summaryrefslogtreecommitdiff
path: root/arch
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2017-07-03 23:38:28 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-03 23:38:28 +0300
commit48b5259cf0a2b86b978da122f9459e22a2d1e8f6 (patch)
treeced4acaed86bc4529458dd6b246ccae2ff2f0793 /arch
parent2a275382a4f78f386db3473d9bb9987580de3cf4 (diff)
parent236222d39347e0e486010f10c1493e83dbbdfba8 (diff)
downloadlinux-48b5259cf0a2b86b978da122f9459e22a2d1e8f6.tar.xz
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
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/lib/copy_user_64.S7
1 files changed, 5 insertions, 2 deletions
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index c5959576c315..020f75cc8cf6 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -37,7 +37,7 @@ ENTRY(copy_user_generic_unrolled)
movl %edx,%ecx
andl $63,%edx
shrl $6,%ecx
- jz 17f
+ jz .L_copy_short_string
1: movq (%rsi),%r8
2: movq 1*8(%rsi),%r9
3: movq 2*8(%rsi),%r10
@@ -58,7 +58,8 @@ ENTRY(copy_user_generic_unrolled)
leaq 64(%rdi),%rdi
decl %ecx
jnz 1b
-17: movl %edx,%ecx
+.L_copy_short_string:
+ movl %edx,%ecx
andl $7,%edx
shrl $3,%ecx
jz 20f
@@ -174,6 +175,8 @@ EXPORT_SYMBOL(copy_user_generic_string)
*/
ENTRY(copy_user_enhanced_fast_string)
ASM_STAC
+ cmpl $64,%edx
+ jb .L_copy_short_string /* less then 64 bytes, avoid the costly 'rep' */
movl %edx,%ecx
1: rep
movsb