linux-kernel - Re: [PATCH] tracepoint: Allow trace events in modules with TAINT

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Date:   Mon, 29 Aug 2022 09:39:08 -0700
From:   Alison Schofield <alison.schofield@...el.com>
To:     David Gow <davidgow@...gle.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-cxl@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] tracepoint: Allow trace events in modules with TAINT_TEST

On Sat, Aug 27, 2022 at 09:09:54AM +0800, David Gow wrote:
> On Sat, Aug 27, 2022 at 8:02 AM Alison Schofield
> <alison.schofield@...el.com> wrote:
> >
> > + David Gow - Submitter of the new taint type
> >
> > On Fri, Aug 26, 2022 at 03:35:11PM -0700, alison.schofield@...el.com wrote:
> > > From: Alison Schofield <alison.schofield@...el.com>
> > >
> > > Commit 2852ca7fba9f ("panic: Taint kernel if tests are run")
> > > introduced a new taint type, TAINT_TEST, to signal that an
> > > in-kernel test has been run.
> > >
> > > TAINT_TEST taint type defaults into a 'bad_taint' list for
> > > kernel tracing and blocks the creation of trace events. This
> > > causes a problem for CXL testing where loading the cxl_test
> > > module makes all CXL modules out-of-tree, blocking any trace
> > > events.
> > >
> > > Trace events are in development for CXL at the moment and this
> > > issue was found in test with v6.0-rc1.
> > >
> > > Reported-by: Ira Weiny <ira.weiny@...el.com>
> > > Suggested-by: Dan Williams <dan.j.williams@...el.com>
> > > Signed-off-by: Alison Schofield <alison.schofield@...el.com>
> > > ---
> 
> This seems fine to me: thanks for catching it. Test modules should be
> safe enough to load for this.
> 
> Does the comment in tracepoint_module_coming() need updating as well?
> https://elixir.bootlin.com/linux/v6.0-rc2/source/kernel/tracepoint.c#L650

Yes, ready in a v2:
-	 * Staging, out-of-tree, and unsigned GPL modules are fine.
+	 * Staging, out-of-tree, unsigned GPL, and test modules are fine.

Thanks!
Alison

> 
> Regardless, this is
> Reviewed-by: David Gow <davidgow@...gle.com>
> 
> Cheers,
> -- David
> 
> > >  kernel/tracepoint.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> > > index 64ea283f2f86..5f17378c9dc2 100644
> > > --- a/kernel/tracepoint.c
> > > +++ b/kernel/tracepoint.c
> > > @@ -571,7 +571,8 @@ static void for_each_tracepoint_range(
> > >  bool trace_module_has_bad_taint(struct module *mod)
> > >  {
> > >       return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
> > > -                            (1 << TAINT_UNSIGNED_MODULE));
> > > +                            (1 << TAINT_UNSIGNED_MODULE) |
> > > +                            (1 << TAINT_TEST));
> > >  }
> > >
> > >  static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
> > >
> > > base-commit: 4c612826bec1441214816827979b62f84a097e91
> > > --
> > > 2.31.1
> > >