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

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Message-ID: <66deaafe1974c989e949975bafe3ab0b2ae3f5ff.camel@sipsolutions.net>
Date: Thu, 26 Jun 2025 20:11:17 +0200
From: Benjamin Berg <benjamin@...solutions.net>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>, 
 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>
Cc: 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 Thomas,

I ran into two minor issues trying out the patches, see inline.

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.

> [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.

Benjamin

> [SNIP]