Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Marco Elver <elver@google.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>
Cc:     Alexander Potapenko <glider@google.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        linuxppc-dev@lists.ozlabs.org,
        kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: [RFC PATCH v1] powerpc: Enable KFENCE for PPC32
In-Reply-To: <CANpmjNM9o1s4O4v2T9HUohPdCDJzWcaC5KDrt_7BSVdTUQWagw@mail.gmail.com>
References: <CANpmjNPGj4C2rr2FbSD+FC-GnWUvJrtdLyX5TYpJE_Um8CGu1Q@mail.gmail.com>
 <08a96c5d-4ae7-03b4-208f-956226dee6bb@csgroup.eu>
 <CANpmjNPYEmLtQEu5G=zJLUzOBaGoqNKwLyipDCxvytdKDKb7mg@mail.gmail.com>
 <ad61cb3a-2b4a-3754-5761-832a1dd0c34e@csgroup.eu>
 <CANpmjNOnVzei7frKcMzMHxaDXh5NvTA-Wpa29C2YC1GUxyKfhQ@mail.gmail.com>
 <f036c53d-7e81-763c-47f4-6024c6c5f058@csgroup.eu>
 <CANpmjNMn_CUrgeSqBgiKx4+J8a+XcxkaLPWoDMUvUEXk8+-jxg@mail.gmail.com>
 <7270e1cc-bb6b-99ee-0043-08a027b8d83a@csgroup.eu>
 <YEDXJ5JNkgvDFehc@elver.google.com> <874khqry78.fsf@mpe.ellerman.id.au>
 <YEHiq1ALdPn2crvP@elver.google.com>
 <f6e47f4f-6953-6584-f023-8b9c22d6974e@csgroup.eu>
 <CANpmjNM9o1s4O4v2T9HUohPdCDJzWcaC5KDrt_7BSVdTUQWagw@mail.gmail.com>
Date:   Fri, 05 Mar 2021 22:49:36 +1100
Message-ID: <87tupprfan.fsf@mpe.ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Marco Elver <elver@google.com> writes:
...
>
> The choice is between:
>
> 1. ARCH_FUNC_PREFIX (as a matter of fact, the ARCH_FUNC_PREFIX patch
> is already in -mm). Perhaps we could optimize it further, by checking
> ARCH_FUNC_PREFIX in buf, and advancing buf like you propose, but I'm
> not sure it's worth worrying about.
>
> 2. The dynamic solution that I proposed that does not use a hard-coded
> '.' (or some variation thereof).
>
> Please tell me which solution you prefer, 1 or 2 -- I'd like to stop
> bikeshedding here. If there's a compelling argument for hard-coding
> the '.' in non-arch code, please clarify, but otherwise I'd like to
> keep arch-specific things out of generic code.

It's your choice, I was just trying to minimise the size of the wart you
have to carry in kfence code to deal with it.

The ARCH_FUNC_PREFIX solution is fine by me.

cheers