tracing: Remove get_trigger_ops() and add count_func() from trigger ops

The struct event_command has a callback function called get_trigger_ops().
This callback returns the "trigger_ops" to use for the trigger. These ops
define the trigger function, how to init the trigger, how to print the
trigger and how to free it.

The only reason there's a callback function to get these ops is because
some triggers have two types of operations. One is an "always on"
operation, and the other is a "count down" operation. If a user passes in
a parameter to say how many times the trigger should execute. For example:

  echo stacktrace:5 > events/kmem/kmem_cache_alloc/trigger

It will trigger the stacktrace for the first 5 times the kmem_cache_alloc
event is hit.

Instead of having two different trigger_ops since the only difference
between them is the tigger itself (the print, init and free functions are
all the same), just use a single ops that the event_command points to and
add a function field to the trigger_ops to have a count_func.

When a trigger is added to an event, if there's a count attached to it and
the trigger ops has the count_func field, the data allocated to represent
this trigger will have a new flag set called COUNT.

Then when the trigger executes, it will check if the COUNT data flag is
set, and if so, it will call the ops count_func(). If that returns false,
it returns without executing the trigger.

This removes the need for duplicate event_trigger_ops structures.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://patch.msgid.link/20251125200932.274566147@kernel.org
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: rostedt

kernel/trace/trace.h

@@ -1791,6 +1791,7 @@ extern void clear_event_triggers(struct trace_array *tr);
 
 enum {
 	EVENT_TRIGGER_FL_PROBE		= BIT(0),
+	EVENT_TRIGGER_FL_COUNT		= BIT(1),
 };
 
 struct event_trigger_data {
@@ -1822,6 +1823,10 @@ struct enable_trigger_data {
 	bool				hist;
 };
 
+bool event_trigger_count(struct event_trigger_data *data,
+			 struct trace_buffer *buffer,  void *rec,
+			 struct ring_buffer_event *event);
+
 extern int event_enable_trigger_print(struct seq_file *m,
 				      struct event_trigger_data *data);
 extern void event_enable_trigger_free(struct event_trigger_data *data);
@@ -1909,6 +1914,11 @@ extern void event_file_put(struct trace_event_file *file);
  *	registered the trigger (see struct event_command) along with
  *	the trace record, rec.
  *
+ * @count_func: If defined and a numeric parameter is passed to the
+ *	trigger, then this function will be called before @trigger
+ *	is called. If this function returns false, then @trigger is not
+ *	executed.
+ *
  * @init: An optional initialization function called for the trigger
  *	when the trigger is registered (via the event_command reg()
  *	function).  This can be used to perform per-trigger
@@ -1936,6 +1946,10 @@ struct event_trigger_ops {
 					   struct trace_buffer *buffer,
 					   void *rec,
 					   struct ring_buffer_event *rbe);
+	bool			(*count_func)(struct event_trigger_data *data,
+					      struct trace_buffer *buffer,
+					      void *rec,
+					      struct ring_buffer_event *rbe);
 	int			(*init)(struct event_trigger_data *data);
 	void			(*free)(struct event_trigger_data *data);
 	int			(*print)(struct seq_file *m,
@@ -1962,6 +1976,9 @@ struct event_trigger_ops {
  * @name: The unique name that identifies the event command.  This is
  *	the name used when setting triggers via trigger files.
  *
+ * @trigger_ops: The event_trigger_ops implementation associated with
+ *	the command.
+ *
  * @trigger_type: A unique id that identifies the event command
  *	'type'.  This value has two purposes, the first to ensure that
  *	only one trigger of the same type can be set at a given time
@@ -2013,17 +2030,11 @@ struct event_trigger_ops {
  *	event command, filters set by the user for the command will be
  *	ignored.  This is usually implemented by the generic utility
  *	function @set_trigger_filter() (see trace_event_triggers.c).
- *
- * @get_trigger_ops: The callback function invoked to retrieve the
- *	event_trigger_ops implementation associated with the command.
- *	This callback function allows a single event_command to
- *	support multiple trigger implementations via different sets of
- *	event_trigger_ops, depending on the value of the @param
- *	string.
  */
 struct event_command {
 	struct list_head	list;
 	char			*name;
+	const struct event_trigger_ops *trigger_ops;
 	enum event_trigger_type	trigger_type;
 	int			flags;
 	int			(*parse)(struct event_command *cmd_ops,
@@ -2040,7 +2051,6 @@ struct event_command {
 	int			(*set_filter)(char *filter_str,
 					      struct event_trigger_data *data,
 					      struct trace_event_file *file);
-	const struct event_trigger_ops *(*get_trigger_ops)(char *cmd, char *param);
 };
 
 /**

kernel/trace/trace_eprobe.c

@@ -513,21 +513,15 @@ static void eprobe_trigger_unreg_func(char *glob,
 
 }
 
-static const struct event_trigger_ops *eprobe_trigger_get_ops(char *cmd,
-							      char *param)
-{
-	return &eprobe_trigger_ops;
-}
-
 static struct event_command event_trigger_cmd = {
 	.name			= "eprobe",
 	.trigger_type		= ETT_EVENT_EPROBE,
 	.flags			= EVENT_CMD_FL_NEEDS_REC,
+	.trigger_ops		= &eprobe_trigger_ops,
 	.parse			= eprobe_trigger_cmd_parse,
 	.reg			= eprobe_trigger_reg_func,
 	.unreg			= eprobe_trigger_unreg_func,
 	.unreg_all		= NULL,
-	.get_trigger_ops	= eprobe_trigger_get_ops,
 	.set_filter		= NULL,
 };
 

kernel/trace/trace_events_hist.c

@@ -6363,12 +6363,6 @@ static const struct event_trigger_ops event_hist_trigger_named_ops = {
 	.free			= event_hist_trigger_named_free,
 };
 
-static const struct event_trigger_ops *event_hist_get_trigger_ops(char *cmd,
-								  char *param)
-{
-	return &event_hist_trigger_ops;
-}
-
 static void hist_clear(struct event_trigger_data *data)
 {
 	struct hist_trigger_data *hist_data = data->private_data;
@@ -6908,11 +6902,11 @@ static struct event_command trigger_hist_cmd = {
 	.name			= "hist",
 	.trigger_type		= ETT_EVENT_HIST,
 	.flags			= EVENT_CMD_FL_NEEDS_REC,
+	.trigger_ops		= &event_hist_trigger_ops,
 	.parse			= event_hist_trigger_parse,
 	.reg			= hist_register_trigger,
 	.unreg			= hist_unregister_trigger,
 	.unreg_all		= hist_unreg_all,
-	.get_trigger_ops	= event_hist_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };
 
@@ -6945,66 +6939,22 @@ hist_enable_trigger(struct event_trigger_data *data,
 	}
 }
 
-static void
-hist_enable_count_trigger(struct event_trigger_data *data,
-			  struct trace_buffer *buffer,  void *rec,
-			  struct ring_buffer_event *event)
-{
-	if (!data->count)
-		return;
-
-	if (data->count != -1)
-		(data->count)--;
-
-	hist_enable_trigger(data, buffer, rec, event);
-}
-
 static const struct event_trigger_ops hist_enable_trigger_ops = {
 	.trigger		= hist_enable_trigger,
-	.print			= event_enable_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_enable_trigger_free,
-};
-
-static const struct event_trigger_ops hist_enable_count_trigger_ops = {
-	.trigger		= hist_enable_count_trigger,
+	.count_func		= event_trigger_count,
 	.print			= event_enable_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_enable_trigger_free,
 };
 
 static const struct event_trigger_ops hist_disable_trigger_ops = {
 	.trigger		= hist_enable_trigger,
+	.count_func		= event_trigger_count,
 	.print			= event_enable_trigger_print,
 	.init			= event_trigger_init,
 	.free			= event_enable_trigger_free,
 };
 
-static const struct event_trigger_ops hist_disable_count_trigger_ops = {
-	.trigger		= hist_enable_count_trigger,
-	.print			= event_enable_trigger_print,
-	.init			= event_trigger_init,
-	.free			= event_enable_trigger_free,
-};
-
-static const struct event_trigger_ops *
-hist_enable_get_trigger_ops(char *cmd, char *param)
-{
-	const struct event_trigger_ops *ops;
-	bool enable;
-
-	enable = (strcmp(cmd, ENABLE_HIST_STR) == 0);
-
-	if (enable)
-		ops = param ? &hist_enable_count_trigger_ops :
-			&hist_enable_trigger_ops;
-	else
-		ops = param ? &hist_disable_count_trigger_ops :
-			&hist_disable_trigger_ops;
-
-	return ops;
-}
-
 static void hist_enable_unreg_all(struct trace_event_file *file)
 {
 	struct event_trigger_data *test, *n;
@@ -7023,22 +6973,22 @@ static void hist_enable_unreg_all(struct trace_event_file *file)
 static struct event_command trigger_hist_enable_cmd = {
 	.name			= ENABLE_HIST_STR,
 	.trigger_type		= ETT_HIST_ENABLE,
+	.trigger_ops		= &hist_enable_trigger_ops,
 	.parse			= event_enable_trigger_parse,
 	.reg			= event_enable_register_trigger,
 	.unreg			= event_enable_unregister_trigger,
 	.unreg_all		= hist_enable_unreg_all,
-	.get_trigger_ops	= hist_enable_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };
 
 static struct event_command trigger_hist_disable_cmd = {
 	.name			= DISABLE_HIST_STR,
 	.trigger_type		= ETT_HIST_ENABLE,
+	.trigger_ops		= &hist_disable_trigger_ops,
 	.parse			= event_enable_trigger_parse,
 	.reg			= event_enable_register_trigger,
 	.unreg			= event_enable_unregister_trigger,
 	.unreg_all		= hist_enable_unreg_all,
-	.get_trigger_ops	= hist_enable_get_trigger_ops,
 	.set_filter		= set_trigger_filter,
 };