[PATCH] perf timechart: dynamically determine event data offset

[Stanislav Fomichev <stfomichev@yandex-team.ru>]

Since b000c8065a92 "tracing: Remove the extra 4 bytes of padding in events"
removed padding bytes, perf timechart got out of sync with the kernel's
trace_entry structure.
We can't just align perf's trace_entry definition with the kernel because we
want timechart to continue working with old perf.data. Instead, we now
calculate event data offset dynamically using offset of first non-common
event field in the perf.data.

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
---
 tools/perf/builtin-timechart.c | 56 +++++++++++++++++++++++++++---------------
 tools/perf/util/evsel.c        |  5 ++++
 tools/perf/util/evsel.h        |  1 +
 3 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c
index 41c9bde2fb67..5c76a914031b 100644
--- a/tools/perf/builtin-timechart.c
+++ b/tools/perf/builtin-timechart.c
@@ -41,6 +41,24 @@
 #define SUPPORT_OLD_POWER_EVENTS 1
 #define PWR_EVENT_EXIT -1
 
+static unsigned int payload_offset;
+
+static int timechart__set_payload_offset(struct perf_evlist *evlist)
+{
+	struct perf_evsel *evsel = perf_evlist__first(evlist);
+	struct format_field *field = perf_evsel__fields(evsel);
+
+	if (!field)
+		return -1;
+
+	payload_offset = field->offset;
+	return 0;
+}
+
+static void *timechart__payload(struct perf_sample *sample)
+{
+	return sample->raw_data + payload_offset;
+}
 
 static unsigned int	numcpus;
 static u64		min_freq;	/* Lowest CPU frequency seen */
@@ -304,13 +322,11 @@ struct trace_entry {
 	unsigned char		flags;
 	unsigned char		preempt_count;
 	int			pid;
-	int			lock_depth;
 };
 
 #ifdef SUPPORT_OLD_POWER_EVENTS
 static int use_old_power_events;
 struct power_entry_old {
-	struct trace_entry te;
 	u64	type;
 	u64	value;
 	u64	cpu_id;
@@ -318,14 +334,12 @@ struct power_entry_old {
 #endif
 
 struct power_processor_entry {
-	struct trace_entry te;
 	u32	state;
 	u32	cpu_id;
 };
 
 #define TASK_COMM_LEN 16
 struct wakeup_entry {
-	struct trace_entry te;
 	char comm[TASK_COMM_LEN];
 	int   pid;
 	int   prio;
@@ -333,7 +347,6 @@ struct wakeup_entry {
 };
 
 struct sched_switch {
-	struct trace_entry te;
 	char prev_comm[TASK_COMM_LEN];
 	int  prev_pid;
 	int  prev_prio;
@@ -402,11 +415,13 @@ static void p_state_change(int cpu, u64 timestamp, u64 new_freq)
 			turbo_frequency = max_freq;
 }
 
-static void
-sched_wakeup(int cpu, u64 timestamp, int pid, struct trace_entry *te)
+static void sched_wakeup(struct perf_sample *sample)
 {
+	struct trace_entry *te = sample->raw_data;
+	struct wakeup_entry *wake = timechart__payload(sample);
+	u64 timestamp = sample->time;
+	int pid = sample->pid, cpu = sample->cpu;
 	struct per_pid *p;
-	struct wakeup_entry *wake = (void *)te;
 	struct wake_event *we = zalloc(sizeof(*we));
 
 	if (!we)
@@ -434,11 +449,9 @@ sched_wakeup(int cpu, u64 timestamp, int pid, struct trace_entry *te)
 	}
 }
 
-static void sched_switch(int cpu, u64 timestamp, struct trace_entry *te)
+static void sched_switch(int cpu, u64 timestamp, struct sched_switch *sw)
 {
 	struct per_pid *p = NULL, *prev_p;
-	struct sched_switch *sw = (void *)te;
-
 
 	prev_p = find_create_pid(sw->prev_pid);
 
@@ -495,7 +508,7 @@ static int
 process_sample_cpu_idle(struct perf_evsel *evsel __maybe_unused,
 			struct perf_sample *sample)
 {
-	struct power_processor_entry *ppe = sample->raw_data;
+	struct power_processor_entry *ppe = timechart__payload(sample);
 
 	if (ppe->state == (u32) PWR_EVENT_EXIT)
 		c_state_end(ppe->cpu_id, sample->time);
@@ -508,7 +521,7 @@ static int
 process_sample_cpu_frequency(struct perf_evsel *evsel __maybe_unused,
 			     struct perf_sample *sample)
 {
-	struct power_processor_entry *ppe = sample->raw_data;
+	struct power_processor_entry *ppe = timechart__payload(sample);
 
 	p_state_change(ppe->cpu_id, sample->time, ppe->state);
 	return 0;
@@ -518,9 +531,7 @@ static int
 process_sample_sched_wakeup(struct perf_evsel *evsel __maybe_unused,
 			    struct perf_sample *sample)
 {
-	struct trace_entry *te = sample->raw_data;
-
-	sched_wakeup(sample->cpu, sample->time, sample->pid, te);
+	sched_wakeup(sample);
 	return 0;
 }
 
@@ -528,9 +539,9 @@ static int
 process_sample_sched_switch(struct perf_evsel *evsel __maybe_unused,
 			    struct perf_sample *sample)
 {
-	struct trace_entry *te = sample->raw_data;
+	struct sched_switch *sw = timechart__payload(sample);
 
-	sched_switch(sample->cpu, sample->time, te);
+	sched_switch(sample->cpu, sample->time, sw);
 	return 0;
 }
 
@@ -539,7 +550,7 @@ static int
 process_sample_power_start(struct perf_evsel *evsel __maybe_unused,
 			   struct perf_sample *sample)
 {
-	struct power_entry_old *peo = sample->raw_data;
+	struct power_entry_old *peo = timechart__payload(sample);
 
 	c_state_start(peo->cpu_id, sample->time, peo->value);
 	return 0;
@@ -557,7 +568,7 @@ static int
 process_sample_power_frequency(struct perf_evsel *evsel __maybe_unused,
 			       struct perf_sample *sample)
 {
-	struct power_entry_old *peo = sample->raw_data;
+	struct power_entry_old *peo = timechart__payload(sample);
 
 	p_state_change(peo->cpu_id, sample->time, peo->value);
 	return 0;
@@ -1012,6 +1023,11 @@ static int __cmd_timechart(const char *output_name)
 		goto out_delete;
 	}
 
+	if (timechart__set_payload_offset(session->evlist)) {
+		pr_err("Field format not found, please try updating this tool\n");
+		goto out_delete;
+	}
+
 	ret = perf_session__process_events(session, &perf_timechart);
 	if (ret)
 		goto out_delete;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 46dd4c2a41ce..4847d373fe2a 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1767,6 +1767,11 @@ struct format_field *perf_evsel__field(struct perf_evsel *evsel, const char *nam
 	return pevent_find_field(evsel->tp_format, name);
 }
 
+struct format_field *perf_evsel__fields(struct perf_evsel *evsel)
+{
+	return evsel->tp_format->format.fields;
+}
+
 void *perf_evsel__rawptr(struct perf_evsel *evsel, struct perf_sample *sample,
 			 const char *name)
 {
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 1ea7c92e6e33..3d50dc01bb1d 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -193,6 +193,7 @@ static inline char *perf_evsel__strval(struct perf_evsel *evsel,
 struct format_field;
 
 struct format_field *perf_evsel__field(struct perf_evsel *evsel, const char *name);
+struct format_field *perf_evsel__fields(struct perf_evsel *evsel);
 
 #define perf_evsel__match(evsel, t, c)		\
 	(evsel->attr.type == PERF_TYPE_##t &&	\
-- 
1.8.3.2