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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright 2008 Vitaly Mayatskikh <vmayatsk@redhat.com>
* Copyright 2002 Andi Kleen, SuSE Labs.
*
* Functions to copy from and to user space.
*/
#include <linux/export.h>
#include <linux/linkage.h>
#include <asm/cpufeatures.h>
#include <asm/alternative.h>
#include <asm/asm.h>
/*
* rep_movs_alternative - memory copy with exception handling.
* This version is for CPUs that don't have FSRM (Fast Short Rep Movs)
*
* Input:
* rdi destination
* rsi source
* rcx count
*
* Output:
* rcx uncopied bytes or 0 if successful.
*
* NOTE! The calling convention is very intentionally the same as
* for 'rep movs', so that we can rewrite the function call with
* just a plain 'rep movs' on machines that have FSRM. But to make
* it simpler for us, we can clobber rsi/rdi and rax freely.
*/
SYM_FUNC_START(rep_movs_alternative)
cmpq $64,%rcx
jae .Llarge
cmp $8,%ecx
jae .Lword
testl %ecx,%ecx
je .Lexit
.Lcopy_user_tail:
0: movb (%rsi),%al
1: movb %al,(%rdi)
inc %rdi
inc %rsi
dec %rcx
jne .Lcopy_user_tail
.Lexit:
RET
_ASM_EXTABLE_UA( 0b, .Lexit)
_ASM_EXTABLE_UA( 1b, .Lexit)
.p2align 4
.Lword:
2: movq (%rsi),%rax
3: movq %rax,(%rdi)
addq $8,%rsi
addq $8,%rdi
sub $8,%ecx
je .Lexit
cmp $8,%ecx
jae .Lword
jmp .Lcopy_user_tail
_ASM_EXTABLE_UA( 2b, .Lcopy_user_tail)
_ASM_EXTABLE_UA( 3b, .Lcopy_user_tail)
.Llarge:
0: ALTERNATIVE "jmp .Llarge_movsq", "rep movsb", X86_FEATURE_ERMS
1: RET
_ASM_EXTABLE_UA( 0b, 1b)
.Llarge_movsq:
movq %rcx,%rax
shrq $3,%rcx
andl $7,%eax
0: rep movsq
movl %eax,%ecx
testl %ecx,%ecx
jne .Lcopy_user_tail
RET
1: leaq (%rax,%rcx,8),%rcx
jmp .Lcopy_user_tail
_ASM_EXTABLE_UA( 0b, 1b)
SYM_FUNC_END(rep_movs_alternative)
EXPORT_SYMBOL(rep_movs_alternative)
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