linux-kernel - Re: [PATCH] modpost: Add flag -f for making section mismatches fatal

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Message-ID: <87a8s2njr4.fsf@rustcorp.com.au>
Date:	Fri, 02 Oct 2015 10:56:23 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Nicolas Boichat <drinkcat@...omium.org>,
	linux-kbuild@...r.kernel.org
Cc:	Michal Marek <mmarek@...e.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Pranith Kumar <bobby.prani@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Vladimir Murzin <vladimir.murzin@....com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	John Stultz <john.stultz@...aro.org>,
	Jan Kiszka <jan.kiszka@...mens.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	Takashi Iwai <tiwai@...e.de>,
	Nicolas Boichat <drinkcat@...omium.org>,
	Kyle McMartin <kyle@...hat.com>, linux-kernel@...r.kernel.org,
	Jonathan Kliegman <kliegs@...omium.org>, olofj@...omium.org,
	Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH] modpost: Add flag -f for making section mismatches fatal

Nicolas Boichat <drinkcat@...omium.org> writes:
> The section mismatch warning can be easy to miss during the kernel build
> process. Allow it to be marked as fatal to be easily caught and prevent
> bugs from slipping in.
>
> Setting CONFIG_SECTION_MISMATCH_WARNING=y causes these warnings to be
> non-fatal, since there are a number of section mismatches when using
> allmodconfig on some architectures, and we do not want to break these
> builds by default.
>
> Signed-off-by: Nicolas Boichat <drinkcat@...omium.org>
>
> Change-Id: Ic346706e3297c9f0d790e3552aa94e5cff9897a6
> ---
>
> I'm trying to revive this old patch. When it was first submitted [1],
> Jonathan got the following feedback:
>  - The logic of the option should be inverted (i.e. SECTION_MISMATCH_WARNING),
>    so that is not not enabled in allmodconfig for some architectures that do
>    have section mismatches. I've seen some failures (namely, on arm64), so I
>    did that.
>  - CONFIG_DEBUG_SECTION_MISMATCH should be removed and warnings should always
>    be shown verbosely. This option does 3 things:
>      1. Enable -fno-inline-functions-called-onc
>      2. Run the section mismatch analysis for each module/built-in.o
>      3. Enable verbose reporting from modpost
>    We definitely do not want 1 by default, so I think we should keep the option.
>    If we enable 2 & 3 by default, which I think would be reasonable, then the
>    option name does not make much sense anymore, and I'm not sure what to do
>    with the documentation that is currently provided in the Kconfig description.
>
> Tested on x86-64 allmodconfig, setting the option to =n, and creating a
> section mismatch by running:
> sed -i -e 's/\(ssize_t soc_codec_reg_show\)/__init \1/' sound/soc/soc-core.c

Minor feedback:

1) Please rename to CONFIG_SECTION_MISMATCH_WARN_ONLY.
2) -f means force, perhaps -E for error?

Otherwise, quite nice.

Thanks,
Rusty.
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