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Subject[PATCH] x86: Set clear flag in copy_from_user/copy_to_user
Date
Only copy_to_user should clear the rest of uncopied area. copy_user
routines were modified for passing clear flag to handle tail routine,
clear flag set/reset explicitly in copy_to_user/copy_from_user.

Signed-off-by: Vitaly Mayatskikh <v.mayatskih@gmail.com>

diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index dfdf428..dd59c48 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -38,21 +38,21 @@
.macro ALIGN_DESTINATION
#ifdef FIX_ALIGNMENT
/* check for bad alignment of destination */
- movl %edi,%ecx
- andl $7,%ecx
+ movl %edi,%r8d
+ andl $7,%r8d
jz 102f /* already aligned */
- subl $8,%ecx
- negl %ecx
- subl %ecx,%edx
+ subl $8,%r8d
+ negl %r8d
+ subl %r8d,%edx
100: movb (%rsi),%al
101: movb %al,(%rdi)
incq %rsi
incq %rdi
- decl %ecx
+ decl %r8d
jnz 100b
102:
.section .fixup,"ax"
-103: addl %r8d,%edx /* ecx is zerorest also */
+103: addl %r8d,%edx
jmp copy_user_handle_tail
.previous

@@ -73,6 +73,7 @@ ENTRY(copy_to_user)
jc bad_to_user
cmpq TI_addr_limit(%rax),%rcx
jae bad_to_user
+ movl $1,%ecx /* clear tail */
ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
CFI_ENDPROC

@@ -85,18 +86,21 @@ ENTRY(copy_from_user)
jc bad_from_user
cmpq TI_addr_limit(%rax),%rcx
jae bad_from_user
+ xorl %ecx,%ecx
ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
CFI_ENDPROC
ENDPROC(copy_from_user)

ENTRY(copy_user_generic)
CFI_STARTPROC
+ xorl %ecx,%ecx
ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
CFI_ENDPROC
ENDPROC(copy_user_generic)

ENTRY(__copy_from_user_inatomic)
CFI_STARTPROC
+ xorl %ecx,%ecx
ALTERNATIVE_JUMP X86_FEATURE_REP_GOOD,copy_user_generic_unrolled,copy_user_generic_string
CFI_ENDPROC
ENDPROC(__copy_from_user_inatomic)
@@ -125,7 +129,8 @@ ENDPROC(bad_from_user)
* Input:
* rdi destination
* rsi source
- * rdx count
+ * edx count
+ * ecx clear flag
*
* Output:
* eax uncopied bytes or 0 if successfull.
@@ -135,6 +140,7 @@ ENTRY(copy_user_generic_unrolled)
cmpl $8,%edx
jb 20f /* less then 8 bytes, go to byte copy loop */
ALIGN_DESTINATION
+ movl %ecx,%eax /* save clear flag in eax */
movl %edx,%ecx
andl $63,%edx
shrl $6,%ecx
@@ -169,11 +175,11 @@ ENTRY(copy_user_generic_unrolled)
leaq 8(%rdi),%rdi
decl %ecx
jnz 18b
-20: andl %edx,%edx
+20: testl %edx,%edx
jz 23f
movl %edx,%ecx
-21: movb (%rsi),%al
-22: movb %al,(%rdi)
+21: movb (%rsi),%dl
+22: movb %dl,(%rdi)
incq %rsi
incq %rdi
decl %ecx
@@ -188,7 +194,8 @@ ENTRY(copy_user_generic_unrolled)
40: lea (%rdx,%rcx,8),%rdx
jmp 60f
50: movl %ecx,%edx
-60: jmp copy_user_handle_tail /* ecx is zerorest also */
+60: movl %eax,%ecx /* get clear flag back to ecx*/
+ jmp copy_user_handle_tail
.previous

.section __ex_table,"a"
@@ -230,15 +237,15 @@ ENDPROC(copy_user_generic_unrolled)
* Input:
* rdi destination
* rsi source
- * rdx count
+ * edx count
+ * ecx clear flag
*
* Output:
* eax uncopied bytes or 0 if successful.
*/
ENTRY(copy_user_generic_string)
CFI_STARTPROC
- andl %edx,%edx
- jz 4f
+ movl %ecx,%eax /* save clear_rest flag */
cmpl $8,%edx
jb 2f /* less than 8 bytes, go to byte copy loop */
ALIGN_DESTINATION
@@ -250,12 +257,13 @@ ENTRY(copy_user_generic_string)
2: movl %edx,%ecx
3: rep
movsb
-4: xorl %eax,%eax
+ xorl %eax,%eax
ret

.section .fixup,"ax"
11: lea (%rdx,%rcx,8),%rcx
-12: movl %ecx,%edx /* ecx is zerorest also */
+12: movl %ecx,%edx
+ movl %eax,%ecx /* get clear flag back to ecx */
jmp copy_user_handle_tail
.previous

diff --git a/arch/x86/lib/copy_user_nocache_64.S b/arch/x86/lib/copy_user_nocache_64.S
index 40e0e30..d3a5358 100644
--- a/arch/x86/lib/copy_user_nocache_64.S
+++ b/arch/x86/lib/copy_user_nocache_64.S
@@ -18,21 +18,21 @@
.macro ALIGN_DESTINATION
#ifdef FIX_ALIGNMENT
/* check for bad alignment of destination */
- movl %edi,%ecx
- andl $7,%ecx
+ movl %edi,%r8d
+ andl $7,%r8d
jz 102f /* already aligned */
- subl $8,%ecx
- negl %ecx
- subl %ecx,%edx
+ subl $8,%r8d
+ negl %r8d
+ subl %r8d,%edx
100: movb (%rsi),%al
101: movb %al,(%rdi)
incq %rsi
incq %rdi
- decl %ecx
+ decl %r8d
jnz 100b
102:
.section .fixup,"ax"
-103: addl %r8d,%edx /* ecx is zerorest also */
+103: addl %r8d,%edx
jmp copy_user_handle_tail
.previous

@@ -53,6 +53,7 @@ ENTRY(__copy_user_nocache)
cmpl $8,%edx
jb 20f /* less then 8 bytes, go to byte copy loop */
ALIGN_DESTINATION
+ movl %ecx,%eax /* save clear flag in eax */
movl %edx,%ecx
andl $63,%edx
shrl $6,%ecx
@@ -87,11 +88,11 @@ ENTRY(__copy_user_nocache)
leaq 8(%rdi),%rdi
decl %ecx
jnz 18b
-20: andl %edx,%edx
+20: testl %edx,%edx
jz 23f
movl %edx,%ecx
-21: movb (%rsi),%al
-22: movb %al,(%rdi)
+21: movb (%rsi),%dl
+22: movb %dl,(%rdi)
incq %rsi
incq %rdi
decl %ecx
@@ -108,7 +109,7 @@ ENTRY(__copy_user_nocache)
jmp 60f
50: movl %ecx,%edx
60: sfence
- movl %r8d,%ecx
+ movl %eax,%ecx /* get clear flag back to ecx*/
jmp copy_user_handle_tail
.previous


--
wbr, Vitaly


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