Re: [PATCH v4 17/21] LoongArch Linux User Emulation

[Song Gao]

Hi, Richard.

On 09/10/2021 08:52 PM, Richard Henderson wrote:
> On 9/8/21 11:50 AM, Song Gao wrote:
>>
>> Hi Richard,
>>
>> On 09/05/2021 06:04 PM, Richard Henderson wrote:
>>>> +struct sigframe {
>>>> +    uint32_t sf_ass[4];             /* argument save space for o32 */
>>>
>>> Surely there is no "o32" for loongarch?
>>>
>>
>> Yes, qemu only support 64bit. but the kernel has 'o32'.  Should we have to 
>> be consistent with the kernel?
> 
> Yes, you need to be consistent with the kernel.  However... the kernel is not 
> yet upstream, and therefore the ABI is (officially) still malleable.
> 
> Anyway, this padding was copied from mips o32, and should not have been.  
> Looking at the loongarch gcc sources, REG_PARM_STACK_SPACE is always 0, and 
> thus the 4 words reserved here are never used.
> 
> I see that gcc/libgcc/config/loongarch/linux-unwind.h builds in knowledge of 
> these unused words.  I also see that linux/arch/loongarch/vdso/sigreturn.S 
> does not provide correct unwind info.  Certainly the kernel vdso should be 
> fixed, so that code within gcc should not be needed.  At which point the ABI 
> for the signal frame is entirely private to the kernel.
> 

We are cleanning up 'o32' code for gcc and kernel.   

By the way, We have already prepared V5 patches. but I see that patches [1] and 
[2] have not push into master. How can I use these patches? 

[1]: 
https://patchew.org/QEMU/20210618192951.125651-1-richard.henderson@linaro.org/
[2]: 
https://patchew.org/QEMU/20210822035537.283193-1-richard.henderson@linaro.org/


Song Gao
thanks
> 
> r~