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_output.h" /* for trace_event_sem */
17 #include "trace_dynevent.h"
18
19 static DEFINE_MUTEX(dyn_event_ops_mutex);
20 static LIST_HEAD(dyn_event_ops_list);
21
22 bool trace_event_dyn_try_get_ref(struct trace_event_call *dyn_call)
23 {
24 struct trace_event_call *call;
25 bool ret = false;
26
27 if (WARN_ON_ONCE(!(dyn_call->flags & TRACE_EVENT_FL_DYNAMIC)))
28 return false;
29
30 down_read(&trace_event_sem);
31 list_for_each_entry(call, &ftrace_events, list) {
32 if (call == dyn_call) {
33 atomic_inc(&dyn_call->refcnt);
34 ret = true;
35 }
36 }
37 up_read(&trace_event_sem);
38 return ret;
39 }
40
41 void trace_event_dyn_put_ref(struct trace_event_call *call)
42 {
43 if (WARN_ON_ONCE(!(call->flags & TRACE_EVENT_FL_DYNAMIC)))
44 return;
45
46 if (WARN_ON_ONCE(atomic_read(&call->refcnt) <= 0)) {
47 atomic_set(&call->refcnt, 0);
48 return;
49 }
50
51 atomic_dec(&call->refcnt);
52 }
53
54 bool trace_event_dyn_busy(struct trace_event_call *call)
55 {
56 return atomic_read(&call->refcnt) != 0;
57 }
58
59 int dyn_event_register(struct dyn_event_operations *ops)
60 {
61 if (!ops || !ops->create || !ops->show || !ops->is_busy ||
62 !ops->free || !ops->match)
63 return -EINVAL;
64
65 INIT_LIST_HEAD(&ops->list);
66 mutex_lock(&dyn_event_ops_mutex);
67 list_add_tail(&ops->list, &dyn_event_ops_list);
68 mutex_unlock(&dyn_event_ops_mutex);
69 return 0;
70 }
71
72 int dyn_event_release(const char *raw_command, struct dyn_event_operations *type)
73 {
74 struct dyn_event *pos, *n;
75 char *system = NULL, *event, *p;
76 int argc, ret = -ENOENT;
77 char **argv;
78
79 argv = argv_split(GFP_KERNEL, raw_command, &argc);
80 if (!argv)
81 return -ENOMEM;
82
83 if (argv[0][0] == '-') {
84 if (argv[0][1] != ':') {
85 ret = -EINVAL;
86 goto out;
87 }
88 event = &argv[0][2];
89 } else {
90 event = strchr(argv[0], ':');
91 if (!event) {
92 ret = -EINVAL;
93 goto out;
94 }
95 event++;
96 }
97
98 p = strchr(event, '/');
99 if (p) {
100 system = event;
101 event = p + 1;
102 *p = '\0';
103 }
104 if (!system && event[0] == '\0') {
105 ret = -EINVAL;
106 goto out;
107 }
108
109 mutex_lock(&event_mutex);
110 for_each_dyn_event_safe(pos, n) {
111 if (type && type != pos->ops)
112 continue;
113 if (!pos->ops->match(system, event,
114 argc - 1, (const char **)argv + 1, pos))
115 continue;
116
117 ret = pos->ops->free(pos);
118 if (ret)
119 break;
120 }
121 tracing_reset_all_online_cpus();
122 mutex_unlock(&event_mutex);
123 out:
124 argv_free(argv);
125 return ret;
126 }
127
128 static int create_dyn_event(const char *raw_command)
129 {
130 struct dyn_event_operations *ops;
131 int ret = -ENODEV;
132
133 if (raw_command[0] == '-' || raw_command[0] == '!')
134 return dyn_event_release(raw_command, NULL);
135
136 mutex_lock(&dyn_event_ops_mutex);
137 list_for_each_entry(ops, &dyn_event_ops_list, list) {
138 ret = ops->create(raw_command);
139 if (!ret || ret != -ECANCELED)
140 break;
141 }
142 mutex_unlock(&dyn_event_ops_mutex);
143 if (ret == -ECANCELED)
144 ret = -EINVAL;
145
146 return ret;
147 }
148
149 /* Protected by event_mutex */
150 LIST_HEAD(dyn_event_list);
151
152 void *dyn_event_seq_start(struct seq_file *m, loff_t *pos)
153 {
154 mutex_lock(&event_mutex);
155 return seq_list_start(&dyn_event_list, *pos);
156 }
157
158 void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
159 {
160 return seq_list_next(v, &dyn_event_list, pos);
161 }
162
163 void dyn_event_seq_stop(struct seq_file *m, void *v)
164 {
165 mutex_unlock(&event_mutex);
166 }
167
168 static int dyn_event_seq_show(struct seq_file *m, void *v)
169 {
170 struct dyn_event *ev = v;
171
172 if (ev && ev->ops)
173 return ev->ops->show(m, ev);
174
175 return 0;
176 }
177
178 static const struct seq_operations dyn_event_seq_op = {
179 .start = dyn_event_seq_start,
180 .next = dyn_event_seq_next,
181 .stop = dyn_event_seq_stop,
182 .show = dyn_event_seq_show
183 };
184
185 /*
186 * dyn_events_release_all - Release all specific events
187 * @type: the dyn_event_operations * which filters releasing events
188 *
189 * This releases all events which ->ops matches @type. If @type is NULL,
190 * all events are released.
191 * Return -EBUSY if any of them are in use, and return other errors when
192 * it failed to free the given event. Except for -EBUSY, event releasing
193 * process will be aborted at that point and there may be some other
194 * releasable events on the list.
195 */
196 int dyn_events_release_all(struct dyn_event_operations *type)
197 {
198 struct dyn_event *ev, *tmp;
199 int ret = 0;
200
201 mutex_lock(&event_mutex);
202 for_each_dyn_event(ev) {
203 if (type && ev->ops != type)
204 continue;
205 if (ev->ops->is_busy(ev)) {
206 ret = -EBUSY;
207 goto out;
208 }
209 }
210 for_each_dyn_event_safe(ev, tmp) {
211 if (type && ev->ops != type)
212 continue;
213 ret = ev->ops->free(ev);
214 if (ret)
215 break;
216 }
217 out:
218 tracing_reset_all_online_cpus();
219 mutex_unlock(&event_mutex);
220
221 return ret;
222 }
223
224 static int dyn_event_open(struct inode *inode, struct file *file)
225 {
226 int ret;
227
228 ret = tracing_check_open_get_tr(NULL);
229 if (ret)
230 return ret;
231
232 if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
233 ret = dyn_events_release_all(NULL);
234 if (ret < 0)
235 return ret;
236 }
237
238 return seq_open(file, &dyn_event_seq_op);
239 }
240
241 static ssize_t dyn_event_write(struct file *file, const char __user *buffer,
242 size_t count, loff_t *ppos)
243 {
244 return trace_parse_run_command(file, buffer, count, ppos,
245 create_dyn_event);
246 }
247
248 static const struct file_operations dynamic_events_ops = {
249 .owner = THIS_MODULE,
250 .open = dyn_event_open,
251 .read = seq_read,
252 .llseek = seq_lseek,
253 .release = seq_release,
254 .write = dyn_event_write,
255 };
256
257 /* Make a tracefs interface for controlling dynamic events */
258 static __init int init_dynamic_event(void)
259 {
260 int ret;
261
262 ret = tracing_init_dentry();
263 if (ret)
264 return 0;
265
266 trace_create_file("dynamic_events", TRACE_MODE_WRITE, NULL,
267 NULL, &dynamic_events_ops);
268
269 return 0;
270 }
271 fs_initcall(init_dynamic_event);
272
273 /**
274 * dynevent_arg_add - Add an arg to a dynevent_cmd
275 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
276 * @arg: The argument to append to the current cmd
277 * @check_arg: An (optional) pointer to a function checking arg sanity
278 *
279 * Append an argument to a dynevent_cmd. The argument string will be
280 * appended to the current cmd string, followed by a separator, if
281 * applicable. Before the argument is added, the @check_arg function,
282 * if present, will be used to check the sanity of the current arg
283 * string.
284 *
285 * The cmd string and separator should be set using the
286 * dynevent_arg_init() before any arguments are added using this
287 * function.
288 *
289 * Return: 0 if successful, error otherwise.
290 */
291 int dynevent_arg_add(struct dynevent_cmd *cmd,
292 struct dynevent_arg *arg,
293 dynevent_check_arg_fn_t check_arg)
294 {
295 int ret = 0;
296
297 if (check_arg) {
298 ret = check_arg(arg);
299 if (ret)
300 return ret;
301 }
302
303 ret = seq_buf_printf(&cmd->seq, " %s%c", arg->str, arg->separator);
304 if (ret) {
305 pr_err("String is too long: %s%c\n", arg->str, arg->separator);
306 return -E2BIG;
307 }
308
309 return ret;
310 }
311
312 /**
313 * dynevent_arg_pair_add - Add an arg pair to a dynevent_cmd
314 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
315 * @arg_pair: The argument pair to append to the current cmd
316 * @check_arg: An (optional) pointer to a function checking arg sanity
317 *
318 * Append an argument pair to a dynevent_cmd. An argument pair
319 * consists of a left-hand-side argument and a right-hand-side
320 * argument separated by an operator, which can be whitespace, all
321 * followed by a separator, if applicable. This can be used to add
322 * arguments of the form 'type variable_name;' or 'x+y'.
323 *
324 * The lhs argument string will be appended to the current cmd string,
325 * followed by an operator, if applicable, followed by the rhs string,
326 * followed finally by a separator, if applicable. Before the
327 * argument is added, the @check_arg function, if present, will be
328 * used to check the sanity of the current arg strings.
329 *
330 * The cmd strings, operator, and separator should be set using the
331 * dynevent_arg_pair_init() before any arguments are added using this
332 * function.
333 *
334 * Return: 0 if successful, error otherwise.
335 */
336 int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
337 struct dynevent_arg_pair *arg_pair,
338 dynevent_check_arg_fn_t check_arg)
339 {
340 int ret = 0;
341
342 if (check_arg) {
343 ret = check_arg(arg_pair);
344 if (ret)
345 return ret;
346 }
347
348 ret = seq_buf_printf(&cmd->seq, " %s%c%s%c", arg_pair->lhs,
349 arg_pair->operator, arg_pair->rhs,
350 arg_pair->separator);
351 if (ret) {
352 pr_err("field string is too long: %s%c%s%c\n", arg_pair->lhs,
353 arg_pair->operator, arg_pair->rhs,
354 arg_pair->separator);
355 return -E2BIG;
356 }
357
358 return ret;
359 }
360
361 /**
362 * dynevent_str_add - Add a string to a dynevent_cmd
363 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
364 * @str: The string to append to the current cmd
365 *
366 * Append a string to a dynevent_cmd. The string will be appended to
367 * the current cmd string as-is, with nothing prepended or appended.
368 *
369 * Return: 0 if successful, error otherwise.
370 */
371 int dynevent_str_add(struct dynevent_cmd *cmd, const char *str)
372 {
373 int ret = 0;
374
375 ret = seq_buf_puts(&cmd->seq, str);
376 if (ret) {
377 pr_err("String is too long: %s\n", str);
378 return -E2BIG;
379 }
380
381 return ret;
382 }
383
384 /**
385 * dynevent_cmd_init - Initialize a dynevent_cmd object
386 * @cmd: A pointer to the dynevent_cmd struct representing the cmd
387 * @buf: A pointer to the buffer to generate the command into
388 * @maxlen: The length of the buffer the command will be generated into
389 * @type: The type of the cmd, checked against further operations
390 * @run_command: The type-specific function that will actually run the command
391 *
392 * Initialize a dynevent_cmd. A dynevent_cmd is used to build up and
393 * run dynamic event creation commands, such as commands for creating
394 * synthetic and kprobe events. Before calling any of the functions
395 * used to build the command, a dynevent_cmd object should be
396 * instantiated and initialized using this function.
397 *
398 * The initialization sets things up by saving a pointer to the
399 * user-supplied buffer and its length via the @buf and @maxlen
400 * params, and by saving the cmd-specific @type and @run_command
401 * params which are used to check subsequent dynevent_cmd operations
402 * and actually run the command when complete.
403 */
404 void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
405 enum dynevent_type type,
406 dynevent_create_fn_t run_command)
407 {
408 memset(cmd, '\0', sizeof(*cmd));
409
410 seq_buf_init(&cmd->seq, buf, maxlen);
411 cmd->type = type;
412 cmd->run_command = run_command;
413 }
414
415 /**
416 * dynevent_arg_init - Initialize a dynevent_arg object
417 * @arg: A pointer to the dynevent_arg struct representing the arg
418 * @separator: An (optional) separator, appended after adding the arg
419 *
420 * Initialize a dynevent_arg object. A dynevent_arg represents an
421 * object used to append single arguments to the current command
422 * string. After the arg string is successfully appended to the
423 * command string, the optional @separator is appended. If no
424 * separator was specified when initializing the arg, a space will be
425 * appended.
426 */
427 void dynevent_arg_init(struct dynevent_arg *arg,
428 char separator)
429 {
430 memset(arg, '\0', sizeof(*arg));
431
432 if (!separator)
433 separator = ' ';
434 arg->separator = separator;
435 }
436
437 /**
438 * dynevent_arg_pair_init - Initialize a dynevent_arg_pair object
439 * @arg_pair: A pointer to the dynevent_arg_pair struct representing the arg
440 * @operator: An (optional) operator, appended after adding the first arg
441 * @separator: An (optional) separator, appended after adding the second arg
442 *
443 * Initialize a dynevent_arg_pair object. A dynevent_arg_pair
444 * represents an object used to append argument pairs such as 'type
445 * variable_name;' or 'x+y' to the current command string. An
446 * argument pair consists of a left-hand-side argument and a
447 * right-hand-side argument separated by an operator, which can be
448 * whitespace, all followed by a separator, if applicable. After the
449 * first arg string is successfully appended to the command string,
450 * the optional @operator is appended, followed by the second arg and
451 * optional @separator. If no separator was specified when
452 * initializing the arg, a space will be appended.
453 */
454 void dynevent_arg_pair_init(struct dynevent_arg_pair *arg_pair,
455 char operator, char separator)
456 {
457 memset(arg_pair, '\0', sizeof(*arg_pair));
458
459 if (!operator)
460 operator = ' ';
461 arg_pair->operator = operator;
462
463 if (!separator)
464 separator = ' ';
465 arg_pair->separator = separator;
466 }
467
468 /**
469 * dynevent_create - Create the dynamic event contained in dynevent_cmd
470 * @cmd: The dynevent_cmd object containing the dynamic event creation command
471 *
472 * Once a dynevent_cmd object has been successfully built up via the
473 * dynevent_cmd_init(), dynevent_arg_add() and dynevent_arg_pair_add()
474 * functions, this function runs the final command to actually create
475 * the event.
476 *
477 * Return: 0 if the event was successfully created, error otherwise.
478 */
479 int dynevent_create(struct dynevent_cmd *cmd)
480 {
481 return cmd->run_command(cmd);
482 }
483 EXPORT_SYMBOL_GPL(dynevent_create);
484
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