1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Generic dynamic event control interface
  4 *
  5 * Copyright (C) 2018 Masami Hiramatsu <mhiramat@kernel.org>
  6 */
  7
  8#include <linux/debugfs.h>
  9#include <linux/kernel.h>
 10#include <linux/list.h>
 11#include <linux/mm.h>
 12#include <linux/mutex.h>
 13#include <linux/tracefs.h>
 14
 15#include "trace.h"
 16#include "trace_dynevent.h"
 17
 18static DEFINE_MUTEX(dyn_event_ops_mutex);
 19static LIST_HEAD(dyn_event_ops_list);
 20
 21int dyn_event_register(struct dyn_event_operations *ops)
 22{
 23	if (!ops || !ops->create || !ops->show || !ops->is_busy ||
 24	    !ops->free || !ops->match)
 25		return -EINVAL;
 26
 27	INIT_LIST_HEAD(&ops->list);
 28	mutex_lock(&dyn_event_ops_mutex);
 29	list_add_tail(&ops->list, &dyn_event_ops_list);
 30	mutex_unlock(&dyn_event_ops_mutex);
 31	return 0;
 32}
 33
 34int dyn_event_release(int argc, char **argv, struct dyn_event_operations *type)
 35{
 36	struct dyn_event *pos, *n;
 37	char *system = NULL, *event, *p;
 38	int ret = -ENOENT;
 39
 40	if (argv[0][0] == '-') {
 41		if (argv[0][1] != ':')
 42			return -EINVAL;
 43		event = &argv[0][2];
 44	} else {
 45		event = strchr(argv[0], ':');
 46		if (!event)
 47			return -EINVAL;
 48		event++;
 49	}
 50	argc--; argv++;
 51
 52	p = strchr(event, '/');
 53	if (p) {
 54		system = event;
 55		event = p + 1;
 56		*p = '\0';
 57	}
 58	if (event[0] == '\0')
 59		return -EINVAL;
 60
 61	mutex_lock(&event_mutex);
 62	for_each_dyn_event_safe(pos, n) {
 63		if (type && type != pos->ops)
 64			continue;
 65		if (!pos->ops->match(system, event,
 66				argc, (const char **)argv, pos))
 67			continue;
 68
 69		ret = pos->ops->free(pos);
 70		if (ret)
 71			break;
 72	}
 73	mutex_unlock(&event_mutex);
 74
 75	return ret;
 76}
 77
 78static int create_dyn_event(int argc, char **argv)
 79{
 80	struct dyn_event_operations *ops;
 81	int ret = -ENODEV;
 82
 83	if (argv[0][0] == '-' || argv[0][0] == '!')
 84		return dyn_event_release(argc, argv, NULL);
 85
 86	mutex_lock(&dyn_event_ops_mutex);
 87	list_for_each_entry(ops, &dyn_event_ops_list, list) {
 88		ret = ops->create(argc, (const char **)argv);
 89		if (!ret || ret != -ECANCELED)
 90			break;
 91	}
 92	mutex_unlock(&dyn_event_ops_mutex);
 93	if (ret == -ECANCELED)
 94		ret = -EINVAL;
 95
 96	return ret;
 97}
 98
 99/* Protected by event_mutex */
100LIST_HEAD(dyn_event_list);
101
102void *dyn_event_seq_start(struct seq_file *m, loff_t *pos)
103{
104	mutex_lock(&event_mutex);
105	return seq_list_start(&dyn_event_list, *pos);
106}
107
108void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
109{
110	return seq_list_next(v, &dyn_event_list, pos);
111}
112
113void dyn_event_seq_stop(struct seq_file *m, void *v)
114{
115	mutex_unlock(&event_mutex);
116}
117
118static int dyn_event_seq_show(struct seq_file *m, void *v)
119{
120	struct dyn_event *ev = v;
121
122	if (ev && ev->ops)
123		return ev->ops->show(m, ev);
124
125	return 0;
126}
127
128static const struct seq_operations dyn_event_seq_op = {
129	.start	= dyn_event_seq_start,
130	.next	= dyn_event_seq_next,
131	.stop	= dyn_event_seq_stop,
132	.show	= dyn_event_seq_show
133};
134
135/*
136 * dyn_events_release_all - Release all specific events
137 * @type:	the dyn_event_operations * which filters releasing events
138 *
139 * This releases all events which ->ops matches @type. If @type is NULL,
140 * all events are released.
141 * Return -EBUSY if any of them are in use, and return other errors when
142 * it failed to free the given event. Except for -EBUSY, event releasing
143 * process will be aborted at that point and there may be some other
144 * releasable events on the list.
145 */
146int dyn_events_release_all(struct dyn_event_operations *type)
147{
148	struct dyn_event *ev, *tmp;
149	int ret = 0;
150
151	mutex_lock(&event_mutex);
152	for_each_dyn_event(ev) {
153		if (type && ev->ops != type)
154			continue;
155		if (ev->ops->is_busy(ev)) {
156			ret = -EBUSY;
157			goto out;
158		}
159	}
160	for_each_dyn_event_safe(ev, tmp) {
161		if (type && ev->ops != type)
162			continue;
163		ret = ev->ops->free(ev);
164		if (ret)
165			break;
166	}
167out:
168	mutex_unlock(&event_mutex);
169
170	return ret;
171}
172
173static int dyn_event_open(struct inode *inode, struct file *file)
174{
175	int ret;
176
177	ret = tracing_check_open_get_tr(NULL);
178	if (ret)
179		return ret;
180
181	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
182		ret = dyn_events_release_all(NULL);
183		if (ret < 0)
184			return ret;
185	}
186
187	return seq_open(file, &dyn_event_seq_op);
188}
189
190static ssize_t dyn_event_write(struct file *file, const char __user *buffer,
191				size_t count, loff_t *ppos)
192{
193	return trace_parse_run_command(file, buffer, count, ppos,
194				       create_dyn_event);
195}
196
197static const struct file_operations dynamic_events_ops = {
198	.owner          = THIS_MODULE,
199	.open           = dyn_event_open,
200	.read           = seq_read,
201	.llseek         = seq_lseek,
202	.release        = seq_release,
203	.write		= dyn_event_write,
204};
205
206/* Make a tracefs interface for controlling dynamic events */
207static __init int init_dynamic_event(void)
208{
209	struct dentry *d_tracer;
210	struct dentry *entry;
211
212	d_tracer = tracing_init_dentry();
213	if (IS_ERR(d_tracer))
214		return 0;
215
216	entry = tracefs_create_file("dynamic_events", 0644, d_tracer,
217				    NULL, &dynamic_events_ops);
218
219	/* Event list interface */
220	if (!entry)
221		pr_warn("Could not create tracefs 'dynamic_events' entry\n");
222
223	return 0;
224}
225fs_initcall(init_dynamic_event);