perf inject: Adjust output data offset for backward compatibility

When 'perf inject' creates a new file, it reuses the data offset from
the input file. If there has been a change on the size of the header, as
happened in v5.12 -> v5.13, the new offsets will be wrong, resulting in
a corrupted output file.

This change adds the function perf_session__data_offset to compute the
data offset based on the current header size, and uses that instead of
the offset from the original input file.

Signed-off-by: Raul Silvera <rsilvera@google.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Colin Ian King <colin.king@intel.com>
Cc: Dave Marchevsky <davemarchevsky@fb.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220621152725.2668041-1-rsilvera@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 53332da100e8..6ad629db63b7 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3686,6 +3686,20 @@ int perf_session__write_header(struct perf_session *session,
 	return perf_session__do_write_header(session, evlist, fd, at_exit, NULL);
 }
 
+size_t perf_session__data_offset(const struct evlist *evlist)
+{
+	struct evsel *evsel;
+	size_t data_offset;
+
+	data_offset = sizeof(struct perf_file_header);
+	evlist__for_each_entry(evlist, evsel) {
+		data_offset += evsel->core.ids * sizeof(u64);
+	}
+	data_offset += evlist->core.nr_entries * sizeof(struct perf_file_attr);
+
+	return data_offset;
+}
+
 int perf_session__inject_header(struct perf_session *session,
 				struct evlist *evlist,
 				int fd,