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

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Message-ID: <b89947c3216d1e59374672931edc2b14763fd81f.camel@massaru.org>
Date:   Thu, 16 Jul 2020 13:21:17 -0300
From:   Vitor Massaru Iha <vitor@...saru.org>
To:     David Gow <davidgow@...gle.com>
Cc:     KUnit Development <kunit-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [RFC 0/3] kunit: add support to use modules

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@...saru.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.