x86: change testing logic in putuser_64.S.

Instead of operating over a register we need to put back
into normal state afterwards (the memory position), just
sub from rbx, which is trashed anyway. We can save a few instructions.

Also, this is the i386 way.

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 12 insertions, 21 deletions

diff --git a/arch/x86/lib/putuser_64.S b/arch/x86/lib/putuser_64.S
index ce5fcd5d8c16..a96bd8a5298e 100644
--- a/arch/x86/lib/putuser_64.S
+++ b/arch/x86/lib/putuser_64.S
@@ -46,48 +46,39 @@ ENDPROC(__put_user_1)
 ENTRY(__put_user_2)
         CFI_STARTPROC
         GET_THREAD_INFO(%rbx)
-        addq $1,%rcx
-        jc 20f
-        cmpq TI_addr_limit(%rbx),%rcx
-        jae 20f
-        decq %rcx
+        mov TI_addr_limit(%rbx),%rbx
+        sub  $1, %rbx
+        cmpq %rbx ,%rcx
+        jae  bad_put_user
 2:      movw %ax,(%rcx)
         xorl %eax,%eax
         ret
-20:     decq %rcx
-        jmp bad_put_user
         CFI_ENDPROC
 ENDPROC(__put_user_2)
 
 ENTRY(__put_user_4)
         CFI_STARTPROC
         GET_THREAD_INFO(%rbx)
-        addq $3,%rcx
-        jc 30f
-        cmpq TI_addr_limit(%rbx),%rcx
-        jae 30f
-        subq $3,%rcx
+        mov TI_addr_limit(%rbx),%rbx
+        sub  $3, %rbx
+        cmp  %rbx, %rcx
+        jae bad_put_user
 3:      movl %eax,(%rcx)
         xorl %eax,%eax
         ret
-30:     subq $3,%rcx
-        jmp bad_put_user
         CFI_ENDPROC
 ENDPROC(__put_user_4)
 
 ENTRY(__put_user_8)
         CFI_STARTPROC
         GET_THREAD_INFO(%rbx)
-        addq $7,%rcx
-        jc 40f
-        cmpq TI_addr_limit(%rbx),%rcx
-        jae 40f
-        subq $7,%rcx
+        mov TI_addr_limit(%rbx),%rbx
+        sub  $7, %rbx
+        cmp  %rbx, %rcx
+        jae bad_put_user
 4:      movq %rax,(%rcx)
         xorl %eax,%eax
         ret
-40:     subq $7,%rcx
-        jmp bad_put_user
         CFI_ENDPROC
 ENDPROC(__put_user_8)