diff options
Diffstat (limited to 'arch/x86/lib/memcpy_64.S')
| -rw-r--r-- | arch/x86/lib/memcpy_64.S | 68 |
1 files changed, 21 insertions, 47 deletions
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S index 89b53c9968e7..b046664f5a1c 100644 --- a/arch/x86/lib/memcpy_64.S +++ b/arch/x86/lib/memcpy_64.S @@ -1,12 +1,20 @@ /* 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. * * Input: @@ -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 - -.weak memcpy +ENDPROC(memcpy_erms) -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 - altinstruction_entry __memcpy,.Lmemcpy_c_e,X86_FEATURE_ERMS, \ - .Lmemcpy_e_e-.Lmemcpy_c_e,.Lmemcpy_e_e-.Lmemcpy_c_e - .previous +ENDPROC(memcpy_orig) |