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Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 asm updates from Ingo Molnar:
 "A single commit micro-optimizing short user copies on certain Intel
  CPUs"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/uaccess: Optimize copy_user_enhanced_fast_string() for short strings
This commit is contained in:
Linus Torvalds 2017-07-03 13:38:28 -07:00
parent 2a275382a4 236222d393
commit 48b5259cf0
1 changed files with 5 additions and 2 deletions
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7
arch/x86/lib/copy_user_64.S
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@ -37,7 +37,7 @@ ENTRY(copy_user_generic_unrolled)
movl %edx,%ecx movl %edx,%ecx
andl $63,%edx andl $63,%edx
shrl $6,%ecx shrl $6,%ecx
jz 17f jz .L_copy_short_string
1: movq (%rsi),%r8 1: movq (%rsi),%r8
2: movq 1*8(%rsi),%r9 2: movq 1*8(%rsi),%r9
3: movq 2*8(%rsi),%r10 3: movq 2*8(%rsi),%r10
@ -58,7 +58,8 @@ ENTRY(copy_user_generic_unrolled)
leaq 64(%rdi),%rdi leaq 64(%rdi),%rdi
decl %ecx decl %ecx
jnz 1b jnz 1b
17: movl %edx,%ecx .L_copy_short_string:
movl %edx,%ecx
andl $7,%edx andl $7,%edx
shrl $3,%ecx shrl $3,%ecx
jz 20f jz 20f
@ -174,6 +175,8 @@ EXPORT_SYMBOL(copy_user_generic_string)
*/ */
ENTRY(copy_user_enhanced_fast_string) ENTRY(copy_user_enhanced_fast_string)
ASM_STAC ASM_STAC
cmpl $64,%edx
jb .L_copy_short_string /* less then 64 bytes, avoid the costly 'rep' */
movl %edx,%ecx movl %edx,%ecx
1: rep 1: rep
movsb movsb