[PATCH v3 3/9] tracing: add 'traceon' and 'traceoff' event trigger commands

[Tom Zanussi]

Add 'traceon' and 'traceoff' ftrace_func_command commands.  traceon
and traceoff event triggers are added by the user via these commands
in a similar way and using practically the same syntax as the
analagous 'traceon' and 'traceoff' ftrace function commands, but
instead of writing to the set_ftrace_filter file, the traceon and
traceoff triggers are written to the per-event 'trigger' files:

    echo 'traceon' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff' > .../tracing/events/somesys/someevent/trigger

The above command will turn tracing on or off whenever someevent is
hit.

This also adds a 'count' version that limits the number of times the
command will be invoked:

    echo 'traceon:N' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff:N' > .../tracing/events/somesys/someevent/trigger

Where N is the number of times the command will be invoked.

The above commands will will turn tracing on or off whenever someevent
is hit, but only N times.

The event_trigger_init() and event_trigger_free() are meant to be
common implementations of the event_trigger_ops init() and free() ops.
Most trigger_ops implementations will use these, but some will
override and possibly reuse them.

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
---
 include/linux/ftrace_event.h        |   1 +
 kernel/trace/trace_events_trigger.c | 313 ++++++++++++++++++++++++++++++++++++
 2 files changed, 314 insertions(+)

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 6cd5bbc..c794686 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -316,6 +316,7 @@ struct ftrace_event_file {
 
 enum trigger_mode {
 	TM_NONE			= (0),
+	TM_TRACE_ONOFF		= (1 << 0),
 };
 
 extern void destroy_preds(struct ftrace_event_call *call);
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 1f0565c..f2b97b6 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -355,7 +355,320 @@ static void unregister_trigger(char *glob, struct event_trigger_ops *ops,
 		data->ops->free(data->ops, (void **)&data);
 }
 
+int
+event_trigger_print(const char *name, struct seq_file *m,
+		    void *data, char *filter_str)
+{
+	long count = (long)data;
+
+	seq_printf(m, "%s", name);
+
+	if (count == -1)
+		seq_puts(m, ":unlimited");
+	else
+		seq_printf(m, ":count=%ld", count);
+
+	if (filter_str)
+		seq_printf(m, " if %s\n", filter_str);
+	else
+		seq_puts(m, "\n");
+
+	return 0;
+}
+
+static int
+event_trigger_init(struct event_trigger_ops *ops, void **_data)
+{
+	struct event_trigger_data **p = (struct event_trigger_data **)_data;
+	struct event_trigger_data *data = *p;
+
+	data->ref++;
+	return 0;
+}
+
+static void
+event_trigger_free(struct event_trigger_ops *ops, void **_data)
+{
+	struct event_trigger_data **p = (struct event_trigger_data **)_data;
+	struct event_trigger_data *data = *p;
+
+	if (WARN_ON_ONCE(data->ref <= 0))
+		return;
+
+	data->ref--;
+	if (!data->ref)
+		kfree(data);
+}
+
+static int
+event_trigger_callback(struct event_command *cmd_ops, void *cmd_data,
+		       char *glob, char *cmd, char *param, int enabled)
+{
+	struct event_trigger_ops *trigger_ops;
+	struct event_trigger_data *trigger_data;
+	char *trigger = NULL;
+	char *number;
+	int ret;
+
+	if (!enabled)
+		return -EINVAL;
+
+	/* separate the trigger from the filter (t:n [if filter]) */
+	if (param && isdigit(param[0]))
+		trigger = strsep(&param, " \t");
+
+	mutex_lock(&event_mutex);
+
+	trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
+
+	ret = -ENOMEM;
+	trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
+	if (!trigger_data)
+		goto out;
+
+	trigger_data->count = -1;
+	trigger_data->ops = trigger_ops;
+	trigger_data->mode = cmd_ops->trigger_mode;
+	INIT_LIST_HEAD(&trigger_data->list);
+
+	if (glob[0] == '!') {
+		cmd_ops->unreg(glob+1, trigger_ops, trigger_data, cmd_data);
+		kfree(trigger_data);
+		ret = 0;
+		goto out;
+	}
+
+	if (trigger) {
+		number = strsep(&trigger, ":");
+
+		ret = -EINVAL;
+		if (!strlen(number))
+			goto out_free;
+
+		/*
+		 * We use the callback data field (which is a pointer)
+		 * as our counter.
+		 */
+		ret = kstrtoul(number, 0, &trigger_data->count);
+		if (ret)
+			goto out_free;
+	}
+
+	if (!param) /* if param is non-empty, it's supposed to be a filter */
+		goto out_reg;
+
+	if (!cmd_ops->set_filter)
+		goto out_reg;
+
+	ret = cmd_ops->set_filter(param, trigger_data, cmd_data);
+	if (ret < 0)
+		goto out_free;
+
+ out_reg:
+	ret = cmd_ops->reg(glob, trigger_ops, trigger_data, cmd_data);
+	/*
+	 * The above returns on success the # of functions enabled,
+	 * but if it didn't find any functions it returns zero.
+	 * Consider no functions a failure too.
+	 */
+	if (!ret) {
+		ret = -ENOENT;
+		goto out_free;
+	} else if (ret < 0)
+		goto out_free;
+	ret = 0;
+ out:
+	mutex_unlock(&event_mutex);
+	return ret;
+
+ out_free:
+	kfree(trigger_data);
+	goto out;
+}
+
+static void
+traceon_trigger(void **_data)
+{
+	struct event_trigger_data **p = (struct event_trigger_data **)_data;
+	struct event_trigger_data *data = *p;
+
+	if (!data)
+		return;
+
+	if (tracing_is_on())
+		return;
+
+	tracing_on();
+}
+
+static void
+traceon_count_trigger(void **_data)
+{
+	struct event_trigger_data **p = (struct event_trigger_data **)_data;
+	struct event_trigger_data *data = *p;
+
+	if (!data)
+		return;
+
+	if (!data->count)
+		return;
+
+	if (data->count != -1)
+		(data->count)--;
+
+	traceon_trigger(_data);
+}
+
+static void
+traceoff_trigger(void **_data)
+{
+	struct event_trigger_data **p = (struct event_trigger_data **)_data;
+	struct event_trigger_data *data = *p;
+
+	if (!data)
+		return;
+
+	if (!tracing_is_on())
+		return;
+
+	tracing_off();
+}
+
+static void
+traceoff_count_trigger(void **_data)
+{
+	struct event_trigger_data **p = (struct event_trigger_data **)_data;
+	struct event_trigger_data *data = *p;
+
+	if (!data)
+		return;
+
+	if (!data->count)
+		return;
+
+	if (data->count != -1)
+		(data->count)--;
+
+	traceoff_trigger(_data);
+}
+
+static int
+traceon_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
+		      void *_data)
+{
+	struct event_trigger_data *data = _data;
+
+	return event_trigger_print("traceon", m, (void *)data->count,
+				   data->filter_str);
+}
+
+static int
+traceoff_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
+		       void *_data)
+{
+	struct event_trigger_data *data = _data;
+
+	return event_trigger_print("traceoff", m, (void *)data->count,
+				   data->filter_str);
+}
+
+static struct event_trigger_ops traceon_trigger_ops = {
+	.func			= traceon_trigger,
+	.print			= traceon_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_trigger_free,
+};
+
+static struct event_trigger_ops traceon_count_trigger_ops = {
+	.func			= traceon_count_trigger,
+	.print			= traceon_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_trigger_free,
+};
+
+static struct event_trigger_ops traceoff_trigger_ops = {
+	.func			= traceoff_trigger,
+	.print			= traceoff_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_trigger_free,
+};
+
+static struct event_trigger_ops traceoff_count_trigger_ops = {
+	.func			= traceoff_count_trigger,
+	.print			= traceoff_trigger_print,
+	.init			= event_trigger_init,
+	.free			= event_trigger_free,
+};
+
+static struct event_trigger_ops *
+onoff_get_trigger_ops(char *cmd, char *param)
+{
+	struct event_trigger_ops *ops;
+
+	/* we register both traceon and traceoff to this callback */
+	if (strcmp(cmd, "traceon") == 0)
+		ops = param ? &traceon_count_trigger_ops :
+			&traceon_trigger_ops;
+	else
+		ops = param ? &traceoff_count_trigger_ops :
+			&traceoff_trigger_ops;
+
+	return ops;
+}
+
+static struct event_command trigger_traceon_cmd = {
+	.name			= "traceon",
+	.trigger_mode		= TM_TRACE_ONOFF,
+	.func			= event_trigger_callback,
+	.reg			= register_trigger,
+	.unreg			= unregister_trigger,
+	.get_trigger_ops	= onoff_get_trigger_ops,
+};
+
+static struct event_command trigger_traceoff_cmd = {
+	.name			= "traceoff",
+	.trigger_mode		= TM_TRACE_ONOFF,
+	.func			= event_trigger_callback,
+	.reg			= register_trigger,
+	.unreg			= unregister_trigger,
+	.get_trigger_ops	= onoff_get_trigger_ops,
+};
+
+static __init void unregister_trigger_traceon_traceoff_cmds(void)
+{
+	unregister_event_command(&trigger_traceon_cmd,
+				 &trigger_commands,
+				 &trigger_cmd_mutex);
+	unregister_event_command(&trigger_traceoff_cmd,
+				 &trigger_commands,
+				 &trigger_cmd_mutex);
+}
+
+static __init int register_trigger_traceon_traceoff_cmds(void)
+{
+	int ret;
+
+	ret = register_event_command(&trigger_traceon_cmd, &trigger_commands,
+				     &trigger_cmd_mutex);
+	if (WARN_ON(ret < 0))
+		return ret;
+	ret = register_event_command(&trigger_traceoff_cmd, &trigger_commands,
+				     &trigger_cmd_mutex);
+	if (WARN_ON(ret < 0))
+		unregister_trigger_traceon_traceoff_cmds();
+
+	return ret;
+}
+
 __init int register_trigger_cmds(void)
 {
+	int ret;
+
+	ret = register_trigger_traceon_traceoff_cmds();
+	if (ret) {
+		unregister_trigger_traceon_traceoff_cmds();
+		return ret;
+	}
+
 	return 0;
 }
-- 
1.7.11.4

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