Subject: [PATCH V2] ARM: SWP emulation: Restore original *data when failed

From: [email-masked] (Vladimir Murzin)
Date: Tue, 08 Dec 2015 12:41:50 +0000

On 08/12/15 10:44, Russell King - ARM Linux wrote:
> On Tue, Dec 08, 2015 at 10:22:53AM +0000, Vladimir Murzin wrote:
>> On 15/10/15 10:30, Shengjiu Wang wrote:
>>> __user_swpX_asm maybe failed in first STREX operation, emulate_swpX
>>> will try again, but the *data has been changed in first time. which
>>> causes the result is wrong.
>>> This patch is to fix this issue. When STREX succeed, change the *data.
>>> if it fail, *data is not changed.
>>>
>>> Signed-off-by: Shengjiu Wang <[email-masked]>
>>> ---
>>>  arch/arm/kernel/swp_emulate.c | 6 +++---
>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/arm/kernel/swp_emulate.c b/arch/arm/kernel/swp_emulate.c
>>> index 5b26e7e..c3fe769d 100644
>>> --- a/arch/arm/kernel/swp_emulate.c
>>> +++ b/arch/arm/kernel/swp_emulate.c
>>> @@ -36,10 +36,10 @@
>>>   */
>>>  #define __user_swpX_asm(data, addr, res, temp, B)		\
>>>  	__asm__ __volatile__(					\
>>> -	"	mov		%2, %1\n"			\
>>> -	"0:	ldrex"B"	%1, [%3]\n"			\
>>> -	"1:	strex"B"	%0, %2, [%3]\n"			\
>>> +	"0:	ldrex"B"	%2, [%3]\n"			\
>>> +	"1:	strex"B"	%0, %1, [%3]\n"			\
>>>  	"	cmp		%0, #0\n"			\
>>> +	"	moveq		%1, %2\n"			\
>>>  	"	movne		%0, %4\n"			\
>>>  	"2:\n"							\
>>>  	"	.section	 .text.fixup,\"ax\"\n"		\
>>>
>>
>> I wonder what is status of this patch? I see that arm64 counterpart has
>> landed in mainline, but I didn't manage to track down this one - is it
>> because it never been submitted to patch system?
> 
> Most probably.
> 

I've just submitted (on behalf of Shengjiu) it as 8475/1 with assumption
you have no concerns about the patch.

Thanks
Vladimir