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From:   Arnd Bergmann <arnd@kernel.org>
Date:   Thu, 29 Oct 2020 14:35:53 +0100
Message-ID: <CAK8P3a2W-BcRyxx7+JXr+MCBLSuLzLdEDzM8LMk5y1rjaEuXbw@mail.gmail.com>
Subject: Re: [PATCH 2/4] arm64: hide more compat_vdso code
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Andrei Vagin <avagin@gmail.com>,
        Michel Lespinasse <walken@google.com>,
        Mark Brown <broonie@kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Dmitry Safonov <dima@arista.com>,
        Andrew Morton <akpm@linux-foundation.org>
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On Mon, Oct 26, 2020 at 5:55 PM Mark Rutland <mark.rutland@arm.com> wrote:
> On Mon, Oct 26, 2020 at 05:03:29PM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > When CONFIG_COMPAT_VDSO is disabled, we get a warning
> > about a potential out-of-bounds access:
> >
> > arch/arm64/kernel/vdso.c: In function 'aarch32_vdso_mremap':
> > arch/arm64/kernel/vdso.c:86:37: warning: array subscript 1 is above array bounds of 'struct vdso_abi_info[1]' [-Warray-bounds]
> >    86 |  unsigned long vdso_size = vdso_info[abi].vdso_code_end -
> >       |                            ~~~~~~~~~^~~~~
> >
> > This is all in dead code however that the compiler is unable to
> > eliminate by itself.
> >
> > Change the array to individual local variables that can be
> > dropped in dead code elimination to let the compiler understand
> > this better.
> >
> > Fixes: 0cbc2659123e ("arm64: vdso32: Remove a bunch of #ifdef CONFIG_COMPAT_VDSO guards")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> This looks like a nice cleanup to me! I agree we don't need the array
> here.
>
> Reviewed-by: Mark Rutland <mark.rutland@arm.com>

Thanks!

I see the patch now conflicts with "mm: forbid splitting special mappings"
in -mm, by Dmitry Safonov. I have rebased my patch on top, should
I send it to Andrew for inclusion in -mm then?

      Arnd