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Commit 3cd715de authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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tracing: Add function probe triggers to enable/disable events 



Add triggers to function tracer that lets an event get enabled or
disabled when a function is called:

format is:

 <function>:enable_event:<system>:<event>[:<count>]
 <function>:disable_event:<system>:<event>[:<count>]

 echo 'schedule:enable_event:sched:sched_switch' > /debug/tracing/set_ftrace_filter

Every time schedule is called, it will enable the sched_switch event.

 echo 'schedule:disable_event:sched:sched_switch:2' > /debug/tracing/set_ftrace_filter

The first two times schedule is called while the sched_switch
event is enabled, it will disable it. It will not count for a time
that the event is already disabled (or enabled for enable_event).

[ fixed return without mutex_unlock() - thanks to Dan Carpenter and smatch ]

Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 417944c4

kernel/trace/trace_events.c

+279 −0
Original line number Diff line number Diff line
@@ -1798,6 +1798,283 @@ __trace_add_event_dirs(struct trace_array *tr) 
	}

}



#ifdef CONFIG_DYNAMIC_FTRACE



/* Avoid typos */

#define ENABLE_EVENT_STR	"enable_event"

#define DISABLE_EVENT_STR	"disable_event"



struct event_probe_data {

	struct ftrace_event_file	*file;

	unsigned long			count;

	int				ref;

	bool				enable;

};



static struct ftrace_event_file *

find_event_file(struct trace_array *tr, const char *system,  const char *event)

{

	struct ftrace_event_file *file;

	struct ftrace_event_call *call;



	list_for_each_entry(file, &tr->events, list) {



		call = file->event_call;



		if (!call->name || !call->class || !call->class->reg)

			continue;



		if (call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)

			continue;



		if (strcmp(event, call->name) == 0 &&

		    strcmp(system, call->class->system) == 0)

			return file;

	}

	return NULL;

}



static void

event_enable_probe(unsigned long ip, unsigned long parent_ip, void **_data)

{

	struct event_probe_data **pdata = (struct event_probe_data **)_data;

	struct event_probe_data *data = *pdata;



	if (!data)

		return;



	if (data->enable)

		clear_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &data->file->flags);

	else

		set_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &data->file->flags);

}



static void

event_enable_count_probe(unsigned long ip, unsigned long parent_ip, void **_data)

{

	struct event_probe_data **pdata = (struct event_probe_data **)_data;

	struct event_probe_data *data = *pdata;



	if (!data)

		return;



	if (!data->count)

		return;



	/* Skip if the event is in a state we want to switch to */

	if (data->enable == !(data->file->flags & FTRACE_EVENT_FL_SOFT_DISABLED))

		return;



	if (data->count != -1)

		(data->count)--;



	event_enable_probe(ip, parent_ip, _data);

}



static int

event_enable_print(struct seq_file *m, unsigned long ip,

		      struct ftrace_probe_ops *ops, void *_data)

{

	struct event_probe_data *data = _data;



	seq_printf(m, "%ps:", (void *)ip);



	seq_printf(m, "%s:%s:%s",

		   data->enable ? ENABLE_EVENT_STR : DISABLE_EVENT_STR,

		   data->file->event_call->class->system,

		   data->file->event_call->name);



	if (data->count == -1)

		seq_printf(m, ":unlimited\n");

	else

		seq_printf(m, ":count=%ld\n", data->count);



	return 0;

}



static int

event_enable_init(struct ftrace_probe_ops *ops, unsigned long ip,

		  void **_data)

{

	struct event_probe_data **pdata = (struct event_probe_data **)_data;

	struct event_probe_data *data = *pdata;



	data->ref++;

	return 0;

}



static void

event_enable_free(struct ftrace_probe_ops *ops, unsigned long ip,

		  void **_data)

{

	struct event_probe_data **pdata = (struct event_probe_data **)_data;

	struct event_probe_data *data = *pdata;



	if (WARN_ON_ONCE(data->ref <= 0))

		return;



	data->ref--;

	if (!data->ref) {

		/* Remove the SOFT_MODE flag */

		__ftrace_event_enable_disable(data->file, 0, 1);

		module_put(data->file->event_call->mod);

		kfree(data);

	}

	*pdata = NULL;

}



static struct ftrace_probe_ops event_enable_probe_ops = {

	.func			= event_enable_probe,

	.print			= event_enable_print,

	.init			= event_enable_init,

	.free			= event_enable_free,

};



static struct ftrace_probe_ops event_enable_count_probe_ops = {

	.func			= event_enable_count_probe,

	.print			= event_enable_print,

	.init			= event_enable_init,

	.free			= event_enable_free,

};



static struct ftrace_probe_ops event_disable_probe_ops = {

	.func			= event_enable_probe,

	.print			= event_enable_print,

	.init			= event_enable_init,

	.free			= event_enable_free,

};



static struct ftrace_probe_ops event_disable_count_probe_ops = {

	.func			= event_enable_count_probe,

	.print			= event_enable_print,

	.init			= event_enable_init,

	.free			= event_enable_free,

};



static int

event_enable_func(struct ftrace_hash *hash,

		  char *glob, char *cmd, char *param, int enabled)

{

	struct trace_array *tr = top_trace_array();

	struct ftrace_event_file *file;

	struct ftrace_probe_ops *ops;

	struct event_probe_data *data;

	const char *system;

	const char *event;

	char *number;

	bool enable;

	int ret;



	/* hash funcs only work with set_ftrace_filter */

	if (!enabled)

		return -EINVAL;



	if (!param)

		return -EINVAL;



	system = strsep(&param, ":");

	if (!param)

		return -EINVAL;



	event = strsep(&param, ":");



	mutex_lock(&event_mutex);



	ret = -EINVAL;

	file = find_event_file(tr, system, event);

	if (!file)

		goto out;



	enable = strcmp(cmd, ENABLE_EVENT_STR) == 0;



	if (enable)

		ops = param ? &event_enable_count_probe_ops : &event_enable_probe_ops;

	else

		ops = param ? &event_disable_count_probe_ops : &event_disable_probe_ops;



	if (glob[0] == '!') {

		unregister_ftrace_function_probe_func(glob+1, ops);

		ret = 0;

		goto out;

	}



	ret = -ENOMEM;

	data = kzalloc(sizeof(*data), GFP_KERNEL);

	if (!data)

		goto out;



	data->enable = enable;

	data->count = -1;

	data->file = file;



	if (!param)

		goto out_reg;



	number = strsep(&param, ":");



	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, &data->count);

	if (ret)

		goto out_free;



 out_reg:

	/* Don't let event modules unload while probe registered */

	ret = try_module_get(file->event_call->mod);

	if (!ret)

		goto out_free;



	ret = __ftrace_event_enable_disable(file, 1, 1);

	if (ret < 0)

		goto out_put;

	ret = register_ftrace_function_probe(glob, ops, data);

	if (!ret)

		goto out_disable;

 out:

	mutex_unlock(&event_mutex);

	return ret;



 out_disable:

	__ftrace_event_enable_disable(file, 0, 1);

 out_put:

	module_put(file->event_call->mod);

 out_free:

	kfree(data);

	goto out;

}



static struct ftrace_func_command event_enable_cmd = {

	.name			= ENABLE_EVENT_STR,

	.func			= event_enable_func,

};



static struct ftrace_func_command event_disable_cmd = {

	.name			= DISABLE_EVENT_STR,

	.func			= event_enable_func,

};



static __init int register_event_cmds(void)

{

	int ret;



	ret = register_ftrace_command(&event_enable_cmd);

	if (WARN_ON(ret < 0))

		return ret;

	ret = register_ftrace_command(&event_disable_cmd);

	if (WARN_ON(ret < 0))

		unregister_ftrace_command(&event_enable_cmd);

	return ret;

}

#else

static inline int register_event_cmds(void) { return 0; }

#endif /* CONFIG_DYNAMIC_FTRACE */



/*

 * The top level array has already had its ftrace_event_file

 * descriptors created in order to allow for early events to
@@ -2058,6 +2335,8 @@ static __init int event_trace_enable(void) 


	trace_printk_start_comm();



	register_event_cmds();



	return 0;

}