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

Al Grant
2020-08-26T13:24:05Z

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@google.com>
>> Signed-off-by: Al Grant <al.grant@foss.arm.com>
>
> 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@google.com>

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 = {