netdev - Re: [PATCH v4 02/12] selftests/harness: Merge TEST_F_FORK() into TEST

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Message-ID: <20240301.Miem9Kei4eev@digikod.net>
Date: Mon, 4 Mar 2024 20:27:49 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com, 
	pabeni@...hat.com, shuah@...nel.org, linux-kselftest@...r.kernel.org, 
	linux-security-module@...r.kernel.org, keescook@...omium.org, jakub@...udflare.com, 
	Günther Noack <gnoack@...gle.com>, Will Drewry <wad@...omium.org>
Subject: Re: [PATCH v4 02/12] selftests/harness: Merge TEST_F_FORK() into
 TEST_F()

Testing the whole series, I found that some Landlock tests are flaky
starting with this patch.  I tried to not use the longjmp in the
grandchild but it didn't change.  I suspect missing volatiles but I
didn't find the faulty one(s) yet. :/
I'll continue investigating tomorrow but help would be much appreciated!


On Wed, Feb 28, 2024 at 04:59:09PM -0800, Jakub Kicinski wrote:
> From: Mickaël Salaün <mic@...ikod.net>
> 
> Replace Landlock-specific TEST_F_FORK() with an improved TEST_F() which
> brings four related changes:
> 
> Run TEST_F()'s tests in a grandchild process to make it possible to
> drop privileges and delegate teardown to the parent.
> 
> Compared to TEST_F_FORK(), simplify handling of the test grandchild
> process thanks to vfork(2), and makes it generic (e.g. no explicit
> conversion between exit code and _metadata).
> 
> Compared to TEST_F_FORK(), run teardown even when tests failed with an
> assert thanks to commit 63e6b2a42342 ("selftests/harness: Run TEARDOWN
> for ASSERT failures").
> 
> Simplify the test harness code by removing the no_print and step fields
> which are not used.  I added this feature just after I made
> kselftest_harness.h more broadly available but this step counter
> remained even though it wasn't needed after all. See commit 369130b63178
> ("selftests: Enhance kselftest_harness.h to print which assert failed").
> 
> Replace spaces with tabs in one line of __TEST_F_IMPL().
> 
> Cc: Günther Noack <gnoack@...gle.com>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Will Drewry <wad@...omium.org>
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Reviewed-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> --
> v4:
>  - GAND -> GRAND
>  - init child to 1, otherwise assert in setup triggers a longjmp
>    which in turn reads child without it ever getting initialized
>    (or being 0, i.e. we mistakenly assume we're in the grandchild)

Good catch!