arm64: uaccess: Don't bother eliding access_ok checks in __{get, put}_user

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access_ok isn't an expensive operation once the addr_limit for the current
thread has been loaded into the cache. Given that the initial access_ok
check preceding a sequence of __{get,put}_user operations will take
the brunt of the miss, we can make the __* variants identical to the
full-fat versions, which brings with it the benefits of address masking.

The likely cost in these sequences will be from toggling PAN/UAO, which
we can address later by implementing the *_unsafe versions.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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Will Deacon 2018-02-05 15:34:22 +00:00 • committed by Catalin Marinas

parent c2f0ad4fc0

commit 84624087dd

1 changed files with 32 additions and 22 deletions

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arch/arm64/include/asm/uaccess.h

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