arm64: entry: Add fake CPU feature for unmapping the kernel at EL0

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Commit ea1e3de85e upstream.

Allow explicit disabling of the entry trampoline on the kernel command
line (kpti=off) by adding a fake CPU feature (ARM64_UNMAP_KERNEL_AT_EL0)
that can be used to toggle the alternative sequences in our entry code and
avoid use of the trampoline altogether if desired. This also allows us to
make use of a static key in arm64_kernel_unmapped_at_el0().

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
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>

...

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Will Deacon 2017-11-14 14:38:19 +00:00 • committed by Greg Kroah-Hartman

parent 2843ade2da

commit 7fafcbb04f

4 changed files with 50 additions and 6 deletions

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3

arch/arm64/include/asm/cpucaps.h

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3

arch/arm64/include/asm/mmu.h

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41

arch/arm64/kernel/cpufeature.c

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9

arch/arm64/kernel/entry.S

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