Subject: [PATCH 1/1] ARM : missing corrupted reg in __do_div_asm

From: [email-masked] (Chen Gang)
Date: Sun, 28 Jun 2015 19:29:06 +0800

Hi, Russell

I have uploaded V2 of the patch based on your comments on Jun-19. Hope 
you can review that again.

Br, Chen Gang

On 06/09/2015 09:09 PM, Russell King - ARM Linux wrote:
> On Tue, Jun 02, 2015 at 02:13:29PM +0800, Chen Gang wrote:
>> __xl (r0 in little endian system, or R1 in big endian system) is corrupted
>> after calling __do_div64 and compiler is not informed about this in
>> macro __do_div_asm. If n is used again afterwards, __xl won't be
>> reloaded and n will contain incorrect value.
>> ---
> This commit message needs improving.  Please either upper case both r0
> and r1 in the first line, or lower case them both.  Secondly, the Linux
> kernel has a requirement that all contributions are signed-off.  Please
> read Documentation/SubmittingPatches for information, particularly
> section 11.
>
> Other than that, the patch looks fine, thanks.
>
>>   arch/arm/include/asm/div64.h | 10 ++++++----
>>   1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/div64.h b/arch/arm/include/asm/div64.h
>> index 662c7bd..fa9489e 100644
>> --- a/arch/arm/include/asm/div64.h
>> +++ b/arch/arm/include/asm/div64.h
>> @@ -34,12 +34,14 @@
>>   	register unsigned long long __n   asm("r0") = n;	\
>>   	register unsigned long long __res asm("r2");		\
>>   	register unsigned int __rem       asm(__xh);		\
>> +	register unsigned int __clobber   asm(__xl);		\
>>   	asm(	__asmeq("%0", __xh)				\
>> -		__asmeq("%1", "r2")				\
>> -		__asmeq("%2", "r0")				\
>> -		__asmeq("%3", "r4")				\
>> +		__asmeq("%1", __xl)				\
>> +		__asmeq("%2", "r2")				\
>> +		__asmeq("%3", "r0")				\
>> +		__asmeq("%4", "r4")				\
>>   		"bl	__do_div64"				\
>> -		: "=r" (__rem), "=r" (__res)			\
>> +		: "=r" (__rem), "=r" (__clobber), "=r" (__res)  \
>>   		: "r" (__n), "r" (__base)			\
>>   		: "ip", "lr", "cc");				\
>>   	n = __res;						\
>> -- 
>> 1.9.1
>>
>>