[S390] broken copy_in_user function.

The copy_in_user primitive does not work as advertised. If the source
and target area are available copy_in_user copies one byte too much.
If one of the memory areas is not available it does not copy as much
data as it can, but up to 257 bytes less.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 17 insertions, 16 deletions

diff --git a/arch/s390/lib/uaccess.S b/arch/s390/lib/uaccess.S
index 5d59e2625048..837275284d9f 100644
--- a/arch/s390/lib/uaccess.S
+++ b/arch/s390/lib/uaccess.S
@@ -88,30 +88,31 @@ __copy_to_user_asm:
         .globl __copy_in_user_asm
         # %r2 = from, %r3 = n, %r4 = to
 __copy_in_user_asm:
+        ahi     %r3,-1
+        jo      6f
         sacf    256
-        bras    1,1f
-        mvc     0(1,%r4),0(%r2)
-0:      mvc     0(256,%r4),0(%r2)
-        la      %r2,256(%r2)
-        la      %r4,256(%r4)
-1:      ahi     %r3,-256
-        jnm     0b
-2:      ex      %r3,0(%r1)
-        sacf    0
-        slr     %r2,%r2
-        br      14
-3:      mvc     0(1,%r4),0(%r2)
+        bras    %r1,4f
+0:      ahi     %r3,257
+1:      mvc     0(1,%r4),0(%r2)
         la      %r2,1(%r2)
         la      %r4,1(%r4)
         ahi     %r3,-1
+        jnz     1b
+2:      lr      %r2,%r3
+        br      %r14
+3:      mvc     0(256,%r4),0(%r2)
+        la      %r2,256(%r2)
+        la      %r4,256(%r4)
+4:      ahi     %r3,-256
         jnm     3b
-4:      lr      %r2,%r3
+5:      ex      %r3,4(%r1)
         sacf    0
+6:      slr     %r2,%r2
         br      %r14
         .section __ex_table,"a"
-        .long   0b,3b
-        .long   2b,3b
-        .long   3b,4b
+        .long   1b,2b
+        .long   3b,0b
+        .long   5b,0b
         .previous
 
         .align 4