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
19static DEFINE_MUTEX(dyn_event_ops_mutex);
20static LIST_HEAD(dyn_event_ops_list);
21
22bool 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
41void 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
54bool trace_event_dyn_busy(struct trace_event_call *call)
55{
56	return atomic_read(&call->refcnt) != 0;
57}
58
59int 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
72int 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);
123out:
124	argv_free(argv);
125	return ret;
126}
127
128static 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 */
150LIST_HEAD(dyn_event_list);
151
152void *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
158void *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
163void dyn_event_seq_stop(struct seq_file *m, void *v)
164{
165	mutex_unlock(&event_mutex);
166}
167
168static 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
178static 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 */
196int 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	}
217out:
218	tracing_reset_all_online_cpus();
219	mutex_unlock(&event_mutex);
220
221	return ret;
222}
223
224static 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
241static 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
248static 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 */
258static __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}
271fs_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 */
291int 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 */
336int 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 */
371int 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 */
404void 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 */
427void 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 */
454void 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 */
479int dynevent_create(struct dynevent_cmd *cmd)
480{
481	return cmd->run_command(cmd);
482}
483EXPORT_SYMBOL_GPL(dynevent_create);
484