[PATCH V2]sh: cmpxchg: fix a bit shift bug in big_endian os

From: Pan Xinhui
Date: Wed Apr 20 2016 - 02:42:44 EST


From: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>

Correct bitoff in big endian OS.
Current code works correctly for 1 byte but not for 2 bytes.

Fixes: 3226aad81aa6 ("sh: support 1 and 2 byte xchg")
Signed-off-by: Pan Xinhui <xinhui.pan@xxxxxxxxxxxxxxxxxx>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
changes from V1:
just add some patch comments. no code changes.
---
arch/sh/include/asm/cmpxchg-xchg.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sh/include/asm/cmpxchg-xchg.h b/arch/sh/include/asm/cmpxchg-xchg.h
index 7219719..1e881f5 100644
--- a/arch/sh/include/asm/cmpxchg-xchg.h
+++ b/arch/sh/include/asm/cmpxchg-xchg.h
@@ -21,7 +21,7 @@ static inline u32 __xchg_cmpxchg(volatile void *ptr, u32 x, int size)
int off = (unsigned long)ptr % sizeof(u32);
volatile u32 *p = ptr - off;
#ifdef __BIG_ENDIAN
- int bitoff = (sizeof(u32) - 1 - off) * BITS_PER_BYTE;
+ int bitoff = (sizeof(u32) - size - off) * BITS_PER_BYTE;
#else
int bitoff = off * BITS_PER_BYTE;
#endif
--
1.9.1