[PATCH stable 4.9 v3 0/2] arm64: entry: Place an SB sequence following an ERET instruction

[PATCH stable 4.9 v3 0/2] arm64: entry: Place an SB sequence following an ERET instruction

[Florian Fainelli]

Changes in v3:

- included missing preliminary patch to define the SB barrier instruction, see
  patch change log for details on how it was back ported into v4.9

Changes in v2:

- added missing hunk in hyp/entry.S per Will's feedback

Will Deacon (2):
  arm64: Add support for SB barrier and patch in over DSB; ISB sequences
  arm64: entry: Place an SB sequence following an ERET instruction

 arch/arm64/include/asm/assembler.h  | 13 +++++++++++++
 arch/arm64/include/asm/barrier.h    |  4 ++++
 arch/arm64/include/asm/cpucaps.h    |  3 ++-
 arch/arm64/include/asm/sysreg.h     | 13 +++++++++++++
 arch/arm64/include/asm/uaccess.h    |  3 +--
 arch/arm64/include/uapi/asm/hwcap.h |  1 +
 arch/arm64/kernel/cpufeature.c      | 22 +++++++++++++++++++++-
 arch/arm64/kernel/cpuinfo.c         |  1 +
 arch/arm64/kernel/entry.S           |  2 ++
 arch/arm64/kvm/hyp/entry.S          |  2 ++
 arch/arm64/kvm/hyp/hyp-entry.S      |  4 ++++
 11 files changed, 64 insertions(+), 4 deletions(-)

-- 
2.7.4

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[PATCH stable 4.9 v3 1/2] arm64: Add support for SB barrier and patch in over DSB; ISB sequences

[Florian Fainelli]

From: Will Deacon <will.deacon@arm.com>

commit bd4fb6d270bc423a9a4098108784f7f9254c4e6d upstream

We currently use a DSB; ISB sequence to inhibit speculation in set_fs().
Whilst this works for current CPUs, future CPUs may implement a new SB
barrier instruction which acts as an architected speculation barrier.

On CPUs that support it, patch in an SB; NOP sequence over the DSB; ISB
sequence and advertise the presence of the new instruction to userspace.

Signed-off-by: Will Deacon <will.deacon@arm.com>
[florian:
- adjust number capabilities
- wire decoding of ftr_id_aa64_isar1
- __emit_inst -> __inst_arm
- sys_insn -> sys_reg]
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 arch/arm64/include/asm/assembler.h  | 13 +++++++++++++
 arch/arm64/include/asm/barrier.h    |  4 ++++
 arch/arm64/include/asm/cpucaps.h    |  3 ++-
 arch/arm64/include/asm/sysreg.h     | 13 +++++++++++++
 arch/arm64/include/asm/uaccess.h    |  3 +--
 arch/arm64/include/uapi/asm/hwcap.h |  1 +
 arch/arm64/kernel/cpufeature.c      | 22 +++++++++++++++++++++-
 arch/arm64/kernel/cpuinfo.c         |  1 +
 8 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 3f85bbcd7e40..0f689aa0b300 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -95,6 +95,19 @@
 	.endm
 
 /*
+ * Speculation barrier
+ */
+	.macro	sb
+alternative_if_not ARM64_HAS_SB
+	dsb	nsh
+	isb
+alternative_else
+	SB_BARRIER_INSN
+	nop
+alternative_endif
+	.endm
+
+/*
  * Sanitise a 64-bit bounded index wrt speculation, returning zero if out
  * of bounds.
  */
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 0b0755c961ac..159329160fb4 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -33,6 +33,10 @@
 
 #define csdb()		asm volatile("hint #20" : : : "memory")
 
+#define spec_bar()	asm volatile(ALTERNATIVE("dsb nsh\nisb\n",		\
+						 SB_BARRIER_INSN"nop\n",	\
+						 ARM64_HAS_SB))
+
 #define mb()		dsb(sy)
 #define rmb()		dsb(ld)
 #define wmb()		dsb(st)
diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 8c7c4b23a8b1..8a25f6e39f3a 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -38,7 +38,8 @@
 #define ARM64_HARDEN_BRANCH_PREDICTOR		17
 #define ARM64_SSBD				18
 #define ARM64_MISMATCHED_CACHE_TYPE		19
+#define ARM64_HAS_SB				20
 
-#define ARM64_NCAPS				20
+#define ARM64_NCAPS				21
 
 #endif /* __ASM_CPUCAPS_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 88bbe364b6ae..1c49eaac1938 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -86,6 +86,12 @@
 #define SET_PSTATE_UAO(x) __inst_arm(0xd5000000 | REG_PSTATE_UAO_IMM |\
 				     (!!x)<<8 | 0x1f)
 
+#define __SYS_BARRIER_INSN(CRm, op2, Rt) \
+	__inst_arm(0xd5000000 | sys_reg(0, 3, 3, (CRm), (op2)) | ((Rt) & 0x1f))
+
+#define SB_BARRIER_INSN			__SYS_BARRIER_INSN(0, 7, 31)
+
+
 /* Common SCTLR_ELx flags. */
 #define SCTLR_ELx_EE    (1 << 25)
 #define SCTLR_ELx_I	(1 << 12)
@@ -116,6 +122,13 @@
 #define ID_AA64ISAR0_SHA1_SHIFT		8
 #define ID_AA64ISAR0_AES_SHIFT		4
 
+/* id_aa64isar1 */
+#define ID_AA64ISAR1_SB_SHIFT		36
+#define ID_AA64ISAR1_LRCPC_SHIFT	20
+#define ID_AA64ISAR1_FCMA_SHIFT		16
+#define ID_AA64ISAR1_JSCVT_SHIFT	12
+#define ID_AA64ISAR1_DPB_SHIFT		0
+
 /* id_aa64pfr0 */
 #define ID_AA64PFR0_CSV3_SHIFT		60
 #define ID_AA64PFR0_CSV2_SHIFT		56
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index f5cd96c60eb9..195323089e5a 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -71,8 +71,7 @@ static inline void set_fs(mm_segment_t fs)
 	 * Prevent a mispredicted conditional call to set_fs from forwarding
 	 * the wrong address limit to access_ok under speculation.
 	 */
-	dsb(nsh);
-	isb();
+	spec_bar();
 
 	/*
 	 * Enable/disable UAO so that copy_to_user() etc can access
diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
index a739287ef6a3..3aa659624968 100644
--- a/arch/arm64/include/uapi/asm/hwcap.h
+++ b/arch/arm64/include/uapi/asm/hwcap.h
@@ -30,5 +30,6 @@
 #define HWCAP_ATOMICS		(1 << 8)
 #define HWCAP_FPHP		(1 << 9)
 #define HWCAP_ASIMDHP		(1 << 10)
+#define HWCAP_SB		(1 << 29)
 
 #endif /* _UAPI__ASM_HWCAP_H */
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 8cf001baee21..1a5879c0b711 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -93,6 +93,15 @@ static const struct arm64_ftr_bits ftr_id_aa64isar0[] = {
 	ARM64_FTR_END,
 };
 
+static const struct arm64_ftr_bits ftr_id_aa64isar1[] = {
+	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_SB_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_LRCPC_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_FCMA_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_JSCVT_SHIFT, 4, 0),
+	ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR1_DPB_SHIFT, 4, 0),
+	ARM64_FTR_END,
+};
+
 static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
 	ARM64_FTR_BITS(FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0),
 	ARM64_FTR_BITS(FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV2_SHIFT, 4, 0),
@@ -326,7 +335,7 @@ static const struct __ftr_reg_entry {
 
 	/* Op1 = 0, CRn = 0, CRm = 6 */
 	ARM64_FTR_REG(SYS_ID_AA64ISAR0_EL1, ftr_id_aa64isar0),
-	ARM64_FTR_REG(SYS_ID_AA64ISAR1_EL1, ftr_aa64raz),
+	ARM64_FTR_REG(SYS_ID_AA64ISAR1_EL1, ftr_id_aa64isar1),
 
 	/* Op1 = 0, CRn = 0, CRm = 7 */
 	ARM64_FTR_REG(SYS_ID_AA64MMFR0_EL1, ftr_id_aa64mmfr0),
@@ -949,6 +958,16 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		.enable = kpti_install_ng_mappings,
 	},
 #endif
+	{
+		.desc = "Speculation barrier (SB)",
+		.capability = ARM64_HAS_SB,
+		.def_scope = SCOPE_SYSTEM,
+		.matches = has_cpuid_feature,
+		.sys_reg = SYS_ID_AA64ISAR1_EL1,
+		.field_pos = ID_AA64ISAR1_SB_SHIFT,
+		.sign = FTR_UNSIGNED,
+		.min_field_value = 1,
+	},
 	{},
 };
 
@@ -976,6 +995,7 @@ static const struct arm64_cpu_capabilities arm64_elf_hwcaps[] = {
 	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, HWCAP_FPHP),
 	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 0, CAP_HWCAP, HWCAP_ASIMD),
 	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, HWCAP_ASIMDHP),
+	HWCAP_CAP(SYS_ID_AA64ISAR1_EL1, ID_AA64ISAR1_SB_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_SB),
 	{},
 };
 
diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index b3d5b3e8fbcb..5de2d55a999e 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -63,6 +63,7 @@ static const char *const hwcap_str[] = {
 	"atomics",
 	"fphp",
 	"asimdhp",
+	"sb",
 	NULL
 };
 
-- 
2.7.4

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[PATCH stable 4.9 v3 2/2] arm64: entry: Place an SB sequence following an ERET instruction

[Florian Fainelli]

From: Will Deacon <will.deacon@arm.com>

commit 679db70801da9fda91d26caf13bf5b5ccc74e8e8 upstream

Some CPUs can speculate past an ERET instruction and potentially perform
speculative accesses to memory before processing the exception return.
Since the register state is often controlled by a lower privilege level
at the point of an ERET, this could potentially be used as part of a
side-channel attack.

This patch emits an SB sequence after each ERET so that speculation is
held up on exception return.

Signed-off-by: Will Deacon <will.deacon@arm.com>
[florian: Adjust hyp-entry.S to account for the label
 added change to hyp/entry.S]
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 arch/arm64/kernel/entry.S      | 2 ++
 arch/arm64/kvm/hyp/entry.S     | 2 ++
 arch/arm64/kvm/hyp/hyp-entry.S | 4 ++++
 3 files changed, 8 insertions(+)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index ca978d7d98eb..3408c782702c 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -255,6 +255,7 @@ alternative_insn eret, nop, ARM64_UNMAP_KERNEL_AT_EL0
 	.else
 	eret
 	.endif
+	sb
 	.endm
 
 	.macro	get_thread_info, rd
@@ -945,6 +946,7 @@ __ni_sys_trace:
 	mrs	x30, far_el1
 	.endif
 	eret
+	sb
 	.endm
 
 	.align	11
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index a360ac6e89e9..93704e6894d2 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -83,6 +83,7 @@ ENTRY(__guest_enter)
 
 	// Do not touch any register after this!
 	eret
+	sb
 ENDPROC(__guest_enter)
 
 ENTRY(__guest_exit)
@@ -195,4 +196,5 @@ alternative_endif
 	ldp	x0, x1, [sp], #16
 
 	eret
+	sb
 ENDPROC(__fpsimd_guest_restore)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index bf4988f9dae8..3675e7f0ab72 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -97,6 +97,7 @@ el1_sync:				// Guest trapped into EL2
 	do_el2_call
 
 2:	eret
+	sb
 
 el1_hvc_guest:
 	/*
@@ -147,6 +148,7 @@ wa_epilogue:
 	mov	x0, xzr
 	add	sp, sp, #16
 	eret
+	sb
 
 el1_trap:
 	get_vcpu_ptr	x1, x0
@@ -198,6 +200,7 @@ el2_error:
 	b.ne	__hyp_panic
 	mov	x0, #(1 << ARM_EXIT_WITH_SERROR_BIT)
 	eret
+	sb
 
 ENTRY(__hyp_do_panic)
 	mov	lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
@@ -206,6 +209,7 @@ ENTRY(__hyp_do_panic)
 	ldr	lr, =panic
 	msr	elr_el2, lr
 	eret
+	sb
 ENDPROC(__hyp_do_panic)
 
 ENTRY(__hyp_panic)
-- 
2.7.4

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