rtla/trace: Add trace event filter helpers

Add a set of helper functions to allow rtla tools to filter events
in the trace instance.

Link: https://lkml.kernel.org/r/12623b1684684549d53b90f4bf66fae44584fd14.1646247211.git.bristot@kernel.org

Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

tools/tracing/rtla/src/trace.c

@@ -204,6 +204,8 @@ static void trace_events_free(struct trace_events *events)
 
 		tevent = tevent->next;
 
+		if (free_event->filter)
+			free(free_event->filter);
 		if (free_event->trigger)
 			free(free_event->trigger);
 		free(free_event->system);
@@ -237,6 +239,21 @@ struct trace_events *trace_event_alloc(const char *event_string)
 	return tevent;
 }
 
+/*
+ * trace_event_add_filter - record an event filter
+ */
+int trace_event_add_filter(struct trace_events *event, char *filter)
+{
+	if (event->filter)
+		free(event->filter);
+
+	event->filter = strdup(filter);
+	if (!event->filter)
+		return 1;
+
+	return 0;
+}
+
 /*
  * trace_event_add_trigger - record an event trigger action
  */
@@ -252,6 +269,33 @@ int trace_event_add_trigger(struct trace_events *event, char *trigger)
 	return 0;
 }
 
+/*
+ * trace_event_disable_filter - disable an event filter
+ */
+static void trace_event_disable_filter(struct trace_instance *instance,
+				       struct trace_events *tevent)
+{
+	char filter[1024];
+	int retval;
+
+	if (!tevent->filter)
+		return;
+
+	if (!tevent->filter_enabled)
+		return;
+
+	debug_msg("Disabling %s:%s filter %s\n", tevent->system,
+		  tevent->event ? : "*", tevent->filter);
+
+	snprintf(filter, 1024, "!%s\n", tevent->filter);
+
+	retval = tracefs_event_file_write(instance->inst, tevent->system,
+					  tevent->event, "filter", filter);
+	if (retval < 0)
+		err_msg("Error disabling %s:%s filter %s\n", tevent->system,
+			tevent->event ? : "*", tevent->filter);
+}
+
 /*
  * trace_event_disable_trigger - disable an event trigger
  */
@@ -293,6 +337,7 @@ void trace_events_disable(struct trace_instance *instance,
 	while (tevent) {
 		debug_msg("Disabling event %s:%s\n", tevent->system, tevent->event ? : "*");
 		if (tevent->enabled) {
+			trace_event_disable_filter(instance, tevent);
 			trace_event_disable_trigger(instance, tevent);
 			tracefs_event_disable(instance->inst, tevent->system, tevent->event);
 		}
@@ -302,6 +347,41 @@ void trace_events_disable(struct trace_instance *instance,
 	}
 }
 
+/*
+ * trace_event_enable_filter - enable an event filter associated with an event
+ */
+static int trace_event_enable_filter(struct trace_instance *instance,
+				     struct trace_events *tevent)
+{
+	char filter[1024];
+	int retval;
+
+	if (!tevent->filter)
+		return 0;
+
+	if (!tevent->event) {
+		err_msg("Filter %s applies only for single events, not for all %s:* events\n",
+			tevent->filter, tevent->system);
+		return 1;
+	}
+
+	snprintf(filter, 1024, "%s\n", tevent->filter);
+
+	debug_msg("Enabling %s:%s filter %s\n", tevent->system,
+		  tevent->event ? : "*", tevent->filter);
+
+	retval = tracefs_event_file_write(instance->inst, tevent->system,
+					  tevent->event, "filter", filter);
+	if (retval < 0) {
+		err_msg("Error enabling %s:%s filter %s\n", tevent->system,
+			tevent->event ? : "*", tevent->filter);
+		return 1;
+	}
+
+	tevent->filter_enabled = 1;
+	return 0;
+}
+
 /*
  * trace_event_enable_trigger - enable an event trigger associated with an event
  */
@@ -356,6 +436,9 @@ int trace_events_enable(struct trace_instance *instance,
 			return 1;
 		}
 
+		retval = trace_event_enable_filter(instance, tevent);
+		if (retval)
+			return 1;
 
 		retval = trace_event_enable_trigger(instance, tevent);
 		if (retval)

tools/tracing/rtla/src/trace.h

@@ -6,8 +6,10 @@ struct trace_events {
 	struct trace_events *next;
 	char *system;
 	char *event;
+	char *filter;
 	char *trigger;
 	char enabled;
+	char filter_enabled;
 	char trigger_enabled;
 };
 
@@ -43,4 +45,5 @@ void trace_events_destroy(struct trace_instance *instance,
 int trace_events_enable(struct trace_instance *instance,
 			  struct trace_events *events);
 
+int trace_event_add_filter(struct trace_events *event, char *filter);
 int trace_event_add_trigger(struct trace_events *event, char *trigger);