arm64: add basic pointer authentication support

This patch adds basic support for pointer authentication, allowing
userspace to make use of APIAKey, APIBKey, APDAKey, APDBKey, and
APGAKey. The kernel maintains key values for each process (shared by all
threads within), which are initialised to random values at exec() time.

The ID_AA64ISAR1_EL1.{APA,API,GPA,GPI} fields are exposed to userspace,
to describe that pointer authentication instructions are available and
that the kernel is managing the keys. Two new hwcaps are added for the
same reason: PACA (for address authentication) and PACG (for generic
authentication).

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>
Tested-by: Adam Wallis <awallis@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Ramana Radhakrishnan <ramana.radhakrishnan@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
[will: Fix sizeof() usage and unroll address key initialisation]
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
index 7cb0b08ab0a7..ca0685f33900 100644
--- a/arch/arm64/kernel/cpuinfo.c
+++ b/arch/arm64/kernel/cpuinfo.c
@@ -83,6 +83,8 @@ static const char *const hwcap_str[] = {
 	"flagm",
 	"ssbs",
 	"sb",
+	"paca",
+	"pacg",
 	NULL
 };