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authorBorislav Petkov <bp@suse.de>2015-02-04 08:57:00 +0100
committerBorislav Petkov <bp@suse.de>2015-02-23 13:50:59 +0100
commit84d95ad4cb9015ea953bf14cea05ba371d4d42bb (patch)
tree92667e47bc9e3dfee4c147141da1cf0d07777b13 /arch/x86/lib
parenta930dc4543a2b213deb9fde12682716edff8a4a6 (diff)
downloadlinux-84d95ad4cb9015ea953bf14cea05ba371d4d42bb.tar.bz2
x86/lib/memset_64.S: Convert to ALTERNATIVE_2 macro
Make alternatives replace single JMPs instead of whole memset functions, thus decreasing the amount of instructions copied during patching time at boot. While at it, make it use the REP_GOOD version by default which means alternatives NOP out the JMP to the other versions, as REP_GOOD is set by default on the majority of relevant x86 processors. Signed-off-by: Borislav Petkov <bp@suse.de>
Diffstat (limited to 'arch/x86/lib')
-rw-r--r--arch/x86/lib/memset_64.S61
1 files changed, 24 insertions, 37 deletions
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index f6153c1cdddc..93118fb23976 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -5,19 +5,30 @@
#include <asm/cpufeature.h>
#include <asm/alternative-asm.h>
+.weak memset
+
/*
* ISO C memset - set a memory block to a byte value. This function uses fast
* string to get better performance than the original function. The code is
* simpler and shorter than the orignal function as well.
- *
+ *
* rdi destination
- * rsi value (char)
- * rdx count (bytes)
- *
+ * rsi value (char)
+ * rdx count (bytes)
+ *
* rax original destination
- */
- .section .altinstr_replacement, "ax", @progbits
-.Lmemset_c:
+ */
+ENTRY(memset)
+ENTRY(__memset)
+ /*
+ * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended
+ * to use it when possible. If not available, use fast string instructions.
+ *
+ * Otherwise, use original memset function.
+ */
+ ALTERNATIVE_2 "jmp memset_orig", "", X86_FEATURE_REP_GOOD, \
+ "jmp memset_erms", X86_FEATURE_ERMS
+
movq %rdi,%r9
movq %rdx,%rcx
andl $7,%edx
@@ -31,8 +42,8 @@
rep stosb
movq %r9,%rax
ret
-.Lmemset_e:
- .previous
+ENDPROC(memset)
+ENDPROC(__memset)
/*
* ISO C memset - set a memory block to a byte value. This function uses
@@ -45,21 +56,16 @@
*
* rax original destination
*/
- .section .altinstr_replacement, "ax", @progbits
-.Lmemset_c_e:
+ENTRY(memset_erms)
movq %rdi,%r9
movb %sil,%al
movq %rdx,%rcx
rep stosb
movq %r9,%rax
ret
-.Lmemset_e_e:
- .previous
-
-.weak memset
+ENDPROC(memset_erms)
-ENTRY(memset)
-ENTRY(__memset)
+ENTRY(memset_orig)
CFI_STARTPROC
movq %rdi,%r10
@@ -134,23 +140,4 @@ ENTRY(__memset)
jmp .Lafter_bad_alignment
.Lfinal:
CFI_ENDPROC
-ENDPROC(memset)
-ENDPROC(__memset)
-
- /* Some CPUs support enhanced REP MOVSB/STOSB feature.
- * It is recommended to use this when possible.
- *
- * If enhanced REP MOVSB/STOSB feature is not available, use fast string
- * instructions.
- *
- * Otherwise, use original memset function.
- *
- * In .altinstructions section, ERMS feature is placed after REG_GOOD
- * feature to implement the right patch order.
- */
- .section .altinstructions,"a"
- altinstruction_entry __memset,.Lmemset_c,X86_FEATURE_REP_GOOD,\
- .Lfinal-__memset,.Lmemset_e-.Lmemset_c,0
- altinstruction_entry __memset,.Lmemset_c_e,X86_FEATURE_ERMS, \
- .Lfinal-__memset,.Lmemset_e_e-.Lmemset_c_e,0
- .previous
+ENDPROC(memset_orig)