xref: /linux/kernel/trace/trace_dynevent.c (revision 7ae9fb1b7ecbb5d85d07857943f677fd1a559b18)
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 
trace_event_dyn_try_get_ref(struct trace_event_call * dyn_call)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 
trace_event_dyn_put_ref(struct trace_event_call * call)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 
trace_event_dyn_busy(struct trace_event_call * call)54 bool trace_event_dyn_busy(struct trace_event_call *call)
55 {
56 	return atomic_read(&call->refcnt) != 0;
57 }
58 
dyn_event_register(struct dyn_event_operations * ops)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 
dyn_event_release(const char * raw_command,struct dyn_event_operations * type)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 
create_dyn_event(const char * raw_command)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 
dyn_event_seq_start(struct seq_file * m,loff_t * pos)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 
dyn_event_seq_next(struct seq_file * m,void * v,loff_t * pos)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 
dyn_event_seq_stop(struct seq_file * m,void * v)163 void dyn_event_seq_stop(struct seq_file *m, void *v)
164 {
165 	mutex_unlock(&event_mutex);
166 }
167 
dyn_event_seq_show(struct seq_file * m,void * v)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  */
dyn_events_release_all(struct dyn_event_operations * type)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 
dyn_event_open(struct inode * inode,struct file * file)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 
dyn_event_write(struct file * file,const char __user * buffer,size_t count,loff_t * ppos)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 */
init_dynamic_event(void)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  */
dynevent_arg_add(struct dynevent_cmd * cmd,struct dynevent_arg * arg,dynevent_check_arg_fn_t check_arg)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  */
dynevent_arg_pair_add(struct dynevent_cmd * cmd,struct dynevent_arg_pair * arg_pair,dynevent_check_arg_fn_t check_arg)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  */
dynevent_str_add(struct dynevent_cmd * cmd,const char * str)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  */
dynevent_cmd_init(struct dynevent_cmd * cmd,char * buf,int maxlen,enum dynevent_type type,dynevent_create_fn_t run_command)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  */
dynevent_arg_init(struct dynevent_arg * arg,char separator)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  */
dynevent_arg_pair_init(struct dynevent_arg_pair * arg_pair,char operator,char separator)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  */
dynevent_create(struct dynevent_cmd * cmd)479 int dynevent_create(struct dynevent_cmd *cmd)
480 {
481 	return cmd->run_command(cmd);
482 }
483 EXPORT_SYMBOL_GPL(dynevent_create);
484