[18/65] ARM: 7720/1: ARM v6/v7 cmpxchg64 shouldnt clear upper 32 bits of the old/new value

Steven Rostedt
2013-06-03T22:21:46Z

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3.6.11.5 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Jaccon Bastiaansen <jaccon.bastiaansen@gmail.com>

[ Upstream commit 6eabb3301b1facee669d9938f7c5a0295c21d71d ]

The implementation of cmpxchg64() for the ARM v6 and v7 architecture
casts parameter 2 and 3 (the old and new 64bit values) to an unsigned
long before calling the atomic_cmpxchg64() function. This clears
the top 32 bits of the old and new values, resulting in the wrong
values being compare-exchanged. Luckily, this only appears to be used
for 64-bit sched_clock, which we don't (yet) have on ARM.

This bug was introduced by commit 3e0f5a15f500 ("ARM: 7404/1: cmpxchg64:
use atomic64 and local64 routines for cmpxchg64").

Cc: <stable@vger.kernel.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Jaccon Bastiaansen <jaccon.bastiaansen@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
arch/arm/include/asm/cmpxchg.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h
index 7eb18c1..4f009c1 100644
--- a/arch/arm/include/asm/cmpxchg.h
+++ b/arch/arm/include/asm/cmpxchg.h
@@ -233,15 +233,15 @@ static inline unsigned long __cmpxchg_local(volatile void *ptr,
((__typeof__(*(ptr)))atomic64_cmpxchg(container_of((ptr), \
atomic64_t, \
counter), \
- (unsigned long)(o), \
- (unsigned long)(n)))
+ (unsigned long long)(o), \
+ (unsigned long long)(n)))

#define cmpxchg64_local(ptr, o, n) \
((__typeof__(*(ptr)))local64_cmpxchg(container_of((ptr), \
local64_t, \
a), \
- (unsigned long)(o), \
- (unsigned long)(n)))
+ (unsigned long long)(o), \
+ (unsigned long long)(n)))

#endif /* __LINUX_ARM_ARCH__ >= 6 */

--
1.7.10.4