arch/x86/lib/clear_page_64.S

   1 #include <linux/linkage.h>
   2 #include <asm/cpufeatures.h>
   3 #include <asm/alternative-asm.h>
   4 #include <asm/export.h>
   5
   6 /*
   7  * Most CPUs support enhanced REP MOVSB/STOSB instructions. It is
   8  * recommended to use this when possible and we do use them by default.
   9  * If enhanced REP MOVSB/STOSB is not available, try to use fast string.
  10  * Otherwise, use original.
  11  */
  12
  13 /*
  14  * Zero a page.
  15  * %rdi - page
  16  */
  17 ENTRY(clear_page)
  18
  19         ALTERNATIVE_2 "jmp clear_page_orig", "", X86_FEATURE_REP_GOOD, \
  20                       "jmp clear_page_c_e", X86_FEATURE_ERMS
  21
  22         movl $4096/8,%ecx
  23         xorl %eax,%eax
  24         rep stosq
  25         ret
  26 ENDPROC(clear_page)
  27 EXPORT_SYMBOL(clear_page)
  28
  29 ENTRY(clear_page_orig)
  30
  31         xorl   %eax,%eax
  32         movl   $4096/64,%ecx
  33         .p2align 4
  34 .Lloop:
  35         decl    %ecx
  36 #define PUT(x) movq %rax,x*8(%rdi)
  37         movq %rax,(%rdi)
  38         PUT(1)
  39         PUT(2)
  40         PUT(3)
  41         PUT(4)
  42         PUT(5)
  43         PUT(6)
  44         PUT(7)
  45         leaq    64(%rdi),%rdi
  46         jnz     .Lloop
  47         nop
  48         ret
  49 ENDPROC(clear_page_orig)
  50
  51 ENTRY(clear_page_c_e)
  52         movl $4096,%ecx
  53         xorl %eax,%eax
  54         rep stosb
  55         ret
  56 ENDPROC(clear_page_c_e)