root/arch/x86/lib/clear_page_64.S

   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  */
  16 ENTRY(clear_page_rep)
  17         movl $4096/8,%ecx
  18         xorl %eax,%eax
  19         rep stosq
  20         ret
  21 ENDPROC(clear_page_rep)
  22 EXPORT_SYMBOL_GPL(clear_page_rep)
  23 
  24 ENTRY(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
  43 ENDPROC(clear_page_orig)
  44 EXPORT_SYMBOL_GPL(clear_page_orig)
  45 
  46 ENTRY(clear_page_erms)
  47         movl $4096,%ecx
  48         xorl %eax,%eax
  49         rep stosb
  50         ret
  51 ENDPROC(clear_page_erms)
  52 EXPORT_SYMBOL_GPL(clear_page_erms)