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arm64: Turn on KPTI only on CPUs that need it

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Commit 0ba2e29c7fc1 upstream.

Whitelist Broadcom Vulcan/Cavium ThunderX2 processors in
unmap_kernel_at_el0(). These CPUs are not vulnerable to
CVE-2017-5754 and do not need KPTI when KASLR is off.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jayachandran C <jnair@caviumnetworks.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jayachandran C 2018-01-19 04:22:48 -08:00 committed by Greg Kroah-Hartman
parent 7aca19ea5a
commit c98c8c2358
1 changed files with 7 additions and 0 deletions
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7
arch/arm64/kernel/cpufeature.c
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@ -816,6 +816,13 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
return true;
/* Don't force KPTI for CPUs that are not vulnerable */
switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) {
case MIDR_CAVIUM_THUNDERX2:
case MIDR_BRCM_VULCAN:
return false;
}
/* Defer to CPU feature registers */
return !cpuid_feature_extract_unsigned_field(pfr0,
ID_AA64PFR0_CSV3_SHIFT);