linux-kernel - Re: [PATCH] drm/bridge: fix stack usage warning on old gcc

Open Source and information security mailing list archives

Message-ID: <20200429204613.GA24103@ravnborg.org>
Date:   Wed, 29 Apr 2020 22:46:13 +0200
From:   Sam Ravnborg <sam@...nborg.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Jonas Karlman <jonas@...boo.se>,
        Sebastian Reichel <sebastian.reichel@...labora.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Boris Brezillon <boris.brezillon@...labora.com>
Subject: Re: [PATCH] drm/bridge: fix stack usage warning on old gcc

Hi Arnd.

On Tue, Apr 28, 2020 at 11:53:54PM +0200, Arnd Bergmann wrote:
> Some older versions of gcc badly optimize code that passes
> an inline function argument into another function by reference,
> causing huge stack usage:
> 
> drivers/gpu/drm/bridge/tc358768.c: In function 'tc358768_bridge_pre_enable':
> drivers/gpu/drm/bridge/tc358768.c:840:1: error: the frame size of 2256 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]
> 
> Use a temporary variable as a workaround and add a comment pointing
> to the gcc bug.
> 
> Fixes: ff1ca6397b1d ("drm/bridge: Add tc358768 driver")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks, pushed to drm-misc-next with Tomi's r-b.

	Sam

> ---
>  drivers/gpu/drm/bridge/tc358768.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
> index 1b39e8d37834..6650fe4cfc20 100644
> --- a/drivers/gpu/drm/bridge/tc358768.c
> +++ b/drivers/gpu/drm/bridge/tc358768.c
> @@ -178,6 +178,8 @@ static int tc358768_clear_error(struct tc358768_priv *priv)
>  
>  static void tc358768_write(struct tc358768_priv *priv, u32 reg, u32 val)
>  {
> +	/* work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
> +	int tmpval = val;
>  	size_t count = 2;
>  
>  	if (priv->error)
> @@ -187,7 +189,7 @@ static void tc358768_write(struct tc358768_priv *priv, u32 reg, u32 val)
>  	if (reg < 0x100 || reg >= 0x600)
>  		count = 1;
>  
> -	priv->error = regmap_bulk_write(priv->regmap, reg, &val, count);
> +	priv->error = regmap_bulk_write(priv->regmap, reg, &tmpval, count);
>  }
>  
>  static void tc358768_read(struct tc358768_priv *priv, u32 reg, u32 *val)
> -- 
> 2.26.0
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives