linux-kernel - Re: [RFC PATCH v1] powerpc: Enable KFENCE for PPC32

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Date:   Fri, 5 Mar 2021 14:46:58 +0100
From:   Marco Elver <elver@...gle.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Alexander Potapenko <glider@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org,
        kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [RFC PATCH v1] powerpc: Enable KFENCE for PPC32

On Fri, 5 Mar 2021 at 12:49, Michael Ellerman <mpe@...erman.id.au> wrote:
> Marco Elver <elver@...gle.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.

Thank you -- the ARCH_FUNC_PREFIX version is already in -mm, so let's
keep it. It's purely static vs the other options. Should another
debugging tool need something similar we can revisit whether to change
or move it.

Thanks,
-- Marco