perf record: Add 8-byte aligned event type PERF_RECORD_COMPRESSED2

The original PERF_RECORD_COMPRESS is not 8-byte aligned, which can cause
asan runtime error:

  # Build with asan
  $ make -C tools/perf O=/tmp/perf DEBUG=1 EXTRA_CFLAGS="-O0 -g -fno-omit-frame-pointer -fsanitize=undefined"
  # Test success with many asan runtime errors:
  $ /tmp/perf/perf test "Zstd perf.data compression/decompression" -vv
   83: Zstd perf.data compression/decompression:
  ...
  util/session.c:1959:13: runtime error: member access within misaligned address 0x7f69e3f99653 for type 'union perf_event', which requires 13 byte alignment
  0x7f69e3f99653: note: pointer points here
   d0  3a 50 69 44 00 00 00 00  00 08 00 bb 07 00 00 00  00 00 00 44 00 00 00 00  00 00 00 ff 07 00 00
                ^
  util/session.c:2163:22: runtime error: member access within misaligned address 0x7f69e3f99653 for type 'union perf_event', which requires 8 byte alignment
  0x7f69e3f99653: note: pointer points here
   d0  3a 50 69 44 00 00 00 00  00 08 00 bb 07 00 00 00  00 00 00 44 00 00 00 00  00 00 00 ff 07 00 00
                ^
  ...

Since there is no way to align compressed data in zstd compression, this
patch add a new event type `PERF_RECORD_COMPRESSED2`, which adds a field
`data_size` to specify the actual compressed data size.

The `header.size` contains the total record size, including the padding
at the end to make it 8-byte aligned.

Tested with `Zstd perf.data compression/decompression`

Signed-off-by: Chun-Tse Shao <ctshao@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ben Gainey <ben.gainey@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Leo Yan <leo.yan@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Terrell <terrelln@fb.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303183646.327510-1-ctshao@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/tools/perf/Documentation/perf.data-file-format.txt b/tools/perf/Documentation/perf.data-file-format.txt
index 010a4edcd384..cd95ba09f727 100644
--- a/tools/perf/Documentation/perf.data-file-format.txt
+++ b/tools/perf/Documentation/perf.data-file-format.txt
@@ -370,7 +370,7 @@ struct {
 	u32	mmap_len;
 };
 
-Indicates that trace contains records of PERF_RECORD_COMPRESSED type
+Indicates that trace contains records of PERF_RECORD_COMPRESSED2 type
 that have perf_events records in compressed form.
 
 	HEADER_CPU_PMU_CAPS = 28,
@@ -602,7 +602,14 @@ struct auxtrace_error_event {
 Describes a header feature. These are records used in pipe-mode that
 contain information that otherwise would be in perf.data file's header.
 
-	PERF_RECORD_COMPRESSED 			= 81,
+	PERF_RECORD_COMPRESSED 			= 81, /* deprecated */
+
+The header is followed by compressed data frame that can be decompressed
+into array of perf trace records. The size of the entire compressed event
+record including the header is limited by the max value of header.size.
+
+It is deprecated and new files should use PERF_RECORD_COMPRESSED2 to gurantee
+8-byte alignment.
 
 struct compressed_event {
 	struct perf_event_header	header;
@@ -618,10 +625,17 @@ This is used, for instance, to 'perf inject' events after init and before
 regular events, those emitted by the kernel, to support combining guest and
 host records.
 
+	PERF_RECORD_COMPRESSED2			= 83,
 
-The header is followed by compressed data frame that can be decompressed
-into array of perf trace records. The size of the entire compressed event
-record including the header is limited by the max value of header.size.
+8-byte aligned version of `PERF_RECORD_COMPRESSED`. `header.size` indicates the
+total record size, including padding for 8-byte alignment, and `data_size`
+specifies the actual size of the compressed data.
+
+struct perf_record_compressed2 {
+	struct perf_event_header	header;
+	__u64				data_size;
+	char				data[];
+};
 
 Event types