linux-kernel - Re: [PATCH v3 linux-kselftest-test 5/6] kunit: allow kunit to be loaded as a module

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Date:   Thu, 7 Nov 2019 19:02:40 -0800
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        catalin.marinas@....com, joe.lawrence@...hat.com,
        penguin-kernel@...ove.sakura.ne.jp, schowdary@...dia.com,
        urezki@...il.com, andriy.shevchenko@...ux.intel.com,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Knut Omang <knut.omang@...cle.com>
Subject: Re: [PATCH v3 linux-kselftest-test 5/6] kunit: allow kunit to be
 loaded as a module

On Thu, Nov 07, 2019 at 06:43:11PM -0800, Brendan Higgins wrote:
> On Thu, Oct 17, 2019 at 11:09 AM Alan Maguire <alan.maguire@...cle.com> wrote:
> >
> > Making kunit itself buildable as a module allows for "always-on"
> > kunit configuration; specifying CONFIG_KUNIT=m means the module
> > is built but only used when loaded.  Kunit test modules will load
> > kunit.ko as an implicit dependency, so simply running
> > "modprobe my-kunit-tests" will load the tests along with the kunit
> > module and run them.
> >
> > Signed-off-by: Alan Maguire <alan.maguire@...cle.com>
> > Signed-off-by: Knut Omang <knut.omang@...cle.com>
> > ---
> >  lib/kunit/Kconfig     | 2 +-
> >  lib/kunit/Makefile    | 4 +++-
> >  lib/kunit/test.c      | 2 ++
> >  lib/kunit/try-catch.c | 3 +++
> >  4 files changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/kunit/Kconfig b/lib/kunit/Kconfig
> > index 9ebd5e6..065aa16 100644
> > --- a/lib/kunit/Kconfig
> > +++ b/lib/kunit/Kconfig
> > @@ -3,7 +3,7 @@
> >  #
> >
> >  menuconfig KUNIT
> > -       bool "KUnit - Enable support for unit tests"
> > +       tristate "KUnit - Enable support for unit tests"
> >         help
> >           Enables support for kernel unit tests (KUnit), a lightweight unit
> >           testing and mocking framework for the Linux kernel. These tests are
> > diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
> > index 769d940..8e2635a 100644
> > --- a/lib/kunit/Makefile
> > +++ b/lib/kunit/Makefile
> > @@ -1,4 +1,6 @@
> > -obj-$(CONFIG_KUNIT) +=                 test.o \
> > +obj-$(CONFIG_KUNIT) +=                 kunit.o
> > +
> > +kunit-objs +=                          test.o \
> >                                         string-stream.o \
> >                                         assert.o \
> >                                         try-catch.o
> > diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> > index e8b2443..c0ace36 100644
> > --- a/lib/kunit/test.c
> > +++ b/lib/kunit/test.c
> > @@ -523,3 +523,5 @@ void *kunit_find_symbol(const char *sym)
> >         return ERR_PTR(-ENOENT);
> >  }
> >  EXPORT_SYMBOL(kunit_find_symbol);
> > +
> > +MODULE_LICENSE("GPL");
> > diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
> > index 1c1e9af..72fc8ed 100644
> > --- a/lib/kunit/try-catch.c
> > +++ b/lib/kunit/try-catch.c
> > @@ -31,6 +31,8 @@ static int kunit_generic_run_threadfn_adapter(void *data)
> >         complete_and_exit(try_catch->try_completion, 0);
> >  }
> >
> > +KUNIT_VAR_SYMBOL(sysctl_hung_task_timeout_secs, unsigned long);
> 
> Can you just export sysctl_hung_task_timeout_secs?
> 
> I don't mean to make you redo all this work for one symbol twice, but
> I thought we agreed on just exposing this symbol, but in a namespace.
> It seemed like a good use case for that namespaced exporting thing
> that Luis was talking about. As I understood it, you would have to
> export it in the module that defines it, and then use the new
> MODULE_IMPORT_NS() macro here.

Also, I tried applying this and running this on kselftest/test and got
the following build error:

In file included from lib/kunit/try-catch.c:10:
lib/kunit/try-catch.c: In function ‘kunit_test_timeout’:
./include/kunit/test.h:132:19: error: lvalue required as unary ‘&’ operand
  kunit_##symbol = &(symbol)
                   ^
lib/kunit/try-catch.c:57:2: note: in expansion of macro ‘KUNIT_INIT_VAR_SYMBOL’
  KUNIT_INIT_VAR_SYMBOL(NULL, sysctl_hung_task_timeout_secs);
  ^~~~~~~~~~~~~~~~~~~~~

> > +
> >  static unsigned long kunit_test_timeout(void)
> >  {
> >         unsigned long timeout_msecs;
> > @@ -52,6 +54,7 @@ static unsigned long kunit_test_timeout(void)
> >          * For more background on this topic, see:
> >          * https://mike-bland.com/2011/11/01/small-medium-large.html
> >          */
> > +       KUNIT_INIT_VAR_SYMBOL(NULL, sysctl_hung_task_timeout_secs);
> >         if (sysctl_hung_task_timeout_secs) {
> >                 /*
> >                  * If sysctl_hung_task is active, just set the timeout to some
> > --
> > 1.8.3.1
> >