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);
226
227/**
228 * dynevent_arg_add - Add an arg to a dynevent_cmd
229 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
230 * @arg: The argument to append to the current cmd
231 * @check_arg: An (optional) pointer to a function checking arg sanity
232 *
233 * Append an argument to a dynevent_cmd.  The argument string will be
234 * appended to the current cmd string, followed by a separator, if
235 * applicable.  Before the argument is added, the @check_arg function,
236 * if present, will be used to check the sanity of the current arg
237 * string.
238 *
239 * The cmd string and separator should be set using the
240 * dynevent_arg_init() before any arguments are added using this
241 * function.
242 *
243 * Return: 0 if successful, error otherwise.
244 */
245int dynevent_arg_add(struct dynevent_cmd *cmd,
246		     struct dynevent_arg *arg,
247		     dynevent_check_arg_fn_t check_arg)
248{
249	int ret = 0;
250
251	if (check_arg) {
252		ret = check_arg(arg);
253		if (ret)
254			return ret;
255	}
256
257	ret = seq_buf_printf(&cmd->seq, " %s%c", arg->str, arg->separator);
258	if (ret) {
259		pr_err("String is too long: %s%c\n", arg->str, arg->separator);
260		return -E2BIG;
261	}
262
263	return ret;
264}
265
266/**
267 * dynevent_arg_pair_add - Add an arg pair to a dynevent_cmd
268 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
269 * @arg_pair: The argument pair to append to the current cmd
270 * @check_arg: An (optional) pointer to a function checking arg sanity
271 *
272 * Append an argument pair to a dynevent_cmd.  An argument pair
273 * consists of a left-hand-side argument and a right-hand-side
274 * argument separated by an operator, which can be whitespace, all
275 * followed by a separator, if applicable.  This can be used to add
276 * arguments of the form 'type variable_name;' or 'x+y'.
277 *
278 * The lhs argument string will be appended to the current cmd string,
279 * followed by an operator, if applicable, followd by the rhs string,
280 * followed finally by a separator, if applicable.  Before the
281 * argument is added, the @check_arg function, if present, will be
282 * used to check the sanity of the current arg strings.
283 *
284 * The cmd strings, operator, and separator should be set using the
285 * dynevent_arg_pair_init() before any arguments are added using this
286 * function.
287 *
288 * Return: 0 if successful, error otherwise.
289 */
290int dynevent_arg_pair_add(struct dynevent_cmd *cmd,
291			  struct dynevent_arg_pair *arg_pair,
292			  dynevent_check_arg_fn_t check_arg)
293{
294	int ret = 0;
295
296	if (check_arg) {
297		ret = check_arg(arg_pair);
298		if (ret)
299			return ret;
300	}
301
302	ret = seq_buf_printf(&cmd->seq, " %s%c%s%c", arg_pair->lhs,
303			     arg_pair->operator, arg_pair->rhs,
304			     arg_pair->separator);
305	if (ret) {
306		pr_err("field string is too long: %s%c%s%c\n", arg_pair->lhs,
307		       arg_pair->operator, arg_pair->rhs,
308		       arg_pair->separator);
309		return -E2BIG;
310	}
311
312	return ret;
313}
314
315/**
316 * dynevent_str_add - Add a string to a dynevent_cmd
317 * @cmd: A pointer to the dynevent_cmd struct representing the new event cmd
318 * @str: The string to append to the current cmd
319 *
320 * Append a string to a dynevent_cmd.  The string will be appended to
321 * the current cmd string as-is, with nothing prepended or appended.
322 *
323 * Return: 0 if successful, error otherwise.
324 */
325int dynevent_str_add(struct dynevent_cmd *cmd, const char *str)
326{
327	int ret = 0;
328
329	ret = seq_buf_puts(&cmd->seq, str);
330	if (ret) {
331		pr_err("String is too long: %s\n", str);
332		return -E2BIG;
333	}
334
335	return ret;
336}
337
338/**
339 * dynevent_cmd_init - Initialize a dynevent_cmd object
340 * @cmd: A pointer to the dynevent_cmd struct representing the cmd
341 * @buf: A pointer to the buffer to generate the command into
342 * @maxlen: The length of the buffer the command will be generated into
343 * @type: The type of the cmd, checked against further operations
344 * @run_command: The type-specific function that will actually run the command
345 *
346 * Initialize a dynevent_cmd.  A dynevent_cmd is used to build up and
347 * run dynamic event creation commands, such as commands for creating
348 * synthetic and kprobe events.  Before calling any of the functions
349 * used to build the command, a dynevent_cmd object should be
350 * instantiated and initialized using this function.
351 *
352 * The initialization sets things up by saving a pointer to the
353 * user-supplied buffer and its length via the @buf and @maxlen
354 * params, and by saving the cmd-specific @type and @run_command
355 * params which are used to check subsequent dynevent_cmd operations
356 * and actually run the command when complete.
357 */
358void dynevent_cmd_init(struct dynevent_cmd *cmd, char *buf, int maxlen,
359		       enum dynevent_type type,
360		       dynevent_create_fn_t run_command)
361{
362	memset(cmd, '\0', sizeof(*cmd));
363
364	seq_buf_init(&cmd->seq, buf, maxlen);
365	cmd->type = type;
366	cmd->run_command = run_command;
367}
368
369/**
370 * dynevent_arg_init - Initialize a dynevent_arg object
371 * @arg: A pointer to the dynevent_arg struct representing the arg
372 * @separator: An (optional) separator, appended after adding the arg
373 *
374 * Initialize a dynevent_arg object.  A dynevent_arg represents an
375 * object used to append single arguments to the current command
376 * string.  After the arg string is successfully appended to the
377 * command string, the optional @separator is appended.  If no
378 * separator was specified when initializing the arg, a space will be
379 * appended.
380 */
381void dynevent_arg_init(struct dynevent_arg *arg,
382		       char separator)
383{
384	memset(arg, '\0', sizeof(*arg));
385
386	if (!separator)
387		separator = ' ';
388	arg->separator = separator;
389}
390
391/**
392 * dynevent_arg_pair_init - Initialize a dynevent_arg_pair object
393 * @arg_pair: A pointer to the dynevent_arg_pair struct representing the arg
394 * @operator: An (optional) operator, appended after adding the first arg
395 * @separator: An (optional) separator, appended after adding the second arg
396 *
397 * Initialize a dynevent_arg_pair object.  A dynevent_arg_pair
398 * represents an object used to append argument pairs such as 'type
399 * variable_name;' or 'x+y' to the current command string.  An
400 * argument pair consists of a left-hand-side argument and a
401 * right-hand-side argument separated by an operator, which can be
402 * whitespace, all followed by a separator, if applicable.  After the
403 * first arg string is successfully appended to the command string,
404 * the optional @operator is appended, followed by the second arg and
405 * and optional @separator.  If no separator was specified when
406 * initializing the arg, a space will be appended.
407 */
408void dynevent_arg_pair_init(struct dynevent_arg_pair *arg_pair,
409			    char operator, char separator)
410{
411	memset(arg_pair, '\0', sizeof(*arg_pair));
412
413	if (!operator)
414		operator = ' ';
415	arg_pair->operator = operator;
416
417	if (!separator)
418		separator = ' ';
419	arg_pair->separator = separator;
420}
421
422/**
423 * dynevent_create - Create the dynamic event contained in dynevent_cmd
424 * @cmd: The dynevent_cmd object containing the dynamic event creation command
425 *
426 * Once a dynevent_cmd object has been successfully built up via the
427 * dynevent_cmd_init(), dynevent_arg_add() and dynevent_arg_pair_add()
428 * functions, this function runs the final command to actually create
429 * the event.
430 *
431 * Return: 0 if the event was successfully created, error otherwise.
432 */
433int dynevent_create(struct dynevent_cmd *cmd)
434{
435	return cmd->run_command(cmd);
436}
437EXPORT_SYMBOL_GPL(dynevent_create);