Re: [PATCH 2/5 v16] ARM: Replace string mem* functions for KASan

From: Ard Biesheuvel <ardb@kernel.org>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Ahmad Fatoum <a.fatoum@pengutronix.de>,
	Arnd Bergmann <arnd@arndb.de>,
	Abbott Liu <liuwenliang@huawei.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	kasan-dev <kasan-dev@googlegroups.com>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Linux-Next Mailing List <linux-next@vger.kernel.org>,
	Alexander Potapenko <glider@google.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Naresh Kamboju <naresh.kamboju@linaro.org>,
	Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH 2/5 v16] ARM: Replace string mem* functions for KASan
Date: Fri, 6 Nov 2020 16:18:43 +0100	[thread overview]
Message-ID: <CAMj1kXHoKOTtzB645EYZzGtt2tJaZS15Hzn+yoeV3_Ffer_DQw@mail.gmail.com> (raw)
In-Reply-To: <20201106151554.GU1551@shell.armlinux.org.uk>

On Fri, 6 Nov 2020 at 16:16, Russell King - ARM Linux admin
<linux@armlinux.org.uk> wrote:
>
> On Fri, Nov 06, 2020 at 02:37:21PM +0100, Linus Walleij wrote:
> > On Fri, Nov 6, 2020 at 10:44 AM Nathan Chancellor
> > <natechancellor@gmail.com> wrote:
> > > On Fri, Nov 06, 2020 at 09:28:09AM +0100, Ard Biesheuvel wrote:
> >
> > > > AFAIK there is an incompatible change in -next to change the
> > > > definition of the __alias() macro
> > >
> > > Indeed. The following diff needs to be applied as a fixup to
> > > treewide-remove-stringification-from-__alias-macro-definition.patch in
> > > mmotm.
> > >
> > > Cheers,
> > > Nathan
> > >
> > > diff --git a/arch/arm/boot/compressed/string.c b/arch/arm/boot/compressed/string.c
> > > index 8c0fa276d994..cc6198f8a348 100644
> > > --- a/arch/arm/boot/compressed/string.c
> > > +++ b/arch/arm/boot/compressed/string.c
> > > @@ -21,9 +21,9 @@
> > >  #undef memcpy
> > >  #undef memmove
> > >  #undef memset
> > > -void *__memcpy(void *__dest, __const void *__src, size_t __n) __alias(memcpy);
> > > -void *__memmove(void *__dest, __const void *__src, size_t count) __alias(memmove);
> > > -void *__memset(void *s, int c, size_t count) __alias(memset);
> > > +void *__memcpy(void *__dest, __const void *__src, size_t __n) __alias("memcpy");
> > > +void *__memmove(void *__dest, __const void *__src, size_t count) __alias("memmove");
> > > +void *__memset(void *s, int c, size_t count) __alias("memset");
> > >  #endif
> > >
> > >  void *memcpy(void *__dest, __const void *__src, size_t __n)
> >
> > Aha. So shall we submit this to Russell? I figure that his git will not
> > build *without* the changes from mmotm?
> >
> > That tree isn't using git either is it?
> >
> > Is this one of those cases where we should ask Stephen R
> > to carry this patch on top of -next until the merge window?
>
> Another solution would be to drop 9017/2 ("Enable KASan for ARM")
> until the following merge window, and queue up the non-conflicing
> ARM KASan fixes in my "misc" branch along with the rest of KASan,
> and the conflicting patches along with 9017/2 in the following
> merge window.
>
> That means delaying KASan enablement another three months or so,
> but should result in less headaches about how to avoid build
> breakage with different bits going through different trees.
>
> Comments?
>

Alternatively, we could simply switch these to the bare
__attribute__((alias(".."))) syntax now, and revert that change again
one cycle later.

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