libtracefs: Add tracefs_tracer_available() helper

Add tracefs_tracer_available() helper function to check if a giver tracer
is available.

Link: https://lore.kernel.org/linux-trace-devel/20220826142420.29911-1-alexandre.vicenzi@suse.com

Signed-off-by: Alexandre Vicenzi <alexandre.vicenzi@suse.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

5 files changed, 43 insertions, 2 deletions

diff --git a/Documentation/libtracefs-utils.txt b/Documentation/libtracefs-utils.txt
index ddbd675..ab16cc6 100644
--- a/Documentation/libtracefs-utils.txt
+++ b/Documentation/libtracefs-utils.txt
@@ -3,8 +3,8 @@ libtracefs(3)
 
 NAME
 ----
-tracefs_tracers, tracefs_get_clock, tracefs_list_free, tracefs_list_add,
-tracefs_list_size - Helper functions for working with trace file system.
+tracefs_tracers, tracefs_tracer_available, tracefs_get_clock, tracefs_list_free,
+tracefs_list_add, tracefs_list_size - Helper functions for working with trace file system.
 
 SYNOPSIS
 --------
@@ -13,6 +13,7 @@ SYNOPSIS
 *#include <tracefs.h>*
 
 char pass:[*]pass:[*]*tracefs_tracers*(const char pass:[*]_tracing_dir_);
+bool *tracefs_tracer_available*(const char pass:[*]_tracing_dir_, const char pass:[*]_tracer_);
 char pass:[*]*tracefs_get_clock*(struct tracefs_instance pass:[*]_instance_);
 void *tracefs_list_free*(char pass:[*]pass:[*]_list_);
 char pass:[**]*tracefs_list_add*(char **_list_, const char *_string_);
@@ -30,6 +31,9 @@ for the trace systems of the local machine, or it may be a path to a copy
 of the tracefs directory from another machine. The last entry in the array
 as a NULL pointer. The array must be freed with *tracefs_list_free()* API.
 
+The *tracefs_tracer_available()* returns true if the _tracer_ is available
+in the given _tracing_dir_director_, and false otherwise.
+
 The *tracefs_get_clock()* function returns name of the current trace clock,
 used in the given _instance_. If _instance_ is NULL, the clock of the main
 trace instance is returned. The returned string must be freed with free().
@@ -56,6 +60,9 @@ The *tracefs_tracers()* returns array of strings. The last element in that
 array is a NULL pointer. The array must be freed with *tracefs_list_free()* API.
 In case of an error, NULL is returned.
 
+The *tracefs_tracer_available()* returns true if the _tracer_ is available,
+and false otherwise.
+
 The *tracefs_get_clock()* returns string, that must be freed with free(), or NULL
 in case of an error.
 
diff --git a/Documentation/libtracefs.txt b/Documentation/libtracefs.txt
index eb2eff4..986557b 100644
--- a/Documentation/libtracefs.txt
+++ b/Documentation/libtracefs.txt
@@ -113,6 +113,7 @@ Trace options:
 
 Ftrace tracers:
 	char pass:[*]pass:[*]*tracefs_tracers*(const char pass:[*]_tracing_dir_);
+	bool *tracefs_tracer_available*(const char pass:[*]_tracing_dir_, const char pass:[*]_tracer_);
 	int *tracefs_tracer_set*(struct tracefs_instance pass:[*]_instance_, enum tracefs_tracers _tracer_);
 	int *tracefs_tracer_set*(struct tracefs_instance pass:[*]_instance_, enum tracefs_tracers _tracer_, const char pass:[*]_name_);
 	int *tracefs_tracer_clear*(struct tracefs_instance pass:[*]_instance_);
diff --git a/include/tracefs.h b/include/tracefs.h
index fd2240a..5b9bf6e 100644
--- a/include/tracefs.h
+++ b/include/tracefs.h
@@ -78,6 +78,8 @@ void tracefs_list_free(char **list);
 char **tracefs_list_add(char **list, const char *string);
 int tracefs_list_size(char **list);
 
+bool tracefs_tracer_available(const char *tracing_dir, const char *tracer);
+
 /**
  * tracefs_trace_on_get_fd - Get a file descriptor of "tracing_on" in given instance
  * @instance: ftrace instance, can be NULL for the top instance
diff --git a/src/tracefs-utils.c b/src/tracefs-utils.c
index 55a2f0a..a38da66 100644
--- a/src/tracefs-utils.c
+++ b/src/tracefs-utils.c
@@ -544,3 +544,31 @@ int tracefs_list_size(char **list)
 	list--;
 	return (int)*(unsigned long *)list;
 }
+
+/**
+ * tracefs_tracer_available - test if a tracer is available
+ * @tracing_dir: The directory that contains the tracing directory
+ * @tracer: The name of the tracer
+ *
+ * Return true if the tracer is available
+ */
+bool tracefs_tracer_available(const char *tracing_dir, const char *tracer)
+{
+	bool ret = false;
+	char **tracers = NULL;
+	int i;
+
+	tracers = tracefs_tracers(tracing_dir);
+	if (!tracers)
+		return false;
+
+	for (i = 0; tracers[i]; i++) {
+		if (strcmp(tracer, tracers[i]) == 0) {
+			ret = true;
+			break;
+		}
+	}
+
+	tracefs_list_free(tracers);
+	return ret;
+}
diff --git a/utest/tracefs-utest.c b/utest/tracefs-utest.c
index 6f083db..cfb8090 100644
--- a/utest/tracefs-utest.c
+++ b/utest/tracefs-utest.c
@@ -1405,6 +1405,9 @@ static void test_instance_tracers(struct tracefs_instance *instance)
 	tracers = tracefs_tracers(tdir);
 	CU_TEST(tracers != NULL);
 
+	for (i = 0; tracers[i]; i++)
+		CU_TEST(tracefs_tracer_available(tdir, tracers[i]));
+
 	tfile = tracefs_instance_file_read(NULL, ALL_TRACERS, NULL);
 
 	tracer = strtok(tfile, " ");