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x86/uaccess: Don't jump between functions

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For unwinding sanity, a function shouldn't jump to the middle of another
function.  Move the short string user copy code out to a separate
non-function code snippet.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/9519e4853148b765e047967708f2b61e56c93186.1649718562.git.jpoimboe@redhat.com
This commit is contained in:
Josh Poimboeuf 2022-04-11 16:10:29 -07:00 • committed by Peter Zijlstra
parent b2d229d4dd
commit 02041b3225
1 changed files with 52 additions and 35 deletions
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87
arch/x86/lib/copy_user_64.S
View file

@ -53,12 +53,12 @@
SYM_FUNC_START(copy_user_generic_unrolled)
ASM_STAC
cmpl $8,%edx
jb 20f /* less then 8 bytes, go to byte copy loop */
jb .Lcopy_user_short_string_bytes
ALIGN_DESTINATION
movl %edx,%ecx
andl $63,%edx
shrl $6,%ecx
jz .L_copy_short_string
jz copy_user_short_string
1: movq (%rsi),%r8
2: movq 1*8(%rsi),%r9
3: movq 2*8(%rsi),%r10
@ -79,37 +79,11 @@ SYM_FUNC_START(copy_user_generic_unrolled)
leaq 64(%rdi),%rdi
decl %ecx
jnz 1b
.L_copy_short_string:
movl %edx,%ecx
andl $7,%edx
shrl $3,%ecx
jz 20f
18: movq (%rsi),%r8
19: movq %r8,(%rdi)
leaq 8(%rsi),%rsi
leaq 8(%rdi),%rdi
decl %ecx
jnz 18b
20: andl %edx,%edx
jz 23f
movl %edx,%ecx
21: movb (%rsi),%al
22: movb %al,(%rdi)
incq %rsi
incq %rdi
decl %ecx
jnz 21b
23: xor %eax,%eax
ASM_CLAC
RET
jmp copy_user_short_string
30: shll $6,%ecx
addl %ecx,%edx
jmp 60f
40: leal (%rdx,%rcx,8),%edx
jmp 60f
50: movl %ecx,%edx
60: jmp .Lcopy_user_handle_tail /* ecx is zerorest also */
jmp .Lcopy_user_handle_tail
_ASM_EXTABLE_CPY(1b, 30b)
_ASM_EXTABLE_CPY(2b, 30b)
@ -127,10 +101,6 @@ SYM_FUNC_START(copy_user_generic_unrolled)
_ASM_EXTABLE_CPY(14b, 30b)
_ASM_EXTABLE_CPY(15b, 30b)
_ASM_EXTABLE_CPY(16b, 30b)
_ASM_EXTABLE_CPY(18b, 40b)
_ASM_EXTABLE_CPY(19b, 40b)
_ASM_EXTABLE_CPY(21b, 50b)
_ASM_EXTABLE_CPY(22b, 50b)
SYM_FUNC_END(copy_user_generic_unrolled)
EXPORT_SYMBOL(copy_user_generic_unrolled)
@ -191,7 +161,7 @@ EXPORT_SYMBOL(copy_user_generic_string)
SYM_FUNC_START(copy_user_enhanced_fast_string)
ASM_STAC
/* CPUs without FSRM should avoid rep movsb for short copies */
ALTERNATIVE "cmpl $64, %edx; jb .L_copy_short_string", "", X86_FEATURE_FSRM
ALTERNATIVE "cmpl $64, %edx; jb copy_user_short_string", "", X86_FEATURE_FSRM
movl %edx,%ecx
1: rep movsb
xorl %eax,%eax
@ -243,6 +213,53 @@ SYM_CODE_START_LOCAL(.Lcopy_user_handle_tail)
SYM_CODE_END(.Lcopy_user_handle_tail)
/*
* Finish memcpy of less than 64 bytes. #AC should already be set.
*
* Input:
* rdi destination
* rsi source
* rdx count (< 64)
*
* Output:
* eax uncopied bytes or 0 if successful.
*/
SYM_CODE_START_LOCAL(copy_user_short_string)
movl %edx,%ecx
andl $7,%edx
shrl $3,%ecx
jz .Lcopy_user_short_string_bytes
18: movq (%rsi),%r8
19: movq %r8,(%rdi)
leaq 8(%rsi),%rsi
leaq 8(%rdi),%rdi
decl %ecx
jnz 18b
.Lcopy_user_short_string_bytes:
andl %edx,%edx
jz 23f
movl %edx,%ecx
21: movb (%rsi),%al
22: movb %al,(%rdi)
incq %rsi
incq %rdi
decl %ecx
jnz 21b
23: xor %eax,%eax
ASM_CLAC
RET
40: leal (%rdx,%rcx,8),%edx
jmp 60f
50: movl %ecx,%edx /* ecx is zerorest also */
60: jmp .Lcopy_user_handle_tail
_ASM_EXTABLE_CPY(18b, 40b)
_ASM_EXTABLE_CPY(19b, 40b)
_ASM_EXTABLE_CPY(21b, 50b)
_ASM_EXTABLE_CPY(22b, 50b)
SYM_CODE_END(copy_user_short_string)
/*
* copy_user_nocache - Uncached memory copy with exception handling
* This will force destination out of cache for more performance.