linux-kernel - Re: [PATCH 22/28] x86: apm: avoid uninitialized data

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Date:   Tue, 18 Oct 2016 15:05:59 +0200 (CEST)
From:   Jiri Kosina <jikos@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: Re: [PATCH 22/28] x86: apm: avoid uninitialized data

On Tue, 18 Oct 2016, Arnd Bergmann wrote:

> apm_bios_call() can fail, and return a status in its argument
> structure. If that status however is zero during a call from
> apm_get_power_status(), we end up using data that may have
> never been set, as reported by "gcc -Wmaybe-uninitialized":
> 
> arch/x86/kernel/apm_32.c: In function ‘apm’:
> arch/x86/kernel/apm_32.c:1729:17: error: ‘bx’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> arch/x86/kernel/apm_32.c:1835:5: error: ‘cx’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> arch/x86/kernel/apm_32.c:1730:17: note: ‘cx’ was declared here
> arch/x86/kernel/apm_32.c:1842:27: error: ‘dx’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> arch/x86/kernel/apm_32.c:1731:17: note: ‘dx’ was declared here
> 
> This changes the function to return "APM_NO_ERROR" here, which
> makes the code more robust to broken BIOS versions, and avoids
> the warning.
> 
> Cc: x86@...nel.org
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Makes sense.

Reviewed-by: Jiri Kosina <jkosina@...e.cz>

Thanks,

-- 
Jiri Kosina
SUSE Labs