arch/x86/lib/clear_page_64.S

   1 #include <linux/linkage.h>
   2 #include <asm/dwarf2.h>
   3
   4 /*
   5  * Zero a page.
   6  * rdi  page
   7  */
   8         ALIGN
   9 clear_page_c:
  10         CFI_STARTPROC
  11         movl $4096/8,%ecx
  12         xorl %eax,%eax
  13         rep stosq
  14         ret
  15         CFI_ENDPROC
  16 ENDPROC(clear_page)
  17
  18 ENTRY(clear_page)
  19         CFI_STARTPROC
  20         xorl   %eax,%eax
  21         movl   $4096/64,%ecx
  22         .p2align 4
  23 .Lloop:
  24         decl    %ecx
  25 #define PUT(x) movq %rax,x*8(%rdi)
  26         movq %rax,(%rdi)
  27         PUT(1)
  28         PUT(2)
  29         PUT(3)
  30         PUT(4)
  31         PUT(5)
  32         PUT(6)
  33         PUT(7)
  34         leaq    64(%rdi),%rdi
  35         jnz     .Lloop
  36         nop
  37         ret
  38         CFI_ENDPROC
  39 .Lclear_page_end:
  40 ENDPROC(clear_page)
  41
  42         /* Some CPUs run faster using the string instructions.
  43            It is also a lot simpler. Use this when possible */
  44
  45 #include <asm/cpufeature.h>
  46
  47         .section .altinstr_replacement,"ax"
  48 1:      .byte 0xeb                                      /* jmp <disp8> */
  49         .byte (clear_page_c - clear_page) - (2f - 1b)   /* offset */
  50 2:
  51         .previous
  52         .section .altinstructions,"a"
  53         .align 8
  54         .quad clear_page
  55         .quad 1b
  56         .byte X86_FEATURE_REP_GOOD
  57         .byte .Lclear_page_end - clear_page
  58         .byte 2b - 1b
  59         .previous