arch/x86/lib/clear_page_64.S

   1 #include <linux/linkage.h>
   2 #include <asm/dwarf2.h>
   3 #include <asm/alternative-asm.h>
   4
   5 /*
   6  * Zero a page.
   7  * rdi  page
   8  */
   9 ENTRY(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_c)
  17
  18 ENTRY(clear_page_c_e)
  19         CFI_STARTPROC
  20         movl $4096,%ecx
  21         xorl %eax,%eax
  22         rep stosb
  23         ret
  24         CFI_ENDPROC
  25 ENDPROC(clear_page_c_e)
  26
  27 ENTRY(clear_page)
  28         CFI_STARTPROC
  29         xorl   %eax,%eax
  30         movl   $4096/64,%ecx
  31         .p2align 4
  32 .Lloop:
  33         decl    %ecx
  34 #define PUT(x) movq %rax,x*8(%rdi)
  35         movq %rax,(%rdi)
  36         PUT(1)
  37         PUT(2)
  38         PUT(3)
  39         PUT(4)
  40         PUT(5)
  41         PUT(6)
  42         PUT(7)
  43         leaq    64(%rdi),%rdi
  44         jnz     .Lloop
  45         nop
  46         ret
  47         CFI_ENDPROC
  48 .Lclear_page_end:
  49 ENDPROC(clear_page)
  50
  51         /*
  52          * Some CPUs support enhanced REP MOVSB/STOSB instructions.
  53          * It is recommended to use this when possible.
  54          * If enhanced REP MOVSB/STOSB is not available, try to use fast string.
  55          * Otherwise, use original function.
  56          *
  57          */
  58
  59 #include <asm/cpufeature.h>
  60
  61         .section .altinstr_replacement,"ax"
  62 1:      .byte 0xeb                                      /* jmp <disp8> */
  63         .byte (clear_page_c - clear_page) - (2f - 1b)   /* offset */
  64 2:      .byte 0xeb                                      /* jmp <disp8> */
  65         .byte (clear_page_c_e - clear_page) - (3f - 2b) /* offset */
  66 3:
  67         .previous
  68         .section .altinstructions,"a"
  69         altinstruction_entry clear_page,1b,X86_FEATURE_REP_GOOD,\
  70                              .Lclear_page_end-clear_page, 2b-1b
  71         altinstruction_entry clear_page,2b,X86_FEATURE_ERMS,   \
  72                              .Lclear_page_end-clear_page,3b-2b
  73         .previous