[PATCH 23/29] perf session: Add byte-swap handler for PERF_RECORD_COMPRESSED2

[Arnaldo Carvalho de Melo]

From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>

PERF_RECORD_COMPRESSED2 events carry a data_size field that must be
byte-swapped when reading cross-endian perf.data files.  Without a
swap handler, reading COMPRESSED2 events on a different-endian machine
would misinterpret data_size as a garbage value, causing the
decompression path to read the wrong number of bytes.

The compressed payload itself is a raw byte stream and needs no
swapping.

Fixes: 208c0e16834472bb ("perf record: Add 8-byte aligned event type PERF_RECORD_COMPRESSED2")
Reported-by: sashiko-bot@xxxxxxxxxx # Running on a local machine
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Chun-Tse Shao <ctshao@xxxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Assisted-by: Claude Opus 4.6 (1M context) <noreply@xxxxxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/session.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 8280413f4528f53c..9271885e3920f897 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1056,6 +1056,14 @@ static int perf_event__time_conv_swap(union perf_event *event,
 	return 0;
 }
 
+static int perf_event__compressed2_swap(union perf_event *event,
+					bool sample_id_all __maybe_unused)
+{
+	/* Only data_size needs swapping — compressed payload is a raw byte stream */
+	event->pack2.data_size = bswap_64(event->pack2.data_size);
+	return 0;
+}
+
 static int perf_event__bpf_metadata_swap(union perf_event *event,
 					 bool sample_id_all __maybe_unused)
 {
@@ -1197,6 +1205,7 @@ static perf_event__swap_op perf_event__swap_ops[] = {
 	[PERF_RECORD_STAT_ROUND]	  = perf_event__stat_round_swap,
 	[PERF_RECORD_EVENT_UPDATE]	  = perf_event__event_update_swap,
 	[PERF_RECORD_TIME_CONV]		  = perf_event__time_conv_swap,
+	[PERF_RECORD_COMPRESSED2]	  = perf_event__compressed2_swap,
 	[PERF_RECORD_BPF_METADATA]	  = perf_event__bpf_metadata_swap,
 	[PERF_RECORD_SCHEDSTAT_CPU]	  = perf_event__schedstat_cpu_swap,
 	[PERF_RECORD_SCHEDSTAT_DOMAIN]	  = perf_event__schedstat_domain_swap,
-- 
2.54.0