linux-kernel - Re: perf report segfault

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Date:   Wed, 10 Oct 2018 09:14:58 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Sandipan Das <sandipan@...ux.ibm.com>
Cc:     Anthony LaTorre <tlatorre9@...il.com>, peterz@...radead.org,
        mingo@...hat.com, jolsa@...nel.org, acme@...nel.org,
        alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
        linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Milian Wolff <milian.wolff@...b.com>
Subject: Re: perf report segfault

On Wed, Oct 10, 2018 at 11:13:47AM +0530, Sandipan Das wrote:
> Hi Jiri,
> 
> Yes, this happens when entry->map is NULL. While your fix seems correct, the
> following commit from Milian Wolff had already addressed this. I think this
> was pulled in with one of Arnaldo's recent perf/urgent updates.
> 
> ff4ce2885af8 ("perf report: Don't try to map ip to invalid map")
> 
> Adding Milian to the loop as well.

yea.. I knew I saw that code just recently ;-)

thanks,
jirka

> 
> With Regards,
> Sandipan
> 
> On 10/10/18 3:50 AM, Jiri Olsa wrote:
> > On Tue, Oct 09, 2018 at 04:47:31PM -0500, Anthony LaTorre wrote:
> >> I can try building perf from the latest sources. I've attached the
> >> perf.data and perf.data.tar.bz2 from the test program I sent earlier.
> > 
> > cool, reproduced.. it seems to get introduced by:
> >   2a9d5050dc84 perf script: Show correct offsets for DWARF-based unwinding
> > 
> > reverting that patch fixes the issue for me, but looks like
> > we could just make th attached check and prevent the crash
> > 
> > adding Sandipan Das to the loop, the author of that commit, any idea?
> > 
> > thanks,
> > jirka
> > 
> > 
> > ---
> > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> > index c4acd2001db0..ea68c805c7ac 100644
> > --- a/tools/perf/util/machine.c
> > +++ b/tools/perf/util/machine.c
> > @@ -2312,7 +2312,6 @@ static int unwind_entry(struct unwind_entry *entry, void *arg)
> >  {
> >  	struct callchain_cursor *cursor = arg;
> >  	const char *srcline = NULL;
> > -	u64 addr;
> >  
> >  	if (symbol_conf.hide_unresolved && entry->sym == NULL)
> >  		return 0;
> > @@ -2320,13 +2319,15 @@ static int unwind_entry(struct unwind_entry *entry, void *arg)
> >  	if (append_inlines(cursor, entry->map, entry->sym, entry->ip) == 0)
> >  		return 0;
> >  
> > -	/*
> > -	 * Convert entry->ip from a virtual address to an offset in
> > -	 * its corresponding binary.
> > -	 */
> > -	addr = map__map_ip(entry->map, entry->ip);
> > +	if (entry->map) {
> > +		/*
> > +		 * Convert entry->ip from a virtual address to an offset in
> > +		 * its corresponding binary.
> > +		 */
> > +		u64 addr = map__map_ip(entry->map, entry->ip);
> > +		srcline = callchain_srcline(entry->map, entry->sym, addr);
> > +	}
> >  
> > -	srcline = callchain_srcline(entry->map, entry->sym, addr);
> >  	return callchain_cursor_append(cursor, entry->ip,
> >  				       entry->map, entry->sym,
> >  				       false, NULL, 0, 0, 0, srcline);
> > 
>