perf/core: Restore mmap record type correctly
authorStephane Eranian <eranian@google.com>
Thu, 7 Mar 2019 18:52:33 +0000 (10:52 -0800)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 20 Apr 2019 07:14:59 +0000 (09:14 +0200)
commit103eb70cf4eb7fb263d1e337811217e2e4c53731
treec5592e63df421894df5acdd8fa92d3e4bf29e186
parent2d6453a3e9e08b40c93b1049a591c6caa5dfa06a
perf/core: Restore mmap record type correctly

[ Upstream commit d9c1bb2f6a2157b38e8eb63af437cb22701d31ee ]

On mmap(), perf_events generates a RECORD_MMAP record and then checks
which events are interested in this record. There are currently 2
versions of mmap records: RECORD_MMAP and RECORD_MMAP2. MMAP2 is larger.
The event configuration controls which version the user level tool
accepts.

If the event->attr.mmap2=1 field then MMAP2 record is returned.  The
perf_event_mmap_output() takes care of this. It checks attr->mmap2 and
corrects the record fields before putting it in the sampling buffer of
the event.  At the end the function restores the modified MMAP record
fields.

The problem is that the function restores the size but not the type.
Thus, if a subsequent event only accepts MMAP type, then it would
instead receive an MMAP2 record with a size of MMAP record.

This patch fixes the problem by restoring the record type on exit.

Signed-off-by: Stephane Eranian <eranian@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Fixes: 13d7a2410fa6 ("perf: Add attr->mmap2 attribute to an event")
Link: http://lkml.kernel.org/r/20190307185233.225521-1-eranian@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
kernel/events/core.c