linux-kernel - Re: [PATCH v4 12/15] kunit: Introduce UAPI testing framework

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Message-ID: <20250627060129-4fe09191-4714-4856-9de5-c8e5cf5ed0d6@linutronix.de>
Date: Fri, 27 Jun 2025 06:20:05 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Benjamin Berg <benjamin@...solutions.net>
Cc: Masahiro Yamada <masahiroy@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Willy Tarreau <w@....eu>, Thomas Weißschuh <linux@...ssschuh.net>, 
	Brendan Higgins <brendan.higgins@...ux.dev>, David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>, 
	Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>, 
	Nicolas Schier <nicolas.schier@...ux.dev>, Christophe Leroy <christophe.leroy@...roup.eu>, 
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
	kunit-dev@...glegroups.com, linux-doc@...r.kernel.org, workflows@...r.kernel.org, 
	Kees Cook <kees@...nel.org>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, linux-mm@...ck.org, 
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v4 12/15] kunit: Introduce UAPI testing framework

Hi Benjamin,

On Thu, Jun 26, 2025 at 08:11:17PM +0200, Benjamin Berg wrote:
> I ran into two minor issues trying out the patches, see inline.

Thanks for testing the series.

> On Thu, 2025-06-26 at 08:10 +0200, Thomas Weißschuh wrote:
> > Enable running UAPI tests as part of kunit.
> > The selftests are embedded into the kernel image and their output is
> > forwarded to kunit for unified reporting.
> > 
> > The implementation reuses parts of usermode drivers and usermode
> > helpers. However these frameworks are not used directly as they make it
> > impossible to retrieve a thread's exit code.
> > 
> > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> > 
> > [SNIP]
> > +/**
> > + * KUNIT_UAPI_EMBED_BLOB() - Embed another build artifact into the kernel
> > + * @_name: The name of symbol under which the artifact is embedded.
> > + * @_path: Path to the artifact on disk.
> > + *
> > + * Embeds a build artifact like a userspace executable into the kernel or current module.
> > + * The build artifact is read from disk and needs to be already built.
> > + */
> > +#define KUNIT_UAPI_EMBED_BLOB(_name, _path)					\
> > +	asm (									\
> > +	"	.pushsection .rodata, \"a\"				\n"	\
> > +	"	.global " __stringify(CONCATENATE(_name, _data)) "	\n"	\
> > +	__stringify(CONCATENATE(_name, _data)) ":			\n"	\
> > +	"	.incbin " __stringify(_path) "				\n"	\
> > +	"	.size " __stringify(CONCATENATE(_name, _data)) ", "		\
> > +			". - " __stringify(CONCATENATE(_name, _data)) "	\n"	\
> > +	"	.global " __stringify(CONCATENATE(_name, _end)) "	\n"	\
> > +	__stringify(CONCATENATE(_name, _end)) ":			\n"	\
> > +	"	.popsection						\n"	\
> > +	);									\
> > +										\
> > +	extern const char CONCATENATE(_name, _data)[];				\
> > +	extern const char CONCATENATE(_name, _end)[];				\
> > +										\
> > +	static const struct kunit_uapi_blob _name = {				\
> > +		.path	= _path,						\
> > +		.data	= CONCATENATE(_name, _data),				\
> > +		.end	= CONCATENATE(_name, _end),				\
> > +	}									\
> 
> For me, the compiler could not find the files for the ".incbin" unless
> I added an include path. i.e. adding
>   ccflags-y := -I$(obj)
> to lib/kunit/Makefile fixed the problem for me.

Can you share some more details on your build setup?
This worked for me as-is and also passed 0day build testing.

> > [SNIP]
> > +static int kunit_uapi_run_executable_in_mount(struct kunit *test, const char *executable,
> > +						   struct vfsmount *mnt)
> > +{
> > +	struct kunit_uapi_user_mode_thread_ctx ctx = {
> > +		.setup_done	= COMPLETION_INITIALIZER_ONSTACK(ctx.setup_done),
> > +		.executable	= executable,
> > +		.pwd		= {
> > +			.mnt	= mnt,
> > +			.dentry	= mnt->mnt_root,
> > +		},
> > +	};
> > +	int forward_err, wait_err, ret;
> 
> ret needs to be initialized to zero here as the kernel_wait function
> will only set "ret" if wo.wo_stat is non-zero.

Ack.

> > [SNIP]


Thomas