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:

    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-xbh5ca1azdcdqyep653vb...@git.kernel.org
Signed-off-by: Jiri Olsa <jo...@kernel.org>
---
 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

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