diff options
Diffstat (limited to 'arch/x86/lib/clear_page_64.S')
| -rw-r--r-- | arch/x86/lib/clear_page_64.S | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S new file mode 100644 index 00000000..f2145cfa --- /dev/null +++ b/arch/x86/lib/clear_page_64.S @@ -0,0 +1,73 @@ +#include <linux/linkage.h> +#include <asm/dwarf2.h> +#include <asm/alternative-asm.h> + +/* + * Zero a page. + * rdi page + */ +ENTRY(clear_page_c) + CFI_STARTPROC + movl $4096/8,%ecx + xorl %eax,%eax + rep stosq + ret + CFI_ENDPROC +ENDPROC(clear_page_c) + +ENTRY(clear_page_c_e) + CFI_STARTPROC + movl $4096,%ecx + xorl %eax,%eax + rep stosb + ret + CFI_ENDPROC +ENDPROC(clear_page_c_e) + +ENTRY(clear_page) + CFI_STARTPROC + xorl %eax,%eax + movl $4096/64,%ecx + .p2align 4 +.Lloop: + decl %ecx +#define PUT(x) movq %rax,x*8(%rdi) + movq %rax,(%rdi) + PUT(1) + PUT(2) + PUT(3) + PUT(4) + PUT(5) + PUT(6) + PUT(7) + leaq 64(%rdi),%rdi + jnz .Lloop + nop + ret + CFI_ENDPROC +.Lclear_page_end: +ENDPROC(clear_page) + + /* + * Some CPUs support enhanced REP MOVSB/STOSB instructions. + * It is recommended to use this when possible. + * If enhanced REP MOVSB/STOSB is not available, try to use fast string. + * Otherwise, use original function. + * + */ + +#include <asm/cpufeature.h> + + .section .altinstr_replacement,"ax" +1: .byte 0xeb /* jmp <disp8> */ + .byte (clear_page_c - clear_page) - (2f - 1b) /* offset */ +2: .byte 0xeb /* jmp <disp8> */ + .byte (clear_page_c_e - clear_page) - (3f - 2b) /* offset */ +3: + .previous + .section .altinstructions,"a" + altinstruction_entry clear_page,1b,X86_FEATURE_REP_GOOD,\ + .Lclear_page_end-clear_page, 2b-1b + altinstruction_entry clear_page,2b,X86_FEATURE_ERMS, \ + .Lclear_page_end-clear_page,3b-2b + .previous |