linux-kernel - Re: [PATCH] perf script: Fix segfault using --show-mmap-events

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Message-ID: <20150820192425.GB3154@kernel.org>
Date:	Thu, 20 Aug 2015 16:24:25 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	linux-kernel@...r.kernel.org, Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] perf script: Fix segfault using --show-mmap-events

Em Thu, Aug 20, 2015 at 11:26:45AM +0300, Adrian Hunter escreveu:
> Patch "perf script: Don't assume evsel position of tracking events"
> changed 'perf script' to use 'perf_evlist__id2evsel()'. That results
> in a segfault if there is more than 1 event and there are
> synthesized mmap events e.g.
> 
> 	$ perf record -e cycles,instructions -p$$ sleep 1
> 	$ perf script --show-mmap-events
> 	Segmentation fault (core dumped)

Please next time tell what branch this affects, otherwise I'll have to
try it on perf/urgent, notice that the problem is not there, then try it
again on perf/core, where it is, to then apply...

Applied to perf/core.

Thanks,

- Arnaldo
 
> That happens because these synthesized events have an 'id' of zero
> which does not match any 'evsel'.
> 
> Currently, these synthesized events use the sample type of the first
> evsel.
> 
> Change 'perf_evlist__id2evsel()' to reflect that which also makes
> it consistent with 'perf_evlist__event2evsel()'.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
>  tools/perf/util/evlist.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 373f65b02545..e9a5d432902c 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -573,7 +573,7 @@ struct perf_evsel *perf_evlist__id2evsel(struct perf_evlist *evlist, u64 id)
>  {
>  	struct perf_sample_id *sid;
>  
> -	if (evlist->nr_entries == 1)
> +	if (evlist->nr_entries == 1 || !id)
>  		return perf_evlist__first(evlist);
>  
>  	sid = perf_evlist__id2sid(evlist, id);
> -- 
> 1.9.1
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