perf jit: Let convert_timestamp() to be backwards-compatible

Commit d110162cafc80dad ("perf tsc: Support cap_user_time_short for
event TIME_CONV") supports the extended parameters for event TIME_CONV,
but it broke the backwards compatibility, so any perf data file with old
event format fails to convert timestamp.

This patch introduces a helper event_contains() to check if an event
contains a specific member or not.  For the backwards-compatibility, if
the event size confirms the extended parameters are supported in the
event TIME_CONV, then copies these parameters.

Committer notes:

To make this compiler backwards compatible add this patch:

  -       struct perf_tsc_conversion tc = { 0 };
  +       struct perf_tsc_conversion tc = { .time_shift = 0, };

Fixes: d110162cafc8 ("perf tsc: Support cap_user_time_short for event TIME_CONV")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steve MacLean <Steve.MacLean@Microsoft.com>
Cc: Yonatan Goldschmidt <yonatan.goldschmidt@granulate.io>
Link: https://lore.kernel.org/r/20210428120915.7123-3-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index 48583e441d9b..4d0c02ba3f7d 100644
--- a/tools/lib/perf/include/perf/event.h
+++ b/tools/lib/perf/include/perf/event.h
@@ -8,6 +8,8 @@
 #include <linux/bpf.h>
 #include <sys/types.h> /* pid_t */
 
+#define event_contains(obj, mem) ((obj).header.size > offsetof(typeof(obj), mem))
+
 struct perf_record_mmap {
 	struct perf_event_header header;
 	__u32			 pid, tid;