linux-kernel - Re: [RFC v3 06/19] arch: um: enable running kunit from User Mode Linux

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Date:   Mon, 3 Dec 2018 15:22:32 -0800
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     mcgrof@...nel.org
Cc:     Rob Herring <robh@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...gle.com>, shuah@...nel.org,
        Joel Stanley <joel@....id.au>, mpe@...erman.id.au,
        joe@...ches.com, brakmo@...com, rostedt@...dmis.org,
        Tim.Bird@...y.com, khilman@...libre.com,
        Julia Lawall <julia.lawall@...6.fr>,
        linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        jdike@...toit.com, richard@....at, linux-um@...ts.infradead.org,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, dan.j.williams@...el.com,
        linux-nvdimm@...ts.01.org, kieran.bingham@...asonboard.com,
        Frank Rowand <frowand.list@...il.com>,
        Knut Omang <knut.omang@...cle.com>
Subject: Re: [RFC v3 06/19] arch: um: enable running kunit from User Mode Linux

On Fri, Nov 30, 2018 at 10:22 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
>
> On Fri, Nov 30, 2018 at 08:05:34AM -0600, Rob Herring wrote:
> > On Thu, Nov 29, 2018 at 9:37 PM Luis Chamberlain <mcgrof@...nel.org> wrote:
> > >
> > > On Wed, Nov 28, 2018 at 03:26:03PM -0600, Rob Herring wrote:
> > > > On Wed, Nov 28, 2018 at 1:37 PM Brendan Higgins
> > > > <brendanhiggins@...gle.com> wrote:
> > > > >
> > > > > Make minimum number of changes outside of the KUnit directories for
> > > > > KUnit to build and run using UML.
> > > >
> > > > There's nothing in this patch limiting this to UML.
> > >
> > > Not that one, but the abort thing segv thing is, eventually.
> > > To support other architectures we'd need to make a wrapper to that
> > > hack which Brendan added, and then allow each os to implement
> > > its own call, and add an asm-generic helper.

I think Rob is referring to the description for this patch. This patch
previously did what you suggested, Luis, (source the KUnit kconfig
from arch/um/) but Kees asked me to change it to how it is now (which
probably makes sense if we are saying KUnit is not intended to be tied
to a particular architecture, no?), and I forgot to update the commit
description, sorry.

> >
> > I've not looked into why this is needed, but can't you make the abort
> > support optional and arches can select it when they support it.
>
> Its why I have asked for it to be properly documented. The patches in no
> way illustrate *why* such thing is done. And if we are going to
> potentially have other archs do something similar best to make it
> explicit.

Yeah, I should better document it. I should also probably not include
any UML specific header files in kunit/test.h; that seems like I am
asking to get more tightly coupled if I am not careful about exactly
what things I depend on.

I think Luis is right, I need to add a wrapper around the features
needed for the hack to support abort() and then write a UML specific
implementation.

For the asm-generic case, we could probably just have abort() call
BUG(), with that KUnit should work on most architectures, albeit with
pretty reduced functionality.

>
> > At
> > least before, the DT unittests didn't need this to run and shouldn't
> > depend on it after converting to kunit.

Fair enough.