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x86/lib/memcpy_64.S: Convert memcpy to ALTERNATIVE_2 macro

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Make REP_GOOD variant the default after alternatives have run.

Signed-off-by: Borislav Petkov <bp@suse.de>
This commit is contained in:
Borislav Petkov 2015-02-04 15:36:49 +01:00
parent a77600cd03
commit e0bc8d179e
1 changed files with 21 additions and 47 deletions
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68
arch/x86/lib/memcpy_64.S
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@ -1,11 +1,19 @@
/* Copyright 2002 Andi Kleen */
#include <linux/linkage.h>
#include <asm/cpufeature.h>
#include <asm/dwarf2.h>
#include <asm/alternative-asm.h>
/*
* We build a jump to memcpy_orig by default which gets NOPped out on
* the majority of x86 CPUs which set REP_GOOD. In addition, CPUs which
* have the enhanced REP MOVSB/STOSB feature (ERMS), change those NOPs
* to a jmp to memcpy_erms which does the REP; MOVSB mem copy.
*/
.weak memcpy
/*
* memcpy - Copy a memory block.
*
@ -17,15 +25,11 @@
* Output:
* rax original destination
*/
ENTRY(__memcpy)
ENTRY(memcpy)
ALTERNATIVE_2 "jmp memcpy_orig", "", X86_FEATURE_REP_GOOD, \
"jmp memcpy_erms", X86_FEATURE_ERMS
/*
* memcpy_c() - fast string ops (REP MOVSQ) based variant.
*
* This gets patched over the unrolled variant (below) via the
* alternative instructions framework:
*/
.section .altinstr_replacement, "ax", @progbits
.Lmemcpy_c:
movq %rdi, %rax
movq %rdx, %rcx
shrq $3, %rcx
@ -34,29 +38,21 @@
movl %edx, %ecx
rep movsb
ret
.Lmemcpy_e:
.previous
ENDPROC(memcpy)
ENDPROC(__memcpy)
/*
* memcpy_c_e() - enhanced fast string memcpy. This is faster and simpler than
* memcpy_c. Use memcpy_c_e when possible.
*
* This gets patched over the unrolled variant (below) via the
* alternative instructions framework:
* memcpy_erms() - enhanced fast string memcpy. This is faster and
* simpler than memcpy. Use memcpy_erms when possible.
*/
.section .altinstr_replacement, "ax", @progbits
.Lmemcpy_c_e:
ENTRY(memcpy_erms)
movq %rdi, %rax
movq %rdx, %rcx
rep movsb
ret
.Lmemcpy_e_e:
.previous
ENDPROC(memcpy_erms)
.weak memcpy
ENTRY(__memcpy)
ENTRY(memcpy)
ENTRY(memcpy_orig)
CFI_STARTPROC
movq %rdi, %rax
@ -183,26 +179,4 @@ ENTRY(memcpy)
.Lend:
retq
CFI_ENDPROC
ENDPROC(memcpy)
ENDPROC(__memcpy)
/*
* Some CPUs are adding enhanced REP MOVSB/STOSB feature
* If the feature is supported, memcpy_c_e() is the first choice.
* If enhanced rep movsb copy is not available, use fast string copy
* memcpy_c() when possible. This is faster and code is simpler than
* original memcpy().
* Otherwise, original memcpy() is used.
* In .altinstructions section, ERMS feature is placed after REG_GOOD
* feature to implement the right patch order.
*
* Replace only beginning, memcpy is used to apply alternatives,
* so it is silly to overwrite itself with nops - reboot is the
* only outcome...
*/
.section .altinstructions, "a"
altinstruction_entry __memcpy,.Lmemcpy_c,X86_FEATURE_REP_GOOD,\
.Lmemcpy_e-.Lmemcpy_c,.Lmemcpy_e-.Lmemcpy_c,0
altinstruction_entry __memcpy,.Lmemcpy_c_e,X86_FEATURE_ERMS, \
.Lmemcpy_e_e-.Lmemcpy_c_e,.Lmemcpy_e_e-.Lmemcpy_c_e,0
.previous
ENDPROC(memcpy_orig)