[PATCH v2 2/4] arm64: cpufeature: Warn if mutually exclusive PAuth algorithms detected

From: Vladimir Murzin <vladimir.murzin@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: maz@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com,
	will@kernel.org
Subject: [PATCH v2 2/4] arm64: cpufeature: Warn if mutually exclusive PAuth algorithms detected
Date: Mon, 31 Jan 2022 17:06:52 +0000	[thread overview]
Message-ID: <20220131170654.62381-3-vladimir.murzin@arm.com> (raw)
In-Reply-To: <20220131170654.62381-1-vladimir.murzin@arm.com>

ARM ARM states for address authentication algorithms

APA, bits [7:4] If the value of ID_AA64ISAR1_EL1.API is non-zero, this
                field must have the value 0b0000.

API, bits [11:8] If the value of ID_AA64ISAR1_EL1.APA is non-zero,
                 this field must have the value 0b0000.

Similarly for generic code authentication algorithms

GPA, bits [27:24] If the value of ID_AA64ISAR1_EL1.GPI is non-zero,
                  this field must have the value 0b0000.

GPI, bits [31:28] If the value of ID_AA64ISAR1_EL1.GPA is non-zero,
                  this field must have the value 0b0000.

Let's add a warning if that not true.

Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
---
 arch/arm64/kernel/cpufeature.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index b0ec125..9dad0a3 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1832,15 +1832,23 @@ static bool has_address_auth_cpucap(const struct arm64_cpu_capabilities *entry,
 static bool has_address_auth_metacap(const struct arm64_cpu_capabilities *entry,
 				     int scope)
 {
-	return has_address_auth_cpucap(cpu_hwcaps_ptrs[ARM64_HAS_ADDRESS_AUTH_ARCH], scope) ||
-	       has_address_auth_cpucap(cpu_hwcaps_ptrs[ARM64_HAS_ADDRESS_AUTH_IMP_DEF], scope);
+	bool api = has_address_auth_cpucap(cpu_hwcaps_ptrs[ARM64_HAS_ADDRESS_AUTH_IMP_DEF], scope);
+	bool apa = has_address_auth_cpucap(cpu_hwcaps_ptrs[ARM64_HAS_ADDRESS_AUTH_ARCH], scope);
+
+	WARN_ON(apa && api);
+
+	return apa || api;
 }
 
 static bool has_generic_auth(const struct arm64_cpu_capabilities *entry,
 			     int __unused)
 {
-	return __system_matches_cap(ARM64_HAS_GENERIC_AUTH_ARCH) ||
-	       __system_matches_cap(ARM64_HAS_GENERIC_AUTH_IMP_DEF);
+	bool gpi = __system_matches_cap(ARM64_HAS_GENERIC_AUTH_IMP_DEF);
+	bool gpa = __system_matches_cap(ARM64_HAS_GENERIC_AUTH_ARCH);
+
+	WARN_ON(gpa && gpi);
+
+	return gpa || gpi;
 }
 #endif /* CONFIG_ARM64_PTR_AUTH */
 
-- 
2.7.4


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