Commit-ID: 84d95ad4cb9015ea953bf14cea05ba371d4d42bb Gitweb: http://git.kernel.org/tip/84d95ad4cb9015ea953bf14cea05ba371d4d42bb Author: Borislav Petkov <bp@xxxxxxx> AuthorDate: Wed, 4 Feb 2015 08:57:00 +0100 Committer: Borislav Petkov <bp@xxxxxxx> CommitDate: Mon, 23 Feb 2015 13:50:59 +0100 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@xxxxxxx> --- arch/x86/lib/memset_64.S | 61 +++++++++++++++++++----------------------------- 1 file changed, 24 insertions(+), 37 deletions(-) diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S index f6153c1..93118fb 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) -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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