linux-kernel - Re: [PATCH v2 08/10] drivers/auxdisplay: add a KFuzzTest for parse

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Message-ID: <aM6ibO75IidHOO3m@wunner.de>
Date: Sat, 20 Sep 2025 14:47:40 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Alexander Potapenko <glider@...gle.com>
Cc: Andy Shevchenko <andy.shevchenko@...il.com>,
	Ethan Graham <ethan.w.s.graham@...il.com>, ethangraham@...gle.com,
	andreyknvl@...il.com, andy@...nel.org, brauner@...nel.org,
	brendan.higgins@...ux.dev, davem@...emloft.net, davidgow@...gle.com,
	dhowells@...hat.com, dvyukov@...gle.com, elver@...gle.com,
	herbert@...dor.apana.org.au, ignat@...udflare.com, jack@...e.cz,
	jannh@...gle.com, johannes@...solutions.net,
	kasan-dev@...glegroups.com, kees@...nel.org,
	kunit-dev@...glegroups.com, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, rmoar@...gle.com,
	shuah@...nel.org, sj@...nel.org, tarasmadan@...gle.com
Subject: Re: [PATCH v2 08/10] drivers/auxdisplay: add a KFuzzTest for
 parse_xy()

On Sat, Sep 20, 2025 at 02:08:01PM +0200, Alexander Potapenko wrote:
> On Sat, Sep 20, 2025 at 12:54 PM Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > On Fri, Sep 19, 2025 at 5:58 PM Ethan Graham <ethan.w.s.graham@...il.com> wrote:
> > > +++ b/drivers/auxdisplay/charlcd.c
> > > @@ -682,3 +682,11 @@ EXPORT_SYMBOL_GPL(charlcd_unregister);
> > >
> > >  MODULE_DESCRIPTION("Character LCD core support");
> > >  MODULE_LICENSE("GPL");
> > > +
> > > +/*
> > > + * When CONFIG_KFUZZTEST is enabled, we include this _kfuzz.c file to ensure
> > > + * that KFuzzTest targets are built.
> > > + */
> > > +#ifdef CONFIG_KFUZZTEST
> > > +#include "tests/charlcd_kfuzz.c"
> > > +#endif /* CONFIG_KFUZZTEST */
> >
> > No, NAK. We don't want to see these in each and every module. Please,
> > make sure that nothing, except maybe Kconfig, is modified in this
> > folder (yet, you may add a _separate_ test module, as you already have
> > done in this patch).
> 
> This is one of the cases in which we can't go without changing the
> original code, because parse_xy() is a static function.
> Including the test into the source is not the only option, we could as
> well make the function visible unconditionally, or introduce a macro
> similar to VISIBLE_IF_KUNIT.
> Do you prefer any of those?

Just add something like this to drivers/auxdisplay/Makefile:

ifeq ($(CONFIG_KFUZZTEST),y)
CFLAGS_charlcd.o := -include $(src)/tests/charlcd_kfuzz.c
endif

Alternatively, if the file in tests/ always has the same name
as the source file but with "_kfuzz.c" suffix, consider amending
scripts/Makefile.build to always include the "_kfuzz.c" file
if it exists and CONFIG_KFUZZTEST=y, thus avoiding the need
to amend all the individual Makefiles in the tree.

Thanks,

Lukas