[PATCH v3] libtracefs: New APIs for getting the raw format of synth event

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

The following APIs are added:
int tracefs_synth_echo_fmt(struct trace_seq *, struct tracefs_synth *)
const char *tracefs_synth_show_event(struct tracefs_synth *)
const char *tracefs_synth_show_start_hist(struct tracefs_synth *)
const char *tracefs_synth_show_end_hist(struct tracefs_synth *)

The new APIs can be useful in the case whene the user wants to
check what exactly gets passed to the kernel as definition of
a synth event.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 Documentation/libtracefs-synth2.txt | 23 ++++++-
 include/tracefs.h                   |  5 ++
 src/tracefs-hist.c                  | 94 +++++++++++++++++++++++------
 3 files changed, 102 insertions(+), 20 deletions(-)

diff --git a/Documentation/libtracefs-synth2.txt b/Documentation/libtracefs-synth2.txt
index 569819a..e557bc9 100644
--- a/Documentation/libtracefs-synth2.txt
+++ b/Documentation/libtracefs-synth2.txt
@@ -5,7 +5,8 @@ NAME
 ----
 tracefs_synth_create, tracefs_synth_destroy, tracefs_synth_echo_cmd, tracefs_synth_complete,
 tracefs_synth_get_start_hist, tracefs_synth_trace, tracefs_synth_snapshot,
-tracefs_synth_get_name - Creation of synthetic events
+tracefs_synth_get_name, tracefs_synth_echo_fmt, tracefs_synth_show_event,
+tracefs_synth_show_start_hist, tracefs_synth_show_end_hist - Creation of synthetic events
 
 SYNOPSIS
 --------
@@ -27,6 +28,11 @@ int tracefs_synth_save(struct tracefs_synth pass:[*]synth,
 		       enum tracefs_synth_handler type, const char pass:[*]var,
 		       char pass:[**]save_fields);
 const char *tracefs_synth_get_name(struct tracefs_synth pass:[*]synth);
+int tracefs_synth_echo_fmt(struct trace_seq pass:[*]seq, struct tracefs_synth pass:[*]synth);
+const char *tracefs_synth_show_event(struct tracefs_synth pass:[*]synth);
+const char *tracefs_synth_show_start_hist(struct tracefs_synth pass:[*]synth);
+const char *tracefs_synth_show_end_hist(struct tracefs_synth pass:[*]synth);
+
 --
 
 DESCRIPTION
@@ -93,9 +99,22 @@ _var_ changes. _var_ must be one of the _name_ elements used in *tracefs_synth_a
 The returned string belongs to the synth event object and is freed with the event
 by *tracefs_synth_free*().
 
+*tracefs_synth_show_event*() returns the format of the dynamic event used by the synthetic
+event or NULL on error. The returned string belongs to the synth event object and is freed
+with the event by *tracefs_synth_free*().
+
+*tracefs_synth_show_start_hist*() returns the format of the start histogram used by the
+synthetic event or NULL on error. The returned string belongs to the synth event object
+and is freed with the event by *tracefs_synth_free*().
+
+*tracefs_synth_show_end_hist*() returns the format of the end histogram used by the
+synthetic event or NULL on error. The returned string belongs to the synth event object
+and is freed with the event by *tracefs_synth_free*().
+
 RETURN VALUE
 ------------
-*tracefs_synth_get_name*() returns a string owned by the synth event object.
+*tracefs_synth_get_name*(), *tracefs_synth_show_event*(), *tracefs_synth_show_start_hist*()
+and *tracefs_synth_show_end_hist*()  return a string owned by the synth event object.
 
 All other functions return zero on success or -1 on error.
 
diff --git a/include/tracefs.h b/include/tracefs.h
index 967690f..b772f5a 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -250,6 +250,7 @@ enum tracefs_dynevent_type {
 	TRACEFS_DYNEVENT_SYNTH		= 1 << 5,
 	TRACEFS_DYNEVENT_MAX		= 1 << 6,
 };
+
 int tracefs_dynevent_create(struct tracefs_dynevent *devent);
 int tracefs_dynevent_destroy(struct tracefs_dynevent *devent, bool force);
 int tracefs_dynevent_destroy_all(unsigned int types, bool force);
@@ -550,6 +551,10 @@ int tracefs_synth_create(struct tracefs_synth *synth);
 int tracefs_synth_destroy(struct tracefs_synth *synth);
 void tracefs_synth_free(struct tracefs_synth *synth);
 int tracefs_synth_echo_cmd(struct trace_seq *seq, struct tracefs_synth *synth);
+int tracefs_synth_echo_fmt(struct trace_seq *seq, struct tracefs_synth *synth);
+const char *tracefs_synth_show_event(struct tracefs_synth *synth);
+const char *tracefs_synth_show_start_hist(struct tracefs_synth *synth);
+const char *tracefs_synth_show_end_hist(struct tracefs_synth *synth);
 
 struct tracefs_synth *tracefs_sql(struct tep_handle *tep, const char *name,
 				  const char *sql_buffer, char **err);
diff --git a/src/tracefs-hist.c b/src/tracefs-hist.c
index 6051ecc..f5359a5 100644
--- a/src/tracefs-hist.c
+++ b/src/tracefs-hist.c
@@ -683,6 +683,8 @@ struct tracefs_synth {
 	struct action		*actions;
 	struct action		**next_action;
 	struct tracefs_dynevent	*dyn_event;
+	char			*start_hist;
+	char			*end_hist;
 	char			*name;
 	char			**synthetic_fields;
 	char			**synthetic_args;
@@ -737,6 +739,8 @@ void tracefs_synth_free(struct tracefs_synth *synth)
 		return;
 
 	free(synth->name);
+	free(synth->start_hist);
+	free(synth->end_hist);
 	tracefs_list_free(synth->synthetic_fields);
 	tracefs_list_free(synth->synthetic_args);
 	tracefs_list_free(synth->start_keys);
@@ -1802,6 +1806,67 @@ static char *create_end_hist(struct tracefs_synth *synth)
 	return create_actions(end_hist, synth);
 }
 
+/*
+ * tracefs_synth_echo_fmt - show the raw format of a synthetic event
+ * @seq: A trace_seq to store the format string
+ * @synth: The synthetic event to read format from
+ *
+ * This shows the raw format that describes the synthetic event, including
+ * the format of the dynamic event and the start / end histograms.
+ *
+ * Returns 0 on succes -1 on error.
+ */
+int tracefs_synth_echo_fmt(struct trace_seq *seq, struct tracefs_synth *synth)
+{
+	if (!synth->dyn_event)
+		return -1;
+
+	trace_seq_printf(seq, "%s", synth->dyn_event->format);
+	trace_seq_printf(seq, "\n%s", synth->start_hist);
+	trace_seq_printf(seq, "\n%s", synth->end_hist);
+
+	return 0;
+}
+
+/*
+ * tracefs_synth_show_event - show the dynamic event used by a synth event
+ * @synth: The synthetic event to read format from
+ *
+ * This shows the raw format of the dynamic event used by the synthetic event.
+ *
+ * Returns format string owned by @synth on success, or NULL on error.
+ */
+const char *tracefs_synth_show_event(struct tracefs_synth *synth)
+{
+	return synth->dyn_event ? synth->dyn_event->format : NULL;
+}
+
+/*
+ * tracefs_synth_show_start_hist - show the start histogram used by a synth event
+ * @synth: The synthetic event to read format from
+ *
+ * This shows the raw format of the start histogram used by the synthetic event.
+ *
+ * Returns format string owned by @synth on success, or NULL on error.
+ */
+const char *tracefs_synth_show_start_hist(struct tracefs_synth *synth)
+{
+	return synth->start_hist;
+}
+
+/*
+ * tracefs_synth_show_end_hist - show the end histogram used by a synth event
+ * @synth: The synthetic event to read format from
+ *
+ * This shows the raw format of the end histogram used by the synthetic event.
+ *
+ * Returns format string owned by @synth on success, or NULL on error.
+ */
+const char *tracefs_synth_show_end_hist(struct tracefs_synth *synth)
+{
+	return synth->end_hist;
+}
+
 static char *append_filter(char *hist, char *filter, unsigned int parens)
 {
 	int i;
@@ -1940,8 +2005,6 @@ tracefs_synth_get_start_hist(struct tracefs_synth *synth)
  */
 int tracefs_synth_create(struct tracefs_synth *synth)
 {
-	char *start_hist = NULL;
-	char *end_hist = NULL;
 	int ret;
 
 	if (!synth) {
@@ -1962,40 +2025,35 @@ int tracefs_synth_create(struct tracefs_synth *synth)
 	if (tracefs_dynevent_create(synth->dyn_event))
 		return -1;
 
-	start_hist = create_hist(synth->start_keys, synth->start_vars);
-	start_hist = append_filter(start_hist, synth->start_filter,
-				   synth->start_parens);
-	if (!start_hist)
+	synth->start_hist = create_hist(synth->start_keys, synth->start_vars);
+	synth->start_hist = append_filter(synth->start_hist, synth->start_filter,
+					  synth->start_parens);
+	if (!synth->start_hist)
 		goto remove_synthetic;
 
-	end_hist = create_end_hist(synth);
-	end_hist = append_filter(end_hist, synth->end_filter,
-				   synth->end_parens);
-	if (!end_hist)
+	synth->end_hist = create_end_hist(synth);
+	synth->end_hist = append_filter(synth->end_hist, synth->end_filter,
+					synth->end_parens);
+	if (!synth->end_hist)
 		goto remove_synthetic;
 
 	ret = tracefs_event_file_append(synth->instance, synth->start_event->system,
 					synth->start_event->name,
-					"trigger", start_hist);
+					"trigger", synth->start_hist);
 	if (ret < 0)
 		goto remove_synthetic;
 
 	ret = tracefs_event_file_append(synth->instance, synth->end_event->system,
 					synth->end_event->name,
-					"trigger", end_hist);
+					"trigger", synth->end_hist);
 	if (ret < 0)
 		goto remove_start_hist;
 
-	free(start_hist);
-	free(end_hist);
-
 	return 0;
 
  remove_start_hist:
-	remove_hist(synth->instance, synth->start_event, start_hist);
+	remove_hist(synth->instance, synth->start_event, synth->start_hist);
  remove_synthetic:
-	free(end_hist);
-	free(start_hist);
 	tracefs_dynevent_destroy(synth->dyn_event, false);
 	return -1;
 }
-- 
2.32.0