[PATCH v3 3/5] perf record off-cpu: processing of embedded sample

[Howard Chu]

In the first evsel__parse_sample, we parse bpf output as raw samples.
After getting the raw_data, parse it the second time to get the embedded
samples.

Also, because we rely on evlist to dump direct off-cpu samples, if we
evsel__open() a bpf output event on a specific pid, it will fail. So pid = -1 for
every bpf output event.

Signed-off-by: Howard Chu <howardchu95@xxxxxxxxx>
Suggested-by: Ian Rogers <irogers@xxxxxxxxxx>
Suggested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/builtin-script.c |  2 +-
 tools/perf/util/evsel.c     | 16 ++++++++++++++--
 tools/perf/util/evsel.h     | 13 +++++++++++++
 tools/perf/util/session.c   | 23 ++++++++++++++++++++++-
 4 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
index c16224b1fef3..c142fb44817f 100644
--- a/tools/perf/builtin-script.c
+++ b/tools/perf/builtin-script.c
@@ -653,7 +653,7 @@ static int perf_session__check_output_opt(struct perf_session *session)
 
 		evlist__for_each_entry(session->evlist, evsel) {
 			not_pipe = true;
-			if (evsel__has_callchain(evsel)) {
+			if (evsel__has_callchain(evsel) || evsel__embed_has_callchain(evsel)) {
 				use_callchain = true;
 				break;
 			}
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index bc603193c477..6c64ec475b80 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -298,6 +298,7 @@ void evsel__init(struct evsel *evsel,
 	evsel->pmu_name      = NULL;
 	evsel->group_pmu_name = NULL;
 	evsel->skippable     = false;
+	evsel->sample_type_embed = 0;
 }
 
 struct evsel *evsel__new_idx(struct perf_event_attr *attr, int idx)
@@ -440,6 +441,7 @@ struct evsel *evsel__clone(struct evsel *orig)
 	evsel->weak_group = orig->weak_group;
 	evsel->use_config_name = orig->use_config_name;
 	evsel->pmu = orig->pmu;
+	evsel->sample_type_embed = orig->sample_type_embed;
 
 	if (evsel__copy_config_terms(evsel, orig) < 0)
 		goto out_err;
@@ -2282,6 +2284,10 @@ static int evsel__open_cpu(struct evsel *evsel, struct perf_cpu_map *cpus,
 
 			test_attr__ready();
 
+			/* BPF output event can only be system-wide, off-cpu filters tasks in BPF */
+			if (evsel__is_bpf_output(evsel))
+				pid = -1;
+
 			/* Debug message used by test scripts */
 			pr_debug2_peo("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx",
 				pid, perf_cpu_map__cpu(cpus, idx).cpu, group_fd, evsel->open_flags);
@@ -2592,6 +2598,14 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
 	 */
 	union u64_swap u;
 
+	array = event->sample.array;
+
+	/* use raw_data passed in to read embedded data */
+	if (evsel__has_embed(evsel) && evsel__is_bpf_output(evsel) && data->raw_data) {
+		array = data->raw_data;
+		type = evsel->sample_type_embed;
+	}
+
 	memset(data, 0, sizeof(*data));
 	data->cpu = data->pid = data->tid = -1;
 	data->stream_id = data->id = data->time = -1ULL;
@@ -2607,8 +2621,6 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
 		return perf_evsel__parse_id_sample(evsel, event, data);
 	}
 
-	array = event->sample.array;
-
 	if (perf_event__check_size(event, evsel->sample_size))
 		return -EFAULT;
 
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 80b5f6dd868e..0d25e82c6154 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -184,6 +184,9 @@ struct evsel {
 	};
 	/* Is the tool's fd for /proc/pid/stat or /proc/stat. */
 	bool pid_stat;
+
+	/* for samples embedded in BPF output */
+	__u64 sample_type_embed;
 };
 
 struct perf_missing_features {
@@ -469,6 +472,11 @@ static inline bool evsel__is_bpf_output(struct evsel *evsel)
 	return evsel__match(evsel, SOFTWARE, SW_BPF_OUTPUT);
 }
 
+static inline bool evsel__has_embed(struct evsel *evsel)
+{
+	return evsel->sample_type_embed != 0;
+}
+
 static inline bool evsel__is_clock(const struct evsel *evsel)
 {
 	return evsel__match(evsel, SOFTWARE, SW_CPU_CLOCK) ||
@@ -525,6 +533,11 @@ static inline bool evsel__has_callchain(const struct evsel *evsel)
 	       evsel->synth_sample_type & PERF_SAMPLE_CALLCHAIN;
 }
 
+static inline bool evsel__embed_has_callchain(const struct evsel *evsel)
+{
+	return evsel->sample_type_embed & PERF_SAMPLE_CALLCHAIN;
+}
+
 static inline bool evsel__has_br_stack(const struct evsel *evsel)
 {
 	/*
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 5596bed1b8c8..d87d85a3e21e 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1528,6 +1528,23 @@ static int evlist__deliver_sample(struct evlist *evlist, struct perf_tool *tool,
 	/* We know evsel != NULL. */
 	u64 sample_type = evsel->core.attr.sample_type;
 	u64 read_format = evsel->core.attr.read_format;
+	struct perf_sample sample_embed;
+
+	if (evsel__is_bpf_output(evsel) && evsel__has_embed(evsel) &&
+	    sample->raw_data && sample->raw_size - sizeof(__u32) > sizeof(struct perf_event_header)) {
+		int err;
+
+		sample_embed.raw_data = sample->raw_data;
+
+		err = evsel__parse_sample(evsel, event, &sample_embed);
+		if (err) {
+			pr_err("Can't parse BPF-embedded sample, err = %d\n", err);
+			return err;
+		}
+
+		sample_type = evsel->sample_type_embed;
+		sample = &sample_embed;
+	}
 
 	/* Standard sample delivery. */
 	if (!(sample_type & PERF_SAMPLE_READ))
@@ -1639,8 +1656,12 @@ static int perf_session__deliver_event(struct perf_session *session,
 				       const char *file_path)
 {
 	struct perf_sample sample;
-	int ret = evlist__parse_sample(session->evlist, event, &sample);
+	int ret;
+
+	/* set to NULL so we don't accidentally parse BPF-embedded sample */
+	sample.raw_data = NULL;
 
+	ret = evlist__parse_sample(session->evlist, event, &sample);
 	if (ret) {
 		pr_err("Can't parse sample, err = %d\n", ret);
 		return ret;
-- 
2.45.2