linux-kernel - Re: [RFC 2/3] lib: Allows to borrow mm in userspace on KUnit

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Date:   Thu, 16 Jul 2020 13:35:14 -0300
From:   Vitor Massaru Iha <vitor@...saru.org>
To:     Brendan Higgins <brendanhiggins@...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>,
        Kees Cook <keescook@...omium.org>,
        David Gow <davidgow@...gle.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [RFC 2/3] lib: Allows to borrow mm in userspace on KUnit

On Wed, 2020-07-15 at 17:37 -0700, Brendan Higgins wrote:
> On Tue, Jul 14, 2020 at 8:11 PM Vitor Massaru Iha <vitor@...saru.org>
> wrote:
> 
> Probably want to add more of a description here as what you are doing
> is not entirely trivial to someone not familiar with mm contexts.
> 
> > Signed-off-by: Vitor Massaru Iha <vitor@...saru.org>
> > ---
> >  include/kunit/test.h  |  1 +
> >  lib/kunit/try-catch.c | 15 ++++++++++++++-
> >  2 files changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/kunit/test.h b/include/kunit/test.h
> > index 59f3144f009a..49c38bdcb93e 100644
> > --- a/include/kunit/test.h
> > +++ b/include/kunit/test.h
> > @@ -222,6 +222,7 @@ struct kunit {
> >          * protect it with some type of lock.
> >          */
> >         struct list_head resources; /* Protected by lock. */
> > +       struct mm_struct *mm;
> 
> Part of me thinks we should put a better name here, part of me thinks
> it is fine because it matches the convention.
> 
> Either way, this DEFINITELY deserves a comment explaining what it is,
> why it exists, and how it should/shouldn't be used.
> 
> >  };
> > 
> >  void kunit_init_test(struct kunit *test, const char *name, char
> > *log);
> > diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
> > index 0dd434e40487..f677c2f2a51a 100644
> > --- a/lib/kunit/try-catch.c
> > +++ b/lib/kunit/try-catch.c
> > @@ -11,7 +11,8 @@
> >  #include <linux/completion.h>
> >  #include <linux/kernel.h>
> >  #include <linux/kthread.h>
> > -
> > +#include <linux/sched/mm.h>
> > +#include <linux/sched/task.h>
> >  #include "try-catch-impl.h"
> > 
> >  void __noreturn kunit_try_catch_throw(struct kunit_try_catch
> > *try_catch)
> > @@ -24,8 +25,17 @@ EXPORT_SYMBOL_GPL(kunit_try_catch_throw);
> >  static int kunit_generic_run_threadfn_adapter(void *data)
> >  {
> >         struct kunit_try_catch *try_catch = data;
> > +       struct kunit *test = try_catch->test;
> > +
> > +       if (test->mm != NULL)
> > +               kthread_use_mm(try_catch->test->mm);
> > 
> >         try_catch->try(try_catch->context);
> > +       if (try_catch->test->mm) {
> 
> Here and below: You already have a pointer to test. You should use
> it.
> 
> > +               if (test->mm != NULL)
> > +                       kthread_unuse_mm(try_catch->test->mm);
> > +               try_catch->test->mm = NULL;
> > +       }
> > 
> >         complete_and_exit(try_catch->try_completion, 0);
> >  }
> > @@ -65,6 +75,9 @@ void kunit_try_catch_run(struct kunit_try_catch
> > *try_catch, void *context)
> >         try_catch->context = context;
> >         try_catch->try_completion = &try_completion;
> >         try_catch->try_result = 0;
> > +
> > +       test->mm = get_task_mm(current);
> > +
> >         task_struct =
> > kthread_run(kunit_generic_run_threadfn_adapter,
> >                                   try_catch,
> >                                   "kunit_try_catch_thread");
> > --
> > 2.26.2
> >