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From: Amit Daniel Kachhap <amit.kachhap@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Mark Brown <broonie@kernel.org>,
	James Morse <james.morse@arm.com>,
	Amit Daniel Kachhap <amit.kachhap@arm.com>,
	Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
	Will Deacon <will@kernel.org>, Dave Martin <Dave.Martin@arm.com>
Subject: [PATCH v4 1/4] arm64: ptrauth: add Armv8.3 pointer authentication enhanced features
Date: Fri, 10 Jul 2020 13:30:07 +0530	[thread overview]
Message-ID: <1594368010-4419-2-git-send-email-amit.kachhap@arm.com> (raw)
In-Reply-To: <1594368010-4419-1-git-send-email-amit.kachhap@arm.com>

Some Armv8.3 Pointer Authentication enhancements have been introduced
which are mandatory for Armv8.6 and optional for ARMv8.3. These features
are,

* ARMv8.3-PAuth2 - An enhanced PAC generation logic is added which hardens
  finding the correct PAC value of the authenticated pointer.

* ARMv8.3-FPAC - Fault is generated now when the ptrauth authentication
  instruction fails in authenticating the PAC present in the address.
  This is different from earlier case when such failures just adds an
  error code in the top byte and waits for subsequent load/store to abort.
  The ptrauth instructions which may cause this fault are autiasp, retaa
  etc.

The above features are now represented by additional configurations
for the Address Authentication cpufeature.

The userspace fault received in the kernel due to ARMv8.3-FPAC is treated
as Illegal instruction and hence signal SIGILL is injected with ILL_ILLOPN
as the signal code. Note that this is different from earlier ARMv8.3
ptrauth where signal SIGSEGV is issued due to Pointer authentication
failures. The in-kernel PAC fault causes kernel to crash.

Signed-off-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
---
Changes since v3:
 * Removed ptrauth fault handler from 32 bit compat layer handler.
 * Added a comment for in-kernel PAC fault kernel crash.
 * Commit logs cleanup.

 arch/arm64/include/asm/esr.h       |  4 +++-
 arch/arm64/include/asm/exception.h |  1 +
 arch/arm64/include/asm/sysreg.h    | 24 ++++++++++++++++--------
 arch/arm64/kernel/entry-common.c   | 21 +++++++++++++++++++++
 arch/arm64/kernel/traps.c          | 10 ++++++++++
 5 files changed, 51 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 035003acfa87..22c81f1edda2 100644
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -35,7 +35,9 @@
 #define ESR_ELx_EC_SYS64	(0x18)
 #define ESR_ELx_EC_SVE		(0x19)
 #define ESR_ELx_EC_ERET		(0x1a)	/* EL2 only */
-/* Unallocated EC: 0x1b - 0x1E */
+/* Unallocated EC: 0x1B */
+#define ESR_ELx_EC_FPAC		(0x1C)	/* EL1 and above */
+/* Unallocated EC: 0x1D - 0x1E */
 #define ESR_ELx_EC_IMP_DEF	(0x1f)	/* EL3 only */
 #define ESR_ELx_EC_IABT_LOW	(0x20)
 #define ESR_ELx_EC_IABT_CUR	(0x21)
diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h
index 7577a754d443..3140b90f2e4f 100644
--- a/arch/arm64/include/asm/exception.h
+++ b/arch/arm64/include/asm/exception.h
@@ -47,4 +47,5 @@ void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr);
 void do_cp15instr(unsigned int esr, struct pt_regs *regs);
 void do_el0_svc(struct pt_regs *regs);
 void do_el0_svc_compat(struct pt_regs *regs);
+void do_ptrauth_fault(struct pt_regs *regs, unsigned long esr);
 #endif	/* __ASM_EXCEPTION_H */
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 463175f80341..c71bcd0c002a 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -633,14 +633,22 @@
 #define ID_AA64ISAR1_APA_SHIFT		4
 #define ID_AA64ISAR1_DPB_SHIFT		0
 
-#define ID_AA64ISAR1_APA_NI		0x0
-#define ID_AA64ISAR1_APA_ARCHITECTED	0x1
-#define ID_AA64ISAR1_API_NI		0x0
-#define ID_AA64ISAR1_API_IMP_DEF	0x1
-#define ID_AA64ISAR1_GPA_NI		0x0
-#define ID_AA64ISAR1_GPA_ARCHITECTED	0x1
-#define ID_AA64ISAR1_GPI_NI		0x0
-#define ID_AA64ISAR1_GPI_IMP_DEF	0x1
+#define ID_AA64ISAR1_APA_NI			0x0
+#define ID_AA64ISAR1_APA_ARCHITECTED		0x1
+#define ID_AA64ISAR1_APA_ARCH_EPAC		0x2
+#define ID_AA64ISAR1_APA_ARCH_EPAC2		0x3
+#define ID_AA64ISAR1_APA_ARCH_EPAC2_FPAC	0x4
+#define ID_AA64ISAR1_APA_ARCH_EPAC2_FPAC_CMB	0x5
+#define ID_AA64ISAR1_API_NI			0x0
+#define ID_AA64ISAR1_API_IMP_DEF		0x1
+#define ID_AA64ISAR1_API_IMP_DEF_EPAC		0x2
+#define ID_AA64ISAR1_API_IMP_DEF_EPAC2		0x3
+#define ID_AA64ISAR1_API_IMP_DEF_EPAC2_FPAC	0x4
+#define ID_AA64ISAR1_API_IMP_DEF_EPAC2_FPAC_CMB	0x5
+#define ID_AA64ISAR1_GPA_NI			0x0
+#define ID_AA64ISAR1_GPA_ARCHITECTED		0x1
+#define ID_AA64ISAR1_GPI_NI			0x0
+#define ID_AA64ISAR1_GPI_IMP_DEF		0x1
 
 /* id_aa64pfr0 */
 #define ID_AA64PFR0_CSV3_SHIFT		60
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 3dbdf9752b11..8380ffb8160a 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -66,6 +66,13 @@ static void notrace el1_dbg(struct pt_regs *regs, unsigned long esr)
 }
 NOKPROBE_SYMBOL(el1_dbg);
 
+static void notrace el1_fpac(struct pt_regs *regs, unsigned long esr)
+{
+	local_daif_inherit(regs);
+	do_ptrauth_fault(regs, esr);
+}
+NOKPROBE_SYMBOL(el1_fpac);
+
 asmlinkage void notrace el1_sync_handler(struct pt_regs *regs)
 {
 	unsigned long esr = read_sysreg(esr_el1);
@@ -92,6 +99,9 @@ asmlinkage void notrace el1_sync_handler(struct pt_regs *regs)
 	case ESR_ELx_EC_BRK64:
 		el1_dbg(regs, esr);
 		break;
+	case ESR_ELx_EC_FPAC:
+		el1_fpac(regs, esr);
+		break;
 	default:
 		el1_inv(regs, esr);
 	}
@@ -227,6 +237,14 @@ static void notrace el0_svc(struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(el0_svc);
 
+static void notrace el0_fpac(struct pt_regs *regs, unsigned long esr)
+{
+	user_exit_irqoff();
+	local_daif_restore(DAIF_PROCCTX);
+	do_ptrauth_fault(regs, esr);
+}
+NOKPROBE_SYMBOL(el0_fpac);
+
 asmlinkage void notrace el0_sync_handler(struct pt_regs *regs)
 {
 	unsigned long esr = read_sysreg(esr_el1);
@@ -272,6 +290,9 @@ asmlinkage void notrace el0_sync_handler(struct pt_regs *regs)
 	case ESR_ELx_EC_BRK64:
 		el0_dbg(regs, esr);
 		break;
+	case ESR_ELx_EC_FPAC:
+		el0_fpac(regs, esr);
+		break;
 	default:
 		el0_inv(regs, esr);
 	}
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 47f651df781c..0f1e587393a0 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -479,6 +479,15 @@ void do_bti(struct pt_regs *regs)
 }
 NOKPROBE_SYMBOL(do_bti);
 
+void do_ptrauth_fault(struct pt_regs *regs, unsigned long esr)
+{
+	/* In-kernel Pointer authentication fault causes kernel crash */
+	BUG_ON(!user_mode(regs));
+	arm64_notify_die("pointer authentication fault", regs, SIGILL,
+			 ILL_ILLOPN, (void __user *)regs->pc, esr);
+}
+NOKPROBE_SYMBOL(do_ptrauth_fault);
+
 #define __user_cache_maint(insn, address, res)			\
 	if (address >= user_addr_max()) {			\
 		res = -EFAULT;					\
@@ -775,6 +784,7 @@ static const char *esr_class_str[] = {
 	[ESR_ELx_EC_SYS64]		= "MSR/MRS (AArch64)",
 	[ESR_ELx_EC_SVE]		= "SVE",
 	[ESR_ELx_EC_ERET]		= "ERET/ERETAA/ERETAB",
+	[ESR_ELx_EC_FPAC]		= "FPAC",
 	[ESR_ELx_EC_IMP_DEF]		= "EL3 IMP DEF",
 	[ESR_ELx_EC_IABT_LOW]		= "IABT (lower EL)",
 	[ESR_ELx_EC_IABT_CUR]		= "IABT (current EL)",
-- 
2.17.1


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  reply	other threads:[~2020-07-10  8:02 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-10  8:00 [PATCH v4 0/4] arm64: add Armv8.3 pointer authentication enhancements Amit Daniel Kachhap
2020-07-10  8:00 ` Amit Daniel Kachhap [this message]
2020-07-29 11:07   ` [PATCH v4 1/4] arm64: ptrauth: add Armv8.3 pointer authentication enhanced features Dave Martin
2020-08-03 10:13     ` Amit Kachhap
2020-07-10  8:00 ` [PATCH v4 2/4] arm64: cpufeature: Modify address authentication cpufeature to exact Amit Daniel Kachhap
2020-07-29 10:36   ` Dave Martin
2020-07-29 12:28     ` Suzuki K Poulose
2020-07-29 14:31       ` Dave Martin
2020-07-29 17:09         ` Suzuki K Poulose
2020-08-05  9:16           ` Amit Kachhap
2020-07-10  8:00 ` [PATCH v4 3/4] arm64: kprobe: disable probe of fault prone ptrauth instruction Amit Daniel Kachhap
2020-07-29 10:43   ` Dave Martin
2020-08-03 10:16     ` Amit Kachhap
2020-07-10  8:00 ` [PATCH v4 4/4] arm64: kprobe: clarify the comment of steppable hint instructions Amit Daniel Kachhap
2020-07-29 10:44   ` Dave Martin

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