[PATCH 0/6] libtracefs fixes and improvements

[PATCH 0/6] libtracefs fixes and improvements

[Tzvetomir Stoyanov (VMware)]

A few final tracefs library fixes and improvements, before releasing it as
an official library.

Tzvetomir Stoyanov (VMware) (6):
  trace-cmd: Change tracefs.h include path
  libtracefs: Change APIs to work with constant strings
  libtracefs: Add new API to check if instance exists
  libtracefs: Combine allocate and create APIs into one
  libtracefs: Add new tracefs API tracefs_instances_walk()
  trace-cmd: Add new libtrasefs API to get the current trace clock

 include/trace-cmd/trace-cmd.h       |   1 +
 include/tracefs/tracefs.h           |  17 ++--
 lib/trace-cmd/trace-timesync.c      |   5 +-
 lib/tracefs/include/tracefs-local.h |   1 +
 lib/tracefs/tracefs-events.c        |  61 +++++-------
 lib/tracefs/tracefs-instance.c      | 141 ++++++++++++++++++++++++++--
 tracecmd/include/trace-local.h      |   4 +-
 tracecmd/trace-record.c             |  68 ++++++--------
 tracecmd/trace-show.c               |   2 +-
 tracecmd/trace-stat.c               |  83 +++++-----------
 utest/tracefs-utest.c               | 120 ++++++++++++++++++-----
 11 files changed, 322 insertions(+), 181 deletions(-)

-- 
2.28.0

[PATCH 1/6] trace-cmd: Change tracefs.h include path

[Tzvetomir Stoyanov (VMware)]

The tracefs.h file is installed in
	<install_prefix>/include/tracefs/tracefs.h.
However, in trace-cmd.h it is inluded just as "tracefs.h".
When trace-cmd.h is used in trace-cmd build context that include is not
a problem, as all local header paths are described in the Makefiles. But
when other application uses trace-cmd.h and tracefs.h, installed in the
system, the compilation fails due to this broken include.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/trace-cmd/trace-cmd.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/trace-cmd/trace-cmd.h b/include/trace-cmd/trace-cmd.h
index f3c95f30..3c2b4745 100644
--- a/include/trace-cmd/trace-cmd.h
+++ b/include/trace-cmd/trace-cmd.h
@@ -7,6 +7,7 @@
 #define _TRACE_CMD_H
 
 #include "traceevent/event-parse.h"
+#include "tracefs/tracefs.h"
 
 #define TRACECMD_MAGIC { 23, 8, 68 }
 
-- 
2.28.0

[PATCH 2/6] libtracefs: Change APIs to work with constant strings

[Tzvetomir Stoyanov (VMware)]

Some tracefs library APIs retrieve trace instance parameters as srings.
As these strings are not meant to be changed by the API callers, set
them to be constant. These APIs are affected:
 tracefs_instance_get_name()
 tracefs_event_systems()
 tracefs_system_events()
 tracefs_tracers()
 tracefs_list_free()

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/tracefs/tracefs.h      | 10 ++++----
 lib/tracefs/tracefs-events.c   | 47 ++++++++++++++--------------------
 lib/tracefs/tracefs-instance.c |  4 +--
 tracecmd/trace-record.c        |  2 +-
 utest/tracefs-utest.c          | 23 +++++++++--------
 5 files changed, 39 insertions(+), 47 deletions(-)

diff --git a/include/tracefs/tracefs.h b/include/tracefs/tracefs.h
index 8ee7ba6e..8d193853 100644
--- a/include/tracefs/tracefs.h
+++ b/include/tracefs/tracefs.h
@@ -24,7 +24,7 @@ struct tracefs_instance *tracefs_instance_alloc(const char *name);
 void tracefs_instance_free(struct tracefs_instance *instance);
 int tracefs_instance_create(struct tracefs_instance *instance);
 int tracefs_instance_destroy(struct tracefs_instance *instance);
-char *tracefs_instance_get_name(struct tracefs_instance *instance);
+const char *tracefs_instance_get_name(struct tracefs_instance *instance);
 char *
 tracefs_instance_get_file(struct tracefs_instance *instance, const char *file);
 char *tracefs_instance_get_dir(struct tracefs_instance *instance);
@@ -37,9 +37,9 @@ bool tracefs_file_exists(struct tracefs_instance *instance, char *name);
 bool tracefs_dir_exists(struct tracefs_instance *instance, char *name);
 
 /* events */
-void tracefs_list_free(char **list);
-char **tracefs_event_systems(const char *tracing_dir);
-char **tracefs_system_events(const char *tracing_dir, const char *system);
+void tracefs_list_free(const char **list);
+const char **tracefs_event_systems(const char *tracing_dir);
+const char **tracefs_system_events(const char *tracing_dir, const char *system);
 int tracefs_iterate_raw_events(struct tep_handle *tep,
 				struct tracefs_instance *instance,
 				int (*callback)(struct tep_event *,
@@ -47,7 +47,7 @@ int tracefs_iterate_raw_events(struct tep_handle *tep,
 						int, void *),
 				void *callback_context);
 
-char **tracefs_tracers(const char *tracing_dir);
+const char **tracefs_tracers(const char *tracing_dir);
 
 struct tep_handle *tracefs_local_events(const char *tracing_dir);
 struct tep_handle *tracefs_local_events_system(const char *tracing_dir,
diff --git a/lib/tracefs/tracefs-events.c b/lib/tracefs/tracefs-events.c
index 8e825f50..19f98058 100644
--- a/lib/tracefs/tracefs-events.c
+++ b/lib/tracefs/tracefs-events.c
@@ -227,7 +227,7 @@ static char *append_file(const char *dir, const char *name)
  *
  *@list pointer to a list of strings, the last one must be NULL
  */
-void tracefs_list_free(char **list)
+void tracefs_list_free(const char **list)
 {
 	int i;
 
@@ -235,7 +235,7 @@ void tracefs_list_free(char **list)
 		return;
 
 	for (i = 0; list[i]; i++)
-		free(list[i]);
+		free((char *)list[i]);
 
 	free(list);
 }
@@ -245,11 +245,11 @@ void tracefs_list_free(char **list)
  * @tracing_dir: directory holding the "events" directory
  *		 if NULL, top tracing directory is used
  *
- * Returns an allocated list of system names. Both the names and
- * the list must be freed with tracefs_list_free()
- * The list returned ends with a "NULL" pointer
+ *
+ * Returns an allocated list of system names, the last element
+ * is a NULL pointer. The list must be freed with tracefs_list_free()*
  */
-char **tracefs_event_systems(const char *tracing_dir)
+const char **tracefs_event_systems(const char *tracing_dir)
 {
 	struct dirent *dent;
 	char **systems = NULL;
@@ -311,7 +311,7 @@ char **tracefs_event_systems(const char *tracing_dir)
 
  out_free:
 	free(events_dir);
-	return systems;
+	return (const char **)systems;
 }
 
 /**
@@ -319,11 +319,10 @@ char **tracefs_event_systems(const char *tracing_dir)
  * @tracing_dir: directory holding the "events" directory
  * @system: the system to return the events for
  *
- * Returns an allocated list of event names. Both the names and
- * the list must be freed with tracefs_list_free()
- * The list returned ends with a "NULL" pointer
+ * Returns an allocated list of event names, the last element
+ * is a NULL pointer. The list must be freed with tracefs_list_free()
  */
-char **tracefs_system_events(const char *tracing_dir, const char *system)
+const char **tracefs_system_events(const char *tracing_dir, const char *system)
 {
 	struct dirent *dent;
 	char **events = NULL;
@@ -376,17 +375,17 @@ char **tracefs_system_events(const char *tracing_dir, const char *system)
  out_free:
 	free(system_dir);
 
-	return events;
+	return (const char **)events;
 }
 
 /**
  * tracefs_tracers - returns an array of available tracers
  * @tracing_dir: The directory that contains the tracing directory
  *
- * Returns an allocate list of plugins. The array ends with NULL
- * Both the plugin names and array must be freed with free()
+ * Returns an allocated list of trace plugin names, the last element
+ * is a NULL pointer. The list must be freed with tracefs_list_free()*
  */
-char **tracefs_tracers(const char *tracing_dir)
+const char **tracefs_tracers(const char *tracing_dir)
 {
 	char *available_tracers;
 	struct stat st;
@@ -438,14 +437,14 @@ char **tracefs_tracers(const char *tracing_dir)
  out_free:
 	free(available_tracers);
 
-	return plugins;
+	return (const char **)plugins;
 }
 
 static int load_events(struct tep_handle *tep,
 		       const char *tracing_dir, const char *system)
 {
+	const char **events = NULL;
 	int ret = 0, failure = 0;
-	char **events = NULL;
 	struct stat st;
 	int len = 0;
 	int i;
@@ -481,11 +480,7 @@ next_event:
 			failure = ret;
 	}
 
-	if (events) {
-		for (i = 0; events[i]; i++)
-			free(events[i]);
-		free(events);
-	}
+	tracefs_list_free(events);
 	return failure;
 }
 
@@ -532,7 +527,7 @@ static int fill_local_events_system(const char *tracing_dir,
 				    const char * const *sys_names,
 				    int *parsing_failures)
 {
-	char **systems = NULL;
+	const char **systems = NULL;
 	int ret;
 	int i;
 
@@ -564,11 +559,7 @@ static int fill_local_events_system(const char *tracing_dir,
 	/* always succeed because parsing failures are not critical */
 	ret = 0;
 out:
-	if (systems) {
-		for (i = 0; systems[i]; i++)
-			free(systems[i]);
-		free(systems);
-	}
+	tracefs_list_free(systems);
 	return ret;
 }
 
diff --git a/lib/tracefs/tracefs-instance.c b/lib/tracefs/tracefs-instance.c
index 50e88534..e9ec3401 100644
--- a/lib/tracefs/tracefs-instance.c
+++ b/lib/tracefs/tracefs-instance.c
@@ -169,7 +169,7 @@ char *tracefs_instance_get_dir(struct tracefs_instance *instance)
  * Returns the name of the given @instance.
  * The returned string must *not* be freed.
  */
-char *tracefs_instance_get_name(struct tracefs_instance *instance)
+const char *tracefs_instance_get_name(struct tracefs_instance *instance)
 {
 	if (instance)
 		return instance->name;
@@ -252,8 +252,8 @@ static bool check_file_exists(struct tracefs_instance *instance,
 			     char *name, bool dir)
 {
 	char file[PATH_MAX];
-	struct stat st;
 	char *path;
+	struct stat st;
 	int ret;
 
 	path = tracefs_instance_get_dir(instance);
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 72a5c8c9..8cd44dd0 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -3861,7 +3861,7 @@ static void connect_to_agent(struct buffer_instance *instance)
 	unsigned int *ports;
 	int i, *fds = NULL;
 	bool use_fifos = false;
-	char *name;
+	const char *name;
 
 	name = tracefs_instance_get_name(instance->tracefs);
 	if (!no_fifos) {
diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c
index 1c146576..31a700ff 100644
--- a/utest/tracefs-utest.c
+++ b/utest/tracefs-utest.c
@@ -180,7 +180,7 @@ static void test_instance_file(void)
 {
 	struct tracefs_instance *instance = NULL;
 	const char *name = get_rand_str();
-	char *inst_name = NULL;
+	const char *inst_name = NULL;
 	const char *tdir;
 	char *inst_file;
 	char *inst_dir;
@@ -308,9 +308,9 @@ static void test_check_files(const char *fdir, char **files)
 
 static void test_system_event(void)
 {
+	const char **systems;
+	const char **events;
 	const char *tdir;
-	char **systems;
-	char **events;
 	char *sdir = NULL;
 
 	tdir  = tracefs_get_tracing_dir();
@@ -324,13 +324,13 @@ static void test_system_event(void)
 
 	asprintf(&sdir, "%s/events/%s", tdir, systems[0]);
 	CU_TEST(sdir != NULL);
-	test_check_files(sdir, events);
+	test_check_files(sdir, (char **)events);
 	free(sdir);
 	sdir = NULL;
 
 	asprintf(&sdir, "%s/events", tdir);
 	CU_TEST(sdir != NULL);
-	test_check_files(sdir, systems);
+	test_check_files(sdir, (char **)systems);
 
 	tracefs_list_free(systems);
 	tracefs_list_free(events);
@@ -340,8 +340,8 @@ static void test_system_event(void)
 
 static void test_tracers(void)
 {
+	const char **tracers;
 	const char *tdir;
-	char **tracers;
 	char *tfile;
 	char *tracer;
 	int i;
@@ -356,7 +356,7 @@ static void test_tracers(void)
 
 	tracer = strtok(tfile, " ");
 	while (tracer) {
-		exclude_string(tracers, tracer);
+		exclude_string((char **)tracers, tracer);
 		tracer = strtok(NULL, " ");
 	}
 
@@ -367,7 +367,8 @@ static void test_tracers(void)
 	free(tfile);
 }
 
-static void test_check_events(struct tep_handle *tep, char *system, bool exist)
+static void test_check_events(struct tep_handle *tep,
+			      const char *system, bool exist)
 {
 	struct dirent *dent;
 	char file[PATH_MAX];
@@ -409,8 +410,8 @@ static void test_check_events(struct tep_handle *tep, char *system, bool exist)
 static void test_local_events(void)
 {
 	struct tep_handle *tep;
+	const char **systems;
 	const char *tdir;
-	char **systems;
 	char *lsystems[3];
 	int i;
 
@@ -430,9 +431,9 @@ static void test_local_events(void)
 	memset(lsystems, 0, sizeof(lsystems));
 	for (i = 0; systems[i]; i++) {
 		if (!lsystems[0])
-			lsystems[0] = systems[i];
+			lsystems[0] = (char *)systems[i];
 		else if (!lsystems[2])
-			lsystems[2] = systems[i];
+			lsystems[2] = (char *)systems[i];
 		else
 			break;
 	}
-- 
2.28.0

[PATCH 3/6] libtracefs: Add new API to check if instance exists

[Tzvetomir Stoyanov (VMware)]

A new API is implemented:
 tracefs_instance_exists()
which can be used to check if ftrace instance with given name exists in
the system.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/tracefs/tracefs.h      |  1 +
 lib/tracefs/tracefs-instance.c | 22 +++++++++++++++++++++-
 utest/tracefs-utest.c          |  2 ++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/include/tracefs/tracefs.h b/include/tracefs/tracefs.h
index 8d193853..e5bf3df4 100644
--- a/include/tracefs/tracefs.h
+++ b/include/tracefs/tracefs.h
@@ -33,6 +33,7 @@ int tracefs_instance_file_write(struct tracefs_instance *instance,
 char *tracefs_instance_file_read(struct tracefs_instance *instance,
 				 char *file, int *psize);
 
+bool tracefs_instance_exists(const char *name);
 bool tracefs_file_exists(struct tracefs_instance *instance, char *name);
 bool tracefs_dir_exists(struct tracefs_instance *instance, char *name);
 
diff --git a/lib/tracefs/tracefs-instance.c b/lib/tracefs/tracefs-instance.c
index e9ec3401..c19dd3b4 100644
--- a/lib/tracefs/tracefs-instance.c
+++ b/lib/tracefs/tracefs-instance.c
@@ -257,7 +257,10 @@ static bool check_file_exists(struct tracefs_instance *instance,
 	int ret;
 
 	path = tracefs_instance_get_dir(instance);
-	snprintf(file, PATH_MAX, "%s/%s", path, name);
+	if (name)
+		snprintf(file, PATH_MAX, "%s/%s", path, name);
+	else
+		snprintf(file, PATH_MAX, "%s", path);
 	tracefs_put_tracing_file(path);
 	ret = stat(file, &st);
 	if (ret < 0)
@@ -266,6 +269,23 @@ static bool check_file_exists(struct tracefs_instance *instance,
 	return !dir == !S_ISDIR(st.st_mode);
 }
 
+/**
+ * tracefs_instance_exists - Check an instance with given name exists
+ * @name: name of the instance
+ *
+ * Returns true if the instance exists, false otherwise
+ *
+ */
+bool tracefs_instance_exists(const char *name)
+{
+	char file[PATH_MAX];
+
+	if (!name)
+		return false;
+	snprintf(file, PATH_MAX, "instances/%s", name);
+	return check_file_exists(NULL, file, true);
+}
+
 /**
  * tracefs_file_exists - Check if a file with given name exists in given instance
  * @instance: ftrace instance, can be NULL for the top instance
diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c
index 31a700ff..292bcab0 100644
--- a/utest/tracefs-utest.c
+++ b/utest/tracefs-utest.c
@@ -197,6 +197,7 @@ static void test_instance_file(void)
 	CU_TEST(asprintf(&inst_dir, "%s/instances/%s", tdir, name) > 0);
 	CU_TEST(stat(inst_dir, &st) != 0);
 
+	CU_TEST(tracefs_instance_exists(name) == false);
 	instance = tracefs_instance_alloc(name);
 	CU_TEST(instance != NULL);
 	CU_TEST(stat(inst_dir, &st) != 0);
@@ -205,6 +206,7 @@ static void test_instance_file(void)
 	CU_TEST(strcmp(inst_name, name) == 0);
 
 	CU_TEST(tracefs_instance_create(instance) == 0);
+	CU_TEST(tracefs_instance_exists(name) == true);
 	CU_TEST(stat(inst_dir, &st) == 0);
 	CU_TEST(S_ISDIR(st.st_mode));
 
-- 
2.28.0

[PATCH 4/6] libtracefs: Combine allocate and create APIs into one

[Tzvetomir Stoyanov (VMware)]

Having two APIs for allocating and creating trace instance can be
confusing. The tracefs_instance_alloc() is removed and its logic is
moved to tracefs_instance_create() API. This single API first creates
the instance in the system (if it does not exist) and then allocates and
initializes tracefs_instance structure. Trace-cmd code and unit tests are
modified to use the new API.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/tracefs/tracefs.h      |  3 +-
 lib/trace-cmd/trace-timesync.c |  5 ++-
 lib/tracefs/tracefs-instance.c | 28 +++++++++++----
 tracecmd/include/trace-local.h |  4 +--
 tracecmd/trace-record.c        | 66 +++++++++++++++-------------------
 tracecmd/trace-show.c          |  2 +-
 tracecmd/trace-stat.c          |  2 +-
 utest/tracefs-utest.c          | 18 +++-------
 8 files changed, 62 insertions(+), 66 deletions(-)

diff --git a/include/tracefs/tracefs.h b/include/tracefs/tracefs.h
index e5bf3df4..d9ede08c 100644
--- a/include/tracefs/tracefs.h
+++ b/include/tracefs/tracefs.h
@@ -20,9 +20,8 @@ char *tracefs_find_tracing_dir(void);
 /* ftarce instances */
 struct tracefs_instance;
 
-struct tracefs_instance *tracefs_instance_alloc(const char *name);
 void tracefs_instance_free(struct tracefs_instance *instance);
-int tracefs_instance_create(struct tracefs_instance *instance);
+int tracefs_instance_create(const char *name, struct tracefs_instance **instance);
 int tracefs_instance_destroy(struct tracefs_instance *instance);
 const char *tracefs_instance_get_name(struct tracefs_instance *instance);
 char *
diff --git a/lib/trace-cmd/trace-timesync.c b/lib/trace-cmd/trace-timesync.c
index 35a41394..c6ec01ec 100644
--- a/lib/trace-cmd/trace-timesync.c
+++ b/lib/trace-cmd/trace-timesync.c
@@ -235,16 +235,15 @@ static int get_vsocket_params(int fd, unsigned int *lcid, unsigned int *lport,
 static struct tracefs_instance *
 clock_synch_create_instance(const char *clock, unsigned int cid)
 {
-	struct tracefs_instance *instance;
+	struct tracefs_instance *instance = NULL;
 	char inst_name[256];
 
 	snprintf(inst_name, 256, "clock_synch-%d", cid);
 
-	instance = tracefs_instance_alloc(inst_name);
+	tracefs_instance_create(inst_name, &instance);
 	if (!instance)
 		return NULL;
 
-	tracefs_instance_create(instance);
 	tracefs_instance_file_write(instance, "trace", "\0");
 	if (clock)
 		tracefs_instance_file_write(instance, "trace_clock", clock);
diff --git a/lib/tracefs/tracefs-instance.c b/lib/tracefs/tracefs-instance.c
index c19dd3b4..8817a95b 100644
--- a/lib/tracefs/tracefs-instance.c
+++ b/lib/tracefs/tracefs-instance.c
@@ -22,12 +22,12 @@ struct tracefs_instance {
 };
 
 /**
- * tracefs_instance_alloc - allocate a new ftrace instance
+ * instance_alloc - allocate a new ftrace instance
  * @name: The name of the instance (instance will point to this)
  *
  * Returns a newly allocated instance, or NULL in case of an error.
  */
-struct tracefs_instance *tracefs_instance_alloc(const char *name)
+static struct tracefs_instance *instance_alloc(const char *name)
 {
 	struct tracefs_instance *instance;
 
@@ -45,7 +45,7 @@ struct tracefs_instance *tracefs_instance_alloc(const char *name)
 
 /**
  * tracefs_instance_free - Free an instance, previously allocated by
-			   tracefs_instance_alloc()
+			   tracefs_instance_create()
  * @instance: Pointer to the instance to be freed
  *
  */
@@ -59,24 +59,38 @@ void tracefs_instance_free(struct tracefs_instance *instance)
 
 /**
  * tracefs_instance_create - Create a new ftrace instance
- * @instance: Pointer to the instance to be created
+ * @name: Name of the instance to be created
+ * @instance: Return, pointer to a newly allocated instance
  *
  * Returns 1 if the instance already exist, 0 if the instance
- * is created successful or -1 in case of an error
+ * is created successful or -1 in case of an error.
+ * If 1 or 0 is returned, @instance points to anewly allocated instance
+ * which must be freed by tracefs_instance_free()
  */
-int tracefs_instance_create(struct tracefs_instance *instance)
+int tracefs_instance_create(const char *name, struct tracefs_instance **instance)
 {
+	struct tracefs_instance *inst;
 	struct stat st;
 	char *path;
 	int ret;
 
-	path = tracefs_instance_get_dir(instance);
+	inst = instance_alloc(name);
+	if (!inst)
+		return -1;
+
+	path = tracefs_instance_get_dir(inst);
 	ret = stat(path, &st);
 	if (ret < 0)
 		ret = mkdir(path, 0777);
 	else
 		ret = 1;
 	tracefs_put_tracing_file(path);
+
+	if (ret < 0)
+		tracefs_instance_free(inst);
+	else
+		*instance = inst;
+
 	return ret;
 }
 
diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h
index d148aa16..207aa68f 100644
--- a/tracecmd/include/trace-local.h
+++ b/tracecmd/include/trace-local.h
@@ -199,6 +199,7 @@ struct filter_pids {
 
 struct buffer_instance {
 	struct buffer_instance	*next;
+	char			*name;
 	struct tracefs_instance	*tracefs;
 	unsigned long long	trace_id;
 	char			*cpumask;
@@ -277,7 +278,7 @@ extern struct buffer_instance *first_instance;
 #define is_agent(instance)	((instance)->flags & BUFFER_FL_AGENT)
 #define is_guest(instance)	((instance)->flags & BUFFER_FL_GUEST)
 
-struct buffer_instance *create_instance(const char *name);
+struct buffer_instance *allocate_instance(const char *name);
 void add_instance(struct buffer_instance *instance, int cpu_count);
 void update_first_instance(struct buffer_instance *instance, int topt);
 
@@ -286,7 +287,6 @@ void show_instance_file(struct buffer_instance *instance, const char *name);
 int get_guest_vcpu_pid(unsigned int guest_cid, unsigned int guest_vcpu);
 
 /* moved from trace-cmd.h */
-void tracecmd_create_top_instance(char *name);
 void tracecmd_remove_instances(void);
 int tracecmd_add_event(const char *event_str, int stack);
 void tracecmd_enable_events(void);
diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c
index 8cd44dd0..6aee00a3 100644
--- a/tracecmd/trace-record.c
+++ b/tracecmd/trace-record.c
@@ -351,27 +351,36 @@ static void test_set_event_pid(struct buffer_instance *instance)
 }
 
 /**
- * create_instance - allocate a new buffer instance
+ * allocate_instance - allocate a new buffer instance,
+ *			it must exist in the ftrace system
  * @name: The name of the instance (instance will point to this)
  *
- * Returns a newly allocated instance. Note that @name will not be
- * copied, and the instance buffer will point to the string itself.
+ * Returns a newly allocated instance. In case of an error or if the
+ * instance does not exist in the ftrace system, NULL is returned.
  */
-struct buffer_instance *create_instance(const char *name)
+struct buffer_instance *allocate_instance(const char *name)
 {
 	struct buffer_instance *instance;
 
-	instance = malloc(sizeof(*instance));
+	instance = calloc(1, sizeof(*instance));
 	if (!instance)
 		return NULL;
-	memset(instance, 0, sizeof(*instance));
-	instance->tracefs = tracefs_instance_alloc(name);
-	if (!instance->tracefs) {
-		free(instance);
-		return NULL;
+	if (name)
+		instance->name = strdup(name);
+	if (tracefs_instance_exists(name)) {
+		if (tracefs_instance_create(name, &instance->tracefs) < 0)
+			goto error;
 	}
 
 	return instance;
+
+error:
+	if (instance) {
+		free(instance->name);
+		tracefs_instance_free(instance->tracefs);
+		free(instance);
+	}
+	return NULL;
 }
 
 static int __add_all_instances(const char *tracing_dir)
@@ -418,7 +427,7 @@ static int __add_all_instances(const char *tracing_dir)
 		}
 		free(instance_path);
 
-		instance = create_instance(name);
+		instance = allocate_instance(name);
 		if (!instance)
 			die("Failed to create instance");
 		add_instance(instance, local_cpu_count);
@@ -5034,7 +5043,8 @@ static void make_instances(void)
 	for_each_instance(instance) {
 		if (is_guest(instance))
 			continue;
-		if (tracefs_instance_create(instance->tracefs) > 0) {
+		if (instance->name && !instance->tracefs &&
+		    tracefs_instance_create(instance->name, &instance->tracefs) > 0) {
 			/* Don't delete instances that already exist */
 			instance->flags |= BUFFER_FL_KEEP;
 		}
@@ -5057,25 +5067,6 @@ void tracecmd_remove_instances(void)
 	}
 }
 
-/**
- * tracecmd_create_top_instance - create a top named instance
- * @name: name of the instance to use.
- *
- * This is a library function for tools that want to do their tracing inside of
- * an instance.  All it does is create an instance and set it as a top instance,
- * you don't want to call this more than once, and you want to call
- * tracecmd_remove_instances to undo your work.
- */
-void tracecmd_create_top_instance(char *name)
-{
-	struct buffer_instance *instance;
-
-	instance = create_instance(name);
-	add_instance(instance, local_cpu_count);
-	update_first_instance(instance, 0);
-	make_instances();
-}
-
 static void check_plugin(const char *plugin)
 {
 	char *buf;
@@ -5533,7 +5524,7 @@ void update_first_instance(struct buffer_instance *instance, int topt)
 void init_top_instance(void)
 {
 	if (!top_instance.tracefs)
-		top_instance.tracefs = tracefs_instance_alloc(NULL);
+		tracefs_instance_create(NULL, &top_instance.tracefs);
 	top_instance.cpu_count = tracecmd_count_cpus();
 	top_instance.flags = BUFFER_FL_KEEP;
 	top_instance.trace_id = tracecmd_generate_traceid();
@@ -5580,7 +5571,7 @@ void trace_stop(int argc, char **argv)
 			usage(argv);
 			break;
 		case 'B':
-			instance = create_instance(optarg);
+			instance = allocate_instance(optarg);
 			if (!instance)
 				die("Failed to create instance");
 			add_instance(instance, local_cpu_count);
@@ -5620,7 +5611,7 @@ void trace_restart(int argc, char **argv)
 			usage(argv);
 			break;
 		case 'B':
-			instance = create_instance(optarg);
+			instance = allocate_instance(optarg);
 			if (!instance)
 				die("Failed to create instance");
 			add_instance(instance, local_cpu_count);
@@ -5678,7 +5669,7 @@ void trace_reset(int argc, char **argv)
 		}
 		case 'B':
 			last_specified_all = 0;
-			instance = create_instance(optarg);
+			instance = allocate_instance(optarg);
 			if (!instance)
 				die("Failed to create instance");
 			add_instance(instance, local_cpu_count);
@@ -5821,6 +5812,7 @@ static inline void remove_instances(struct buffer_instance *instances)
 	while (instances) {
 		del = instances;
 		instances = instances->next;
+		free(del->name);
 		tracefs_instance_destroy(del->tracefs);
 		tracefs_instance_free(del->tracefs);
 		free(del);
@@ -5978,7 +5970,7 @@ static void parse_record_options(int argc,
 					die("Failed to allocate guest name");
 			}
 
-			ctx->instance = create_instance(name);
+			ctx->instance = allocate_instance(name);
 			ctx->instance->flags |= BUFFER_FL_GUEST;
 			ctx->instance->cid = cid;
 			ctx->instance->port = port;
@@ -6173,7 +6165,7 @@ static void parse_record_options(int argc,
 			ctx->instance->buffer_size = atoi(optarg);
 			break;
 		case 'B':
-			ctx->instance = create_instance(optarg);
+			ctx->instance = allocate_instance(optarg);
 			if (!ctx->instance)
 				die("Failed to create instance");
 			ctx->instance->delete = negative;
diff --git a/tracecmd/trace-show.c b/tracecmd/trace-show.c
index a6f21027..eb328527 100644
--- a/tracecmd/trace-show.c
+++ b/tracecmd/trace-show.c
@@ -64,7 +64,7 @@ void trace_show(int argc, char **argv)
 			if (buffer)
 				die("Can only show one buffer at a time");
 			buffer = optarg;
-			instance = create_instance(optarg);
+			instance = allocate_instance(optarg);
 			if (!instance)
 				die("Failed to create instance");
 			break;
diff --git a/tracecmd/trace-stat.c b/tracecmd/trace-stat.c
index 260d0c37..5f79ff8a 100644
--- a/tracecmd/trace-stat.c
+++ b/tracecmd/trace-stat.c
@@ -926,7 +926,7 @@ void trace_stat (int argc, char **argv)
 			usage(argv);
 			break;
 		case 'B':
-			instance = create_instance(optarg);
+			instance = allocate_instance(optarg);
 			if (!instance)
 				die("Failed to create instance");
 			add_instance(instance, tracecmd_count_cpus());
diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c
index 292bcab0..e11a0066 100644
--- a/utest/tracefs-utest.c
+++ b/utest/tracefs-utest.c
@@ -198,17 +198,13 @@ static void test_instance_file(void)
 	CU_TEST(stat(inst_dir, &st) != 0);
 
 	CU_TEST(tracefs_instance_exists(name) == false);
-	instance = tracefs_instance_alloc(name);
-	CU_TEST(instance != NULL);
-	CU_TEST(stat(inst_dir, &st) != 0);
-	inst_name = tracefs_instance_get_name(instance);
-	CU_TEST(inst_name != NULL);
-	CU_TEST(strcmp(inst_name, name) == 0);
-
-	CU_TEST(tracefs_instance_create(instance) == 0);
+	CU_TEST(tracefs_instance_create(name, &instance) == 0);
 	CU_TEST(tracefs_instance_exists(name) == true);
 	CU_TEST(stat(inst_dir, &st) == 0);
 	CU_TEST(S_ISDIR(st.st_mode));
+	inst_name = tracefs_instance_get_name(instance);
+	CU_TEST(inst_name != NULL);
+	CU_TEST(strcmp(inst_name, name) == 0);
 
 	fname = tracefs_instance_get_dir(NULL);
 	CU_TEST(fname != NULL);
@@ -476,11 +472,7 @@ static int test_suite_init(void)
 	if (test_tep == NULL)
 		return 1;
 
-	test_instance = tracefs_instance_alloc(TEST_INSTANCE_NAME);
-	if (test_instance == NULL)
-		return 1;
-
-	if (tracefs_instance_create(test_instance) < 0)
+	if (tracefs_instance_create(TEST_INSTANCE_NAME, &test_instance) < 0)
 		return 1;
 
 	return 0;
-- 
2.28.0

Re: [PATCH 4/6] libtracefs: Combine allocate and create APIs into one

[Steven Rostedt]

Hi Tzvetomir,


On Thu,  5 Nov 2020 11:33:52 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@gmail.com> wrote:

> @@ -59,24 +59,38 @@ void tracefs_instance_free(struct tracefs_instance *instance)
>  
>  /**
>   * tracefs_instance_create - Create a new ftrace instance
> - * @instance: Pointer to the instance to be created
> + * @name: Name of the instance to be created
> + * @instance: Return, pointer to a newly allocated instance
>   *
>   * Returns 1 if the instance already exist, 0 if the instance
> - * is created successful or -1 in case of an error
> + * is created successful or -1 in case of an error.
> + * If 1 or 0 is returned, @instance points to anewly allocated instance
> + * which must be freed by tracefs_instance_free()
>   */
> -int tracefs_instance_create(struct tracefs_instance *instance)
> +int tracefs_instance_create(const char *name, struct tracefs_instance **instance)

I think it makes more sense if we just return the allocated instance.
The return would be the allocated instance or NULL on failure.

-- Steve

[PATCH 5/6] libtracefs: Add new tracefs API tracefs_instances_walk()

[Tzvetomir Stoyanov (VMware)]

The logic for finding all configured ftrace instances is encapuslated in
a new tracefs_instances_walk() API. A user specified callback is
called for each ftrace instance in the system, excpet for the top level
one.
The implementation of "trace-cmd stat" is modified to use the new API.

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/tracefs/tracefs.h           |  1 +
 lib/tracefs/include/tracefs-local.h |  1 +
 lib/tracefs/tracefs-events.c        | 14 ++++----
 lib/tracefs/tracefs-instance.c      | 52 +++++++++++++++++++++++++++++
 tracecmd/trace-stat.c               | 52 ++++++++---------------------
 utest/tracefs-utest.c               | 51 ++++++++++++++++++++++++++++
 6 files changed, 125 insertions(+), 46 deletions(-)

diff --git a/include/tracefs/tracefs.h b/include/tracefs/tracefs.h
index d9ede08c..40781bb2 100644
--- a/include/tracefs/tracefs.h
+++ b/include/tracefs/tracefs.h
@@ -31,6 +31,7 @@ int tracefs_instance_file_write(struct tracefs_instance *instance,
 				const char *file, const char *str);
 char *tracefs_instance_file_read(struct tracefs_instance *instance,
 				 char *file, int *psize);
+int tracefs_instances_walk(int (*callback)(const char *, void *), void *context);
 
 bool tracefs_instance_exists(const char *name);
 bool tracefs_file_exists(struct tracefs_instance *instance, char *name);
diff --git a/lib/tracefs/include/tracefs-local.h b/lib/tracefs/include/tracefs-local.h
index fe327a0f..08b67fa9 100644
--- a/lib/tracefs/include/tracefs-local.h
+++ b/lib/tracefs/include/tracefs-local.h
@@ -9,5 +9,6 @@
 /* Can be overridden */
 void warning(const char *fmt, ...);
 int str_read_file(const char *file, char **buffer);
+char *trace_append_file(const char *dir, const char *name);
 
 #endif /* _TRACE_FS_LOCAL_H */
diff --git a/lib/tracefs/tracefs-events.c b/lib/tracefs/tracefs-events.c
index 19f98058..60797748 100644
--- a/lib/tracefs/tracefs-events.c
+++ b/lib/tracefs/tracefs-events.c
@@ -210,7 +210,7 @@ static char **add_list_string(char **list, const char *name, int len)
 	return list;
 }
 
-static char *append_file(const char *dir, const char *name)
+char *trace_append_file(const char *dir, const char *name)
 {
 	char *file;
 	int ret;
@@ -265,7 +265,7 @@ const char **tracefs_event_systems(const char *tracing_dir)
 	if (!tracing_dir)
 		return NULL;
 
-	events_dir = append_file(tracing_dir, "events");
+	events_dir = trace_append_file(tracing_dir, "events");
 	if (!events_dir)
 		return NULL;
 
@@ -290,14 +290,14 @@ const char **tracefs_event_systems(const char *tracing_dir)
 		    strcmp(name, "..") == 0)
 			continue;
 
-		sys = append_file(events_dir, name);
+		sys = trace_append_file(events_dir, name);
 		ret = stat(sys, &st);
 		if (ret < 0 || !S_ISDIR(st.st_mode)) {
 			free(sys);
 			continue;
 		}
 
-		enable = append_file(sys, "enable");
+		enable = trace_append_file(sys, "enable");
 
 		ret = stat(enable, &st);
 		if (ret >= 0)
@@ -358,7 +358,7 @@ const char **tracefs_system_events(const char *tracing_dir, const char *system)
 		    strcmp(name, "..") == 0)
 			continue;
 
-		event = append_file(system_dir, name);
+		event = trace_append_file(system_dir, name);
 		ret = stat(event, &st);
 		if (ret < 0 || !S_ISDIR(st.st_mode)) {
 			free(event);
@@ -400,7 +400,7 @@ const char **tracefs_tracers(const char *tracing_dir)
 	if (!tracing_dir)
 		return NULL;
 
-	available_tracers = append_file(tracing_dir, "available_tracers");
+	available_tracers = trace_append_file(tracing_dir, "available_tracers");
 	if (!available_tracers)
 		return NULL;
 
@@ -492,7 +492,7 @@ static int read_header(struct tep_handle *tep, const char *tracing_dir)
 	int len;
 	int ret = -1;
 
-	header = append_file(tracing_dir, "events/header_page");
+	header = trace_append_file(tracing_dir, "events/header_page");
 
 	ret = stat(header, &st);
 	if (ret < 0)
diff --git a/lib/tracefs/tracefs-instance.c b/lib/tracefs/tracefs-instance.c
index 8817a95b..777d5965 100644
--- a/lib/tracefs/tracefs-instance.c
+++ b/lib/tracefs/tracefs-instance.c
@@ -13,6 +13,7 @@
 #include <errno.h>
 #include <sys/stat.h>
 #include <fcntl.h>
+#include <dirent.h>
 #include <linux/limits.h>
 #include "tracefs.h"
 #include "tracefs-local.h"
@@ -325,3 +326,54 @@ bool tracefs_dir_exists(struct tracefs_instance *instance, char *name)
 {
 	return check_file_exists(instance, name, true);
 }
+
+/**
+ * tracefs_instances_walk - Iterate through all ftrace instances in the system
+ * @callback: user callback, called for each instance. Instance name is passed
+ *	      as input parameter. If the @callback returns non-zero,
+ *	      the iteration stops.
+ * @context: user context, passed to the @callback.
+ *
+ * Returns -1 in case of an error, 0 otherwise.
+ */
+int tracefs_instances_walk(int (*callback)(const char *, void *), void *context)
+{
+	struct dirent *dent;
+	char *path = NULL;
+	DIR *dir = NULL;
+	struct stat st;
+	int fret = -1;
+	int ret;
+
+	path = tracefs_get_tracing_file("instances");
+	if (!path)
+		return -1;
+	ret = stat(path, &st);
+	if (ret < 0 || !S_ISDIR(st.st_mode))
+		goto out;
+
+	dir = opendir(path);
+	if (!dir)
+		goto out;
+	fret = 0;
+	while ((dent = readdir(dir))) {
+		char *instance;
+
+		if (strcmp(dent->d_name, ".") == 0 ||
+		    strcmp(dent->d_name, "..") == 0)
+			continue;
+		instance = trace_append_file(path, dent->d_name);
+		ret = stat(instance, &st);
+		free(instance);
+		if (ret < 0 || !S_ISDIR(st.st_mode))
+			continue;
+		if (callback(dent->d_name, context))
+			break;
+	}
+
+out:
+	if (dir)
+		closedir(dir);
+	tracefs_put_tracing_file(path);
+	return fret;
+}
diff --git a/tracecmd/trace-stat.c b/tracecmd/trace-stat.c
index 5f79ff8a..e6678eab 100644
--- a/tracecmd/trace-stat.c
+++ b/tracecmd/trace-stat.c
@@ -7,7 +7,6 @@
 #include <sys/stat.h>
 #include <stdlib.h>
 #include <stdio.h>
-#include <dirent.h>
 #include <getopt.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -140,48 +139,23 @@ static void report_file(struct buffer_instance *instance,
 	free(str);
 }
 
-static void report_instances(void)
+static int report_instance(const char *name, void *data)
 {
-	struct dirent *dent;
-	bool first = true;
-	char *path = NULL;
-	DIR *dir = NULL;
-	struct stat st;
-	int ret;
-
-	path = tracefs_get_tracing_file("instances");
-	if (!path)
-		return;
-	ret = stat(path, &st);
-	if (ret < 0 || !S_ISDIR(st.st_mode))
-		goto out;
-
-	dir = opendir(path);
-	if (!dir)
-		goto out;
-
-	while ((dent = readdir(dir))) {
-		char *instance;
+	bool *first = (bool *)data;
 
-		if (strcmp(dent->d_name, ".") == 0 ||
-		    strcmp(dent->d_name, "..") == 0)
-			continue;
-		instance = append_file(path, dent->d_name);
-		ret = stat(instance, &st);
-		free(instance);
-		if (ret < 0 || !S_ISDIR(st.st_mode))
-			continue;
-		if (first) {
-			first = false;
-			printf("\nInstances:\n");
-		}
-		printf(" %s\n", dent->d_name);
+	if (*first) {
+		*first = false;
+		printf("\nInstances:\n");
 	}
+	printf(" %s\n", name);
+	return 0;
+}
 
-out:
-	if (dir)
-		closedir(dir);
-	tracefs_put_tracing_file(path);
+static void report_instances(void)
+{
+	bool first = true;
+
+	tracefs_instances_walk(report_instance, &first);
 }
 
 struct event_iter *trace_event_iter_alloc(const char *path)
diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c
index e11a0066..04fc8a1b 100644
--- a/utest/tracefs-utest.c
+++ b/utest/tracefs-utest.c
@@ -456,6 +456,54 @@ static void test_local_events(void)
 	tracefs_list_free(systems);
 }
 
+struct test_walk_instance {
+	struct tracefs_instance *instance;
+	bool found;
+};
+#define WALK_COUNT 10
+int test_instances_walk_cb(const char *name, void *data)
+{
+	struct test_walk_instance *instances  = (struct test_walk_instance *)data;
+	int i;
+
+	CU_TEST(instances != NULL);
+	CU_TEST(name != NULL);
+
+	for (i = 0; i < WALK_COUNT; i++) {
+		if (!strcmp(name,
+			    tracefs_instance_get_name(instances[i].instance))) {
+			instances[i].found = true;
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static void test_instances_walk(void)
+{
+	struct test_walk_instance instances[WALK_COUNT];
+	int i;
+
+	memset(instances, 0, WALK_COUNT * sizeof(struct test_walk_instance));
+	for (i = 0; i < WALK_COUNT; i++) {
+		CU_TEST(tracefs_instance_create(get_rand_str(), &(instances[i].instance)) >= 0);
+	}
+
+	CU_TEST(tracefs_instances_walk(test_instances_walk_cb, instances) == 0);
+	for (i = 0; i < WALK_COUNT; i++) {
+		CU_TEST(instances[i].found);
+		tracefs_instance_destroy(instances[i].instance);
+		instances[i].found = false;
+	}
+
+	CU_TEST(tracefs_instances_walk(test_instances_walk_cb, instances) == 0);
+	for (i = 0; i < WALK_COUNT; i++) {
+		CU_TEST(!instances[i].found);
+		tracefs_instance_free(instances[i].instance);
+	}
+}
+
 static int test_suite_destroy(void)
 {
 	tracefs_instance_destroy(test_instance);
@@ -499,4 +547,7 @@ void test_tracefs_lib(void)
 		    test_tracers);
 	CU_add_test(suite, "tracefs_local events API",
 		    test_local_events);
+	CU_add_test(suite, "tracefs_instances_walk API",
+		    test_instances_walk);
+
 }
-- 
2.28.0

[PATCH 6/6] trace-cmd: Add new libtrasefs API to get the current trace clock

[Tzvetomir Stoyanov (VMware)]

A new API is added to tracefs library:
	tracefs_get_clock()
It reads the trace_clock file from the ftrace file system, parses it
and returns a string with the current trace clock. The returned string
must be freed by free().

Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
---
 include/tracefs/tracefs.h      |  2 ++
 lib/tracefs/tracefs-instance.c | 35 ++++++++++++++++++++++++++++++++++
 tracecmd/trace-stat.c          | 29 +++++++---------------------
 utest/tracefs-utest.c          | 30 ++++++++++++++++++++++++++++-
 4 files changed, 73 insertions(+), 23 deletions(-)

diff --git a/include/tracefs/tracefs.h b/include/tracefs/tracefs.h
index 40781bb2..ad4ffa07 100644
--- a/include/tracefs/tracefs.h
+++ b/include/tracefs/tracefs.h
@@ -56,4 +56,6 @@ struct tep_handle *tracefs_local_events_system(const char *tracing_dir,
 int tracefs_fill_local_events(const char *tracing_dir,
 			       struct tep_handle *tep, int *parsing_failures);
 
+char *tracefs_get_clock(struct tracefs_instance *instance);
+
 #endif /* _TRACE_FS_H */
diff --git a/lib/tracefs/tracefs-instance.c b/lib/tracefs/tracefs-instance.c
index 777d5965..d3b9e100 100644
--- a/lib/tracefs/tracefs-instance.c
+++ b/lib/tracefs/tracefs-instance.c
@@ -377,3 +377,38 @@ out:
 	tracefs_put_tracing_file(path);
 	return fret;
 }
+
+/**
+ * tracefs_get_clock - Get the current trace clock
+ * @instance: ftrace instance, can be NULL for the top instance
+ *
+ * Returns the current trace clock of the given instance, or NULL in
+ * case of an error.
+ * The return string must be freed by free()
+ */
+char *tracefs_get_clock(struct tracefs_instance *instance)
+{
+	char *all_clocks = NULL;
+	char *ret = NULL;
+	int bytes = 0;
+	char *clock;
+	char *cont;
+
+	all_clocks  = tracefs_instance_file_read(instance, "trace_clock", &bytes);
+	if (!all_clocks || !bytes)
+		goto out;
+
+	clock = strstr(all_clocks, "[");
+	if (!clock)
+		goto out;
+	clock++;
+	cont = strstr(clock, "]");
+	if (!cont)
+		goto out;
+	*cont = '\0';
+
+	ret = strdup(clock);
+out:
+	free(all_clocks);
+	return ret;
+}
diff --git a/tracecmd/trace-stat.c b/tracecmd/trace-stat.c
index e6678eab..9b61a14f 100644
--- a/tracecmd/trace-stat.c
+++ b/tracecmd/trace-stat.c
@@ -710,33 +710,18 @@ static void report_buffers(struct buffer_instance *instance)
 
 static void report_clock(struct buffer_instance *instance)
 {
-	char *str;
-	char *cont;
 	char *clock;
 
-	str = get_instance_file_content(instance, "trace_clock");
-	if (!str)
-		return;
-
-	clock = strstr(str, "[");
-	if (!clock)
-		goto out;
-	clock++;
-
-	cont = strstr(clock, "]");
-	if (!cont) /* should never happen */
-		goto out;
-
-	*cont = '\0';
+	if (instance)
+		clock = tracefs_get_clock(instance->tracefs);
+	else
+		clock = tracefs_get_clock(NULL);
 
 	/* Default clock is "local", only show others */
-	if (strcmp(clock, "local") == 0)
-		goto out;
+	if (clock && !strcmp(clock, "local") == 0)
+		printf("\nClock: %s\n", clock);
 
-	printf("\nClock: %s\n", clock);
-
- out:
-	free(str);
+	free(clock);
 }
 
 static void report_cpumask(struct buffer_instance *instance)
diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c
index 04fc8a1b..3a0347aa 100644
--- a/utest/tracefs-utest.c
+++ b/utest/tracefs-utest.c
@@ -504,6 +504,33 @@ static void test_instances_walk(void)
 	}
 }
 
+static void current_clock_check(const char *clock)
+{
+	int size = 0;
+	char *clocks;
+	char *str;
+
+	clocks = tracefs_instance_file_read(test_instance, "trace_clock", &size);
+	CU_TEST(clocks != NULL);
+	CU_TEST(size > strlen(clock));
+	str = strstr(clocks, clock);
+	CU_TEST(str != NULL);
+	CU_TEST(str != clocks);
+	CU_TEST(*(str - 1) == '[');
+	CU_TEST(*(str + strlen(clock)) == ']');
+	free(clocks);
+}
+
+static void test_get_clock(void)
+{
+	const char *clock;
+
+	clock = tracefs_get_clock(test_instance);
+	CU_TEST(clock != NULL);
+	current_clock_check(clock);
+	free((char *)clock);
+}
+
 static int test_suite_destroy(void)
 {
 	tracefs_instance_destroy(test_instance);
@@ -549,5 +576,6 @@ void test_tracefs_lib(void)
 		    test_local_events);
 	CU_add_test(suite, "tracefs_instances_walk API",
 		    test_instances_walk);
-
+	CU_add_test(suite, "tracefs_get_clock API",
+		    test_get_clock);
 }
-- 
2.28.0