Received-SPF: pass (google.com: domain of linux-kernel+bounces-50348-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240202-exception_ip-v2-0-e6894d5ce705@flygoat.com>
In-Reply-To: <20240202-exception_ip-v2-0-e6894d5ce705@flygoat.com>
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Fri, 2 Feb 2024 10:39:13 -0800
Message-ID: <CAHk-=wiaSjYApqmUYCdCyYfr_bRsfVKDkwU6r6FMmoZzrxHrKQ@mail.gmail.com>
Subject: Re: [PATCH v2 0/3] Handle delay slot for extable lookup
To: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: Oleg Nesterov <oleg@redhat.com>, Thomas Bogendoerfer <tsbogend@alpha.franken.de>, 
	Andrew Morton <akpm@linux-foundation.org>, Ben Hutchings <ben@decadent.org.uk>, 
	linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, 
	linux-mips@vger.kernel.org, linux-mm@kvack.org, 
	Xi Ruoyao <xry111@xry111.site>
Content-Type: text/plain; charset="UTF-8"

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