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Date: Tue, 5 Mar 2024 11:54:06 -0800
From: Kees Cook <keescook@chromium.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: linux-kselftest@vger.kernel.org, David Airlie <airlied@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>,
	=?iso-8859-1?Q?Ma=EDra?= Canal <mcanal@igalia.com>,
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	Arthur Grillo <arthurgrillo@riseup.net>,
	Brendan Higgins <brendan.higgins@linux.dev>,
	Naresh Kamboju <naresh.kamboju@linaro.org>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Maxime Ripard <mripard@kernel.org>,
	Ville =?iso-8859-1?Q?Syrj=E4l=E4?= <ville.syrjala@linux.intel.com>,
	Daniel Vetter <daniel@ffwll.ch>,
	Thomas Zimmermann <tzimmermann@suse.de>,
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	kunit-dev@googlegroups.com, linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH 1/5] bug: Core support for suppressing warning
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Message-ID: <202403051149.547235C794@keescook>
References: <20240305184033.425294-1-linux@roeck-us.net>
 <20240305184033.425294-2-linux@roeck-us.net>
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On Tue, Mar 05, 2024 at 10:40:29AM -0800, Guenter Roeck wrote:
> [...]
>  	warning = (bug->flags & BUGFLAG_WARNING) != 0;
>  	once = (bug->flags & BUGFLAG_ONCE) != 0;
>  	done = (bug->flags & BUGFLAG_DONE) != 0;
>  
> +	if (warning && IS_SUPPRESSED_WARNING(function))
> +		return BUG_TRAP_TYPE_WARN;
> +

I had to re-read __report_bug() more carefully, but yes, this works --
it's basically leaving early, like "once" does.

This looks like a reasonable approach!

Something very similar to this is checking that a warning happens. i.e.
you talk about drm selftests checking function return values, but I've
got a bunch of tests (LKDTM) that live outside of KUnit because I haven't
had a clean way to check for specific warnings/bugs. I feel like future
changes built on top of this series could add counters or something that
KUnit could examine. E.g. I did this manually for some fortify tests:

https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=for-next/hardening&id=4ce615e798a752d4431fcc52960478906dec2f0e

-Kees

-- 
Kees Cook