Re: [PATCH] perf inject: correct event attribute sizes

[Al Grant]

On 26/08/2020 12:27, Mark Rutland wrote:
> On Wed, Aug 26, 2020 at 10:42:04AM +0100, Al Grant wrote:
> > When perf inject reads a perf.data file from an older version of perf,
> > it writes event attributes into the output with the original size field,
> > but lays them out as if they had the size currently used. Readers see
> > a corrupt file. Update the size field to match the layout.
> >
> > From: Denis Nikitin <denik@xxxxxxxxxx>
> > Signed-off-by: Al Grant <al.grant@xxxxxxxxxxxx>
>
> Did Denis write this patch?

Joint work - I fixed the sizes in the event attributes section,
but Denis noticed that the copies in HEADER_EVENT_DESC also need
fixing, so the final text is his.

> If so, we need an S-o-B line from them.

I have his approval to upstream this, so:

Signed-off-by: Denis Nikitin <denik@xxxxxxxxxx>

Al


> Mark.
>
> >   tools/perf/util/header.c | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > index 9cf4efdcbbbd..762eb94bd532 100644
> > --- a/tools/perf/util/header.c
> > +++ b/tools/perf/util/header.c
> > @@ -3326,6 +3326,14 @@ int perf_session__write_header(struct
> > perf_session *session,
> >          attr_offset = lseek(ff.fd, 0, SEEK_CUR);
> >
> >          evlist__for_each_entry(evlist, evsel) {
> > +               if (evsel->core.attr.size < sizeof(evsel->core.attr)) {
> > +                       /*
> > +                        * We are likely in "perf inject" and have read +
> > * from an older file. Update attr size so that
> > +                        * reader gets the right offset to the ids.
> > +                        */
> > +                       evsel->core.attr.size = sizeof(evsel->core.attr);
> > +               }
> >                  f_attr = (struct perf_file_attr){
> >                          .attr = evsel->core.attr,
> >                          .ids  = {