Re: [PATCH 02/18] powerpc: remove arguments from fault handler functions

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 10/11/2020 à 09:29, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of November 6, 2020 5:59 pm:
>>
>>
>> Le 05/11/2020 à 15:34, Nicholas Piggin a écrit :
>>> Make mm fault handlers all just take the pt_regs * argument and load
>>> DAR/DSISR from that. Make those that return a value return long.
>>>
>>> This is done to make the function signatures match other handlers, which
>>> will help with a future patch to add wrappers. Explicit arguments could
>>> be added for performance but that would require more wrapper macro
>>> variants.
>>>
>>> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
>>> ---

[...]

> 
>>> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
>>> index e65a49f246ef..390a296b16a3 100644
>>> --- a/arch/powerpc/mm/fault.c
>>> +++ b/arch/powerpc/mm/fault.c
>>> @@ -549,11 +549,12 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
>>>    }
>>>    NOKPROBE_SYMBOL(__do_page_fault);
>>>    
>>> -int do_page_fault(struct pt_regs *regs, unsigned long address,
>>> -		  unsigned long error_code)
>>> +long do_page_fault(struct pt_regs *regs)
>>>    {
>>>    	enum ctx_state prev_state = exception_enter();
>>> -	int err;
>>> +	unsigned long address = regs->dar;
>>> +	unsigned long error_code = regs->dsisr;
>>> +	long err;
>>
>> By doing something more or less like this (need to be tuned for bookE as well):
>>
>> +	int is_exec = TRAP(regs) == 0x400;
>> +	unsigned long address = is_exec ? regs->ssr0 : regs->dar;
>> +	unsigned long error_code = is_exec ? (regs->ssr1 & DSISR_SRR1_MATCH_32S) : regs->dsisr;
> 
> Ah, I didn't see that you saved these in srr0/1 already. Hmm, not in
> pt_regs though. thread_struct (VMAP_STACK only)? exception_regs (booke
> only)? Doesn't seem so easy.

Oops yes you are right, SRR0/SRR1 are not in pt_regs. And their validity in thread struct is rather 
short ... So forget my comment.

Christophe