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

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Date: Fri, 2 Feb 2024 10:39:13 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Jiaxun Yang <jiaxun.yang@...goat.com>
Cc: Oleg Nesterov <oleg@...hat.com>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, 
	Andrew Morton <akpm@...ux-foundation.org>, Ben Hutchings <ben@...adent.org.uk>, 
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-mips@...r.kernel.org, linux-mm@...ck.org, 
	Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH v2 0/3] Handle delay slot for extable lookup

On Fri, 2 Feb 2024 at 04:30, Jiaxun Yang <jiaxun.yang@...goat.com> 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.

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?

            Linus