Re: [PATCH v2] perf: Adjust perf-inject output data offset for backward compatibility

From: Arnaldo Carvalho de Melo
Date: Thu Jun 23 2022 - 10:46:51 EST


Em Wed, Jun 22, 2022 at 11:36:58AM +0300, Adrian Hunter escreveu:
> On 21/06/22 18:27, Raul Silvera wrote:
> > 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>
>
> Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>

Thanks, applied.

- Arnaldo


> > ---
> > Changes since v1:
> > - Use the adjusted header->data_offset in do_write_header instead of
> > recomputing it.
> > ---
> > tools/perf/builtin-inject.c | 2 +-
> > tools/perf/util/header.c | 14 ++++++++++++++
> > tools/perf/util/header.h | 2 ++
> > 3 files changed, 17 insertions(+), 1 deletion(-)
> >
> > 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..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,
> > 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);

--

- Arnaldo