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