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

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Date:   Sat, 27 Aug 2022 09:09:54 +0800
From:   David Gow <davidgow@...gle.com>
To:     Alison Schofield <alison.schofield@...el.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 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

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
> >