tracing: add trace_set_clr_event to export event enabling function

Other parts of the kernel may need to be able to enable or disable
specific events. Especially parts that create trace events.

[ Impact: allow enabling of trace events by those that create the event ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

include/linux/ftrace_event.h

@@ -127,6 +127,8 @@ extern int trace_define_field(struct ftrace_event_call *call, char *type,
 
 #define is_signed_type(type)	(((type)(-1)) < 0)
 
+int trace_set_clr_event(const char *system, const char *event, int set);
+
 /*
  * The double __builtin_constant_p is because gcc will give us an error
  * if we try to allocate the static variable to fmt if it is not a

kernel/trace/trace_events.c

@@ -177,6 +177,23 @@ static int ftrace_set_clr_event(char *buf, int set)
 	return __ftrace_set_clr_event(match, sub, event, set);
 }
 
+/**
+ * trace_set_clr_event - enable or disable an event
+ * @system: system name to match (NULL for any system)
+ * @event: event name to match (NULL for all events, within system)
+ * @set: 1 to enable, 0 to disable
+ *
+ * This is a way for other parts of the kernel to enable or disable
+ * event recording.
+ *
+ * Returns 0 on success, -EINVAL if the parameters do not match any
+ * registered events.
+ */
+int trace_set_clr_event(const char *system, const char *event, int set)
+{
+	return __ftrace_set_clr_event(NULL, system, event, set);
+}
+
 /* 128 should be much more than enough */
 #define EVENT_BUF_SIZE		127