kernel/trace/trace_events_trigger.c

/*
 * trace_events_trigger - trace event triggers
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (C) 2013 Tom Zanussi <tom.zanussi@linux.intel.com>
 */

#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/mutex.h>
#include <linux/slab.h>

#include "trace.h"

static LIST_HEAD(trigger_commands);
static DEFINE_MUTEX(trigger_cmd_mutex);

/**
 * event_triggers_call - Call triggers associated with a trace event
 * @file: The ftrace_event_file associated with the event
 *
 * For each trigger associated with an event, invoke the trigger
 * function registered with the associated trigger command.
 *
 * Called from tracepoint handlers (with rcu_read_lock_sched() held).
 *
 * Return: an enum event_trigger_type value containing a set bit for
 * any trigger that should be deferred, ETT_NONE if nothing to defer.
 */
void event_triggers_call(struct ftrace_event_file *file)
{
	struct event_trigger_data *data;

	if (list_empty(&file->triggers))
		return;

	list_for_each_entry_rcu(data, &file->triggers, list)
		data->ops->func(data);
}
EXPORT_SYMBOL_GPL(event_triggers_call);

static void *trigger_next(struct seq_file *m, void *t, loff_t *pos)
{
	struct ftrace_event_file *event_file = event_file_data(m->private);

	return seq_list_next(t, &event_file->triggers, pos);
}

static void *trigger_start(struct seq_file *m, loff_t *pos)
{
	struct ftrace_event_file *event_file;

	/* ->stop() is called even if ->start() fails */
	mutex_lock(&event_mutex);
	event_file = event_file_data(m->private);
	if (unlikely(!event_file))
		return ERR_PTR(-ENODEV);

	return seq_list_start(&event_file->triggers, *pos);
}

static void trigger_stop(struct seq_file *m, void *t)
{
	mutex_unlock(&event_mutex);
}

static int trigger_show(struct seq_file *m, void *v)
{
	struct event_trigger_data *data;

	data = list_entry(v, struct event_trigger_data, list);
	data->ops->print(m, data->ops, data);

	return 0;
}

static const struct seq_operations event_triggers_seq_ops = {
	.start = trigger_start,
	.next = trigger_next,
	.stop = trigger_stop,
	.show = trigger_show,
};

static int event_trigger_regex_open(struct inode *inode, struct file *file)
{
	int ret = 0;

	mutex_lock(&event_mutex);

	if (unlikely(!event_file_data(file))) {
		mutex_unlock(&event_mutex);
		return -ENODEV;
	}

	if (file->f_mode & FMODE_READ) {
		ret = seq_open(file, &event_triggers_seq_ops);
		if (!ret) {
			struct seq_file *m = file->private_data;
			m->private = file;
		}
	}

	mutex_unlock(&event_mutex);

	return ret;
}

static int trigger_process_regex(struct ftrace_event_file *file, char *buff)
{
	char *command, *next = buff;
	struct event_command *p;
	int ret = -EINVAL;

	command = strsep(&next, ": \t");
	command = (command[0] != '!') ? command : command + 1;

	mutex_lock(&trigger_cmd_mutex);
	list_for_each_entry(p, &trigger_commands, list) {
		if (strcmp(p->name, command) == 0) {
			ret = p->func(p, file, buff, command, next);
			goto out_unlock;
		}
	}
 out_unlock:
	mutex_unlock(&trigger_cmd_mutex);

	return ret;
}

static ssize_t event_trigger_regex_write(struct file *file,
					 const char __user *ubuf,
					 size_t cnt, loff_t *ppos)
{
	struct ftrace_event_file *event_file;
	ssize_t ret;
	char *buf;

	if (!cnt)
		return 0;

	if (cnt >= PAGE_SIZE)
		return -EINVAL;

	buf = (char *)__get_free_page(GFP_TEMPORARY);
	if (!buf)
		return -ENOMEM;

	if (copy_from_user(buf, ubuf, cnt)) {
		free_page((unsigned long)buf);
		return -EFAULT;
	}
	buf[cnt] = '\0';
	strim(buf);

	mutex_lock(&event_mutex);
	event_file = event_file_data(file);
	if (unlikely(!event_file)) {
		mutex_unlock(&event_mutex);
		free_page((unsigned long)buf);
		return -ENODEV;
	}
	ret = trigger_process_regex(event_file, buf);
	mutex_unlock(&event_mutex);

	free_page((unsigned long)buf);
	if (ret < 0)
		goto out;

	*ppos += cnt;
	ret = cnt;
 out:
	return ret;
}

static int event_trigger_regex_release(struct inode *inode, struct file *file)
{
	mutex_lock(&event_mutex);

	if (file->f_mode & FMODE_READ)
		seq_release(inode, file);

	mutex_unlock(&event_mutex);

	return 0;
}

static ssize_t
event_trigger_write(struct file *filp, const char __user *ubuf,
		    size_t cnt, loff_t *ppos)
{
	return event_trigger_regex_write(filp, ubuf, cnt, ppos);
}

static int
event_trigger_open(struct inode *inode, struct file *filp)
{
	return event_trigger_regex_open(inode, filp);
}

static int
event_trigger_release(struct inode *inode, struct file *file)
{
	return event_trigger_regex_release(inode, file);
}

const struct file_operations event_trigger_fops = {
	.open = event_trigger_open,
	.read = seq_read,
	.write = event_trigger_write,
	.llseek = ftrace_filter_lseek,
	.release = event_trigger_release,
};

static int trace_event_trigger_enable_disable(struct ftrace_event_file *file,
					      int trigger_enable)
{
	int ret = 0;

	if (trigger_enable) {
		if (atomic_inc_return(&file->tm_ref) > 1)
			return ret;
		set_bit(FTRACE_EVENT_FL_TRIGGER_MODE_BIT, &file->flags);
		ret = trace_event_enable_disable(file, 1, 1);
	} else {
		if (atomic_dec_return(&file->tm_ref) > 0)
			return ret;
		clear_bit(FTRACE_EVENT_FL_TRIGGER_MODE_BIT, &file->flags);
		ret = trace_event_enable_disable(file, 0, 1);
	}

	return ret;
}

/**
 * clear_event_triggers - Clear all triggers associated with a trace array
 * @tr: The trace array to clear
 *
 * For each trigger, the triggering event has its tm_ref decremented
 * via trace_event_trigger_enable_disable(), and any associated event
 * (in the case of enable/disable_event triggers) will have its sm_ref
 * decremented via free()->trace_event_enable_disable().  That
 * combination effectively reverses the soft-mode/trigger state added
 * by trigger registration.
 *
 * Must be called with event_mutex held.
 */
void
clear_event_triggers(struct trace_array *tr)
{
	struct ftrace_event_file *file;

	list_for_each_entry(file, &tr->events, list) {
		struct event_trigger_data *data;
		list_for_each_entry_rcu(data, &file->triggers, list) {
			trace_event_trigger_enable_disable(file, 0);
			if (data->ops->free)
				data->ops->free(data->ops, data);
		}
	}
}

__init int register_trigger_cmds(void)
{
	return 0;
}