			return true;
-		} else {
-			return false;
-		}
-	default:
-		return false;
-	}
-}
-
 /*
  * Issue a DIV 0/1 insn to clear any division data from previous DIV
  * operations.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bdd3e29..b0ae985 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2404,27 +2404,16 @@ early_param("spec_rstack_overflow", srso_parse_cmdline);
 
 static void __init srso_select_mitigation(void)
 {
-	bool has_microcode;
+	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	/*
-	 * The first check is for the kernel running as a guest in order
-	 * for guests to verify whether IBPB is a viable mitigation.
-	 */
-	has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) || cpu_has_ibpb_brtype_microcode();
 	if (!has_microcode) {
 		pr_warn("IBPB-extending microcode not applied!\n");
 		pr_warn(SRSO_NOTICE);
 	} else {
 		/*
-		 * Enable the synthetic (even if in a real CPUID leaf)
-		 * flags for guests.
-		 */
-		setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
-
-		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
 		 */

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Don't probe microcode in a guest
  2023-09-05  5:04 ` [PATCH v3 03/20] x86/srso: Don't probe microcode in a guest Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Andrew Cooper, Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD),
	x86, linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     7e0a668e6a292d4b47e638078a21736bb3a73ffb
Gitweb:        https://git.kernel.org/tip/7e0a668e6a292d4b47e638078a21736bb3a73ffb
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:47 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:06 +02:00

x86/srso: Don't probe microcode in a guest

To support live migration, the hypervisor sets the "lowest common
denominator" of features.  Probing the microcode isn't allowed because
any detected features might go away after a migration.

As Andy Cooper states:

  "Linux must not probe microcode when virtualised.  What it may see
  instantaneously on boot (owing to MSR_PRED_CMD being fully passed
  through) is not accurate for the lifetime of the VM."

Rely on the hypervisor to set the needed IBPB_BRTYPE and SBPB bits.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/3938a7209606c045a3f50305d201d840e8c834c7.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index afacc48..03ef962 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -767,7 +767,7 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 	if (cpu_has(c, X86_FEATURE_TOPOEXT))
 		smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1;
 
-	if (!cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
+	if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
 		if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB))
 			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
 		else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix srso_show_state() side effect
  2023-09-05  5:04 ` [PATCH v3 01/20] x86/srso: Fix srso_show_state() side effect Josh Poimboeuf
@ 2023-09-05 10:09   ` tip-bot2 for Josh Poimboeuf
  2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-05 10:09 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Nikolay Borisov,
	Borislav Petkov (AMD), x86, linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     272386dcbc4d775a0508dc8c185c248fec56c238
Gitweb:        https://git.kernel.org/tip/272386dcbc4d775a0508dc8c185c248fec56c238
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:45 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 05 Sep 2023 12:05:06 +02:00

x86/srso: Fix srso_show_state() side effect

Reading the 'spec_rstack_overflow' sysfs file can trigger an unnecessary
MSR write, and possibly even a (handled) exception if the microcode
hasn't been updated.

Avoid all that by just checking X86_FEATURE_IBPB_BRTYPE instead, which
gets set by srso_select_mitigation() if the updated microcode exists.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/27d128899cb8aee9eb2b57ddc996742b0c1d776b.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f081d26..bdd3e29 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2717,7 +2717,7 @@ static ssize_t srso_show_state(char *buf)
 
 	return sysfs_emit(buf, "%s%s\n",
 			  srso_strings[srso_mitigation],
-			  (cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));
+			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
 }
 
 static ssize_t gds_show_state(char *buf)

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/urgent] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off
  2023-09-05  5:04 ` [PATCH v3 04/20] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:45   ` tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:45 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     01b057b2f4cc2d905a0bd92195657dbd9a7005ab
Gitweb:        https://git.kernel.org/tip/01b057b2f4cc2d905a0bd92195657dbd9a7005ab
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:48 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 19 Sep 2023 10:54:39 +02:00

x86/srso: Fix SBPB enablement for spec_rstack_overflow=off

If the user has requested no SRSO mitigation, other mitigations can use
the lighter-weight SBPB instead of IBPB.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/b20820c3cfd1003171135ec8d762a0b957348497.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b0ae985..10499bc 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2433,7 +2433,7 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		return;
+		goto pred_cmd;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/urgent] x86/srso: Don't probe microcode in a guest
  2023-09-05  5:04 ` [PATCH v3 03/20] x86/srso: Don't probe microcode in a guest Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:45   ` tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:45 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Andrew Cooper, Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD),
	x86, linux-kernel

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     02428d0366a27c2f33bc4361eb10467777804f29
Gitweb:        https://git.kernel.org/tip/02428d0366a27c2f33bc4361eb10467777804f29
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:47 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 19 Sep 2023 10:54:23 +02:00

x86/srso: Don't probe microcode in a guest

To support live migration, the hypervisor sets the "lowest common
denominator" of features.  Probing the microcode isn't allowed because
any detected features might go away after a migration.

As Andy Cooper states:

  "Linux must not probe microcode when virtualised.  What it may see
  instantaneously on boot (owing to MSR_PRED_CMD being fully passed
  through) is not accurate for the lifetime of the VM."

Rely on the hypervisor to set the needed IBPB_BRTYPE and SBPB bits.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/3938a7209606c045a3f50305d201d840e8c834c7.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/amd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index afacc48..03ef962 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -767,7 +767,7 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 	if (cpu_has(c, X86_FEATURE_TOPOEXT))
 		smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1;
 
-	if (!cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
+	if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
 		if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB))
 			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
 		else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/urgent] x86/srso: Set CPUID feature bits independently of bug or mitigation status
  2023-09-05  5:04 ` [PATCH v3 02/20] x86/srso: Set CPUID feature bits independently of bug or mitigation status Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:45   ` tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:45 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD),
	Nikolay Borisov, x86, linux-kernel

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     91857ae20303cc98ed36720d9868fcd604a2ee75
Gitweb:        https://git.kernel.org/tip/91857ae20303cc98ed36720d9868fcd604a2ee75
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:46 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 19 Sep 2023 10:54:07 +02:00

x86/srso: Set CPUID feature bits independently of bug or mitigation status

Booting with mitigations=off incorrectly prevents the
X86_FEATURE_{IBPB_BRTYPE,SBPB} CPUID bits from getting set.

Also, future CPUs without X86_BUG_SRSO might still have IBPB with branch
type prediction flushing, in which case SBPB should be used instead of
IBPB.  The current code doesn't allow for that.

Also, cpu_has_ibpb_brtype_microcode() has some surprising side effects
and the setting of these feature bits really doesn't belong in the
mitigation code anyway.  Move it to earlier.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/869a1709abfe13b673bdd10c2f4332ca253a40bc.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/processor.h |  2 --
 arch/x86/kernel/cpu/amd.c        | 28 +++++++++-------------------
 arch/x86/kernel/cpu/bugs.c       | 13 +------------
 3 files changed, 10 insertions(+), 33 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 0086920..a3669a7 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -683,13 +683,11 @@ extern u16 get_llc_id(unsigned int cpu);
 #ifdef CONFIG_CPU_SUP_AMD
 extern u32 amd_get_nodes_per_socket(void);
 extern u32 amd_get_highest_perf(void);
-extern bool cpu_has_ibpb_brtype_microcode(void);
 extern void amd_clear_divider(void);
 extern void amd_check_microcode(void);
 #else
 static inline u32 amd_get_nodes_per_socket(void)	{ return 0; }
 static inline u32 amd_get_highest_perf(void)		{ return 0; }
-static inline bool cpu_has_ibpb_brtype_microcode(void)	{ return false; }
 static inline void amd_clear_divider(void)		{ }
 static inline void amd_check_microcode(void)		{ }
 #endif
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index dd8379d..afacc48 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -766,6 +766,15 @@ static void early_init_amd(struct cpuinfo_x86 *c)
 
 	if (cpu_has(c, X86_FEATURE_TOPOEXT))
 		smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1;
+
+	if (!cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) {
+		if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB))
+			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+		else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
+			setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
+			setup_force_cpu_cap(X86_FEATURE_SBPB);
+		}
+	}
 }
 
 static void init_amd_k8(struct cpuinfo_x86 *c)
@@ -1301,25 +1310,6 @@ void amd_check_microcode(void)
 	on_each_cpu(zenbleed_check_cpu, NULL, 1);
 }
 
-bool cpu_has_ibpb_brtype_microcode(void)
-{
-	switch (boot_cpu_data.x86) {
-	/* Zen1/2 IBPB flushes branch type predictions too. */
-	case 0x17:
-		return boot_cpu_has(X86_FEATURE_AMD_IBPB);
-	case 0x19:
-		/* Poke the MSR bit on Zen3/4 to check its presence. */
-		if (!wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) {
-			setup_force_cpu_cap(X86_FEATURE_SBPB);
-			return true;
-		} else {
-			return false;
-		}
-	default:
-		return false;
-	}
-}
-
 /*
  * Issue a DIV 0/1 insn to clear any division data from previous DIV
  * operations.
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bdd3e29..b0ae985 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2404,27 +2404,16 @@ early_param("spec_rstack_overflow", srso_parse_cmdline);
 
 static void __init srso_select_mitigation(void)
 {
-	bool has_microcode;
+	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	/*
-	 * The first check is for the kernel running as a guest in order
-	 * for guests to verify whether IBPB is a viable mitigation.
-	 */
-	has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) || cpu_has_ibpb_brtype_microcode();
 	if (!has_microcode) {
 		pr_warn("IBPB-extending microcode not applied!\n");
 		pr_warn(SRSO_NOTICE);
 	} else {
 		/*
-		 * Enable the synthetic (even if in a real CPUID leaf)
-		 * flags for guests.
-		 */
-		setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE);
-
-		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
 		 */

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/urgent] x86/srso: Fix srso_show_state() side effect
  2023-09-05  5:04 ` [PATCH v3 01/20] x86/srso: Fix srso_show_state() side effect Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:45   ` tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:45 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD),
	Nikolay Borisov, x86, linux-kernel

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     a8cf700c17d9ca6cb8ee7dc5c9330dbac3948237
Gitweb:        https://git.kernel.org/tip/a8cf700c17d9ca6cb8ee7dc5c9330dbac3948237
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:45 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Tue, 19 Sep 2023 10:53:34 +02:00

x86/srso: Fix srso_show_state() side effect

Reading the 'spec_rstack_overflow' sysfs file can trigger an unnecessary
MSR write, and possibly even a (handled) exception if the microcode
hasn't been updated.

Avoid all that by just checking X86_FEATURE_IBPB_BRTYPE instead, which
gets set by srso_select_mitigation() if the updated microcode exists.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/27d128899cb8aee9eb2b57ddc996742b0c1d776b.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f081d26..bdd3e29 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2717,7 +2717,7 @@ static ssize_t srso_show_state(char *buf)
 
 	return sysfs_emit(buf, "%s%s\n",
 			  srso_strings[srso_mitigation],
-			  (cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));
+			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
 }
 
 static ssize_t gds_show_state(char *buf)

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
  2023-09-05  5:05 ` [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     01e1e86d8d206c2e34e66ff03d0bd5ce49675265
Gitweb:        https://git.kernel.org/tip/01e1e86d8d206c2e34e66ff03d0bd5ce49675265
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:04 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00

x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()

For consistency with the other return thunks, rename __x86_return_skl()
to call_depth_return_thunk().

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ae44e9f9976934e3b5b47a458d523ccb15867561.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 13 ++++---------
 arch/x86/kernel/cpu/bugs.c           |  3 ++-
 arch/x86/lib/retpoline.S             |  4 ++--
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index dcc7847..14cd3cd 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -358,12 +358,7 @@ extern void entry_ibpb(void);
 extern void (*x86_return_thunk)(void);
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
-extern void __x86_return_skl(void);
-
-static inline void x86_set_skl_return_thunk(void)
-{
-	x86_return_thunk = &__x86_return_skl;
-}
+extern void call_depth_return_thunk(void);
 
 #define CALL_DEPTH_ACCOUNT					\
 	ALTERNATIVE("",						\
@@ -376,12 +371,12 @@ DECLARE_PER_CPU(u64, __x86_ret_count);
 DECLARE_PER_CPU(u64, __x86_stuffs_count);
 DECLARE_PER_CPU(u64, __x86_ctxsw_count);
 #endif
-#else
-static inline void x86_set_skl_return_thunk(void) {}
+#else /* !CONFIG_CALL_DEPTH_TRACKING */
 
+static inline void call_depth_return_thunk(void) {}
 #define CALL_DEPTH_ACCOUNT ""
 
-#endif
+#endif /* CONFIG_CALL_DEPTH_TRACKING */
 
 #ifdef CONFIG_RETPOLINE
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9731e81..016a326 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1059,7 +1059,8 @@ do_cmd_auto:
 	case RETBLEED_MITIGATION_STUFF:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
-		x86_set_skl_return_thunk();
+
+		x86_return_thunk = call_depth_return_thunk;
 		break;
 
 	default:
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 49f2be7..6376d01 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -321,7 +321,7 @@ __EXPORT_THUNK(entry_untrain_ret)
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
 	.align 64
-SYM_FUNC_START(__x86_return_skl)
+SYM_FUNC_START(call_depth_return_thunk)
 	ANNOTATE_NOENDBR
 	/*
 	 * Keep the hotpath in a 16byte I-fetch for the non-debug
@@ -348,7 +348,7 @@ SYM_FUNC_START(__x86_return_skl)
 	ANNOTATE_UNRET_SAFE
 	ret
 	int3
-SYM_FUNC_END(__x86_return_skl)
+SYM_FUNC_END(call_depth_return_thunk)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/nospec: Refactor UNTRAIN_RET[_*]
  2023-09-05  5:05 ` [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     82c6462008641aed2f213e7c51394cb8c7c1fce7
Gitweb:        https://git.kernel.org/tip/82c6462008641aed2f213e7c51394cb8c7c1fce7
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:03 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00

x86/nospec: Refactor UNTRAIN_RET[_*]

Factor out the UNTRAIN_RET[_*] common bits into a helper macro.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/f06d45489778bd49623297af2a983eea09067a74.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 31 ++++++++-------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 51e3f1a..dcc7847 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -288,35 +288,24 @@
  * As such, this must be placed after every *SWITCH_TO_KERNEL_CR3 at a point
  * where we have a stack but before any RET instruction.
  */
-.macro UNTRAIN_RET
+.macro __UNTRAIN_RET ibpb_feature, call_depth_insns
 #if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		      "call entry_ibpb", \ibpb_feature,			\
+		     __stringify(\call_depth_insns), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
-.macro UNTRAIN_RET_VM
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH)
 
-.macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET_VM \
+	__UNTRAIN_RET X86_FEATURE_IBPB_ON_VMEXIT, __stringify(RESET_CALL_DEPTH)
+
+#define UNTRAIN_RET_FROM_CALL \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH_FROM_CALL)
 
 
 .macro CALL_DEPTH_ACCOUNT

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/retpoline: Remove .text..__x86.return_thunk section
  2023-09-05  5:05 ` [PATCH v3 18/20] x86/retpoline: Remove .text..__x86.return_thunk section Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     c8b840f7767b3178cc5fd92b70cc4c06c37943ac
Gitweb:        https://git.kernel.org/tip/c8b840f7767b3178cc5fd92b70cc4c06c37943ac
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:02 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00

x86/retpoline: Remove .text..__x86.return_thunk section

The '.text..__x86.return_thunk' section has no purpose.  Remove it and
let the return thunk code live in '.text..__x86.indirect_thunk'.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/291aad1dcb2d27c6241fe3f182d66119857757fd.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/vmlinux.lds.S | 3 ---
 arch/x86/lib/retpoline.S      | 2 --
 2 files changed, 5 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 54a5596..9cdb1a7 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -132,10 +132,7 @@ SECTIONS
 		LOCK_TEXT
 		KPROBES_TEXT
 		SOFTIRQENTRY_TEXT
-#ifdef CONFIG_RETPOLINE
 		*(.text..__x86.indirect_thunk)
-		*(.text..__x86.return_thunk)
-#endif
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 415521d..49f2be7 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -129,8 +129,6 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 
 #ifdef CONFIG_RETHUNK
 
-	.section .text..__x86.return_thunk
-
 #ifdef CONFIG_CPU_SRSO
 
 /*

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
  2023-09-05  5:05 ` [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     ff72a720fbaef33896043fa66043772d0cc3142b
Gitweb:        https://git.kernel.org/tip/ff72a720fbaef33896043fa66043772d0cc3142b
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:01 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00

x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros

Macros already exist for unaligned code block symbols.  Use them.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/26d461bd509cc840af24c94586561c06d39812b2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 8ba79d2..415521d 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -149,7 +149,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
 	.pushsection .text..__x86.rethunk_untrain
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_untrain_ret)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	ASM_NOP2
@@ -159,7 +159,7 @@ SYM_FUNC_END(srso_alias_untrain_ret)
 	.popsection
 
 	.pushsection .text..__x86.rethunk_safe
-SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_safe_ret)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
 	ANNOTATE_UNRET_SAFE
@@ -187,7 +187,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(srso_untrain_ret)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -255,7 +255,7 @@ SYM_CODE_END(srso_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(retbleed_untrain_ret)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Disentangle rethunk-dependent options
  2023-09-05  5:05 ` [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     8976895617cd0d212f90cb55557ec735db632b96
Gitweb:        https://git.kernel.org/tip/8976895617cd0d212f90cb55557ec735db632b96
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:00 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00

x86/srso: Disentangle rethunk-dependent options

CONFIG_RETHUNK, CONFIG_CPU_UNRET_ENTRY and CONFIG_CPU_SRSO are all
tangled up.  De-spaghettify the code a bit.

Some of the rethunk-related code has been shuffled around within the
'.text..__x86.return_thunk' section, but otherwise there are no
functional changes.  srso_alias_untrain_ret() and srso_alias_safe_ret()
((which are very address-sensitive) haven't moved.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h |  25 ++--
 arch/x86/kernel/cpu/bugs.c           |   5 +-
 arch/x86/kernel/vmlinux.lds.S        |   7 +-
 arch/x86/lib/retpoline.S             | 157 ++++++++++++++------------
 4 files changed, 109 insertions(+), 85 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 6c14fd1..51e3f1a 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -289,19 +289,17 @@
  * where we have a stack but before any RET instruction.
  */
 .macro UNTRAIN_RET
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
 .macro UNTRAIN_RET_VM
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -311,8 +309,7 @@
 .endm
 
 .macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -348,6 +345,20 @@ extern void __x86_return_thunk(void);
 static inline void __x86_return_thunk(void) {}
 #endif
 
+#ifdef CONFIG_CPU_UNRET_ENTRY
+extern void retbleed_return_thunk(void);
+#else
+static inline void retbleed_return_thunk(void) {}
+#endif
+
+#ifdef CONFIG_CPU_SRSO
+extern void srso_return_thunk(void);
+extern void srso_alias_return_thunk(void);
+#else
+static inline void srso_return_thunk(void) {}
+static inline void srso_alias_return_thunk(void) {}
+#endif
+
 extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6b443f0..9731e81 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -63,7 +63,7 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd);
 
 static DEFINE_MUTEX(spec_ctrl_mutex);
 
-void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
+void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;
 
 /* Update SPEC_CTRL MSR and its cached copy unconditionally */
 static void update_spec_ctrl(u64 val)
@@ -1041,8 +1041,7 @@ do_cmd_auto:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_UNRET);
 
-		if (IS_ENABLED(CONFIG_RETHUNK))
-			x86_return_thunk = retbleed_return_thunk;
+		x86_return_thunk = retbleed_return_thunk;
 
 		if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 		    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index f15fb71..54a5596 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -139,10 +139,7 @@ SECTIONS
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
-#ifdef CONFIG_CPU_SRSO
 		*(.text..__x86.rethunk_untrain)
-#endif
-
 		ENTRY_TEXT
 
 #ifdef CONFIG_CPU_SRSO
@@ -520,12 +517,12 @@ INIT_PER_CPU(irq_stack_backing_store);
            "fixed_percpu_data is not at start of per-cpu area");
 #endif
 
-#ifdef CONFIG_RETHUNK
+#ifdef CONFIG_CPU_UNRET_ENTRY
 . = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned");
-. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 #endif
 
 #ifdef CONFIG_CPU_SRSO
+. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 /*
  * GNU ld cannot do XOR until 2.41.
  * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index a40ba18..8ba79d2 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -126,12 +126,13 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 #include <asm/GEN-for-each-reg.h>
 #undef GEN
 #endif
-/*
- * This function name is magical and is used by -mfunction-return=thunk-extern
- * for the compiler to generate JMPs to it.
- */
+
 #ifdef CONFIG_RETHUNK
 
+	.section .text..__x86.return_thunk
+
+#ifdef CONFIG_CPU_SRSO
+
 /*
  * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at
  * special addresses:
@@ -147,9 +148,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  *
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
-#ifdef CONFIG_CPU_SRSO
-	.section .text..__x86.rethunk_untrain
-
+	.pushsection .text..__x86.rethunk_untrain
 SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
@@ -157,17 +156,9 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
+	.popsection
 
-	.section .text..__x86.rethunk_safe
-#else
-/* dummy definition for alternatives */
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_FUNC_END(srso_alias_untrain_ret)
-#endif
-
+	.pushsection .text..__x86.rethunk_safe
 SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
@@ -182,8 +173,58 @@ SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
+	.popsection
+
+/*
+ * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
+ * above. On kernel entry, srso_untrain_ret() is executed which is a
+ *
+ * movabs $0xccccc30824648d48,%rax
+ *
+ * and when the return thunk executes the inner label srso_safe_ret()
+ * later, it is a stack manipulation and a RET which is mispredicted and
+ * thus a "safe" one to use.
+ */
+	.align 64
+	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+	ANNOTATE_NOENDBR
+	.byte 0x48, 0xb8
+
+/*
+ * This forces the function return instruction to speculate into a trap
+ * (UD2 in srso_return_thunk() below).  This RET will then mispredict
+ * and execution will continue at the return site read from the top of
+ * the stack.
+ */
+SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
+	lea 8(%_ASM_SP), %_ASM_SP
+	ret
+	int3
+	int3
+	/* end of movabs */
+	lfence
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_safe_ret)
+SYM_FUNC_END(srso_untrain_ret)
+
+SYM_CODE_START(srso_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_return_thunk)
+
+#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret"
+#else /* !CONFIG_CPU_SRSO */
+#define JMP_SRSO_UNTRAIN_RET "ud2"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_SRSO */
+
+#ifdef CONFIG_CPU_UNRET_ENTRY
 
-	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *
@@ -263,64 +304,21 @@ SYM_CODE_END(retbleed_return_thunk)
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
 
-/*
- * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
- * above. On kernel entry, srso_untrain_ret() is executed which is a
- *
- * movabs $0xccccc30824648d48,%rax
- *
- * and when the return thunk executes the inner label srso_safe_ret()
- * later, it is a stack manipulation and a RET which is mispredicted and
- * thus a "safe" one to use.
- */
-	.align 64
-	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
-	ANNOTATE_NOENDBR
-	.byte 0x48, 0xb8
+#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret"
+#else /* !CONFIG_CPU_UNRET_ENTRY */
+#define JMP_RETBLEED_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_UNRET_ENTRY */
 
-/*
- * This forces the function return instruction to speculate into a trap
- * (UD2 in srso_return_thunk() below).  This RET will then mispredict
- * and execution will continue at the return site read from the top of
- * the stack.
- */
-SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
-	lea 8(%_ASM_SP), %_ASM_SP
-	ret
-	int3
-	int3
-	/* end of movabs */
-	lfence
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_safe_ret)
-SYM_FUNC_END(srso_untrain_ret)
-
-SYM_CODE_START(srso_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_return_thunk)
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 
 SYM_FUNC_START(entry_untrain_ret)
-	ALTERNATIVE_2 "jmp retbleed_untrain_ret", \
-		      "jmp srso_untrain_ret", X86_FEATURE_SRSO, \
-		      "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS
+	ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET,				\
+		      JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO,		\
+		      JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS
 SYM_FUNC_END(entry_untrain_ret)
 __EXPORT_THUNK(entry_untrain_ret)
 
-SYM_CODE_START(__x86_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_CODE_END(__x86_return_thunk)
-EXPORT_SYMBOL(__x86_return_thunk)
-
-#endif /* CONFIG_RETHUNK */
+#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
@@ -355,3 +353,22 @@ SYM_FUNC_START(__x86_return_skl)
 SYM_FUNC_END(__x86_return_skl)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
+
+/*
+ * This function name is magical and is used by -mfunction-return=thunk-extern
+ * for the compiler to generate JMPs to it.
+ *
+ * This code is only used during kernel boot or module init.  All
+ * 'JMP __x86_return_thunk' sites are changed to something else by
+ * apply_returns().
+ */
+SYM_CODE_START(__x86_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	ANNOTATE_UNRET_SAFE
+	ret
+	int3
+SYM_CODE_END(__x86_return_thunk)
+EXPORT_SYMBOL(__x86_return_thunk)
+
+#endif /* CONFIG_RETHUNK */

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block
  2023-09-05  5:04 ` [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     27ee0600912c8a02fd6901bc4413709282d7b3f8
Gitweb:        https://git.kernel.org/tip/27ee0600912c8a02fd6901bc4413709282d7b3f8
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:59 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00

x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block

Simplify the code flow a bit by moving the retbleed IBPB check into the
existing 'has_microcode' block.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/0a22b86b1f6b07f9046a9ab763fc0e0d1b7a91d4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 941ac94..6b443f0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2430,10 +2430,8 @@ static void __init srso_select_mitigation(void)
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
 			return;
 		}
-	}
 
-	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
-		if (has_microcode) {
+		if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Remove 'pred_cmd' label
  2023-09-05  5:04 ` [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     73163764dd8d117f2ffa14c0bc816bf1bf8a0e27
Gitweb:        https://git.kernel.org/tip/73163764dd8d117f2ffa14c0bc816bf1bf8a0e27
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:57 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Remove 'pred_cmd' label

SBPB is only enabled in two distinct cases:

1) when SRSO has been disabled with srso=off

2) when SRSO has been fixed (in future HW)

Simplify the control flow by getting rid of the 'pred_cmd' label and
moving the SBPB enablement check to the two corresponding code sites.
This makes it more clear when exactly SBPB gets enabled.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/bb20e8569cfa144def5e6f25e610804bc4974de2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e45dd69..4f1ad23 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2410,13 +2410,21 @@ static void __init srso_select_mitigation(void)
 {
 	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
-		goto pred_cmd;
+	if (cpu_mitigations_off())
+		return;
+
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
+	}
 
 	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
+		 *
+		 * Zen1/2 don't have SBPB, no need to try to enable it here.
 		 */
 		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
@@ -2439,7 +2447,9 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		goto pred_cmd;
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {
@@ -2501,11 +2511,6 @@ static void __init srso_select_mitigation(void)
 
 out:
 	pr_info("%s\n", srso_strings[srso_mitigation]);
-
-pred_cmd:
-	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
-	     boot_cpu_has(X86_FEATURE_SBPB))
-		x86_pred_cmd = PRED_CMD_SBPB;
 }
 
 #undef pr_fmt

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/bugs: Remove default case for fully switched enums
  2023-09-05  5:04 ` [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     44bd14590309118cb0103b51f7681f369cfca6d9
Gitweb:        https://git.kernel.org/tip/44bd14590309118cb0103b51f7681f369cfca6d9
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:58 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:48 +02:00

x86/bugs: Remove default case for fully switched enums

For enum switch statements which handle all possible cases, remove the
default case so a compiler warning gets printed if one of the enums gets
accidentally omitted from the switch statement.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/fcf6feefab991b72e411c2aed688b18e65e06aed.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4f1ad23..941ac94 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1019,7 +1019,6 @@ static void __init retbleed_select_mitigation(void)
 
 do_cmd_auto:
 	case RETBLEED_CMD_AUTO:
-	default:
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
 		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 			if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
@@ -1290,6 +1289,8 @@ spectre_v2_user_select_mitigation(void)
 
 		spectre_v2_user_ibpb = mode;
 		switch (cmd) {
+		case SPECTRE_V2_USER_CMD_NONE:
+			break;
 		case SPECTRE_V2_USER_CMD_FORCE:
 		case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 		case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
@@ -1301,8 +1302,6 @@ spectre_v2_user_select_mitigation(void)
 		case SPECTRE_V2_USER_CMD_SECCOMP:
 			static_branch_enable(&switch_mm_cond_ibpb);
 			break;
-		default:
-			break;
 		}
 
 		pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
@@ -2160,6 +2159,10 @@ static int l1d_flush_prctl_get(struct task_struct *task)
 static int ssb_prctl_get(struct task_struct *task)
 {
 	switch (ssb_mode) {
+	case SPEC_STORE_BYPASS_NONE:
+		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+			return PR_SPEC_ENABLE;
+		return PR_SPEC_NOT_AFFECTED;
 	case SPEC_STORE_BYPASS_DISABLE:
 		return PR_SPEC_DISABLE;
 	case SPEC_STORE_BYPASS_SECCOMP:
@@ -2171,11 +2174,8 @@ static int ssb_prctl_get(struct task_struct *task)
 		if (task_spec_ssb_disable(task))
 			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
-	default:
-		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
-			return PR_SPEC_ENABLE;
-		return PR_SPEC_NOT_AFFECTED;
 	}
+	BUG();
 }
 
 static int ib_prctl_get(struct task_struct *task)
@@ -2504,9 +2504,6 @@ static void __init srso_select_mitigation(void)
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
                 }
 		break;
-
-	default:
-		break;
 	}
 
 out:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Improve i-cache locality for alias mitigation
  2023-09-05  5:04 ` [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     da3bd8872ee00f23b58c7f62dfd403dcc83e074b
Gitweb:        https://git.kernel.org/tip/da3bd8872ee00f23b58c7f62dfd403dcc83e074b
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:55 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Improve i-cache locality for alias mitigation

Move srso_alias_return_thunk() to the same section as
srso_alias_safe_ret() so they can share a cache line.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/eadaf5530b46a7ae8b936522da45ae555d2b3393.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb..9ab634f 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -177,15 +177,14 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
 
-	.section .text..__x86.return_thunk
-
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
 
+	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Unexport untraining functions
  2023-09-05  5:04 ` [PATCH v3 12/20] x86/srso: Unexport untraining functions Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     d1a8e4d9929989ffd74da6b340acf6a4ce03e299
Gitweb:        https://git.kernel.org/tip/d1a8e4d9929989ffd74da6b340acf6a4ce03e299
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:56 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Unexport untraining functions

These functions aren't called outside of retpoline.S.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/1ae080f95ce7266c82cba6d2adde82349b832654.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 arch/x86/lib/retpoline.S             | 7 ++-----
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 197ff4f..6c14fd1 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -352,10 +352,6 @@ extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
 
-extern void retbleed_untrain_ret(void);
-extern void srso_untrain_ret(void);
-extern void srso_alias_untrain_ret(void);
-
 extern void entry_untrain_ret(void);
 extern void entry_ibpb(void);
 
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 9ab634f..a40ba18 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -157,7 +157,6 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
-__EXPORT_THUNK(srso_alias_untrain_ret)
 
 	.section .text..__x86.rethunk_safe
 #else
@@ -215,7 +214,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:
@@ -263,7 +262,6 @@ SYM_CODE_END(retbleed_return_thunk)
 	jmp retbleed_return_thunk
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
-__EXPORT_THUNK(retbleed_untrain_ret)
 
 /*
  * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
@@ -277,7 +275,7 @@ __EXPORT_THUNK(retbleed_untrain_ret)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -298,7 +296,6 @@ SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
 	ud2
 SYM_CODE_END(srso_safe_ret)
 SYM_FUNC_END(srso_untrain_ret)
-__EXPORT_THUNK(srso_untrain_ret)
 
 SYM_CODE_START(srso_return_thunk)
 	UNWIND_HINT_FUNC

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/alternatives: Remove faulty optimization
  2023-09-05  5:04 ` [PATCH v3 10/20] x86/alternatives: Remove faulty optimization Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  1 sibling, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     eae1a2bb7dd350195c18f1788f5d687684d8d92d
Gitweb:        https://git.kernel.org/tip/eae1a2bb7dd350195c18f1788f5d687684d8d92d
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:54 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/alternatives: Remove faulty optimization

The following commit

  095b8303f383 ("x86/alternative: Make custom return thunk unconditional")

made '__x86_return_thunk' a placeholder value.  All code setting
X86_FEATURE_RETHUNK also changes the value of 'x86_return_thunk'.  So
the optimization at the beginning of apply_returns() is dead code.

Also, before the above-mentioned commit, the optimization actually had a
bug It bypassed __static_call_fixup(), causing some raw returns to
remain unpatched in static call trampolines.  Thus the 'Fixes' tag.

Fixes: d2408e043e72 ("x86/alternative: Optimize returns patching")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/16d19d2249d4485d8380fb215ffaae81e6b8119e.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/alternative.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index a5ead6a..c850f5a 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -720,14 +720,6 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end)
 {
 	s32 *s;
 
-	/*
-	 * Do not patch out the default return thunks if those needed are the
-	 * ones generated by the compiler.
-	 */
-	if (cpu_feature_enabled(X86_FEATURE_RETHUNK) &&
-	    (x86_return_thunk == __x86_return_thunk))
-		return;
-
 	for (s = start; s < end; s++) {
 		void *dest = NULL, *addr = (void *)s + *s;
 		struct insn insn;

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix unret validation dependencies
  2023-09-05  5:04 ` [PATCH v3 09/20] x86/srso: Fix unret validation dependencies Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     adc5517ec8157084ba978b25241fc398207d05dd
Gitweb:        https://git.kernel.org/tip/adc5517ec8157084ba978b25241fc398207d05dd
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:53 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Fix unret validation dependencies

CONFIG_CPU_SRSO isn't dependent on CONFIG_CPU_UNRET_ENTRY (AMD
Retbleed), so the two features are independently configurable.  Fix
several issues for the (presumably rare) case where CONFIG_CPU_SRSO is
enabled but CONFIG_CPU_UNRET_ENTRY isn't.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/299fb7740174d0f2335e91c58af0e9c242b4bac1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ++--
 include/linux/objtool.h              | 3 ++-
 scripts/Makefile.vmlinux_o           | 3 ++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c55cc24..197ff4f 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -271,7 +271,7 @@
 .Lskip_rsb_\@:
 .endm
 
-#ifdef CONFIG_CPU_UNRET_ENTRY
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 #define CALL_UNTRAIN_RET	"call entry_untrain_ret"
 #else
 #define CALL_UNTRAIN_RET	""
@@ -312,7 +312,7 @@
 
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING)
+	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 03f82c2..b5440e7 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -130,7 +130,8 @@
  * it will be ignored.
  */
 .macro VALIDATE_UNRET_BEGIN
-#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+#if defined(CONFIG_NOINSTR_VALIDATION) && \
+	(defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO))
 .Lhere_\@:
 	.pushsection .discard.validate_unret
 	.long	.Lhere_\@ - .
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 0edfdb4..25b3b58 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -37,7 +37,8 @@ objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
 
 vmlinux-objtool-args-$(delay-objtool)			+= $(objtool-args-y)
 vmlinux-objtool-args-$(CONFIG_GCOV_KERNEL)		+= --no-unreachable
-vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr $(if $(CONFIG_CPU_UNRET_ENTRY), --unret)
+vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+							   $(if $(or $(CONFIG_CPU_UNRET_ENTRY),$(CONFIG_CPU_SRSO)), --unret)
 
 objtool-args = $(vmlinux-objtool-args-y) --link
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print mitigation for retbleed IBPB case
  2023-09-05  5:04 ` [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     6988c6ceccb03bb29723bbf5645f7f5ab0658816
Gitweb:        https://git.kernel.org/tip/6988c6ceccb03bb29723bbf5645f7f5ab0658816
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:51 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Print mitigation for retbleed IBPB case

When overriding the requested mitigation with IBPB due to retbleed=ibpb,
print the mitigation in the usual format instead of a custom error
message.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ec3af919e267773d896c240faf30bfc6a1fd6304.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 235c0e0..6c47f37 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2425,9 +2425,8 @@ static void __init srso_select_mitigation(void)
 
 	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 		if (has_microcode) {
-			pr_err("Retbleed IBPB mitigation enabled, using same for SRSO\n");
 			srso_mitigation = SRSO_MITIGATION_IBPB;
-			goto pred_cmd;
+			goto out;
 		}
 	}
 
@@ -2490,7 +2489,8 @@ static void __init srso_select_mitigation(void)
 		break;
 	}
 
-	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
+out:
+	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix vulnerability reporting for missing microcode
  2023-09-05  5:04 ` [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     3f0659662ac8e0b76e715c904ccbf2ca9bf64d74
Gitweb:        https://git.kernel.org/tip/3f0659662ac8e0b76e715c904ccbf2ca9bf64d74
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:52 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Fix vulnerability reporting for missing microcode

The SRSO default safe-ret mitigation is reported as "mitigated" even if
microcode hasn't been updated.  That's wrong because userspace may still
be vulnerable to SRSO attacks due to IBPB not flushing branch type
predictions.

Report the safe-ret + !microcode case as vulnerable.

Also report the microcode-only case as vulnerable as it leaves the
kernel open to attacks.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/a8a14f97d1b0e03ec255c81637afdf4cf0ae9c99.1693889988.git.jpoimboe@kernel.org
---
 Documentation/admin-guide/hw-vuln/srso.rst | 24 +++++++++-----
 arch/x86/kernel/cpu/bugs.c                 | 36 ++++++++++++---------
 2 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index b6cfb51..e715bfc 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -46,12 +46,22 @@ The possible values in this file are:
 
    The processor is not vulnerable
 
- * 'Vulnerable: no microcode':
+* 'Vulnerable':
+
+   The processor is vulnerable and no mitigations have been applied.
+
+ * 'Vulnerable: No microcode':
 
    The processor is vulnerable, no microcode extending IBPB
    functionality to address the vulnerability has been applied.
 
- * 'Mitigation: microcode':
+ * 'Vulnerable: Safe RET, no microcode':
+
+   The "Safe RET" mitigation (see below) has been applied to protect the
+   kernel, but the IBPB-extending microcode has not been applied.  User
+   space tasks may still be vulnerable.
+
+ * 'Vulnerable: Microcode, no safe RET':
 
    Extended IBPB functionality microcode patch has been applied. It does
    not address User->Kernel and Guest->Host transitions protection but it
@@ -72,11 +82,11 @@ The possible values in this file are:
 
    (spec_rstack_overflow=microcode)
 
- * 'Mitigation: safe RET':
+ * 'Mitigation: Safe RET':
 
-   Software-only mitigation. It complements the extended IBPB microcode
-   patch functionality by addressing User->Kernel and Guest->Host
-   transitions protection.
+   Combined microcode/software mitigation. It complements the
+   extended IBPB microcode patch functionality by addressing
+   User->Kernel and Guest->Host transitions protection.
 
    Selected by default or by spec_rstack_overflow=safe-ret
 
@@ -129,7 +139,7 @@ an indrect branch prediction barrier after having applied the required
 microcode patch for one's system. This mitigation comes also at
 a performance cost.
 
-Mitigation: safe RET
+Mitigation: Safe RET
 --------------------
 
 The mitigation works by ensuring all RET instructions speculate to
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6c47f37..e45dd69 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2353,6 +2353,8 @@ early_param("l1tf", l1tf_cmdline);
 
 enum srso_mitigation {
 	SRSO_MITIGATION_NONE,
+	SRSO_MITIGATION_UCODE_NEEDED,
+	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,
 	SRSO_MITIGATION_MICROCODE,
 	SRSO_MITIGATION_SAFE_RET,
 	SRSO_MITIGATION_IBPB,
@@ -2368,11 +2370,13 @@ enum srso_mitigation_cmd {
 };
 
 static const char * const srso_strings[] = {
-	[SRSO_MITIGATION_NONE]           = "Vulnerable",
-	[SRSO_MITIGATION_MICROCODE]      = "Mitigation: microcode",
-	[SRSO_MITIGATION_SAFE_RET]	 = "Mitigation: safe RET",
-	[SRSO_MITIGATION_IBPB]		 = "Mitigation: IBPB",
-	[SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only"
+	[SRSO_MITIGATION_NONE]			= "Vulnerable",
+	[SRSO_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",
+	[SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED]	= "Vulnerable: Safe RET, no microcode",
+	[SRSO_MITIGATION_MICROCODE]		= "Vulnerable: Microcode, no safe RET",
+	[SRSO_MITIGATION_SAFE_RET]		= "Mitigation: Safe RET",
+	[SRSO_MITIGATION_IBPB]			= "Mitigation: IBPB",
+	[SRSO_MITIGATION_IBPB_ON_VMEXIT]	= "Mitigation: IBPB on VMEXIT only"
 };
 
 static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE;
@@ -2409,10 +2413,7 @@ static void __init srso_select_mitigation(void)
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	if (!has_microcode) {
-		pr_warn("IBPB-extending microcode not applied!\n");
-		pr_warn(SRSO_NOTICE);
-	} else {
+	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
@@ -2428,6 +2429,12 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}
+	} else {
+		pr_warn("IBPB-extending microcode not applied!\n");
+		pr_warn(SRSO_NOTICE);
+
+		/* may be overwritten by SRSO_CMD_SAFE_RET below */
+		srso_mitigation = SRSO_MITIGATION_UCODE_NEEDED;
 	}
 
 	switch (srso_cmd) {
@@ -2457,7 +2464,10 @@ static void __init srso_select_mitigation(void)
 				setup_force_cpu_cap(X86_FEATURE_SRSO);
 				x86_return_thunk = srso_return_thunk;
 			}
-			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			if (has_microcode)
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			else
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
 		}
@@ -2490,7 +2500,7 @@ static void __init srso_select_mitigation(void)
 	}
 
 out:
-	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
+	pr_info("%s\n", srso_strings[srso_mitigation]);
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
@@ -2701,9 +2711,7 @@ static ssize_t srso_show_state(char *buf)
 	if (boot_cpu_has(X86_FEATURE_SRSO_NO))
 		return sysfs_emit(buf, "Mitigation: SMT disabled\n");
 
-	return sysfs_emit(buf, "%s%s\n",
-			  srso_strings[srso_mitigation],
-			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
+	return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]);
 }
 
 static ssize_t gds_show_state(char *buf)

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print actual mitigation if requested mitigation isn't possible
  2023-09-05  5:04 ` [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     8d1af58569b6b8541c3d6574ba6ef36016a07edb
Gitweb:        https://git.kernel.org/tip/8d1af58569b6b8541c3d6574ba6ef36016a07edb
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:50 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:47 +02:00

x86/srso: Print actual mitigation if requested mitigation isn't possible

If the kernel wasn't compiled to support the requested option, print the
actual option that ends up getting used.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/7e7a12ea9d85a9f76ca16a3efb71f262dee46ab1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2859a54..235c0e0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2461,7 +2461,6 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2473,7 +2472,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2485,7 +2483,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
                 }
 		break;
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix SBPB enablement for (possible) future fixed HW
  2023-09-05  5:04 ` [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
@ 2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-19  9:53 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     01bba38f23ed7ae627442015332333191af37a5a
Gitweb:        https://git.kernel.org/tip/01bba38f23ed7ae627442015332333191af37a5a
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:49 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 19 Sep 2023 11:42:46 +02:00

x86/srso: Fix SBPB enablement for (possible) future fixed HW

Make the SBPB check more robust against the (possible) case where future
HW has SRSO fixed but doesn't have the SRSO_NO bit set.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/cee5050db750b391c9f35f5334f8ff40e66c01b9.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 10499bc..2859a54 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2496,7 +2496,7 @@ static void __init srso_select_mitigation(void)
 	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
 
 pred_cmd:
-	if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) &&
+	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
 	     boot_cpu_has(X86_FEATURE_SBPB))
 		x86_pred_cmd = PRED_CMD_SBPB;
 }

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
  2023-09-05  5:05 ` [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     88494339b5bccf0abea5660228fd066ec2e91dea
Gitweb:        https://git.kernel.org/tip/88494339b5bccf0abea5660228fd066ec2e91dea
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:04 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()

For consistency with the other return thunks, rename __x86_return_skl()
to call_depth_return_thunk().

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ae44e9f9976934e3b5b47a458d523ccb15867561.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 13 ++++---------
 arch/x86/kernel/cpu/bugs.c           |  3 ++-
 arch/x86/lib/retpoline.S             |  4 ++--
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index dcc7847..14cd3cd 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -358,12 +358,7 @@ extern void entry_ibpb(void);
 extern void (*x86_return_thunk)(void);
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
-extern void __x86_return_skl(void);
-
-static inline void x86_set_skl_return_thunk(void)
-{
-	x86_return_thunk = &__x86_return_skl;
-}
+extern void call_depth_return_thunk(void);
 
 #define CALL_DEPTH_ACCOUNT					\
 	ALTERNATIVE("",						\
@@ -376,12 +371,12 @@ DECLARE_PER_CPU(u64, __x86_ret_count);
 DECLARE_PER_CPU(u64, __x86_stuffs_count);
 DECLARE_PER_CPU(u64, __x86_ctxsw_count);
 #endif
-#else
-static inline void x86_set_skl_return_thunk(void) {}
+#else /* !CONFIG_CALL_DEPTH_TRACKING */
 
+static inline void call_depth_return_thunk(void) {}
 #define CALL_DEPTH_ACCOUNT ""
 
-#endif
+#endif /* CONFIG_CALL_DEPTH_TRACKING */
 
 #ifdef CONFIG_RETPOLINE
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9731e81..016a326 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1059,7 +1059,8 @@ do_cmd_auto:
 	case RETBLEED_MITIGATION_STUFF:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
-		x86_set_skl_return_thunk();
+
+		x86_return_thunk = call_depth_return_thunk;
 		break;
 
 	default:
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 49f2be7..6376d01 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -321,7 +321,7 @@ __EXPORT_THUNK(entry_untrain_ret)
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
 	.align 64
-SYM_FUNC_START(__x86_return_skl)
+SYM_FUNC_START(call_depth_return_thunk)
 	ANNOTATE_NOENDBR
 	/*
 	 * Keep the hotpath in a 16byte I-fetch for the non-debug
@@ -348,7 +348,7 @@ SYM_FUNC_START(__x86_return_skl)
 	ANNOTATE_UNRET_SAFE
 	ret
 	int3
-SYM_FUNC_END(__x86_return_skl)
+SYM_FUNC_END(call_depth_return_thunk)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/nospec: Refactor UNTRAIN_RET[_*]
  2023-09-05  5:05 ` [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     e653cf101de2ac99d92049c38735cebc537fa2fb
Gitweb:        https://git.kernel.org/tip/e653cf101de2ac99d92049c38735cebc537fa2fb
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:03 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/nospec: Refactor UNTRAIN_RET[_*]

Factor out the UNTRAIN_RET[_*] common bits into a helper macro.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/f06d45489778bd49623297af2a983eea09067a74.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 31 ++++++++-------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 51e3f1a..dcc7847 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -288,35 +288,24 @@
  * As such, this must be placed after every *SWITCH_TO_KERNEL_CR3 at a point
  * where we have a stack but before any RET instruction.
  */
-.macro UNTRAIN_RET
+.macro __UNTRAIN_RET ibpb_feature, call_depth_insns
 #if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		      "call entry_ibpb", \ibpb_feature,			\
+		     __stringify(\call_depth_insns), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
-.macro UNTRAIN_RET_VM
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH)
 
-.macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET_VM \
+	__UNTRAIN_RET X86_FEATURE_IBPB_ON_VMEXIT, __stringify(RESET_CALL_DEPTH)
+
+#define UNTRAIN_RET_FROM_CALL \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH_FROM_CALL)
 
 
 .macro CALL_DEPTH_ACCOUNT

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/retpoline: Remove .text..__x86.return_thunk section
  2023-09-05  5:05 ` [PATCH v3 18/20] x86/retpoline: Remove .text..__x86.return_thunk section Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     e92626af3234708fe30f53b269d210d202b95206
Gitweb:        https://git.kernel.org/tip/e92626af3234708fe30f53b269d210d202b95206
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:02 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/retpoline: Remove .text..__x86.return_thunk section

The '.text..__x86.return_thunk' section has no purpose.  Remove it and
let the return thunk code live in '.text..__x86.indirect_thunk'.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/291aad1dcb2d27c6241fe3f182d66119857757fd.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/vmlinux.lds.S | 3 ---
 arch/x86/lib/retpoline.S      | 2 --
 2 files changed, 5 deletions(-)

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 54a5596..9cdb1a7 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -132,10 +132,7 @@ SECTIONS
 		LOCK_TEXT
 		KPROBES_TEXT
 		SOFTIRQENTRY_TEXT
-#ifdef CONFIG_RETPOLINE
 		*(.text..__x86.indirect_thunk)
-		*(.text..__x86.return_thunk)
-#endif
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 415521d..49f2be7 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -129,8 +129,6 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 
 #ifdef CONFIG_RETHUNK
 
-	.section .text..__x86.return_thunk
-
 #ifdef CONFIG_CPU_SRSO
 
 /*

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
  2023-09-05  5:05 ` [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     642ff448c87d176aaf923597a70cb55baf2706ef
Gitweb:        https://git.kernel.org/tip/642ff448c87d176aaf923597a70cb55baf2706ef
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:01 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros

Macros already exist for unaligned code block symbols.  Use them.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/26d461bd509cc840af24c94586561c06d39812b2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 8ba79d2..415521d 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -149,7 +149,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
 	.pushsection .text..__x86.rethunk_untrain
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_untrain_ret)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	ASM_NOP2
@@ -159,7 +159,7 @@ SYM_FUNC_END(srso_alias_untrain_ret)
 	.popsection
 
 	.pushsection .text..__x86.rethunk_safe
-SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_safe_ret)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
 	ANNOTATE_UNRET_SAFE
@@ -187,7 +187,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(srso_untrain_ret)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -255,7 +255,7 @@ SYM_CODE_END(srso_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(retbleed_untrain_ret)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Disentangle rethunk-dependent options
  2023-09-05  5:05 ` [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     670bf81b24ed688fe77d8cc1ff3a66b409bf6e08
Gitweb:        https://git.kernel.org/tip/670bf81b24ed688fe77d8cc1ff3a66b409bf6e08
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:00 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/srso: Disentangle rethunk-dependent options

CONFIG_RETHUNK, CONFIG_CPU_UNRET_ENTRY and CONFIG_CPU_SRSO are all
tangled up.  De-spaghettify the code a bit.

Some of the rethunk-related code has been shuffled around within the
'.text..__x86.return_thunk' section, but otherwise there are no
functional changes.  srso_alias_untrain_ret() and srso_alias_safe_ret()
((which are very address-sensitive) haven't moved.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h |  25 ++--
 arch/x86/kernel/cpu/bugs.c           |   5 +-
 arch/x86/kernel/vmlinux.lds.S        |   7 +-
 arch/x86/lib/retpoline.S             | 157 ++++++++++++++------------
 4 files changed, 109 insertions(+), 85 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 6c14fd1..51e3f1a 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -289,19 +289,17 @@
  * where we have a stack but before any RET instruction.
  */
 .macro UNTRAIN_RET
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
 .macro UNTRAIN_RET_VM
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -311,8 +309,7 @@
 .endm
 
 .macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -348,6 +345,20 @@ extern void __x86_return_thunk(void);
 static inline void __x86_return_thunk(void) {}
 #endif
 
+#ifdef CONFIG_CPU_UNRET_ENTRY
+extern void retbleed_return_thunk(void);
+#else
+static inline void retbleed_return_thunk(void) {}
+#endif
+
+#ifdef CONFIG_CPU_SRSO
+extern void srso_return_thunk(void);
+extern void srso_alias_return_thunk(void);
+#else
+static inline void srso_return_thunk(void) {}
+static inline void srso_alias_return_thunk(void) {}
+#endif
+
 extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6b443f0..9731e81 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -63,7 +63,7 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd);
 
 static DEFINE_MUTEX(spec_ctrl_mutex);
 
-void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
+void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;
 
 /* Update SPEC_CTRL MSR and its cached copy unconditionally */
 static void update_spec_ctrl(u64 val)
@@ -1041,8 +1041,7 @@ do_cmd_auto:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_UNRET);
 
-		if (IS_ENABLED(CONFIG_RETHUNK))
-			x86_return_thunk = retbleed_return_thunk;
+		x86_return_thunk = retbleed_return_thunk;
 
 		if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 		    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index f15fb71..54a5596 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -139,10 +139,7 @@ SECTIONS
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
-#ifdef CONFIG_CPU_SRSO
 		*(.text..__x86.rethunk_untrain)
-#endif
-
 		ENTRY_TEXT
 
 #ifdef CONFIG_CPU_SRSO
@@ -520,12 +517,12 @@ INIT_PER_CPU(irq_stack_backing_store);
            "fixed_percpu_data is not at start of per-cpu area");
 #endif
 
-#ifdef CONFIG_RETHUNK
+#ifdef CONFIG_CPU_UNRET_ENTRY
 . = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned");
-. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 #endif
 
 #ifdef CONFIG_CPU_SRSO
+. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 /*
  * GNU ld cannot do XOR until 2.41.
  * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index a40ba18..8ba79d2 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -126,12 +126,13 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 #include <asm/GEN-for-each-reg.h>
 #undef GEN
 #endif
-/*
- * This function name is magical and is used by -mfunction-return=thunk-extern
- * for the compiler to generate JMPs to it.
- */
+
 #ifdef CONFIG_RETHUNK
 
+	.section .text..__x86.return_thunk
+
+#ifdef CONFIG_CPU_SRSO
+
 /*
  * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at
  * special addresses:
@@ -147,9 +148,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  *
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
-#ifdef CONFIG_CPU_SRSO
-	.section .text..__x86.rethunk_untrain
-
+	.pushsection .text..__x86.rethunk_untrain
 SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
@@ -157,17 +156,9 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
+	.popsection
 
-	.section .text..__x86.rethunk_safe
-#else
-/* dummy definition for alternatives */
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_FUNC_END(srso_alias_untrain_ret)
-#endif
-
+	.pushsection .text..__x86.rethunk_safe
 SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
@@ -182,8 +173,58 @@ SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
+	.popsection
+
+/*
+ * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
+ * above. On kernel entry, srso_untrain_ret() is executed which is a
+ *
+ * movabs $0xccccc30824648d48,%rax
+ *
+ * and when the return thunk executes the inner label srso_safe_ret()
+ * later, it is a stack manipulation and a RET which is mispredicted and
+ * thus a "safe" one to use.
+ */
+	.align 64
+	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+	ANNOTATE_NOENDBR
+	.byte 0x48, 0xb8
+
+/*
+ * This forces the function return instruction to speculate into a trap
+ * (UD2 in srso_return_thunk() below).  This RET will then mispredict
+ * and execution will continue at the return site read from the top of
+ * the stack.
+ */
+SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
+	lea 8(%_ASM_SP), %_ASM_SP
+	ret
+	int3
+	int3
+	/* end of movabs */
+	lfence
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_safe_ret)
+SYM_FUNC_END(srso_untrain_ret)
+
+SYM_CODE_START(srso_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_return_thunk)
+
+#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret"
+#else /* !CONFIG_CPU_SRSO */
+#define JMP_SRSO_UNTRAIN_RET "ud2"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_SRSO */
+
+#ifdef CONFIG_CPU_UNRET_ENTRY
 
-	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *
@@ -263,64 +304,21 @@ SYM_CODE_END(retbleed_return_thunk)
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
 
-/*
- * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
- * above. On kernel entry, srso_untrain_ret() is executed which is a
- *
- * movabs $0xccccc30824648d48,%rax
- *
- * and when the return thunk executes the inner label srso_safe_ret()
- * later, it is a stack manipulation and a RET which is mispredicted and
- * thus a "safe" one to use.
- */
-	.align 64
-	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
-	ANNOTATE_NOENDBR
-	.byte 0x48, 0xb8
+#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret"
+#else /* !CONFIG_CPU_UNRET_ENTRY */
+#define JMP_RETBLEED_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_UNRET_ENTRY */
 
-/*
- * This forces the function return instruction to speculate into a trap
- * (UD2 in srso_return_thunk() below).  This RET will then mispredict
- * and execution will continue at the return site read from the top of
- * the stack.
- */
-SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
-	lea 8(%_ASM_SP), %_ASM_SP
-	ret
-	int3
-	int3
-	/* end of movabs */
-	lfence
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_safe_ret)
-SYM_FUNC_END(srso_untrain_ret)
-
-SYM_CODE_START(srso_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_return_thunk)
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 
 SYM_FUNC_START(entry_untrain_ret)
-	ALTERNATIVE_2 "jmp retbleed_untrain_ret", \
-		      "jmp srso_untrain_ret", X86_FEATURE_SRSO, \
-		      "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS
+	ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET,				\
+		      JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO,		\
+		      JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS
 SYM_FUNC_END(entry_untrain_ret)
 __EXPORT_THUNK(entry_untrain_ret)
 
-SYM_CODE_START(__x86_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_CODE_END(__x86_return_thunk)
-EXPORT_SYMBOL(__x86_return_thunk)
-
-#endif /* CONFIG_RETHUNK */
+#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
@@ -355,3 +353,22 @@ SYM_FUNC_START(__x86_return_skl)
 SYM_FUNC_END(__x86_return_skl)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
+
+/*
+ * This function name is magical and is used by -mfunction-return=thunk-extern
+ * for the compiler to generate JMPs to it.
+ *
+ * This code is only used during kernel boot or module init.  All
+ * 'JMP __x86_return_thunk' sites are changed to something else by
+ * apply_returns().
+ */
+SYM_CODE_START(__x86_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	ANNOTATE_UNRET_SAFE
+	ret
+	int3
+SYM_CODE_END(__x86_return_thunk)
+EXPORT_SYMBOL(__x86_return_thunk)
+
+#endif /* CONFIG_RETHUNK */

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/bugs: Remove default case for fully switched enums
  2023-09-05  5:04 ` [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     365d8a5f4fe4faa88a813b849ea8eac58645289b
Gitweb:        https://git.kernel.org/tip/365d8a5f4fe4faa88a813b849ea8eac58645289b
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:58 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/bugs: Remove default case for fully switched enums

For enum switch statements which handle all possible cases, remove the
default case so a compiler warning gets printed if one of the enums gets
accidentally omitted from the switch statement.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/fcf6feefab991b72e411c2aed688b18e65e06aed.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4f1ad23..941ac94 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1019,7 +1019,6 @@ static void __init retbleed_select_mitigation(void)
 
 do_cmd_auto:
 	case RETBLEED_CMD_AUTO:
-	default:
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
 		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 			if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
@@ -1290,6 +1289,8 @@ spectre_v2_user_select_mitigation(void)
 
 		spectre_v2_user_ibpb = mode;
 		switch (cmd) {
+		case SPECTRE_V2_USER_CMD_NONE:
+			break;
 		case SPECTRE_V2_USER_CMD_FORCE:
 		case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 		case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
@@ -1301,8 +1302,6 @@ spectre_v2_user_select_mitigation(void)
 		case SPECTRE_V2_USER_CMD_SECCOMP:
 			static_branch_enable(&switch_mm_cond_ibpb);
 			break;
-		default:
-			break;
 		}
 
 		pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
@@ -2160,6 +2159,10 @@ static int l1d_flush_prctl_get(struct task_struct *task)
 static int ssb_prctl_get(struct task_struct *task)
 {
 	switch (ssb_mode) {
+	case SPEC_STORE_BYPASS_NONE:
+		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+			return PR_SPEC_ENABLE;
+		return PR_SPEC_NOT_AFFECTED;
 	case SPEC_STORE_BYPASS_DISABLE:
 		return PR_SPEC_DISABLE;
 	case SPEC_STORE_BYPASS_SECCOMP:
@@ -2171,11 +2174,8 @@ static int ssb_prctl_get(struct task_struct *task)
 		if (task_spec_ssb_disable(task))
 			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
-	default:
-		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
-			return PR_SPEC_ENABLE;
-		return PR_SPEC_NOT_AFFECTED;
 	}
+	BUG();
 }
 
 static int ib_prctl_get(struct task_struct *task)
@@ -2504,9 +2504,6 @@ static void __init srso_select_mitigation(void)
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
                 }
 		break;
-
-	default:
-		break;
 	}
 
 out:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block
  2023-09-05  5:04 ` [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     074c9666d42211d0f70d5c156d377a4881b2a98c
Gitweb:        https://git.kernel.org/tip/074c9666d42211d0f70d5c156d377a4881b2a98c
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:59 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block

Simplify the code flow a bit by moving the retbleed IBPB check into the
existing 'has_microcode' block.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/0a22b86b1f6b07f9046a9ab763fc0e0d1b7a91d4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 941ac94..6b443f0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2430,10 +2430,8 @@ static void __init srso_select_mitigation(void)
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
 			return;
 		}
-	}
 
-	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
-		if (has_microcode) {
+		if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Remove 'pred_cmd' label
  2023-09-05  5:04 ` [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     e2ea4bea46ad9b71ab0c9617d8f4e09310973344
Gitweb:        https://git.kernel.org/tip/e2ea4bea46ad9b71ab0c9617d8f4e09310973344
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:57 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/srso: Remove 'pred_cmd' label

SBPB is only enabled in two distinct cases:

1) when SRSO has been disabled with srso=off

2) when SRSO has been fixed (in future HW)

Simplify the control flow by getting rid of the 'pred_cmd' label and
moving the SBPB enablement check to the two corresponding code sites.
This makes it more clear when exactly SBPB gets enabled.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/bb20e8569cfa144def5e6f25e610804bc4974de2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e45dd69..4f1ad23 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2410,13 +2410,21 @@ static void __init srso_select_mitigation(void)
 {
 	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
-		goto pred_cmd;
+	if (cpu_mitigations_off())
+		return;
+
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
+	}
 
 	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
+		 *
+		 * Zen1/2 don't have SBPB, no need to try to enable it here.
 		 */
 		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
@@ -2439,7 +2447,9 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		goto pred_cmd;
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {
@@ -2501,11 +2511,6 @@ static void __init srso_select_mitigation(void)
 
 out:
 	pr_info("%s\n", srso_strings[srso_mitigation]);
-
-pred_cmd:
-	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
-	     boot_cpu_has(X86_FEATURE_SBPB))
-		x86_pred_cmd = PRED_CMD_SBPB;
 }
 
 #undef pr_fmt

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Unexport untraining functions
  2023-09-05  5:04 ` [PATCH v3 12/20] x86/srso: Unexport untraining functions Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     ee35f33f13f094151794a02fdb0204ce8ca89af9
Gitweb:        https://git.kernel.org/tip/ee35f33f13f094151794a02fdb0204ce8ca89af9
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:56 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:03 +02:00

x86/srso: Unexport untraining functions

These functions aren't called outside of retpoline.S.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/1ae080f95ce7266c82cba6d2adde82349b832654.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 arch/x86/lib/retpoline.S             | 7 ++-----
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 197ff4f..6c14fd1 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -352,10 +352,6 @@ extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
 
-extern void retbleed_untrain_ret(void);
-extern void srso_untrain_ret(void);
-extern void srso_alias_untrain_ret(void);
-
 extern void entry_untrain_ret(void);
 extern void entry_ibpb(void);
 
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 9ab634f..a40ba18 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -157,7 +157,6 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
-__EXPORT_THUNK(srso_alias_untrain_ret)
 
 	.section .text..__x86.rethunk_safe
 #else
@@ -215,7 +214,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:
@@ -263,7 +262,6 @@ SYM_CODE_END(retbleed_return_thunk)
 	jmp retbleed_return_thunk
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
-__EXPORT_THUNK(retbleed_untrain_ret)
 
 /*
  * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
@@ -277,7 +275,7 @@ __EXPORT_THUNK(retbleed_untrain_ret)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -298,7 +296,6 @@ SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
 	ud2
 SYM_CODE_END(srso_safe_ret)
 SYM_FUNC_END(srso_untrain_ret)
-__EXPORT_THUNK(srso_untrain_ret)
 
 SYM_CODE_START(srso_return_thunk)
 	UNWIND_HINT_FUNC

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Improve i-cache locality for alias mitigation
  2023-09-05  5:04 ` [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     01c032b1b11620232f0405d477d33acb7870388c
Gitweb:        https://git.kernel.org/tip/01c032b1b11620232f0405d477d33acb7870388c
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:55 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:02 +02:00

x86/srso: Improve i-cache locality for alias mitigation

Move srso_alias_return_thunk() to the same section as
srso_alias_safe_ret() so they can share a cache line.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/eadaf5530b46a7ae8b936522da45ae555d2b3393.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb..9ab634f 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -177,15 +177,14 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
 
-	.section .text..__x86.return_thunk
-
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
 
+	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix unret validation dependencies
  2023-09-05  5:04 ` [PATCH v3 09/20] x86/srso: Fix unret validation dependencies Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     ae56e67426368016b4ff9083842210d5e0a09015
Gitweb:        https://git.kernel.org/tip/ae56e67426368016b4ff9083842210d5e0a09015
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:53 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:02 +02:00

x86/srso: Fix unret validation dependencies

CONFIG_CPU_SRSO isn't dependent on CONFIG_CPU_UNRET_ENTRY (AMD
Retbleed), so the two features are independently configurable.  Fix
several issues for the (presumably rare) case where CONFIG_CPU_SRSO is
enabled but CONFIG_CPU_UNRET_ENTRY isn't.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/299fb7740174d0f2335e91c58af0e9c242b4bac1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ++--
 include/linux/objtool.h              | 3 ++-
 scripts/Makefile.vmlinux_o           | 3 ++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c55cc24..197ff4f 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -271,7 +271,7 @@
 .Lskip_rsb_\@:
 .endm
 
-#ifdef CONFIG_CPU_UNRET_ENTRY
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 #define CALL_UNTRAIN_RET	"call entry_untrain_ret"
 #else
 #define CALL_UNTRAIN_RET	""
@@ -312,7 +312,7 @@
 
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING)
+	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 03f82c2..b5440e7 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -130,7 +130,8 @@
  * it will be ignored.
  */
 .macro VALIDATE_UNRET_BEGIN
-#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+#if defined(CONFIG_NOINSTR_VALIDATION) && \
+	(defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO))
 .Lhere_\@:
 	.pushsection .discard.validate_unret
 	.long	.Lhere_\@ - .
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 0edfdb4..25b3b58 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -37,7 +37,8 @@ objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
 
 vmlinux-objtool-args-$(delay-objtool)			+= $(objtool-args-y)
 vmlinux-objtool-args-$(CONFIG_GCOV_KERNEL)		+= --no-unreachable
-vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr $(if $(CONFIG_CPU_UNRET_ENTRY), --unret)
+vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+							   $(if $(or $(CONFIG_CPU_UNRET_ENTRY),$(CONFIG_CPU_SRSO)), --unret)
 
 objtool-args = $(vmlinux-objtool-args-y) --link
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix vulnerability reporting for missing microcode
  2023-09-05  5:04 ` [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     8caca8ceaae016329eb055f39bb0c95246bcc5b1
Gitweb:        https://git.kernel.org/tip/8caca8ceaae016329eb055f39bb0c95246bcc5b1
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:52 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:02 +02:00

x86/srso: Fix vulnerability reporting for missing microcode

The SRSO default safe-ret mitigation is reported as "mitigated" even if
microcode hasn't been updated.  That's wrong because userspace may still
be vulnerable to SRSO attacks due to IBPB not flushing branch type
predictions.

Report the safe-ret + !microcode case as vulnerable.

Also report the microcode-only case as vulnerable as it leaves the
kernel open to attacks.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/a8a14f97d1b0e03ec255c81637afdf4cf0ae9c99.1693889988.git.jpoimboe@kernel.org
---
 Documentation/admin-guide/hw-vuln/srso.rst | 24 +++++++++-----
 arch/x86/kernel/cpu/bugs.c                 | 36 ++++++++++++---------
 2 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index b6cfb51..e715bfc 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -46,12 +46,22 @@ The possible values in this file are:
 
    The processor is not vulnerable
 
- * 'Vulnerable: no microcode':
+* 'Vulnerable':
+
+   The processor is vulnerable and no mitigations have been applied.
+
+ * 'Vulnerable: No microcode':
 
    The processor is vulnerable, no microcode extending IBPB
    functionality to address the vulnerability has been applied.
 
- * 'Mitigation: microcode':
+ * 'Vulnerable: Safe RET, no microcode':
+
+   The "Safe RET" mitigation (see below) has been applied to protect the
+   kernel, but the IBPB-extending microcode has not been applied.  User
+   space tasks may still be vulnerable.
+
+ * 'Vulnerable: Microcode, no safe RET':
 
    Extended IBPB functionality microcode patch has been applied. It does
    not address User->Kernel and Guest->Host transitions protection but it
@@ -72,11 +82,11 @@ The possible values in this file are:
 
    (spec_rstack_overflow=microcode)
 
- * 'Mitigation: safe RET':
+ * 'Mitigation: Safe RET':
 
-   Software-only mitigation. It complements the extended IBPB microcode
-   patch functionality by addressing User->Kernel and Guest->Host
-   transitions protection.
+   Combined microcode/software mitigation. It complements the
+   extended IBPB microcode patch functionality by addressing
+   User->Kernel and Guest->Host transitions protection.
 
    Selected by default or by spec_rstack_overflow=safe-ret
 
@@ -129,7 +139,7 @@ an indrect branch prediction barrier after having applied the required
 microcode patch for one's system. This mitigation comes also at
 a performance cost.
 
-Mitigation: safe RET
+Mitigation: Safe RET
 --------------------
 
 The mitigation works by ensuring all RET instructions speculate to
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6c47f37..e45dd69 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2353,6 +2353,8 @@ early_param("l1tf", l1tf_cmdline);
 
 enum srso_mitigation {
 	SRSO_MITIGATION_NONE,
+	SRSO_MITIGATION_UCODE_NEEDED,
+	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,
 	SRSO_MITIGATION_MICROCODE,
 	SRSO_MITIGATION_SAFE_RET,
 	SRSO_MITIGATION_IBPB,
@@ -2368,11 +2370,13 @@ enum srso_mitigation_cmd {
 };
 
 static const char * const srso_strings[] = {
-	[SRSO_MITIGATION_NONE]           = "Vulnerable",
-	[SRSO_MITIGATION_MICROCODE]      = "Mitigation: microcode",
-	[SRSO_MITIGATION_SAFE_RET]	 = "Mitigation: safe RET",
-	[SRSO_MITIGATION_IBPB]		 = "Mitigation: IBPB",
-	[SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only"
+	[SRSO_MITIGATION_NONE]			= "Vulnerable",
+	[SRSO_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",
+	[SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED]	= "Vulnerable: Safe RET, no microcode",
+	[SRSO_MITIGATION_MICROCODE]		= "Vulnerable: Microcode, no safe RET",
+	[SRSO_MITIGATION_SAFE_RET]		= "Mitigation: Safe RET",
+	[SRSO_MITIGATION_IBPB]			= "Mitigation: IBPB",
+	[SRSO_MITIGATION_IBPB_ON_VMEXIT]	= "Mitigation: IBPB on VMEXIT only"
 };
 
 static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE;
@@ -2409,10 +2413,7 @@ static void __init srso_select_mitigation(void)
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	if (!has_microcode) {
-		pr_warn("IBPB-extending microcode not applied!\n");
-		pr_warn(SRSO_NOTICE);
-	} else {
+	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
@@ -2428,6 +2429,12 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}
+	} else {
+		pr_warn("IBPB-extending microcode not applied!\n");
+		pr_warn(SRSO_NOTICE);
+
+		/* may be overwritten by SRSO_CMD_SAFE_RET below */
+		srso_mitigation = SRSO_MITIGATION_UCODE_NEEDED;
 	}
 
 	switch (srso_cmd) {
@@ -2457,7 +2464,10 @@ static void __init srso_select_mitigation(void)
 				setup_force_cpu_cap(X86_FEATURE_SRSO);
 				x86_return_thunk = srso_return_thunk;
 			}
-			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			if (has_microcode)
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			else
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
 		}
@@ -2490,7 +2500,7 @@ static void __init srso_select_mitigation(void)
 	}
 
 out:
-	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
+	pr_info("%s\n", srso_strings[srso_mitigation]);
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
@@ -2701,9 +2711,7 @@ static ssize_t srso_show_state(char *buf)
 	if (boot_cpu_has(X86_FEATURE_SRSO_NO))
 		return sysfs_emit(buf, "Mitigation: SMT disabled\n");
 
-	return sysfs_emit(buf, "%s%s\n",
-			  srso_strings[srso_mitigation],
-			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
+	return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]);
 }
 
 static ssize_t gds_show_state(char *buf)

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print mitigation for retbleed IBPB case
  2023-09-05  5:04 ` [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     8e7f2ef76ed2360dabe3ccd253042f9f9054db65
Gitweb:        https://git.kernel.org/tip/8e7f2ef76ed2360dabe3ccd253042f9f9054db65
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:51 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:02 +02:00

x86/srso: Print mitigation for retbleed IBPB case

When overriding the requested mitigation with IBPB due to retbleed=ibpb,
print the mitigation in the usual format instead of a custom error
message.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ec3af919e267773d896c240faf30bfc6a1fd6304.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 235c0e0..6c47f37 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2425,9 +2425,8 @@ static void __init srso_select_mitigation(void)
 
 	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 		if (has_microcode) {
-			pr_err("Retbleed IBPB mitigation enabled, using same for SRSO\n");
 			srso_mitigation = SRSO_MITIGATION_IBPB;
-			goto pred_cmd;
+			goto out;
 		}
 	}
 
@@ -2490,7 +2489,8 @@ static void __init srso_select_mitigation(void)
 		break;
 	}
 
-	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
+out:
+	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print actual mitigation if requested mitigation isn't possible
  2023-09-05  5:04 ` [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     f9548addc12d02ee731ccd4a91ae55657e819d7d
Gitweb:        https://git.kernel.org/tip/f9548addc12d02ee731ccd4a91ae55657e819d7d
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:50 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:02 +02:00

x86/srso: Print actual mitigation if requested mitigation isn't possible

If the kernel wasn't compiled to support the requested option, print the
actual option that ends up getting used.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/7e7a12ea9d85a9f76ca16a3efb71f262dee46ab1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2859a54..235c0e0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2461,7 +2461,6 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2473,7 +2472,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2485,7 +2483,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
                 }
 		break;
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix SBPB enablement for (possible) future fixed HW
  2023-09-05  5:04 ` [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW Josh Poimboeuf
  2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
  2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
@ 2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
  2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-09-23 12:20 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     06c8c5f9db4e6103294dd528c09568131c2f520a
Gitweb:        https://git.kernel.org/tip/06c8c5f9db4e6103294dd528c09568131c2f520a
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:49 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 23 Sep 2023 14:13:02 +02:00

x86/srso: Fix SBPB enablement for (possible) future fixed HW

Make the SBPB check more robust against the (possible) case where future
HW has SRSO fixed but doesn't have the SRSO_NO bit set.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/cee5050db750b391c9f35f5334f8ff40e66c01b9.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 10499bc..2859a54 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2496,7 +2496,7 @@ static void __init srso_select_mitigation(void)
 	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
 
 pred_cmd:
-	if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) &&
+	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
 	     boot_cpu_has(X86_FEATURE_SBPB))
 		x86_pred_cmd = PRED_CMD_SBPB;
 }

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()
  2023-09-05  5:05 ` [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     99ee56c7657f939eecc4e8ac96e0aa0cd6ea7cbd
Gitweb:        https://git.kernel.org/tip/99ee56c7657f939eecc4e8ac96e0aa0cd6ea7cbd
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:04 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:45:48 +02:00

x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk()

For consistency with the other return thunks, rename __x86_return_skl()
to call_depth_return_thunk().

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ae44e9f9976934e3b5b47a458d523ccb15867561.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 13 ++++---------
 arch/x86/kernel/cpu/bugs.c           |  3 ++-
 arch/x86/lib/retpoline.S             |  4 ++--
 3 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index dcc7847..14cd3cd 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -358,12 +358,7 @@ extern void entry_ibpb(void);
 extern void (*x86_return_thunk)(void);
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
-extern void __x86_return_skl(void);
-
-static inline void x86_set_skl_return_thunk(void)
-{
-	x86_return_thunk = &__x86_return_skl;
-}
+extern void call_depth_return_thunk(void);
 
 #define CALL_DEPTH_ACCOUNT					\
 	ALTERNATIVE("",						\
@@ -376,12 +371,12 @@ DECLARE_PER_CPU(u64, __x86_ret_count);
 DECLARE_PER_CPU(u64, __x86_stuffs_count);
 DECLARE_PER_CPU(u64, __x86_ctxsw_count);
 #endif
-#else
-static inline void x86_set_skl_return_thunk(void) {}
+#else /* !CONFIG_CALL_DEPTH_TRACKING */
 
+static inline void call_depth_return_thunk(void) {}
 #define CALL_DEPTH_ACCOUNT ""
 
-#endif
+#endif /* CONFIG_CALL_DEPTH_TRACKING */
 
 #ifdef CONFIG_RETPOLINE
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9731e81..016a326 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1059,7 +1059,8 @@ do_cmd_auto:
 	case RETBLEED_MITIGATION_STUFF:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_CALL_DEPTH);
-		x86_set_skl_return_thunk();
+
+		x86_return_thunk = call_depth_return_thunk;
 		break;
 
 	default:
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 415521d..d410aba 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -323,7 +323,7 @@ __EXPORT_THUNK(entry_untrain_ret)
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
 	.align 64
-SYM_FUNC_START(__x86_return_skl)
+SYM_FUNC_START(call_depth_return_thunk)
 	ANNOTATE_NOENDBR
 	/*
 	 * Keep the hotpath in a 16byte I-fetch for the non-debug
@@ -350,7 +350,7 @@ SYM_FUNC_START(__x86_return_skl)
 	ANNOTATE_UNRET_SAFE
 	ret
 	int3
-SYM_FUNC_END(__x86_return_skl)
+SYM_FUNC_END(call_depth_return_thunk)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros
  2023-09-05  5:05 ` [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     0a3c49178c3c3e6f29280567ccb549826dd3a3f1
Gitweb:        https://git.kernel.org/tip/0a3c49178c3c3e6f29280567ccb549826dd3a3f1
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:01 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:40:42 +02:00

x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros

Macros already exist for unaligned code block symbols.  Use them.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/26d461bd509cc840af24c94586561c06d39812b2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 8ba79d2..415521d 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -149,7 +149,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
 	.pushsection .text..__x86.rethunk_untrain
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_untrain_ret)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	ASM_NOP2
@@ -159,7 +159,7 @@ SYM_FUNC_END(srso_alias_untrain_ret)
 	.popsection
 
 	.pushsection .text..__x86.rethunk_safe
-SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_NOALIGN(srso_alias_safe_ret)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
 	ANNOTATE_UNRET_SAFE
@@ -187,7 +187,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(srso_untrain_ret)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -255,7 +255,7 @@ SYM_CODE_END(srso_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(retbleed_untrain_ret)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/nospec: Refactor UNTRAIN_RET[_*]
  2023-09-05  5:05 ` [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     e8efc0800b8b5045ba8c0d1256bfbb47e92e192a
Gitweb:        https://git.kernel.org/tip/e8efc0800b8b5045ba8c0d1256bfbb47e92e192a
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:03 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:41:57 +02:00

x86/nospec: Refactor UNTRAIN_RET[_*]

Factor out the UNTRAIN_RET[_*] common bits into a helper macro.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/f06d45489778bd49623297af2a983eea09067a74.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 31 ++++++++-------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 51e3f1a..dcc7847 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -288,35 +288,24 @@
  * As such, this must be placed after every *SWITCH_TO_KERNEL_CR3 at a point
  * where we have a stack but before any RET instruction.
  */
-.macro UNTRAIN_RET
+.macro __UNTRAIN_RET ibpb_feature, call_depth_insns
 #if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		      "call entry_ibpb", \ibpb_feature,			\
+		     __stringify(\call_depth_insns), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
-.macro UNTRAIN_RET_VM
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_IBPB_ON_VMEXIT,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH)
 
-.macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
-	VALIDATE_UNRET_END
-	ALTERNATIVE_3 "",						\
-		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
-		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH_FROM_CALL), X86_FEATURE_CALL_DEPTH
-#endif
-.endm
+#define UNTRAIN_RET_VM \
+	__UNTRAIN_RET X86_FEATURE_IBPB_ON_VMEXIT, __stringify(RESET_CALL_DEPTH)
+
+#define UNTRAIN_RET_FROM_CALL \
+	__UNTRAIN_RET X86_FEATURE_ENTRY_IBPB, __stringify(RESET_CALL_DEPTH_FROM_CALL)
 
 
 .macro CALL_DEPTH_ACCOUNT

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block
  2023-09-05  5:04 ` [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     351236947a45a512c517153bbe109fe868d05e6d
Gitweb:        https://git.kernel.org/tip/351236947a45a512c517153bbe109fe868d05e6d
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:59 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:29:25 +02:00

x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block

Simplify the code flow a bit by moving the retbleed IBPB check into the
existing 'has_microcode' block.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/0a22b86b1f6b07f9046a9ab763fc0e0d1b7a91d4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 941ac94..6b443f0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2430,10 +2430,8 @@ static void __init srso_select_mitigation(void)
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
 			return;
 		}
-	}
 
-	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
-		if (has_microcode) {
+		if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Disentangle rethunk-dependent options
  2023-09-05  5:05 ` [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     34a3cae7474c6e6f4a85aad4a7b8191b8b35cdcd
Gitweb:        https://git.kernel.org/tip/34a3cae7474c6e6f4a85aad4a7b8191b8b35cdcd
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:05:00 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:30:50 +02:00

x86/srso: Disentangle rethunk-dependent options

CONFIG_RETHUNK, CONFIG_CPU_UNRET_ENTRY and CONFIG_CPU_SRSO are all
tangled up.  De-spaghettify the code a bit.

Some of the rethunk-related code has been shuffled around within the
'.text..__x86.return_thunk' section, but otherwise there are no
functional changes.  srso_alias_untrain_ret() and srso_alias_safe_ret()
((which are very address-sensitive) haven't moved.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/2845084ed303d8384905db3b87b77693945302b4.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h |  25 ++--
 arch/x86/kernel/cpu/bugs.c           |   5 +-
 arch/x86/kernel/vmlinux.lds.S        |   7 +-
 arch/x86/lib/retpoline.S             | 157 ++++++++++++++------------
 4 files changed, 109 insertions(+), 85 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 6c14fd1..51e3f1a 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -289,19 +289,17 @@
  * where we have a stack but before any RET instruction.
  */
 .macro UNTRAIN_RET
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
 		      "call entry_ibpb", X86_FEATURE_ENTRY_IBPB,	\
-		      __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
+		     __stringify(RESET_CALL_DEPTH), X86_FEATURE_CALL_DEPTH
 #endif
 .endm
 
 .macro UNTRAIN_RET_VM
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -311,8 +309,7 @@
 .endm
 
 .macro UNTRAIN_RET_FROM_CALL
-#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
+#if defined(CONFIG_RETHUNK) || defined(CONFIG_CPU_IBPB_ENTRY)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
@@ -348,6 +345,20 @@ extern void __x86_return_thunk(void);
 static inline void __x86_return_thunk(void) {}
 #endif
 
+#ifdef CONFIG_CPU_UNRET_ENTRY
+extern void retbleed_return_thunk(void);
+#else
+static inline void retbleed_return_thunk(void) {}
+#endif
+
+#ifdef CONFIG_CPU_SRSO
+extern void srso_return_thunk(void);
+extern void srso_alias_return_thunk(void);
+#else
+static inline void srso_return_thunk(void) {}
+static inline void srso_alias_return_thunk(void) {}
+#endif
+
 extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6b443f0..9731e81 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -63,7 +63,7 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd);
 
 static DEFINE_MUTEX(spec_ctrl_mutex);
 
-void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
+void (*x86_return_thunk)(void) __ro_after_init = __x86_return_thunk;
 
 /* Update SPEC_CTRL MSR and its cached copy unconditionally */
 static void update_spec_ctrl(u64 val)
@@ -1041,8 +1041,7 @@ do_cmd_auto:
 		setup_force_cpu_cap(X86_FEATURE_RETHUNK);
 		setup_force_cpu_cap(X86_FEATURE_UNRET);
 
-		if (IS_ENABLED(CONFIG_RETHUNK))
-			x86_return_thunk = retbleed_return_thunk;
+		x86_return_thunk = retbleed_return_thunk;
 
 		if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
 		    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index f15fb71..54a5596 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -139,10 +139,7 @@ SECTIONS
 		STATIC_CALL_TEXT
 
 		ALIGN_ENTRY_TEXT_BEGIN
-#ifdef CONFIG_CPU_SRSO
 		*(.text..__x86.rethunk_untrain)
-#endif
-
 		ENTRY_TEXT
 
 #ifdef CONFIG_CPU_SRSO
@@ -520,12 +517,12 @@ INIT_PER_CPU(irq_stack_backing_store);
            "fixed_percpu_data is not at start of per-cpu area");
 #endif
 
-#ifdef CONFIG_RETHUNK
+#ifdef CONFIG_CPU_UNRET_ENTRY
 . = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned");
-. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 #endif
 
 #ifdef CONFIG_CPU_SRSO
+. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
 /*
  * GNU ld cannot do XOR until 2.41.
  * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index a40ba18..8ba79d2 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -126,12 +126,13 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 #include <asm/GEN-for-each-reg.h>
 #undef GEN
 #endif
-/*
- * This function name is magical and is used by -mfunction-return=thunk-extern
- * for the compiler to generate JMPs to it.
- */
+
 #ifdef CONFIG_RETHUNK
 
+	.section .text..__x86.return_thunk
+
+#ifdef CONFIG_CPU_SRSO
+
 /*
  * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at
  * special addresses:
@@ -147,9 +148,7 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  *
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
-#ifdef CONFIG_CPU_SRSO
-	.section .text..__x86.rethunk_untrain
-
+	.pushsection .text..__x86.rethunk_untrain
 SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
@@ -157,17 +156,9 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
+	.popsection
 
-	.section .text..__x86.rethunk_safe
-#else
-/* dummy definition for alternatives */
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_FUNC_END(srso_alias_untrain_ret)
-#endif
-
+	.pushsection .text..__x86.rethunk_safe
 SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
@@ -182,8 +173,58 @@ SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
+	.popsection
+
+/*
+ * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
+ * above. On kernel entry, srso_untrain_ret() is executed which is a
+ *
+ * movabs $0xccccc30824648d48,%rax
+ *
+ * and when the return thunk executes the inner label srso_safe_ret()
+ * later, it is a stack manipulation and a RET which is mispredicted and
+ * thus a "safe" one to use.
+ */
+	.align 64
+	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
+	ANNOTATE_NOENDBR
+	.byte 0x48, 0xb8
+
+/*
+ * This forces the function return instruction to speculate into a trap
+ * (UD2 in srso_return_thunk() below).  This RET will then mispredict
+ * and execution will continue at the return site read from the top of
+ * the stack.
+ */
+SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
+	lea 8(%_ASM_SP), %_ASM_SP
+	ret
+	int3
+	int3
+	/* end of movabs */
+	lfence
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_safe_ret)
+SYM_FUNC_END(srso_untrain_ret)
+
+SYM_CODE_START(srso_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_return_thunk)
+
+#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret"
+#else /* !CONFIG_CPU_SRSO */
+#define JMP_SRSO_UNTRAIN_RET "ud2"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_SRSO */
+
+#ifdef CONFIG_CPU_UNRET_ENTRY
 
-	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *
@@ -263,64 +304,21 @@ SYM_CODE_END(retbleed_return_thunk)
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
 
-/*
- * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
- * above. On kernel entry, srso_untrain_ret() is executed which is a
- *
- * movabs $0xccccc30824648d48,%rax
- *
- * and when the return thunk executes the inner label srso_safe_ret()
- * later, it is a stack manipulation and a RET which is mispredicted and
- * thus a "safe" one to use.
- */
-	.align 64
-	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
-	ANNOTATE_NOENDBR
-	.byte 0x48, 0xb8
+#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret"
+#else /* !CONFIG_CPU_UNRET_ENTRY */
+#define JMP_RETBLEED_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_UNRET_ENTRY */
 
-/*
- * This forces the function return instruction to speculate into a trap
- * (UD2 in srso_return_thunk() below).  This RET will then mispredict
- * and execution will continue at the return site read from the top of
- * the stack.
- */
-SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
-	lea 8(%_ASM_SP), %_ASM_SP
-	ret
-	int3
-	int3
-	/* end of movabs */
-	lfence
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_safe_ret)
-SYM_FUNC_END(srso_untrain_ret)
-
-SYM_CODE_START(srso_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_return_thunk)
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 
 SYM_FUNC_START(entry_untrain_ret)
-	ALTERNATIVE_2 "jmp retbleed_untrain_ret", \
-		      "jmp srso_untrain_ret", X86_FEATURE_SRSO, \
-		      "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS
+	ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET,				\
+		      JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO,		\
+		      JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS
 SYM_FUNC_END(entry_untrain_ret)
 __EXPORT_THUNK(entry_untrain_ret)
 
-SYM_CODE_START(__x86_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_CODE_END(__x86_return_thunk)
-EXPORT_SYMBOL(__x86_return_thunk)
-
-#endif /* CONFIG_RETHUNK */
+#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
@@ -355,3 +353,22 @@ SYM_FUNC_START(__x86_return_skl)
 SYM_FUNC_END(__x86_return_skl)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
+
+/*
+ * This function name is magical and is used by -mfunction-return=thunk-extern
+ * for the compiler to generate JMPs to it.
+ *
+ * This code is only used during kernel boot or module init.  All
+ * 'JMP __x86_return_thunk' sites are changed to something else by
+ * apply_returns().
+ */
+SYM_CODE_START(__x86_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	ANNOTATE_UNRET_SAFE
+	ret
+	int3
+SYM_CODE_END(__x86_return_thunk)
+EXPORT_SYMBOL(__x86_return_thunk)
+
+#endif /* CONFIG_RETHUNK */

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Remove 'pred_cmd' label
  2023-09-05  5:04 ` [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     55ca9010c4a988b48278f81ae4129deea52d2488
Gitweb:        https://git.kernel.org/tip/55ca9010c4a988b48278f81ae4129deea52d2488
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:57 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:26:59 +02:00

x86/srso: Remove 'pred_cmd' label

SBPB is only enabled in two distinct cases:

1) when SRSO has been disabled with srso=off

2) when SRSO has been fixed (in future HW)

Simplify the control flow by getting rid of the 'pred_cmd' label and
moving the SBPB enablement check to the two corresponding code sites.
This makes it more clear when exactly SBPB gets enabled.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/bb20e8569cfa144def5e6f25e610804bc4974de2.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index e45dd69..4f1ad23 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2410,13 +2410,21 @@ static void __init srso_select_mitigation(void)
 {
 	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
-		goto pred_cmd;
+	if (cpu_mitigations_off())
+		return;
+
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
+	}
 
 	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
+		 *
+		 * Zen1/2 don't have SBPB, no need to try to enable it here.
 		 */
 		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
@@ -2439,7 +2447,9 @@ static void __init srso_select_mitigation(void)
 
 	switch (srso_cmd) {
 	case SRSO_CMD_OFF:
-		goto pred_cmd;
+		if (boot_cpu_has(X86_FEATURE_SBPB))
+			x86_pred_cmd = PRED_CMD_SBPB;
+		return;
 
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {
@@ -2501,11 +2511,6 @@ static void __init srso_select_mitigation(void)
 
 out:
 	pr_info("%s\n", srso_strings[srso_mitigation]);
-
-pred_cmd:
-	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
-	     boot_cpu_has(X86_FEATURE_SBPB))
-		x86_pred_cmd = PRED_CMD_SBPB;
 }
 
 #undef pr_fmt

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/bugs: Remove default case for fully switched enums
  2023-09-05  5:04 ` [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     0a0ce0da7fe66d54e497fb4e97d101b478f57e00
Gitweb:        https://git.kernel.org/tip/0a0ce0da7fe66d54e497fb4e97d101b478f57e00
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:58 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:28:44 +02:00

x86/bugs: Remove default case for fully switched enums

For enum switch statements which handle all possible cases, remove the
default case so a compiler warning gets printed if one of the enums gets
accidentally omitted from the switch statement.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/fcf6feefab991b72e411c2aed688b18e65e06aed.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 4f1ad23..941ac94 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1019,7 +1019,6 @@ static void __init retbleed_select_mitigation(void)
 
 do_cmd_auto:
 	case RETBLEED_CMD_AUTO:
-	default:
 		if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
 		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 			if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
@@ -1290,6 +1289,8 @@ spectre_v2_user_select_mitigation(void)
 
 		spectre_v2_user_ibpb = mode;
 		switch (cmd) {
+		case SPECTRE_V2_USER_CMD_NONE:
+			break;
 		case SPECTRE_V2_USER_CMD_FORCE:
 		case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
 		case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
@@ -1301,8 +1302,6 @@ spectre_v2_user_select_mitigation(void)
 		case SPECTRE_V2_USER_CMD_SECCOMP:
 			static_branch_enable(&switch_mm_cond_ibpb);
 			break;
-		default:
-			break;
 		}
 
 		pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
@@ -2160,6 +2159,10 @@ static int l1d_flush_prctl_get(struct task_struct *task)
 static int ssb_prctl_get(struct task_struct *task)
 {
 	switch (ssb_mode) {
+	case SPEC_STORE_BYPASS_NONE:
+		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
+			return PR_SPEC_ENABLE;
+		return PR_SPEC_NOT_AFFECTED;
 	case SPEC_STORE_BYPASS_DISABLE:
 		return PR_SPEC_DISABLE;
 	case SPEC_STORE_BYPASS_SECCOMP:
@@ -2171,11 +2174,8 @@ static int ssb_prctl_get(struct task_struct *task)
 		if (task_spec_ssb_disable(task))
 			return PR_SPEC_PRCTL | PR_SPEC_DISABLE;
 		return PR_SPEC_PRCTL | PR_SPEC_ENABLE;
-	default:
-		if (boot_cpu_has_bug(X86_BUG_SPEC_STORE_BYPASS))
-			return PR_SPEC_ENABLE;
-		return PR_SPEC_NOT_AFFECTED;
 	}
+	BUG();
 }
 
 static int ib_prctl_get(struct task_struct *task)
@@ -2504,9 +2504,6 @@ static void __init srso_select_mitigation(void)
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
                 }
 		break;
-
-	default:
-		break;
 	}
 
 out:

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Unexport untraining functions
  2023-09-05  5:04 ` [PATCH v3 12/20] x86/srso: Unexport untraining functions Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     eb54be26b0d25222809b16f335fe13756ff4a206
Gitweb:        https://git.kernel.org/tip/eb54be26b0d25222809b16f335fe13756ff4a206
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:56 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:21:59 +02:00

x86/srso: Unexport untraining functions

These functions aren't called outside of retpoline.S.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/1ae080f95ce7266c82cba6d2adde82349b832654.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ----
 arch/x86/lib/retpoline.S             | 7 ++-----
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 197ff4f..6c14fd1 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -352,10 +352,6 @@ extern void retbleed_return_thunk(void);
 extern void srso_return_thunk(void);
 extern void srso_alias_return_thunk(void);
 
-extern void retbleed_untrain_ret(void);
-extern void srso_untrain_ret(void);
-extern void srso_alias_untrain_ret(void);
-
 extern void entry_untrain_ret(void);
 extern void entry_ibpb(void);
 
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index 9ab634f..a40ba18 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -157,7 +157,6 @@ SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
-__EXPORT_THUNK(srso_alias_untrain_ret)
 
 	.section .text..__x86.rethunk_safe
 #else
@@ -215,7 +214,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(retbleed_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:
@@ -263,7 +262,6 @@ SYM_CODE_END(retbleed_return_thunk)
 	jmp retbleed_return_thunk
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
-__EXPORT_THUNK(retbleed_untrain_ret)
 
 /*
  * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
@@ -277,7 +275,7 @@ __EXPORT_THUNK(retbleed_untrain_ret)
  */
 	.align 64
 	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_START(srso_untrain_ret, SYM_L_LOCAL, SYM_A_NONE)
 	ANNOTATE_NOENDBR
 	.byte 0x48, 0xb8
 
@@ -298,7 +296,6 @@ SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
 	ud2
 SYM_CODE_END(srso_safe_ret)
 SYM_FUNC_END(srso_untrain_ret)
-__EXPORT_THUNK(srso_untrain_ret)
 
 SYM_CODE_START(srso_return_thunk)
 	UNWIND_HINT_FUNC

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Improve i-cache locality for alias mitigation
  2023-09-05  5:04 ` [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     aa730cff0c26244e88066b5b461a9f5fbac13823
Gitweb:        https://git.kernel.org/tip/aa730cff0c26244e88066b5b461a9f5fbac13823
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:55 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 12:04:18 +02:00

x86/srso: Improve i-cache locality for alias mitigation

Move srso_alias_return_thunk() to the same section as
srso_alias_safe_ret() so they can share a cache line.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/eadaf5530b46a7ae8b936522da45ae555d2b3393.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/lib/retpoline.S | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb..9ab634f 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -177,15 +177,14 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
 
-	.section .text..__x86.return_thunk
-
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
 
+	.section .text..__x86.return_thunk
 /*
  * Some generic notes on the untraining sequences:
  *

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix unret validation dependencies
  2023-09-05  5:04 ` [PATCH v3 09/20] x86/srso: Fix unret validation dependencies Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     eeb9f34df065f42f0c9195b322ba6df420c9fc92
Gitweb:        https://git.kernel.org/tip/eeb9f34df065f42f0c9195b322ba6df420c9fc92
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:53 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 11:46:59 +02:00

x86/srso: Fix unret validation dependencies

CONFIG_CPU_SRSO isn't dependent on CONFIG_CPU_UNRET_ENTRY (AMD
Retbleed), so the two features are independently configurable.  Fix
several issues for the (presumably rare) case where CONFIG_CPU_SRSO is
enabled but CONFIG_CPU_UNRET_ENTRY isn't.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/299fb7740174d0f2335e91c58af0e9c242b4bac1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/include/asm/nospec-branch.h | 4 ++--
 include/linux/objtool.h              | 3 ++-
 scripts/Makefile.vmlinux_o           | 3 ++-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index c55cc24..197ff4f 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -271,7 +271,7 @@
 .Lskip_rsb_\@:
 .endm
 
-#ifdef CONFIG_CPU_UNRET_ENTRY
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 #define CALL_UNTRAIN_RET	"call entry_untrain_ret"
 #else
 #define CALL_UNTRAIN_RET	""
@@ -312,7 +312,7 @@
 
 .macro UNTRAIN_RET_FROM_CALL
 #if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
-	defined(CONFIG_CALL_DEPTH_TRACKING)
+	defined(CONFIG_CALL_DEPTH_TRACKING) || defined(CONFIG_CPU_SRSO)
 	VALIDATE_UNRET_END
 	ALTERNATIVE_3 "",						\
 		      CALL_UNTRAIN_RET, X86_FEATURE_UNRET,		\
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 03f82c2..b5440e7 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -130,7 +130,8 @@
  * it will be ignored.
  */
 .macro VALIDATE_UNRET_BEGIN
-#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
+#if defined(CONFIG_NOINSTR_VALIDATION) && \
+	(defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO))
 .Lhere_\@:
 	.pushsection .discard.validate_unret
 	.long	.Lhere_\@ - .
diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
index 0edfdb4..25b3b58 100644
--- a/scripts/Makefile.vmlinux_o
+++ b/scripts/Makefile.vmlinux_o
@@ -37,7 +37,8 @@ objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
 
 vmlinux-objtool-args-$(delay-objtool)			+= $(objtool-args-y)
 vmlinux-objtool-args-$(CONFIG_GCOV_KERNEL)		+= --no-unreachable
-vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr $(if $(CONFIG_CPU_UNRET_ENTRY), --unret)
+vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+							   $(if $(or $(CONFIG_CPU_UNRET_ENTRY),$(CONFIG_CPU_SRSO)), --unret)
 
 objtool-args = $(vmlinux-objtool-args-y) --link
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix vulnerability reporting for missing microcode
  2023-09-05  5:04 ` [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     dc6306ad5b0dda040baf1fde3cfd458e6abfc4da
Gitweb:        https://git.kernel.org/tip/dc6306ad5b0dda040baf1fde3cfd458e6abfc4da
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:52 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 11:46:09 +02:00

x86/srso: Fix vulnerability reporting for missing microcode

The SRSO default safe-ret mitigation is reported as "mitigated" even if
microcode hasn't been updated.  That's wrong because userspace may still
be vulnerable to SRSO attacks due to IBPB not flushing branch type
predictions.

Report the safe-ret + !microcode case as vulnerable.

Also report the microcode-only case as vulnerable as it leaves the
kernel open to attacks.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/a8a14f97d1b0e03ec255c81637afdf4cf0ae9c99.1693889988.git.jpoimboe@kernel.org
---
 Documentation/admin-guide/hw-vuln/srso.rst | 24 +++++++++-----
 arch/x86/kernel/cpu/bugs.c                 | 36 ++++++++++++---------
 2 files changed, 39 insertions(+), 21 deletions(-)

diff --git a/Documentation/admin-guide/hw-vuln/srso.rst b/Documentation/admin-guide/hw-vuln/srso.rst
index b6cfb51..e715bfc 100644
--- a/Documentation/admin-guide/hw-vuln/srso.rst
+++ b/Documentation/admin-guide/hw-vuln/srso.rst
@@ -46,12 +46,22 @@ The possible values in this file are:
 
    The processor is not vulnerable
 
- * 'Vulnerable: no microcode':
+* 'Vulnerable':
+
+   The processor is vulnerable and no mitigations have been applied.
+
+ * 'Vulnerable: No microcode':
 
    The processor is vulnerable, no microcode extending IBPB
    functionality to address the vulnerability has been applied.
 
- * 'Mitigation: microcode':
+ * 'Vulnerable: Safe RET, no microcode':
+
+   The "Safe RET" mitigation (see below) has been applied to protect the
+   kernel, but the IBPB-extending microcode has not been applied.  User
+   space tasks may still be vulnerable.
+
+ * 'Vulnerable: Microcode, no safe RET':
 
    Extended IBPB functionality microcode patch has been applied. It does
    not address User->Kernel and Guest->Host transitions protection but it
@@ -72,11 +82,11 @@ The possible values in this file are:
 
    (spec_rstack_overflow=microcode)
 
- * 'Mitigation: safe RET':
+ * 'Mitigation: Safe RET':
 
-   Software-only mitigation. It complements the extended IBPB microcode
-   patch functionality by addressing User->Kernel and Guest->Host
-   transitions protection.
+   Combined microcode/software mitigation. It complements the
+   extended IBPB microcode patch functionality by addressing
+   User->Kernel and Guest->Host transitions protection.
 
    Selected by default or by spec_rstack_overflow=safe-ret
 
@@ -129,7 +139,7 @@ an indrect branch prediction barrier after having applied the required
 microcode patch for one's system. This mitigation comes also at
 a performance cost.
 
-Mitigation: safe RET
+Mitigation: Safe RET
 --------------------
 
 The mitigation works by ensuring all RET instructions speculate to
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 6c47f37..e45dd69 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2353,6 +2353,8 @@ early_param("l1tf", l1tf_cmdline);
 
 enum srso_mitigation {
 	SRSO_MITIGATION_NONE,
+	SRSO_MITIGATION_UCODE_NEEDED,
+	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,
 	SRSO_MITIGATION_MICROCODE,
 	SRSO_MITIGATION_SAFE_RET,
 	SRSO_MITIGATION_IBPB,
@@ -2368,11 +2370,13 @@ enum srso_mitigation_cmd {
 };
 
 static const char * const srso_strings[] = {
-	[SRSO_MITIGATION_NONE]           = "Vulnerable",
-	[SRSO_MITIGATION_MICROCODE]      = "Mitigation: microcode",
-	[SRSO_MITIGATION_SAFE_RET]	 = "Mitigation: safe RET",
-	[SRSO_MITIGATION_IBPB]		 = "Mitigation: IBPB",
-	[SRSO_MITIGATION_IBPB_ON_VMEXIT] = "Mitigation: IBPB on VMEXIT only"
+	[SRSO_MITIGATION_NONE]			= "Vulnerable",
+	[SRSO_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",
+	[SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED]	= "Vulnerable: Safe RET, no microcode",
+	[SRSO_MITIGATION_MICROCODE]		= "Vulnerable: Microcode, no safe RET",
+	[SRSO_MITIGATION_SAFE_RET]		= "Mitigation: Safe RET",
+	[SRSO_MITIGATION_IBPB]			= "Mitigation: IBPB",
+	[SRSO_MITIGATION_IBPB_ON_VMEXIT]	= "Mitigation: IBPB on VMEXIT only"
 };
 
 static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_NONE;
@@ -2409,10 +2413,7 @@ static void __init srso_select_mitigation(void)
 	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
 		goto pred_cmd;
 
-	if (!has_microcode) {
-		pr_warn("IBPB-extending microcode not applied!\n");
-		pr_warn(SRSO_NOTICE);
-	} else {
+	if (has_microcode) {
 		/*
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
@@ -2428,6 +2429,12 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_IBPB;
 			goto out;
 		}
+	} else {
+		pr_warn("IBPB-extending microcode not applied!\n");
+		pr_warn(SRSO_NOTICE);
+
+		/* may be overwritten by SRSO_CMD_SAFE_RET below */
+		srso_mitigation = SRSO_MITIGATION_UCODE_NEEDED;
 	}
 
 	switch (srso_cmd) {
@@ -2457,7 +2464,10 @@ static void __init srso_select_mitigation(void)
 				setup_force_cpu_cap(X86_FEATURE_SRSO);
 				x86_return_thunk = srso_return_thunk;
 			}
-			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			if (has_microcode)
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+			else
+				srso_mitigation = SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
 		}
@@ -2490,7 +2500,7 @@ static void __init srso_select_mitigation(void)
 	}
 
 out:
-	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
+	pr_info("%s\n", srso_strings[srso_mitigation]);
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
@@ -2701,9 +2711,7 @@ static ssize_t srso_show_state(char *buf)
 	if (boot_cpu_has(X86_FEATURE_SRSO_NO))
 		return sysfs_emit(buf, "Mitigation: SMT disabled\n");
 
-	return sysfs_emit(buf, "%s%s\n",
-			  srso_strings[srso_mitigation],
-			  boot_cpu_has(X86_FEATURE_IBPB_BRTYPE) ? "" : ", no microcode");
+	return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]);
 }
 
 static ssize_t gds_show_state(char *buf)

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print mitigation for retbleed IBPB case
  2023-09-05  5:04 ` [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     de9f5f7b06a5b7adbfdd8016f011120a4e928add
Gitweb:        https://git.kernel.org/tip/de9f5f7b06a5b7adbfdd8016f011120a4e928add
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:51 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 11:45:24 +02:00

x86/srso: Print mitigation for retbleed IBPB case

When overriding the requested mitigation with IBPB due to retbleed=ibpb,
print the mitigation in the usual format instead of a custom error
message.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/ec3af919e267773d896c240faf30bfc6a1fd6304.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 235c0e0..6c47f37 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2425,9 +2425,8 @@ static void __init srso_select_mitigation(void)
 
 	if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
 		if (has_microcode) {
-			pr_err("Retbleed IBPB mitigation enabled, using same for SRSO\n");
 			srso_mitigation = SRSO_MITIGATION_IBPB;
-			goto pred_cmd;
+			goto out;
 		}
 	}
 
@@ -2490,7 +2489,8 @@ static void __init srso_select_mitigation(void)
 		break;
 	}
 
-	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
+out:
+	pr_info("%s%s\n", srso_strings[srso_mitigation], has_microcode ? "" : ", no microcode");
 
 pred_cmd:
 	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Print actual mitigation if requested mitigation isn't possible
  2023-09-05  5:04 ` [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     3fc7b28e831f15274a5526197b54a73a88620584
Gitweb:        https://git.kernel.org/tip/3fc7b28e831f15274a5526197b54a73a88620584
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:50 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 11:44:26 +02:00

x86/srso: Print actual mitigation if requested mitigation isn't possible

If the kernel wasn't compiled to support the requested option, print the
actual option that ends up getting used.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/7e7a12ea9d85a9f76ca16a3efb71f262dee46ab1.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 2859a54..235c0e0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2461,7 +2461,6 @@ static void __init srso_select_mitigation(void)
 			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2473,7 +2472,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
-			goto pred_cmd;
 		}
 		break;
 
@@ -2485,7 +2483,6 @@ static void __init srso_select_mitigation(void)
 			}
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_SRSO.\n");
-			goto pred_cmd;
                 }
 		break;
 

^ permalink raw reply related	[flat|nested] 92+ messages in thread

* [tip: x86/bugs] x86/srso: Fix SBPB enablement for (possible) future fixed HW
  2023-09-05  5:04 ` [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW Josh Poimboeuf
                     ` (2 preceding siblings ...)
  2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
@ 2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
  3 siblings, 0 replies; 92+ messages in thread
From: tip-bot2 for Josh Poimboeuf @ 2023-10-20 11:37 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Josh Poimboeuf, Ingo Molnar, Borislav Petkov (AMD), x86,
	linux-kernel

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     1d1142ac51307145dbb256ac3535a1d43a1c9800
Gitweb:        https://git.kernel.org/tip/1d1142ac51307145dbb256ac3535a1d43a1c9800
Author:        Josh Poimboeuf <jpoimboe@kernel.org>
AuthorDate:    Mon, 04 Sep 2023 22:04:49 -07:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 20 Oct 2023 11:34:51 +02:00

x86/srso: Fix SBPB enablement for (possible) future fixed HW

Make the SBPB check more robust against the (possible) case where future
HW has SRSO fixed but doesn't have the SRSO_NO bit set.

Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/cee5050db750b391c9f35f5334f8ff40e66c01b9.1693889988.git.jpoimboe@kernel.org
---
 arch/x86/kernel/cpu/bugs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 10499bc..2859a54 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2496,7 +2496,7 @@ static void __init srso_select_mitigation(void)
 	pr_info("%s%s\n", srso_strings[srso_mitigation], (has_microcode ? "" : ", no microcode"));
 
 pred_cmd:
-	if ((boot_cpu_has(X86_FEATURE_SRSO_NO) || srso_cmd == SRSO_CMD_OFF) &&
+	if ((!boot_cpu_has_bug(X86_BUG_SRSO) || srso_cmd == SRSO_CMD_OFF) &&
 	     boot_cpu_has(X86_FEATURE_SBPB))
 		x86_pred_cmd = PRED_CMD_SBPB;
 }

^ permalink raw reply related	[flat|nested] 92+ messages in thread

end of thread, other threads:[~2023-10-20 11:38 UTC | newest]

Thread overview: 92+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-09-05  5:04 [PATCH v3 00/20] SRSO fixes/cleanups Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 01/20] x86/srso: Fix srso_show_state() side effect Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:45   ` [tip: x86/urgent] " tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 02/20] x86/srso: Set CPUID feature bits independently of bug or mitigation status Josh Poimboeuf
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2023-09-05  5:04 ` [PATCH v3 04/20] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off Josh Poimboeuf
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2023-09-05  5:04 ` [PATCH v3 05/20] x86/srso: Fix SBPB enablement for (possible) future fixed HW Josh Poimboeuf
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2023-09-05  5:04 ` [PATCH v3 06/20] x86/srso: Print actual mitigation if requested mitigation isn't possible Josh Poimboeuf
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2023-09-05  5:04 ` [PATCH v3 07/20] x86/srso: Print mitigation for retbleed IBPB case Josh Poimboeuf
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2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
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2023-09-05  5:04 ` [PATCH v3 08/20] x86/srso: Fix vulnerability reporting for missing microcode Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 09/20] x86/srso: Fix unret validation dependencies Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 10/20] x86/alternatives: Remove faulty optimization Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 11/20] x86/srso: Improve i-cache locality for alias mitigation Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 12/20] x86/srso: Unexport untraining functions Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 13/20] x86/srso: Remove 'pred_cmd' label Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 14/20] x86/bugs: Remove default case for fully switched enums Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:04 ` [PATCH v3 15/20] x86/srso: Move retbleed IBPB check into existing 'has_microcode' code block Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:05 ` [PATCH v3 16/20] x86/srso: Disentangle rethunk-dependent options Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:05 ` [PATCH v3 17/20] x86/rethunk: Use SYM_CODE_START[_LOCAL]_NOALIGN macros Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:05 ` [PATCH v3 18/20] x86/retpoline: Remove .text..__x86.return_thunk section Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:05 ` [PATCH v3 19/20] x86/nospec: Refactor UNTRAIN_RET[_*] Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  5:05 ` [PATCH v3 20/20] x86/calldepth: Rename __x86_return_skl() to call_depth_return_thunk() Josh Poimboeuf
2023-09-05 10:09   ` [tip: x86/bugs] " tip-bot2 for Josh Poimboeuf
2023-09-19  9:53   ` tip-bot2 for Josh Poimboeuf
2023-09-23 12:20   ` tip-bot2 for Josh Poimboeuf
2023-10-20 11:37   ` tip-bot2 for Josh Poimboeuf
2023-09-05  6:35 ` [PATCH v3 00/20] SRSO fixes/cleanups Borislav Petkov
2023-09-05 10:02   ` Ingo Molnar

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