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>
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ca7f686a
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