LXR linux/arch/x86/lib/clear_page

   1/* SPDX-License-Identifier: GPL-2.0-only */
   2#include <linux/linkage.h>
   3#include <asm/export.h>
   4
   5/*
   6 * Most CPUs support enhanced REP MOVSB/STOSB instructions. It is
   7 * recommended to use this when possible and we do use them by default.
   8 * If enhanced REP MOVSB/STOSB is not available, try to use fast string.
   9 * Otherwise, use original.
  10 */
  11
  12/*
  13 * Zero a page.
  14 * %rdi - page
  15 */
  16SYM_FUNC_START(clear_page_rep)
  17        movl $4096/8,%ecx
  18        xorl %eax,%eax
  19        rep stosq
  20        ret
  21SYM_FUNC_END(clear_page_rep)
  22EXPORT_SYMBOL_GPL(clear_page_rep)
  23
  24SYM_FUNC_START(clear_page_orig)
  25        xorl   %eax,%eax
  26        movl   $4096/64,%ecx
  27        .p2align 4
  28.Lloop:
  29        decl    %ecx
  30#define PUT(x) movq %rax,x*8(%rdi)
  31        movq %rax,(%rdi)
  32        PUT(1)
  33        PUT(2)
  34        PUT(3)
  35        PUT(4)
  36        PUT(5)
  37        PUT(6)
  38        PUT(7)
  39        leaq    64(%rdi),%rdi
  40        jnz     .Lloop
  41        nop
  42        ret
  43SYM_FUNC_END(clear_page_orig)
  44EXPORT_SYMBOL_GPL(clear_page_orig)
  45
  46SYM_FUNC_START(clear_page_erms)
  47        movl $4096,%ecx
  48        xorl %eax,%eax
  49        rep stosb
  50        ret
  51SYM_FUNC_END(clear_page_erms)
  52EXPORT_SYMBOL_GPL(clear_page_erms)
  53