linux-kernel - [PATCH 1/2] perf script: Skip aggregation for stat events

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Date:   Fri, 5 May 2023 15:32:53 +0530
From:   Sandipan Das <sandipan.das@....com>
To:     <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <acme@...nel.org>, <peterz@...radead.org>, <mingo@...hat.com>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <jolsa@...nel.org>, <namhyung@...nel.org>, <irogers@...gle.com>,
        <adrian.hunter@...el.com>, <terrelln@...com>,
        <ravi.bangoria@....com>, <ananth.narayan@....com>,
        <sandipan.das@....com>
Subject: [PATCH 1/2] perf script: Skip aggregation for stat events

The script command does not support aggregation modes by itself although
that can be achieved using post-processing scripts. Because of this, it
does not allocate memory for aggregated event values.

Upon running perf stat record, the aggregation mode is set in the perf
data file. If the mode is AGGR_GLOBAL, the aggregated event values are
accessed and this leads to a segmentation fault since these were never
allocated to begin with. Set the mode to AGGR_NONE explicitly to avoid
this.

E.g.

  $ perf stat record -e cycles true
  $ perf script

Before:
  Segmentation fault (core dumped)

After:
  CPU   THREAD             VAL             ENA             RUN            TIME EVENT
   -1   231919          162831          362069          362069          935289 cycles:u

Fixes: 8b76a3188b85 ("perf stat: Remove unused perf_counts.aggr field")
Signed-off-by: Sandipan Das <sandipan.das@....com>
Cc: stable@...r.kernel.org # v6.2+
---
 tools/perf/builtin-script.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index 006f522d0e7f..c57be48d65bb 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -3647,6 +3647,13 @@ static int process_stat_config_event(struct perf_session *session __maybe_unused
 				     union perf_event *event)
 {
 	perf_event__read_stat_config(&stat_config, &event->stat_config);
+
+	/*
+	 * Aggregation modes are not used since post-processing scripts are
+	 * supposed to take care of such requirements
+	 */
+	stat_config.aggr_mode = AGGR_NONE;
+
 	return 0;
 }
 
-- 
2.34.1