Re: Strange EFAULT on mips64el returned by syscall when another thread is forking

[Jiaxun Yang]

在2024年1月24日一月 下午10:10，Linus Torvalds写道：
[...]
>
> Anyway, I'm pretty sure this is the bug, now some MIPS person just
> needs to fix the MIPS version of "instruction_pointer()" to do what
> "exception_epc()" already does.

Hi folks,

Kinda MIPS person here, I looked into the problem, and it's not that
easy to fix.

I inspected some existing usage of "instruction_pointer()", and some
of them do want exception return address (which is always CP0_EPC).
Others like this case they want the precise exception instruction
pointer ("exception_epc()" for MIPS).

I'm planning to make "instruction_pointer()" always point to exception
instructions, and implemented a new function called "return_pc()"or
whatever for "exception_epc()". Do you have a better name in mind?

Besides isa16 stuff do require kernel to read user space fault
instruction to determine delay slot size... I don't think it's always
possible when "instruction_pointer()" is called. MIPS16/microMIPS
is rarely used today though.

Thanks

>
>               Linus

-- 
- Jiaxun