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Subject[PATCH 5.10 513/530] perf jit: Let convert_timestamp() to be backwards-compatible
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From: Leo Yan <leo.yan@linaro.org>

[ Upstream commit aa616f5a8a2d22a179d5502ebd85045af66fa656 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/perf/include/perf/event.h | 2 ++
tools/perf/util/jitdump.c | 30 +++++++++++++++++++----------
2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/tools/lib/perf/include/perf/event.h b/tools/lib/perf/include/perf/event.h
index baf64ea74e10..4a24b855d3ce 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;
diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index 055bab7a92b3..64d8f9ba8c03 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -369,21 +369,31 @@ jit_inject_event(struct jit_buf_desc *jd, union perf_event *event)

static uint64_t convert_timestamp(struct jit_buf_desc *jd, uint64_t timestamp)
{
- struct perf_tsc_conversion tc;
+ struct perf_tsc_conversion tc = { .time_shift = 0, };
+ struct perf_record_time_conv *time_conv = &jd->session->time_conv;

if (!jd->use_arch_timestamp)
return timestamp;

- tc.time_shift = jd->session->time_conv.time_shift;
- tc.time_mult = jd->session->time_conv.time_mult;
- tc.time_zero = jd->session->time_conv.time_zero;
- tc.time_cycles = jd->session->time_conv.time_cycles;
- tc.time_mask = jd->session->time_conv.time_mask;
- tc.cap_user_time_zero = jd->session->time_conv.cap_user_time_zero;
- tc.cap_user_time_short = jd->session->time_conv.cap_user_time_short;
+ tc.time_shift = time_conv->time_shift;
+ tc.time_mult = time_conv->time_mult;
+ tc.time_zero = time_conv->time_zero;

- if (!tc.cap_user_time_zero)
- return 0;
+ /*
+ * The event TIME_CONV was extended for the fields from "time_cycles"
+ * when supported cap_user_time_short, for backward compatibility,
+ * checks the event size and assigns these extended fields if these
+ * fields are contained in the event.
+ */
+ if (event_contains(*time_conv, time_cycles)) {
+ tc.time_cycles = time_conv->time_cycles;
+ tc.time_mask = time_conv->time_mask;
+ tc.cap_user_time_zero = time_conv->cap_user_time_zero;
+ tc.cap_user_time_short = time_conv->cap_user_time_short;
+
+ if (!tc.cap_user_time_zero)
+ return 0;
+ }

return tsc_to_perf_time(timestamp, &tc);
}
--
2.30.2


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