linux-kernel - Re: [PATCH] [RFC] ARM: vdso: work around gcc-8 warning

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Message-ID: <CAK8P3a1Qb77Y_9+EJ=eJ7UUEpFj2GUcwPrfc3+v+GZVE-3DCTQ@mail.gmail.com>
Date:   Wed, 23 Aug 2017 16:15:15 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Nathan Lynch <nathan_lynch@...tor.com>,
        Russell King <linux@...linux.org.uk>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Nicolas Pitre <nico@...xnic.net>
Subject: Re: [PATCH] [RFC] ARM: vdso: work around gcc-8 warning

On Wed, Aug 23, 2017 at 4:11 PM, Mark Rutland <mark.rutland@....com> wrote:
> On Wed, Aug 23, 2017 at 03:07:04PM +0100, Ard Biesheuvel wrote:
>> On 23 August 2017 at 15:05, Arnd Bergmann <arnd@...db.de> wrote:

>> > diff --git a/arch/arm/include/asm/vdso.h b/arch/arm/include/asm/vdso.h
>> > index d0295f1dd1a3..eff7d3a1d1ce 100644
>> > --- a/arch/arm/include/asm/vdso.h
>> > +++ b/arch/arm/include/asm/vdso.h
>> > @@ -11,7 +11,7 @@ struct mm_struct;
>> >
>> >  void arm_install_vdso(struct mm_struct *mm, unsigned long addr);
>> >
>> > -extern char vdso_start, vdso_end;
>> > +extern int vdso_start, vdso_end;
>> >
>> >  extern unsigned int vdso_total_pages;
>>
>> May I suggest
>>
>> extern char vdso_start[], vdso_end[];

This was my first attempt, but when I ran into a build error I did not
even look further

> FWIW, arm64 does this to solve this problem, since commit:
>
> dbbb08f500d61463 ("arm64, vdso: Define vdso_{start,end} as array")
>
> ... and x86 has done likewise for a while.

Yes, this looks good, I'll send a patch to do the same.

    Arnd