linux-kernel - Re: [PATCH] Disable -Wframe-larger-than warnings with KASAN=y

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Message-ID: <CAK3bHNWBhSKCLVcJBwsNF6HL3vpGH9dGO2zm_c_v8at1v3BYJw@mail.gmail.com>
Date:	Fri, 16 Oct 2015 19:05:33 +0300
From:	Abylay Ospan <aospan@...up.ru>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andi Kleen <ak@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Kozlov Sergey <serjk@...up.ru>, kbuild-all@...org,
	linux-media <linux-media@...r.kernel.org>
Subject: Re: [PATCH] Disable -Wframe-larger-than warnings with KASAN=y

Hello,

Acked-by: Abylay Ospan <aospan@...up.ru>



2015-10-16 19:02 GMT+03:00 Andrey Ryabinin <aryabinin@...tuozzo.com>:
> When the kernel compiled with KASAN=y, GCC adds redzones
> for each variable on stack. This enlarges function's stack
> frame and causes:
>         'warning: the frame size of X bytes is larger than Y bytes'
>
> The worst case I've seen for now is following:
>  ../net/wireless/nl80211.c: In function ‘nl80211_send_wiphy’:
>  ../net/wireless/nl80211.c:1731:1: warning: the frame size of 5448 bytes is larger than 2048 bytes [-Wframe-larger-than=]
>   }
>    ^
> That kind of warning becomes useless with KASAN=y. It doesn't necessarily
> indicate that there is some problem in the code, thus we should turn it off.
>
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> ---
>  lib/Kconfig.debug | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index ab76b99..1d1521c 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -197,6 +197,7 @@ config ENABLE_MUST_CHECK
>  config FRAME_WARN
>         int "Warn for stack frames larger than (needs gcc 4.4)"
>         range 0 8192
> +       default 0 if KASAN
>         default 1024 if !64BIT
>         default 2048 if 64BIT
>         help
> --
> 2.4.9
>



-- 
Abylay Ospan,
NetUP Inc.
http://www.netup.tv
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