linux-kernel - Re: [PATCH] perf inject: correct event attribute sizes

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Date:   Wed, 26 Aug 2020 14:23:59 +0100
From:   Al Grant <al.grant@...s.arm.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        acme@...hat.com, Denis Nikitin <denik@...gle.com>
Subject: Re: [PATCH] perf inject: correct event attribute sizes

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@...gle.com>
>> Signed-off-by: Al Grant <al.grant@...s.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@...gle.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  = {