Re: [PATCH] perf record: Fix crash in pipe mode
From: Arnaldo Carvalho de Melo
Date: Fri Mar 02 2018 - 12:10:19 EST
Em Fri, Mar 02, 2018 at 05:13:54PM +0100, Jiri Olsa escreveu:
> Currently we can crash perf record when running in pipe mode, like:
>
> $ perf record ls | perf report
> # To display the perf.data header info, please use --header/--header-only options.
> #
> perf: Segmentation fault
> Error:
> The - file has no samples!
>
> The callstack of the crash is:
Thanks, reproduced the problem, applied the patch, tested, fixed, simple
enough, applied.
- Arnaldo
> 0x0000000000515242 in perf_event__synthesize_event_update_name
> 3513 ev = event_update_event__new(len + 1, PERF_EVENT_UPDATE__NAME, evsel->id[0]);
> (gdb) bt
> #0 0x0000000000515242 in perf_event__synthesize_event_update_name
> #1 0x00000000005158a4 in perf_event__synthesize_extra_attr
> #2 0x0000000000443347 in record__synthesize
> #3 0x00000000004438e3 in __cmd_record
> #4 0x000000000044514e in cmd_record
> #5 0x00000000004cbc95 in run_builtin
> #6 0x00000000004cbf02 in handle_internal_command
> #7 0x00000000004cc054 in run_argv
> #8 0x00000000004cc422 in main
>
> The reason of the crash is that the evsel does not have ids array
> allocated and the pipe's synthesize code tries to access it.
>
> We don't force evsel ids allocation when we have single event,
> because it's not needed. However we need it when we are in pipe
> mode even for single event as a key for evsel update event.
>
> Fixing this by forcing evsel ids allocation event for single
> event, when we are in pipe mode.
>
> Link: http://lkml.kernel.org/n/tip-xbh5ca1azdcdqyep653vba7w@xxxxxxxxxxxxxx
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> tools/perf/builtin-record.c | 9 +++++++++
> tools/perf/perf.h | 1 +
> tools/perf/util/record.c | 8 ++++++--
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index a60f398cbc24..eeef1143bae3 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -881,6 +881,15 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
> }
> }
>
> + /*
> + * If we have just single event and are sending data
> + * through pipe, we need to force the ids allocation,
> + * because we synthesize event name through the pipe
> + * and need the id for that.
> + */
> + if (data->is_pipe && rec->evlist->nr_entries == 1)
> + rec->opts.sample_id = true;
> +
> if (record__open(rec) != 0) {
> err = -1;
> goto out_child;
> diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> index 007e0dfd5ce3..8fec1abd0f1f 100644
> --- a/tools/perf/perf.h
> +++ b/tools/perf/perf.h
> @@ -62,6 +62,7 @@ struct record_opts {
> bool overwrite;
> bool ignore_missing_thread;
> bool strict_freq;
> + bool sample_id;
> unsigned int freq;
> unsigned int mmap_pages;
> unsigned int auxtrace_mmap_pages;
> diff --git a/tools/perf/util/record.c b/tools/perf/util/record.c
> index 3878c503f464..867f5937ebb7 100644
> --- a/tools/perf/util/record.c
> +++ b/tools/perf/util/record.c
> @@ -138,6 +138,7 @@ void perf_evlist__config(struct perf_evlist *evlist, struct record_opts *opts,
> struct perf_evsel *evsel;
> bool use_sample_identifier = false;
> bool use_comm_exec;
> + bool sample_id = opts->sample_id;
>
> /*
> * Set the evsel leader links before we configure attributes,
> @@ -164,8 +165,7 @@ void perf_evlist__config(struct perf_evlist *evlist, struct record_opts *opts,
> * match the id.
> */
> use_sample_identifier = perf_can_sample_identifier();
> - evlist__for_each_entry(evlist, evsel)
> - perf_evsel__set_sample_id(evsel, use_sample_identifier);
> + sample_id = true;
> } else if (evlist->nr_entries > 1) {
> struct perf_evsel *first = perf_evlist__first(evlist);
>
> @@ -175,6 +175,10 @@ void perf_evlist__config(struct perf_evlist *evlist, struct record_opts *opts,
> use_sample_identifier = perf_can_sample_identifier();
> break;
> }
> + sample_id = true;
> + }
> +
> + if (sample_id) {
> evlist__for_each_entry(evlist, evsel)
> perf_evsel__set_sample_id(evsel, use_sample_identifier);
> }
> --
> 2.13.6