linux-kernel - [PATCH V2]sh: cmpxchg: fix a bit shift bug in big

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Message-ID: <5717247C.7080002@linux.vnet.ibm.com>
Date:	Wed, 20 Apr 2016 14:41:00 +0800
From:	Pan Xinhui <xinhui@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
CC:	ysato@...rs.sourceforge.jp, dalias@...c.org, mst@...hat.com,
	peterz@...radead.org, linux-sh@...r.kernel.org
Subject: [PATCH V2]sh: cmpxchg: fix a  bit shift bug in big_endian os

From: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>

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@...ux.vnet.ibm.com>
Acked-by: Michael S. Tsirkin <mst@...hat.com>
---
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