x86: Add 1/2/4/8 byte optimization to 64bit __copy_{from,to}_user_inatomic

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The 64bit __copy_{from,to}_user_inatomic always called
copy_from_user_generic, but skipped the special optimizations for 1/2/4/8
byte accesses.

This especially hurts the futex call, which accesses the 4 byte futex
user value with a complicated fast string operation in a function call,
instead of a single movl.

Use __copy_{from,to}_user for _inatomic instead to get the same
optimizations. The only problem was the might_fault() in those functions.
So move that to new wrapper and call __copy_{f,t}_user_nocheck()
from *_inatomic directly.

32bit already did this correctly by duplicating the code.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1376687844-19857-2-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

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Andi Kleen 2013-08-16 14:17:19 -07:00 • committed by H. Peter Anvin

parent 6e4664525b

commit ff47ab4ff3

1 changed files with 18 additions and 6 deletions

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arch/x86/include/asm/uaccess_64.h

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