arm64: cpufeature: Detect SSBS and advertise to userspace
authorWill Deacon <will.deacon@arm.com>
Fri, 15 Jun 2018 10:37:34 +0000 (11:37 +0100)
committerCatalin Marinas <catalin.marinas@arm.com>
Fri, 14 Sep 2018 16:46:01 +0000 (17:46 +0100)
commitd71be2b6c0e19180b5f80a6d42039cc074a693a2
treea76f555a9b74a6a8e8ed9733e7eac60c6f880ec6
parentca7f686ac9fe87a9175696a8744e095ab9749c49
arm64: cpufeature: Detect SSBS and advertise to userspace

Armv8.5 introduces a new PSTATE bit known as Speculative Store Bypass
Safe (SSBS) which can be used as a mitigation against Spectre variant 4.

Additionally, a CPU may provide instructions to manipulate PSTATE.SSBS
directly, so that userspace can toggle the SSBS control without trapping
to the kernel.

This patch probes for the existence of SSBS and advertise the new instructions
to userspace if they exist.

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arch/arm64/include/asm/cpucaps.h
arch/arm64/include/asm/sysreg.h
arch/arm64/include/uapi/asm/hwcap.h
arch/arm64/kernel/cpufeature.c
arch/arm64/kernel/cpuinfo.c