LXR linux/arch/x86/lib/clear_page

   1#include <linux/linkage.h>
   2#include <asm/export.h>
   3
   4/*
   5 * Most CPUs support enhanced REP MOVSB/STOSB instructions. It is
   6 * recommended to use this when possible and we do use them by default.
   7 * If enhanced REP MOVSB/STOSB is not available, try to use fast string.
   8 * Otherwise, use original.
   9 */
  10
  11/*
  12 * Zero a page.
  13 * %rdi - page
  14 */
  15ENTRY(clear_page_rep)
  16        movl $4096/8,%ecx
  17        xorl %eax,%eax
  18        rep stosq
  19        ret
  20ENDPROC(clear_page_rep)
  21EXPORT_SYMBOL_GPL(clear_page_rep)
  22
  23ENTRY(clear_page_orig)
  24        xorl   %eax,%eax
  25        movl   $4096/64,%ecx
  26        .p2align 4
  27.Lloop:
  28        decl    %ecx
  29#define PUT(x) movq %rax,x*8(%rdi)
  30        movq %rax,(%rdi)
  31        PUT(1)
  32        PUT(2)
  33        PUT(3)
  34        PUT(4)
  35        PUT(5)
  36        PUT(6)
  37        PUT(7)
  38        leaq    64(%rdi),%rdi
  39        jnz     .Lloop
  40        nop
  41        ret
  42ENDPROC(clear_page_orig)
  43EXPORT_SYMBOL_GPL(clear_page_orig)
  44
  45ENTRY(clear_page_erms)
  46        movl $4096,%ecx
  47        xorl %eax,%eax
  48        rep stosb
  49        ret
  50ENDPROC(clear_page_erms)
  51EXPORT_SYMBOL_GPL(clear_page_erms)
  52