Re: [PATCH v2 0/3] Handle delay slot for extable lookup

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在 2024/2/2 18:39, Linus Torvalds 写道:
On Fri, 2 Feb 2024 at 04:30, Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote:
       ptrace: Introduce exception_ip arch hook
       MIPS: Clear Cause.BD in instruction_pointer_set
       mm/memory: Use exception ip to search exception tables
Just to clarify: does that second patch fix the problem that
__isa_exception_epc() does a __get_user()?

Because that mm/memory.c use of "exception_ip()" most definitely
cannot take a page fault.

I reconsidered this issue today and I believe that exception_ip() usage here won't trigger
page_fault anyway.

Given that exception_ip is guarded by !user_mode(regs), EPC must points to a kernel text address. There is no way accessing kernel text will generate such exception..


So if MIPS cannot do that whole exception IP thing without potentially
touching user space, I do worry that we might just have to add a

    #ifndef __MIPS__

around this all.

Possibly somehow limited to just the microMIPS/MIPS16e case in Kconfig instead?


Jiaxun Yang

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