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/* SPDX-License-Identifier: GPL-2.0-only */
#include <linux/linkage.h>
#include <asm/asm.h>
#include <asm/export.h>
/*
* Most CPUs support enhanced REP MOVSB/STOSB instructions. It is
* recommended to use this when possible and we do use them by default.
* If enhanced REP MOVSB/STOSB is not available, try to use fast string.
* Otherwise, use original.
*/
/*
* Zero a page.
* %rdi - page
*/
SYM_FUNC_START(clear_page_rep)
movl $4096/8,%ecx
xorl %eax,%eax
rep stosq
RET
SYM_FUNC_END(clear_page_rep)
EXPORT_SYMBOL_GPL(clear_page_rep)
SYM_FUNC_START(clear_page_orig)
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
SYM_FUNC_END(clear_page_orig)
EXPORT_SYMBOL_GPL(clear_page_orig)
SYM_FUNC_START(clear_page_erms)
movl $4096,%ecx
xorl %eax,%eax
rep stosb
RET
SYM_FUNC_END(clear_page_erms)
EXPORT_SYMBOL_GPL(clear_page_erms)
/*
* Default clear user-space.
* Input:
* rdi destination
* rcx count
*
* Output:
* rcx: uncleared bytes or 0 if successful.
*/
SYM_FUNC_START(clear_user_original)
/*
* Copy only the lower 32 bits of size as that is enough to handle the rest bytes,
* i.e., no need for a 'q' suffix and thus a REX prefix.
*/
mov %ecx,%eax
shr $3,%rcx
jz .Lrest_bytes
# do the qwords first
.p2align 4
.Lqwords:
movq $0,(%rdi)
lea 8(%rdi),%rdi
dec %rcx
jnz .Lqwords
.Lrest_bytes:
and $7, %eax
jz .Lexit
# now do the rest bytes
.Lbytes:
movb $0,(%rdi)
inc %rdi
dec %eax
jnz .Lbytes
.Lexit:
/*
* %rax still needs to be cleared in the exception case because this function is called
* from inline asm and the compiler expects %rax to be zero when exiting the inline asm,
* in case it might reuse it somewhere.
*/
xor %eax,%eax
RET
.Lqwords_exception:
# convert remaining qwords back into bytes to return to caller
shl $3, %rcx
and $7, %eax
add %rax,%rcx
jmp .Lexit
.Lbytes_exception:
mov %eax,%ecx
jmp .Lexit
_ASM_EXTABLE_UA(.Lqwords, .Lqwords_exception)
_ASM_EXTABLE_UA(.Lbytes, .Lbytes_exception)
SYM_FUNC_END(clear_user_original)
EXPORT_SYMBOL(clear_user_original)
/*
* Alternative clear user-space when CPU feature X86_FEATURE_REP_GOOD is
* present.
* Input:
* rdi destination
* rcx count
*
* Output:
* rcx: uncleared bytes or 0 if successful.
*/
SYM_FUNC_START(clear_user_rep_good)
# call the original thing for less than a cacheline
cmp $64, %rcx
jb clear_user_original
.Lprep:
# copy lower 32-bits for rest bytes
mov %ecx, %edx
shr $3, %rcx
jz .Lrep_good_rest_bytes
.Lrep_good_qwords:
rep stosq
.Lrep_good_rest_bytes:
and $7, %edx
jz .Lrep_good_exit
mov %edx, %ecx
.Lrep_good_bytes:
rep stosb
.Lrep_good_exit:
# see .Lexit comment above
xor %eax, %eax
RET
.Lrep_good_qwords_exception:
# convert remaining qwords back into bytes to return to caller
shl $3, %rcx
and $7, %edx
add %rdx, %rcx
jmp .Lrep_good_exit
_ASM_EXTABLE_UA(.Lrep_good_qwords, .Lrep_good_qwords_exception)
_ASM_EXTABLE_UA(.Lrep_good_bytes, .Lrep_good_exit)
SYM_FUNC_END(clear_user_rep_good)
EXPORT_SYMBOL(clear_user_rep_good)
/*
* Alternative clear user-space when CPU feature X86_FEATURE_ERMS is present.
* Input:
* rdi destination
* rcx count
*
* Output:
* rcx: uncleared bytes or 0 if successful.
*
*/
SYM_FUNC_START(clear_user_erms)
# call the original thing for less than a cacheline
cmp $64, %rcx
jb clear_user_original
.Lerms_bytes:
rep stosb
.Lerms_exit:
xorl %eax,%eax
RET
_ASM_EXTABLE_UA(.Lerms_bytes, .Lerms_exit)
SYM_FUNC_END(clear_user_erms)
EXPORT_SYMBOL(clear_user_erms)
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