linux-kernel - Re: [PATCHv9] gpio: Remove VLA from gpiolib

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Message-ID: <CACRpkdZNGSd+1Z=GAC1d3sdemM_WG8KztHELtBerwAHUrUvXUA@mail.gmail.com>
Date:   Wed, 23 May 2018 14:03:02 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Laura Abbott <labbott@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>, Lukas Wunner <lukas@...ner.de>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com,
        Phil Reid <preid@...ctromag.com.au>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCHv9] gpio: Remove VLA from gpiolib

On Mon, May 21, 2018 at 7:57 PM, Laura Abbott <labbott@...hat.com> wrote:

> The new challenge is to remove VLAs from the kernel
> (see https://lkml.org/lkml/2018/3/7/621) to eventually
> turn on -Wvla.
>
> Using a kmalloc array is the easy way to fix this but kmalloc is still
> more expensive than stack allocation. Introduce a fast path with a
> fixed size stack array to cover most chip with gpios below some fixed
> amount. The slow path dynamically allocates an array to cover those
> chips with a large number of gpios.
>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
> Reviewed-by: Phil Reid <preid@...ctromag.com.au>
> Reviewed-and-tested-by: Lukas Wunner <lukas@...ner.de>
> Signed-off-by: Lukas Wunner <lukas@...ner.de>
> Signed-off-by: Laura Abbott <labbott@...hat.com>
> ---
> v9: switch to bitmap_zero

This v9 applied with Andy's review tag on top and pushed to
the servers for testing!

THANKS A LOT for your tireless work on this, it looks really
really good now, and as it seems we cleaned up some other
code on the way.

Yours,
Linus Walleij