arm64: cpufeature: Detect SSBS and advertise to userspace

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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>

...

This commit is contained in:

Will Deacon 2018-06-15 11:37:34 +01:00 • committed by Catalin Marinas

parent ca7f686ac9

commit d71be2b6c0

5 changed files with 33 additions and 7 deletions

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3

arch/arm64/include/asm/cpucaps.h

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16

arch/arm64/include/asm/sysreg.h

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1

arch/arm64/include/uapi/asm/hwcap.h

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19

arch/arm64/kernel/cpufeature.c

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1

arch/arm64/kernel/cpuinfo.c

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