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

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Message-ID: <YrR8zDls7y//T7zI@kernel.org>
Date:   Thu, 23 Jun 2022 11:46:36 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Raul Silvera <rsilvera@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Dave Marchevsky <davemarchevsky@...com>,
        Colin Ian King <colin.king@...el.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] perf: Adjust perf-inject output data offset for
 backward compatibility

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@...gle.com>
> 
> Acked-by: Adrian Hunter <adrian.hunter@...el.com>

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