arm64/cpufeature: detect pointer authentication

So that we can dynamically handle the presence of pointer authentication
functionality, wire up probing code in cpufeature.c.

From ARMv8.3 onwards, ID_AA64ISAR1 is no longer entirely RES0, and now
has four fields describing the presence of pointer authentication
functionality:

* APA - address authentication present, using an architected algorithm
* API - address authentication present, using an IMP DEF algorithm
* GPA - generic authentication present, using an architected algorithm
* GPI - generic authentication present, using an IMP DEF algorithm

This patch checks for both address and generic authentication,
separately. It is assumed that if all CPUs support an IMP DEF algorithm,
the same algorithm is used across all CPUs.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 38e674f6e18b..daec4b50d7fb 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -565,6 +565,18 @@ static inline bool system_supports_cnp(void)
 		cpus_have_const_cap(ARM64_HAS_CNP);
 }
 
+static inline bool system_supports_address_auth(void)
+{
+	return IS_ENABLED(CONFIG_ARM64_PTR_AUTH) &&
+		cpus_have_const_cap(ARM64_HAS_ADDRESS_AUTH);
+}
+
+static inline bool system_supports_generic_auth(void)
+{
+	return IS_ENABLED(CONFIG_ARM64_PTR_AUTH) &&
+		cpus_have_const_cap(ARM64_HAS_GENERIC_AUTH);
+}
+
 #define ARM64_SSBD_UNKNOWN		-1
 #define ARM64_SSBD_FORCE_DISABLE	0
 #define ARM64_SSBD_KERNEL		1