trace_dynevent.c

  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
 19DEFINE_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 __free(argv_free) = argv_split(GFP_KERNEL, raw_command, &argc);
 78
 79	if (!argv)
 80		return -ENOMEM;
 81
 82	if (argv[0][0] == '-') {
 83		if (argv[0][1] != ':')
 84			return -EINVAL;
 85		event = &argv[0][2];
 86	} else {
 87		event = strchr(argv[0], ':');
 88		if (!event)
 89			return -EINVAL;
 90		event++;
 91	}
 92
 93	p = strchr(event, '/');
 94	if (p) {
 95		system = event;
 96		event = p + 1;
 97		*p = '\0';
 98	}
 99	if (!system && event[0] == '\0')
100		return -EINVAL;
101
102	mutex_lock(&event_mutex);
103	for_each_dyn_event_safe(pos, n) {
104		if (type && type != pos->ops)
105			continue;
106		if (!pos->ops->match(system, event,
107				argc - 1, (const char **)argv + 1, pos))
108			continue;
109
110		ret = pos->ops->free(pos);
111		if (ret)
112			break;
113	}
114	tracing_reset_all_online_cpus();
115	mutex_unlock(&event_mutex);
116	return ret;
117}
118
119/*
120 * Locked version of event creation. The event creation must be protected by
121 * dyn_event_ops_mutex because of protecting trace_probe_log.
122 */
123int dyn_event_create(const char *raw_command, struct dyn_event_operations *type)
124{
125	int ret;
126
127	mutex_lock(&dyn_event_ops_mutex);
128	ret = type->create(raw_command);
129	mutex_unlock(&dyn_event_ops_mutex);
130	return ret;
131}
132
133static int create_dyn_event(const char *raw_command)
134{
135	struct dyn_event_operations *ops;
136	int ret = -ENODEV;
137
138	if (raw_command[0] == '-' || raw_command[0] == '!')
139		return dyn_event_release(raw_command, NULL);
140
141	mutex_lock(&dyn_event_ops_mutex);
142	list_for_each_entry(ops, &dyn_event_ops_list, list) {
143		ret = ops->create(raw_command);
144		if (!ret || ret != -ECANCELED)
145			break;
146	}
147	if (ret == -ECANCELED) {
148		static const char *err_msg[] = {"No matching dynamic event type"};
149
150		/* Wrong dynamic event. Leave an error message. */
151		tracing_log_err(NULL, "dynevent", raw_command, err_msg,
152				0, 0);
153		ret = -EINVAL;
154	}
155
156	mutex_unlock(&dyn_event_ops_mutex);
157
158	return ret;
159}
160
161/* Protected by event_mutex */
162LIST_HEAD(dyn_event_list);
163
164void *dyn_event_seq_start(struct seq_file *m, loff_t *pos)
165{
166	mutex_lock(&event_mutex);
167	return seq_list_start(&dyn_event_list, *pos);
168}
169
170void *dyn_event_seq_next(struct seq_file *m, void *v, loff_t *pos)
171{
172	return seq_list_next(v, &dyn_event_list, pos);
173}
174
175void dyn_event_seq_stop(struct seq_file *m, void *v)
176{
177	mutex_unlock(&event_mutex);
178}
179
180static int dyn_event_seq_show(struct seq_file *m, void *v)
181{
182	struct dyn_event *ev = v;
183
184	if (ev && ev->ops)
185		return ev->ops->show(m, ev);
186
187	return 0;
188}
189
190static const struct seq_operations dyn_event_seq_op = {
191	.start	= dyn_event_seq_start,
192	.next	= dyn_event_seq_next,
193	.stop	= dyn_event_seq_stop,
194	.show	= dyn_event_seq_show
195};
196
197/*
198 * dyn_events_release_all - Release all specific events
199 * @type:	the dyn_event_operations * which filters releasing events
200 *
201 * This releases all events which ->ops matches @type. If @type is NULL,
202 * all events are released.
203 * Return -EBUSY if any of them are in use, and return other errors when
204 * it failed to free the given event. Except for -EBUSY, event releasing
205 * process will be aborted at that point and there may be some other
206 * releasable events on the list.
207 */
208int dyn_events_release_all(struct dyn_event_operations *type)
209{
210	struct dyn_event *ev, *tmp;
211	int ret = 0;
212
213	mutex_lock(&event_mutex);
214	for_each_dyn_event(ev) {
215		if (type && ev->ops != type)
216			continue;
217		if (ev->ops->is_busy(ev)) {
218			ret = -EBUSY;
219			goto out;
220		}
221	}
222	for_each_dyn_event_safe(ev, tmp) {
223		if (type && ev->ops != type)
224			continue;
225		ret = ev->ops->free(ev);
226		if (ret)
227			break;
228	}
229out:
230	tracing_reset_all_online_cpus();
231	mutex_unlock(&event_mutex);
232
233	return ret;
234}
235
236static int dyn_event_open(struct inode *inode, struct file *file)
237{
238	int ret;
239
240	ret = security_locked_down(LOCKDOWN_TRACEFS);
241	if (ret)
242		return ret;
243
244	ret = tracing_check_open_get_tr(NULL);
245	if (ret)
246		return ret;
247
248	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
249		ret = dyn_events_release_all(NULL);
250		if (ret < 0)
251			return ret;
252	}
253
254	return seq_open(file, &dyn_event_seq_op);
255}
256
257static ssize_t dyn_event_write(struct file *file, const char __user *buffer,
258				size_t count, loff_t *ppos)
259{
260	return trace_parse_run_command(file, buffer, count, ppos,
261				       create_dyn_event);
262}
263
264static const struct file_operations dynamic_events_ops = {
265	.owner          = THIS_MODULE,
266	.open           = dyn_event_open,
267	.read           = seq_read,
268	.llseek         = seq_lseek,
269	.release        = seq_release,
270	.write		= dyn_event_write,
271};
272
273/* Make a tracefs interface for controlling dynamic events */
274static __init int init_dynamic_event(void)
275{
276	int ret;
277
278	ret = tracing_init_dentry();
279	if (ret)
280		return 0;
281
282	trace_create_file("dynamic_events", TRACE_MODE_WRITE, NULL,
283			  NULL, &dynamic_events_ops);
284
285	return 0;
286}
287fs_initcall(init_dynamic_event);
288
289/**
290 * dynevent_arg_add - Add an arg to a dynevent_cmd
291 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
292 * @arg: The argument to append to the current cmd
293 * @check_arg: An (optional) pointer to a function checking arg sanity
294 *
295 * Append an argument to a dynevent_cmd.  The argument string will be
296 * appended to the current cmd string, followed by a separator, if
297 * applicable.  Before the argument is added, the @check_arg function,
298 * if present, will be used to check the sanity of the current arg
299 * string.
300 *
301 * The cmd string and separator should be set using the
302 * dynevent_arg_init() before any arguments are added using this
303 * function.
304 *
305 * Return: 0 if successful, error otherwise.
306 */
307int dynevent_arg_add(struct dynevent_cmd *cmd,
308		     struct dynevent_arg *arg,
309		     dynevent_check_arg_fn_t check_arg)
310{
311	int ret = 0;
312
313	if (check_arg) {
314		ret = check_arg(arg);
315		if (ret)
316			return ret;
317	}
318
319	ret = seq_buf_printf(&cmd->seq, " %s%c", arg->str, arg->separator);
320	if (ret) {
321		pr_err("String is too long: %s%c\n", arg->str, arg->separator);
322		return -E2BIG;
323	}
324
325	return ret;
326}
327
328/**
329 * dynevent_arg_pair_add - Add an arg pair to a dynevent_cmd
330 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
331 * @arg_pair: The argument pair to append to the current cmd
332 * @check_arg: An (optional) pointer to a function checking arg sanity
333 *
334 * Append an argument pair to a dynevent_cmd.  An argument pair
335 * consists of a left-hand-side argument and a right-hand-side
336 * argument separated by an operator, which can be whitespace, all
337 * followed by a separator, if applicable.  This can be used to add
338 * arguments of the form 'type variable_name;' or 'x+y'.
339 *
340 * The lhs argument string will be appended to the current cmd string,
341 * followed by an operator, if applicable, followed by the rhs string,
342 * followed finally by a separator, if applicable.  Before the
343 * argument is added, the @check_arg function, if present, will be
344 * used to check the sanity of the current arg strings.
345 *
346 * The cmd strings, operator, and separator should be set using the
347 * dynevent_arg_pair_init() before any arguments are added using this
348 * function.
349 *
350 * Return: 0 if successful, error otherwise.
351 */
352int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
353			  struct dynevent_arg_pair *arg_pair,
354			  dynevent_check_arg_fn_t check_arg)
355{
356	int ret = 0;
357
358	if (check_arg) {
359		ret = check_arg(arg_pair);
360		if (ret)
361			return ret;
362	}
363
364	ret = seq_buf_printf(&cmd->seq, " %s%c%s%c", arg_pair->lhs,
365			     arg_pair->operator, arg_pair->rhs,
366			     arg_pair->separator);
367	if (ret) {
368		pr_err("field string is too long: %s%c%s%c\n", arg_pair->lhs,
369		       arg_pair->operator, arg_pair->rhs,
370		       arg_pair->separator);
371		return -E2BIG;
372	}
373
374	return ret;
375}
376
377/**
378 * dynevent_str_add - Add a string to a dynevent_cmd
379 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
380 * @str: The string to append to the current cmd
381 *
382 * Append a string to a dynevent_cmd.  The string will be appended to
383 * the current cmd string as-is, with nothing prepended or appended.
384 *
385 * Return: 0 if successful, error otherwise.
386 */
387int dynevent_str_add(struct dynevent_cmd *cmd, const char *str)
388{
389	int ret = 0;
390
391	ret = seq_buf_puts(&cmd->seq, str);
392	if (ret) {
393		pr_err("String is too long: %s\n", str);
394		return -E2BIG;
395	}
396
397	return ret;
398}
399
400/**
401 * dynevent_cmd_init - Initialize a dynevent_cmd object
402 * @cmd: A pointer to the dynevent_cmd struct representing the cmd
403 * @buf: A pointer to the buffer to generate the command into
404 * @maxlen: The length of the buffer the command will be generated into
405 * @type: The type of the cmd, checked against further operations
406 * @run_command: The type-specific function that will actually run the command
407 *
408 * Initialize a dynevent_cmd.  A dynevent_cmd is used to build up and
409 * run dynamic event creation commands, such as commands for creating
410 * synthetic and kprobe events.  Before calling any of the functions
411 * used to build the command, a dynevent_cmd object should be
412 * instantiated and initialized using this function.
413 *
414 * The initialization sets things up by saving a pointer to the
415 * user-supplied buffer and its length via the @buf and @maxlen
416 * params, and by saving the cmd-specific @type and @run_command
417 * params which are used to check subsequent dynevent_cmd operations
418 * and actually run the command when complete.
419 */
420void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
421		       enum dynevent_type type,
422		       dynevent_create_fn_t run_command)
423{
424	memset(cmd, '\0', sizeof(*cmd));
425
426	seq_buf_init(&cmd->seq, buf, maxlen);
427	cmd->type = type;
428	cmd->run_command = run_command;
429}
430
431/**
432 * dynevent_arg_init - Initialize a dynevent_arg object
433 * @arg: A pointer to the dynevent_arg struct representing the arg
434 * @separator: An (optional) separator, appended after adding the arg
435 *
436 * Initialize a dynevent_arg object.  A dynevent_arg represents an
437 * object used to append single arguments to the current command
438 * string.  After the arg string is successfully appended to the
439 * command string, the optional @separator is appended.  If no
440 * separator was specified when initializing the arg, a space will be
441 * appended.
442 */
443void dynevent_arg_init(struct dynevent_arg *arg,
444		       char separator)
445{
446	memset(arg, '\0', sizeof(*arg));
447
448	if (!separator)
449		separator = ' ';
450	arg->separator = separator;
451}
452
453/**
454 * dynevent_arg_pair_init - Initialize a dynevent_arg_pair object
455 * @arg_pair: A pointer to the dynevent_arg_pair struct representing the arg
456 * @operator: An (optional) operator, appended after adding the first arg
457 * @separator: An (optional) separator, appended after adding the second arg
458 *
459 * Initialize a dynevent_arg_pair object.  A dynevent_arg_pair
460 * represents an object used to append argument pairs such as 'type
461 * variable_name;' or 'x+y' to the current command string.  An
462 * argument pair consists of a left-hand-side argument and a
463 * right-hand-side argument separated by an operator, which can be
464 * whitespace, all followed by a separator, if applicable.  After the
465 * first arg string is successfully appended to the command string,
466 * the optional @operator is appended, followed by the second arg and
467 * optional @separator.  If no separator was specified when
468 * initializing the arg, a space will be appended.
469 */
470void dynevent_arg_pair_init(struct dynevent_arg_pair *arg_pair,
471			    char operator, char separator)
472{
473	memset(arg_pair, '\0', sizeof(*arg_pair));
474
475	if (!operator)
476		operator = ' ';
477	arg_pair->operator = operator;
478
479	if (!separator)
480		separator = ' ';
481	arg_pair->separator = separator;
482}
483
484/**
485 * dynevent_create - Create the dynamic event contained in dynevent_cmd
486 * @cmd: The dynevent_cmd object containing the dynamic event creation command
487 *
488 * Once a dynevent_cmd object has been successfully built up via the
489 * dynevent_cmd_init(), dynevent_arg_add() and dynevent_arg_pair_add()
490 * functions, this function runs the final command to actually create
491 * the event.
492 *
493 * Return: 0 if the event was successfully created, error otherwise.
494 */
495int dynevent_create(struct dynevent_cmd *cmd)
496{
497	return cmd->run_command(cmd);
498}
499EXPORT_SYMBOL_GPL(dynevent_create);