[PATCH v2 1/2] arm64: errata: Remove AES hwcap for COMPAT tasks

[James Morse <james.morse@arm.com>]

Cortex-A57 and Cortex-A72 have an erratum where an interrupt that
occurs between a pair of AES instructions in aarch32 mode may corrupt
the ELR. The task will subsequently produce the wrong AES result.

The AES instructions are part of the cryptographic extensions, which are
optional. User-space software will detect the support for these
instructions from the hwcaps. If the platform doesn't support these
instructions a software implementation should be used.

Remove the hwcap bits on affected parts to indicate user-space should
not use the AES instructions.

Signed-off-by: James Morse <james.morse@arm.com>
---
 Documentation/arm64/silicon-errata.rst |  4 ++++
 arch/arm64/Kconfig                     | 16 ++++++++++++++++
 arch/arm64/kernel/cpu_errata.c         | 16 ++++++++++++++++
 arch/arm64/kernel/cpufeature.c         | 11 ++++++++++-
 arch/arm64/tools/cpucaps               |  1 +
 5 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
index 466cb9e89047..053dc12696b5 100644
--- a/Documentation/arm64/silicon-errata.rst
+++ b/Documentation/arm64/silicon-errata.rst
@@ -82,10 +82,14 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A57      | #1319537        | ARM64_ERRATUM_1319367       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-A57      | #1742098        | ARM64_ERRATUM_1742098       |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A72      | #853709         | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A72      | #1319367        | ARM64_ERRATUM_1319367       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-A72      | #1655431        | ARM64_ERRATUM_1742098       |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A73      | #858921         | ARM64_ERRATUM_858921        |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A76      | #1188873,1418040| ARM64_ERRATUM_1418040       |
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 57c4c995965f..df19e60c4c46 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -491,6 +491,22 @@ config ARM64_ERRATUM_834220
 
 	  If unsure, say Y.
 
+config ARM64_ERRATUM_1742098
+	bool "Cortex-A57/A72: 1742098: ELR recorded incorrectly on interrupt taken between cryptographic instructions in a sequence"
+	depends on COMPAT
+	default y
+	help
+	  This option removes the AES hwcap for aarch32 user-space to
+	  workaround erratum 1742098 on Cortex-A57 and Cortex-A72.
+
+	  Affected parts may corrupt the AES state if an interrupt is
+	  taken between a pair of AES instructions. These instructions
+	  are only present if the cryptography extensions are present.
+	  All software should have a fallback implementation for CPUs
+	  that don't implement the cryptography extensions.
+
+	  If unsure, say Y.
+
 config ARM64_ERRATUM_845719
 	bool "Cortex-A53: 845719: a load might read incorrect data"
 	depends on COMPAT
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 4c9b5b4b7a0b..8f85dac4cd79 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -393,6 +393,14 @@ static struct midr_range trbe_write_out_of_range_cpus[] = {
 };
 #endif /* CONFIG_ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE */
 
+#ifdef CONFIG_ARM64_ERRATUM_1742098
+static struct midr_range broken_aarch32_aes[] = {
+	MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
+	MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
+	{},
+};
+#endif /* CONFIG_ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE */
+
 const struct arm64_cpu_capabilities arm64_errata[] = {
 #ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
 	{
@@ -655,6 +663,14 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		/* Cortex-A510 r0p0 - r0p1 */
 		ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A510, 0, 0, 1)
 	},
+#endif
+#ifdef CONFIG_ARM64_ERRATUM_1742098
+	{
+		.desc = "ARM erratum 1742098",
+		.capability = ARM64_WORKAROUND_1742098,
+		CAP_MIDR_RANGE_LIST(broken_aarch32_aes),
+		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
+	},
 #endif
 	{
 	}
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index d72c4b4d389c..3faf16f1c040 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1922,6 +1922,12 @@ static void cpu_enable_mte(struct arm64_cpu_capabilities const *cap)
 }
 #endif /* CONFIG_ARM64_MTE */
 
+static void elf_hwcap_fixup(void)
+{
+	if (cpus_have_const_cap(ARM64_WORKAROUND_1742098))
+		compat_elf_hwcap2 &= ~COMPAT_HWCAP2_AES;
+}
+
 #ifdef CONFIG_KVM
 static bool is_kvm_protected_mode(const struct arm64_cpu_capabilities *entry, int __unused)
 {
@@ -3034,8 +3040,10 @@ void __init setup_cpu_features(void)
 	setup_system_capabilities();
 	setup_elf_hwcaps(arm64_elf_hwcaps);
 
-	if (system_supports_32bit_el0())
+	if (system_supports_32bit_el0()) {
 		setup_elf_hwcaps(compat_elf_hwcaps);
+		elf_hwcap_fixup();
+	}
 
 	if (system_uses_ttbr0_pan())
 		pr_info("emulated: Privileged Access Never (PAN) using TTBR0_EL1 switching\n");
@@ -3087,6 +3095,7 @@ static int enable_mismatched_32bit_el0(unsigned int cpu)
 							 cpu_active_mask);
 	get_cpu_device(lucky_winner)->offline_disabled = true;
 	setup_elf_hwcaps(compat_elf_hwcaps);
+	elf_hwcap_fixup();
 	pr_info("Asymmetric 32-bit EL0 support detected on CPU %u; CPU hot-unplug disabled on CPU %u\n",
 		cpu, lucky_winner);
 	return 0;
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 3ed418f70e3b..8cd6088f8875 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -58,6 +58,7 @@ WORKAROUND_1418040
 WORKAROUND_1463225
 WORKAROUND_1508412
 WORKAROUND_1542419
+WORKAROUND_1742098
 WORKAROUND_1902691
 WORKAROUND_2038923
 WORKAROUND_2064142
-- 
2.30.2


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