From: Nathan Lynch <nathan_lynch@mentor.com>
To: Arnd Bergmann <arnd@arndb.de>
CC: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Nicolas Pitre <nico@fluxnic.net>, Mark Rutland <mark.rutland@arm.com>,
        Arnd Bergmann <arnd@arndb.de>, Will Deacon <will.deacon@arm.com>,
        Marc Zyngier <marc.zyngier@arm.com>,
        <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>,
        Russell King <linux@armlinux.org.uk>
Subject: Re: [PATCH v2] ARM: vdso: Define vdso_{start,end} as array
In-Reply-To: <20170823142419.1811665-1-arnd@arndb.de>
References: <20170823142419.1811665-1-arnd@arndb.de>
Date: Wed, 23 Aug 2017 12:46:28 -0500
Message-ID: <87tw0ytbwr.fsf@mentor.com>
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Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
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Arnd Bergmann <arnd@arndb.de> writes:

> gcc-8 correctly points out that reading four bytes from a pointer to a
> 'char' variable is wrong
>
> arch/arm/kernel/vdso.c: In function 'vdso_init':
> arch/arm/kernel/vdso.c:200:6: error: '__builtin_memcmp_eq' reading 4 bytes from a region of size 1 [-Werror=stringop-overflow=]
>
> However, in this case the variable just stands for the beginning of the
> vdso and is not actually a 'char', so the code is doing what it is meant
> to do.
>
> This uses the same approach as arm64 and x86, declaring the addresses
> as char arrays.
>
> See also: dbbb08f500d6 ("arm64, vdso: Define vdso_{start,end} as array")
>
> Suggested-by: Mark Rutland <mark.rutland@arm.com>
> Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Acked-by: Nathan Lynch <nathan_lynch@mentor.com>

Thanks!