[PATCH] perf: Adjust perf-inject output data offset for backward compatibility

From: Raul Silvera
Date: Mon Jun 20 2022 - 12:50:23 EST


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@xxxxxxxxxx>
---
tools/perf/builtin-inject.c | 2 +-
tools/perf/util/header.c | 16 +++++++++++++++-
tools/perf/util/header.h | 2 ++
3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index a75bf11585b5..1dfdcef36607 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -916,7 +916,7 @@ static int __cmd_inject(struct perf_inject *inject)
inject->tool.tracing_data = perf_event__repipe_tracing_data;
}

- output_data_offset = session->header.data_offset;
+ output_data_offset = perf_session__data_offset(session->evlist);

if (inject->build_id_all) {
inject->tool.mmap = perf_event__repipe_buildid_mmap;
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 53332da100e8..93706ae827f1 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -3660,7 +3660,7 @@ static int perf_session__do_write_header(struct perf_session *session,
.size = evlist->core.nr_entries * sizeof(f_attr),
},
.data = {
- .offset = header->data_offset,
+ .offset = attr_offset + evlist->core.nr_entries * sizeof(f_attr),
.size = header->data_size,
},
/* event_types is ignored, store zeros */
@@ -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,
diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
index 08563c1f1bff..56916dabce7b 100644
--- a/tools/perf/util/header.h
+++ b/tools/perf/util/header.h
@@ -136,6 +136,8 @@ int perf_session__inject_header(struct perf_session *session,
int fd,
struct feat_copier *fc);

+size_t perf_session__data_offset(const struct evlist *evlist);
+
void perf_header__set_feat(struct perf_header *header, int feat);
void perf_header__clear_feat(struct perf_header *header, int feat);
bool perf_header__has_feat(const struct perf_header *header, int feat);
--
2.37.0.rc0.104.g0611611a94-goog