clear_page_64.S
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#include <linux/linkage.h>
#include <asm/dwarf2.h>
#include <asm/alternative-asm.h>
/*
* Zero a page.
* rdi page
*/
ENTRY(clear_page_c)
CFI_STARTPROC
movl $4096/8,%ecx
xorl %eax,%eax
rep stosq
ret
CFI_ENDPROC
ENDPROC(clear_page_c)
ENTRY(clear_page_c_e)
CFI_STARTPROC
movl $4096,%ecx
xorl %eax,%eax
rep stosb
ret
CFI_ENDPROC
ENDPROC(clear_page_c_e)
ENTRY(clear_page)
CFI_STARTPROC
xorl %eax,%eax
movl $4096/64,%ecx
.p2align 4
.Lloop:
decl %ecx
#define PUT(x) movq %rax,x*8(%rdi)
movq %rax,(%rdi)
PUT(1)
PUT(2)
PUT(3)
PUT(4)
PUT(5)
PUT(6)
PUT(7)
leaq 64(%rdi),%rdi
jnz .Lloop
nop
ret
CFI_ENDPROC
.Lclear_page_end:
ENDPROC(clear_page)
/*
* Some CPUs support enhanced REP MOVSB/STOSB instructions.
* It is recommended to use this when possible.
* If enhanced REP MOVSB/STOSB is not available, try to use fast string.
* Otherwise, use original function.
*
*/
#include <asm/cpufeature.h>
.section .altinstr_replacement,"ax"
1: .byte 0xeb /* jmp <disp8> */
.byte (clear_page_c - clear_page) - (2f - 1b) /* offset */
2: .byte 0xeb /* jmp <disp8> */
.byte (clear_page_c_e - clear_page) - (3f - 2b) /* offset */
3:
.previous
.section .altinstructions,"a"
altinstruction_entry clear_page,1b,X86_FEATURE_REP_GOOD,\
.Lclear_page_end-clear_page, 2b-1b
altinstruction_entry clear_page,2b,X86_FEATURE_ERMS, \
.Lclear_page_end-clear_page,3b-2b
.previous