[PATCH 05/15] perf auxtrace: Add support for AUX area sample recording

[Adrian Hunter]

Add support for parsing and validating AUX area sample options. At present,
the only option is the sample size, but it is also necessary to ensure that
events are in a group with an AUX area event as the leader.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
 tools/perf/util/auxtrace.c | 107 +++++++++++++++++++++++++++++++++++++
 tools/perf/util/auxtrace.h |  16 ++++++
 tools/perf/util/pmu.h      |   1 +
 tools/perf/util/record.h   |   2 +
 4 files changed, 126 insertions(+)

diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
index 263d1d9d8987..51fbe01f8a11 100644
--- a/tools/perf/util/auxtrace.c
+++ b/tools/perf/util/auxtrace.c
@@ -69,6 +69,13 @@ static struct perf_pmu *perf_evsel__find_pmu(struct evsel *evsel)
 	return pmu;
 }
 
+static bool perf_evsel__is_aux_event(struct evsel *evsel)
+{
+	struct perf_pmu *pmu = perf_evsel__find_pmu(evsel);
+
+	return pmu && pmu->auxtrace;
+}
+
 static bool auxtrace__dont_decode(struct perf_session *session)
 {
 	return !session->itrace_synth_opts ||
@@ -609,6 +616,106 @@ int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
 	return -EINVAL;
 }
 
+/*
+ * Event record size is 16-bit which results in a maximum size of about 64KiB.
+ * Allow about 4KiB for the rest of the sample record, to give a maximum
+ * AUX area sample size of 60KiB.
+ */
+#define MAX_AUX_SAMPLE_SIZE (60 * 1024)
+
+/* Arbitrary default size if no other default provided */
+#define DEFAULT_AUX_SAMPLE_SIZE (4 * 1024)
+
+static int auxtrace_validate_aux_sample_size(struct evlist *evlist,
+					     struct record_opts *opts)
+{
+	struct evsel *evsel;
+	bool has_aux_leader = false;
+	u32 sz;
+
+	evlist__for_each_entry(evlist, evsel) {
+		sz = evsel->core.attr.aux_sample_size;
+		if (perf_evsel__is_group_leader(evsel)) {
+			has_aux_leader = perf_evsel__is_aux_event(evsel);
+			if (sz) {
+				if (has_aux_leader)
+					pr_err("Cannot add AUX area sampling to an AUX area event\n");
+				else
+					pr_err("Cannot add AUX area sampling to a group leader\n");
+				return -EINVAL;
+			}
+		}
+		if (sz > MAX_AUX_SAMPLE_SIZE) {
+			pr_err("AUX area sample size %u too big, max. %d\n",
+			       sz, MAX_AUX_SAMPLE_SIZE);
+			return -EINVAL;
+		}
+		if (sz) {
+			if (!has_aux_leader) {
+				pr_err("Cannot add AUX area sampling because group leader is not an AUX area event\n");
+				return -EINVAL;
+			}
+			perf_evsel__set_sample_bit(evsel, AUX);
+			opts->auxtrace_sample_mode = true;
+		} else {
+			perf_evsel__reset_sample_bit(evsel, AUX);
+		}
+	}
+
+	if (!opts->auxtrace_sample_mode) {
+		pr_err("AUX area sampling requires an AUX area event group leader plus other events to which to add samples\n");
+		return -EINVAL;
+	}
+
+	if (!perf_can_aux_sample()) {
+		pr_err("AUX area sampling is not supported by kernel\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int auxtrace_parse_sample_options(struct auxtrace_record *itr,
+				  struct evlist *evlist,
+				  struct record_opts *opts, const char *str)
+{
+	bool has_aux_leader = false;
+	struct evsel *evsel;
+	char *endptr;
+	unsigned long sz;
+
+	if (!str)
+		return 0;
+
+	if (!itr) {
+		pr_err("No AUX area event to sample\n");
+		return -EINVAL;
+	}
+
+	sz = strtoul(str, &endptr, 0);
+	if (*endptr || sz > UINT_MAX) {
+		pr_err("Bad AUX area sampling option: '%s'\n", str);
+		return -EINVAL;
+	}
+
+	if (!sz)
+		sz = itr->default_aux_sample_size;
+
+	if (!sz)
+		sz = DEFAULT_AUX_SAMPLE_SIZE;
+
+	/* Set aux_sample_size based on --aux-sample option */
+	evlist__for_each_entry(evlist, evsel) {
+		if (perf_evsel__is_group_leader(evsel)) {
+			has_aux_leader = perf_evsel__is_aux_event(evsel);
+		} else if (has_aux_leader) {
+			evsel->core.attr.aux_sample_size = sz;
+		}
+	}
+
+	return auxtrace_validate_aux_sample_size(evlist, opts);
+}
+
 struct auxtrace_record *__weak
 auxtrace_record__init(struct evlist *evlist __maybe_unused, int *err)
 {
diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
index 3f4aa5427d76..12b02eb4e01c 100644
--- a/tools/perf/util/auxtrace.h
+++ b/tools/perf/util/auxtrace.h
@@ -313,6 +313,7 @@ struct auxtrace_mmap_params {
  * @reference: provide a 64-bit reference number for auxtrace_event
  * @read_finish: called after reading from an auxtrace mmap
  * @alignment: alignment (if any) for AUX area data
+ * @default_aux_sample_size: default sample size for --aux sample option
  */
 struct auxtrace_record {
 	int (*recording_options)(struct auxtrace_record *itr,
@@ -336,6 +337,7 @@ struct auxtrace_record {
 	u64 (*reference)(struct auxtrace_record *itr);
 	int (*read_finish)(struct auxtrace_record *itr, int idx);
 	unsigned int alignment;
+	unsigned int default_aux_sample_size;
 };
 
 /**
@@ -498,6 +500,9 @@ struct auxtrace_record *auxtrace_record__init(struct evlist *evlist,
 int auxtrace_parse_snapshot_options(struct auxtrace_record *itr,
 				    struct record_opts *opts,
 				    const char *str);
+int auxtrace_parse_sample_options(struct auxtrace_record *itr,
+				  struct evlist *evlist,
+				  struct record_opts *opts, const char *str);
 int auxtrace_record__options(struct auxtrace_record *itr,
 			     struct evlist *evlist,
 			     struct record_opts *opts);
@@ -648,6 +653,17 @@ int auxtrace_parse_snapshot_options(struct auxtrace_record *itr __maybe_unused,
 	return -EINVAL;
 }
 
+int auxtrace_parse_sample_options(struct auxtrace_record *itr __maybe_unused,
+				  struct evlist *evlist __maybe_unused,
+				  struct record_opts *opts __maybe_unused,
+				  const char *str)
+{
+	if (!str)
+		return 0;
+	pr_err("AUX area tracing not supported\n");
+	return -EINVAL;
+}
+
 static inline
 int auxtrace__process_event(struct perf_session *session __maybe_unused,
 			    union perf_event *event __maybe_unused,
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 3e8cd31a89cc..2eb7a7001307 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -26,6 +26,7 @@ struct perf_pmu {
 	__u32 type;
 	bool selectable;
 	bool is_uncore;
+	bool auxtrace;
 	int max_precise;
 	struct perf_event_attr *default_config;
 	struct perf_cpu_map *cpus;
diff --git a/tools/perf/util/record.h b/tools/perf/util/record.h
index 948bbcf9aef3..5421fd2ad383 100644
--- a/tools/perf/util/record.h
+++ b/tools/perf/util/record.h
@@ -32,6 +32,7 @@ struct record_opts {
 	bool	      full_auxtrace;
 	bool	      auxtrace_snapshot_mode;
 	bool	      auxtrace_snapshot_on_exit;
+	bool	      auxtrace_sample_mode;
 	bool	      record_namespaces;
 	bool	      record_switch_events;
 	bool	      all_kernel;
@@ -56,6 +57,7 @@ struct record_opts {
 	u64	      user_interval;
 	size_t	      auxtrace_snapshot_size;
 	const char    *auxtrace_snapshot_opts;
+	const char    *auxtrace_sample_opts;
 	bool	      sample_transaction;
 	unsigned      initial_delay;
 	bool	      use_clockid;
-- 
2.17.1