On 02/08/2013 09:18 AM, Ville Syrjälä wrote:
>>
>> diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
>> index 1709801..1e96326 100644
>> --- a/arch/x86/include/asm/uaccess.h
>> +++ b/arch/x86/include/asm/uaccess.h
>> @@ -151,8 +151,15 @@ extern int __get_user_bad(void);
>> * On error, the variable @x is set to zero.
>> */
>> #ifdef CONFIG_X86_32
>> -#define __get_user_8(__ret_gu, __val_gu, ptr) \
>> - __get_user_x(X, __ret_gu, __val_gu, ptr)
>> +#define __get_user_8(ret, x, ptr) \
>> +do { \
>> + register unsigned long long __xx asm("%edx"); \
>> + asm volatile("call __get_user_8" \
>> + : "=a" (ret), "=r" (__xx) \
>> + : "0" (ptr)); \
>> + (x) = __xx; \
>> +} while (0)
>
> I'm no inline asm guy so I don't claim to know whether this always
> works. I'll have to take your word for it. While gcc documentation
> does mention explicit register variables, it doesn't tell you
> anything about using multiple registers for one such variable.
>
gcc always uses two consecutive registers for wide integers; however, it
uses the register sequence:
eax, edx, ecx, ebx, esp, ebp, esi, edi
ecx and edx are swapped versus x86 register numbering so that the
standard register pairs edx:eax and ebx:ecx are contiguous.
-hpa
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