Re: [Linux-kernel-mentees] [RFC 0/3] kunit: add support to use modules

From: Vitor Massaru Iha <vitor@massaru.org>
To: David Gow <davidgow@google.com>
Cc: Kees Cook <keescook@chromium.org>,
	Brendan Higgins <brendanhiggins@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK"
	<linux-kselftest@vger.kernel.org>,
	linux-kernel-mentees@lists.linuxfoundation.org,
	KUnit Development <kunit-dev@googlegroups.com>
Subject: Re: [Linux-kernel-mentees] [RFC 0/3] kunit: add support to use modules
Date: Thu, 16 Jul 2020 13:21:17 -0300	[thread overview]
Message-ID: <b89947c3216d1e59374672931edc2b14763fd81f.camel@massaru.org> (raw)
In-Reply-To: <CABVgOSkBAiMSMzCx62_CRo_0e2SGdvRWZ0dSC4t628YJBw-3Aw@mail.gmail.com>

On Wed, 2020-07-15 at 11:47 +0800, David Gow wrote:
> On Wed, Jul 15, 2020 at 11:11 AM Vitor Massaru Iha <vitor@massaru.org
> > wrote:
> > Currently, KUnit does not allow the use of tests as a module.
> > This prevents the implementation of tests that require userspace.
> 
> If this is what I think it is, thanks! I'll hopefully get a chance to
> play with it over the next few days.
> 
> Can we clarify what this means: the current description is a little
> misleading, as KUnit tests can already be built and run as modules,
> and "tests that require userspace" is a bit broad.
> 
> As I understand it, this patchset does three things:
> - Let kunit_tool install modules to a root filesystem and boot UML
> with that filesystem.
> - Have tests inherit the mm of the process that started them, which
> (if the test is in a module), provides a user-space memory context so
> that copy_{from,to}_user() works.
> - Port the test_user_copy.c tests to KUnit, using this new feature.
> 
> A few comments from my quick glance over it:
> - The rootfs support is useful: I'm curious how it'll interact with
> non-UML architectures in [1]. It'd be nice for this to be extensible
> and to not explicitly state UML where possible.

Hm, I didn't think about other architectures. Which ones are you
thinking ?

> - The inheriting of the mm stuff still means that
> copy_{from,to}_user() will only work if loaded as a module. This
> really needs to be documented. (Ideally, we'd find a way of having
> this work even for built-in tests, but I don't have any real ideas as
> to how that could be done).

Sure, I'll write the documentation.

> - It'd be nice to split the test_user_copy.c test port into a
> separate
> commit. In fact, it may make sense to also split the kunit_tool
> changes and the mm changes into separate series, as they're both
> quite
> useful independently.
> 

I'll do it.

Thanks for the review.

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