linux-kernel - Re: [tip:tracing/ftrace] tracing: fix oops in tracepoint_update_probe

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Message-ID: <20090318180007.GE5981@nowhere>
Date:	Wed, 18 Mar 2009 19:00:08 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
	jaswinderrajput@...il.com, rostedt@...dmis.org, tglx@...utronix.de,
	mingo@...e.hu, linux-tip-commits@...r.kernel.org
Subject: Re: [tip:tracing/ftrace] tracing: fix oops in
	tracepoint_update_probe_range()

On Wed, Mar 18, 2009 at 11:26:37PM +0530, Jaswinder Singh Rajput wrote:
> On Wed, 2009-03-18 at 17:51 +0000, Jaswinder Singh Rajput wrote:
> > Commit-ID:  966a6fdf6210e3ac8ce00b61cd1107cdf97ce744
> > Gitweb:     http://git.kernel.org/tip/966a6fdf6210e3ac8ce00b61cd1107cdf97ce744
> > Author:     Jaswinder Singh Rajput <jaswinder@...nel.org>
> > AuthorDate: Wed, 18 Mar 2009 22:18:56 +0530
> > Commit:     Ingo Molnar <mingo@...e.hu>
> > CommitDate: Wed, 18 Mar 2009 18:48:43 +0100
> > 
> > tracing: fix oops in tracepoint_update_probe_range()
> > 
> > Change this crash:
> > 
> >  BUG: unable to handle kernel NULL pointer dereference at (null)
> >  IP: [<ffffffff8107d4de>] tracepoint_update_probe_range+0x1f/0x9b
> >  PGD 13d5fb067 PUD 13d688067 PMD 0
> >  Oops: 0000 [#1] SMP
> > 
> > To a more debuggable WARN_ONCE().
> > 
> > Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@...il.com>
> > Cc: Frederic Weisbecker <fweisbec@...il.com>
> > Cc: Steven Rostedt <rostedt@...dmis.org>
> > LKML-Reference: <1237394936.3132.1.camel@...alhost.localdomain>
> > [ moved the check outside the lock and added a WARN_ON(). ]
> > Signed-off-by: Ingo Molnar <mingo@...e.hu>
> > 
> > 
> > ---
> >  kernel/tracepoint.c |    9 +++++++--
> >  1 files changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> > index 7960274..dd15df9 100644
> > --- a/kernel/tracepoint.c
> > +++ b/kernel/tracepoint.c
> > @@ -272,12 +272,17 @@ static void disable_tracepoint(struct tracepoint *elem)
> >   *
> >   * Updates the probe callback corresponding to a range of tracepoints.
> >   */
> > -void tracepoint_update_probe_range(struct tracepoint *begin,
> > -	struct tracepoint *end)
> > +void
> > +tracepoint_update_probe_range(struct tracepoint *begin, struct tracepoint *end)
> >  {
> >  	struct tracepoint *iter;
> >  	struct tracepoint_entry *mark_entry;
> >  
> > +	if (!iter) {
> > +		WARN_ON_ONCE(1);
> > +		return;
> > +	}
> > +
> >  	mutex_lock(&tracepoints_mutex);
> >  	for (iter = begin; iter < end; iter++) {
> >  		mark_entry = get_tracepoint(iter->name);
> 
> my original patch was correct.
> 
> --
> JSR
> 
> 

Jaswinder, It's hard for me to reproduce it via your config.
May be it's because I had to update it to match latest -tip tree and
then I inserted some noise inside.

Could you please send me your bad vmlinux, so that I can have a first look at
your elf sections and see if there is something helpful inside.

Thanks.

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