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f99be407 PMF |
1 | /* |
2 | * Copyright (C) 2008 Mathieu Desnoyers | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License as published by | |
6 | * the Free Software Foundation; either version 2 of the License, or | |
7 | * (at your option) any later version. | |
8 | * | |
9 | * This program is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | * GNU General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU General Public License | |
15 | * along with this program; if not, write to the Free Software | |
16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
17 | */ | |
18 | #include <linux/module.h> | |
19 | #include <linux/mutex.h> | |
20 | #include <linux/types.h> | |
21 | #include <linux/jhash.h> | |
22 | #include <linux/list.h> | |
23 | #include <linux/rcupdate.h> | |
24 | #include <linux/tracepoint.h> | |
25 | #include <linux/err.h> | |
26 | #include <linux/slab.h> | |
27 | #include <linux/immediate.h> | |
28 | ||
29 | extern struct tracepoint __start___tracepoints[]; | |
30 | extern struct tracepoint __stop___tracepoints[]; | |
31 | ||
32 | /* Set to 1 to enable tracepoint debug output */ | |
33 | static const int tracepoint_debug; | |
34 | ||
35 | /* | |
36 | * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the | |
37 | * builtin and module tracepoints and the hash table. | |
38 | */ | |
39 | static DEFINE_MUTEX(tracepoints_mutex); | |
40 | ||
41 | /* | |
42 | * Tracepoint hash table, containing the active tracepoints. | |
43 | * Protected by tracepoints_mutex. | |
44 | */ | |
45 | #define TRACEPOINT_HASH_BITS 6 | |
46 | #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS) | |
47 | static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE]; | |
48 | ||
49 | /* | |
50 | * Note about RCU : | |
51 | * It is used to to delay the free of multiple probes array until a quiescent | |
52 | * state is reached. | |
53 | * Tracepoint entries modifications are protected by the tracepoints_mutex. | |
54 | */ | |
55 | struct tracepoint_entry { | |
56 | struct hlist_node hlist; | |
57 | void **funcs; | |
58 | int refcount; /* Number of times armed. 0 if disarmed. */ | |
59 | char name[0]; | |
60 | }; | |
61 | ||
62 | struct tp_probes { | |
63 | union { | |
64 | struct rcu_head rcu; | |
65 | struct list_head list; | |
66 | } u; | |
67 | void *probes[0]; | |
68 | }; | |
69 | ||
70 | static inline void *allocate_probes(int count) | |
71 | { | |
72 | struct tp_probes *p = kmalloc(count * sizeof(void *) | |
73 | + sizeof(struct tp_probes), GFP_KERNEL); | |
74 | return p == NULL ? NULL : p->probes; | |
75 | } | |
76 | ||
77 | static void rcu_free_old_probes(struct rcu_head *head) | |
78 | { | |
79 | kfree(container_of(head, struct tp_probes, u.rcu)); | |
80 | } | |
81 | ||
82 | static inline void release_probes(void *old) | |
83 | { | |
84 | if (old) { | |
85 | struct tp_probes *tp_probes = container_of(old, | |
86 | struct tp_probes, probes[0]); | |
87 | call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes); | |
88 | } | |
89 | } | |
90 | ||
91 | static void debug_print_probes(struct tracepoint_entry *entry) | |
92 | { | |
93 | int i; | |
94 | ||
95 | if (!tracepoint_debug || !entry->funcs) | |
96 | return; | |
97 | ||
98 | for (i = 0; entry->funcs[i]; i++) | |
99 | printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i]); | |
100 | } | |
101 | ||
102 | static void * | |
103 | tracepoint_entry_add_probe(struct tracepoint_entry *entry, void *probe) | |
104 | { | |
105 | int nr_probes = 0; | |
106 | void **old, **new; | |
107 | ||
108 | WARN_ON(!probe); | |
109 | ||
110 | debug_print_probes(entry); | |
111 | old = entry->funcs; | |
112 | if (old) { | |
113 | /* (N -> N+1), (N != 0, 1) probes */ | |
114 | for (nr_probes = 0; old[nr_probes]; nr_probes++) | |
115 | if (old[nr_probes] == probe) | |
116 | return ERR_PTR(-EEXIST); | |
117 | } | |
118 | /* + 2 : one for new probe, one for NULL func */ | |
119 | new = allocate_probes(nr_probes + 2); | |
120 | if (new == NULL) | |
121 | return ERR_PTR(-ENOMEM); | |
122 | if (old) | |
123 | memcpy(new, old, nr_probes * sizeof(void *)); | |
124 | new[nr_probes] = probe; | |
125 | new[nr_probes + 1] = NULL; | |
126 | entry->refcount = nr_probes + 1; | |
127 | entry->funcs = new; | |
128 | debug_print_probes(entry); | |
129 | return old; | |
130 | } | |
131 | ||
132 | static void * | |
133 | tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe) | |
134 | { | |
135 | int nr_probes = 0, nr_del = 0, i; | |
136 | void **old, **new; | |
137 | ||
138 | old = entry->funcs; | |
139 | ||
140 | if (!old) | |
141 | return ERR_PTR(-ENOENT); | |
142 | ||
143 | debug_print_probes(entry); | |
144 | /* (N -> M), (N > 1, M >= 0) probes */ | |
145 | for (nr_probes = 0; old[nr_probes]; nr_probes++) { | |
146 | if ((!probe || old[nr_probes] == probe)) | |
147 | nr_del++; | |
148 | } | |
149 | ||
150 | if (nr_probes - nr_del == 0) { | |
151 | /* N -> 0, (N > 1) */ | |
152 | entry->funcs = NULL; | |
153 | entry->refcount = 0; | |
154 | debug_print_probes(entry); | |
155 | return old; | |
156 | } else { | |
157 | int j = 0; | |
158 | /* N -> M, (N > 1, M > 0) */ | |
159 | /* + 1 for NULL */ | |
160 | new = allocate_probes(nr_probes - nr_del + 1); | |
161 | if (new == NULL) | |
162 | return ERR_PTR(-ENOMEM); | |
163 | for (i = 0; old[i]; i++) | |
164 | if ((probe && old[i] != probe)) | |
165 | new[j++] = old[i]; | |
166 | new[nr_probes - nr_del] = NULL; | |
167 | entry->refcount = nr_probes - nr_del; | |
168 | entry->funcs = new; | |
169 | } | |
170 | debug_print_probes(entry); | |
171 | return old; | |
172 | } | |
173 | ||
174 | /* | |
175 | * Get tracepoint if the tracepoint is present in the tracepoint hash table. | |
176 | * Must be called with tracepoints_mutex held. | |
177 | * Returns NULL if not present. | |
178 | */ | |
179 | static struct tracepoint_entry *get_tracepoint(const char *name) | |
180 | { | |
181 | struct hlist_head *head; | |
182 | struct hlist_node *node; | |
183 | struct tracepoint_entry *e; | |
184 | u32 hash = jhash(name, strlen(name), 0); | |
185 | ||
186 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; | |
187 | hlist_for_each_entry(e, node, head, hlist) { | |
188 | if (!strcmp(name, e->name)) | |
189 | return e; | |
190 | } | |
191 | return NULL; | |
192 | } | |
193 | ||
194 | /* | |
195 | * Add the tracepoint to the tracepoint hash table. Must be called with | |
196 | * tracepoints_mutex held. | |
197 | */ | |
198 | static struct tracepoint_entry *add_tracepoint(const char *name) | |
199 | { | |
200 | struct hlist_head *head; | |
201 | struct hlist_node *node; | |
202 | struct tracepoint_entry *e; | |
203 | size_t name_len = strlen(name) + 1; | |
204 | u32 hash = jhash(name, name_len-1, 0); | |
205 | ||
206 | head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)]; | |
207 | hlist_for_each_entry(e, node, head, hlist) { | |
208 | if (!strcmp(name, e->name)) { | |
209 | printk(KERN_NOTICE | |
210 | "tracepoint %s busy\n", name); | |
211 | return ERR_PTR(-EEXIST); /* Already there */ | |
212 | } | |
213 | } | |
214 | /* | |
215 | * Using kmalloc here to allocate a variable length element. Could | |
216 | * cause some memory fragmentation if overused. | |
217 | */ | |
218 | e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL); | |
219 | if (!e) | |
220 | return ERR_PTR(-ENOMEM); | |
221 | memcpy(&e->name[0], name, name_len); | |
222 | e->funcs = NULL; | |
223 | e->refcount = 0; | |
224 | hlist_add_head(&e->hlist, head); | |
225 | return e; | |
226 | } | |
227 | ||
228 | /* | |
229 | * Remove the tracepoint from the tracepoint hash table. Must be called with | |
230 | * mutex_lock held. | |
231 | */ | |
232 | static inline void remove_tracepoint(struct tracepoint_entry *e) | |
233 | { | |
234 | hlist_del(&e->hlist); | |
235 | kfree(e); | |
236 | } | |
237 | ||
238 | /* | |
239 | * Sets the probe callback corresponding to one tracepoint. | |
240 | */ | |
241 | static void set_tracepoint(struct tracepoint_entry **entry, | |
242 | struct tracepoint *elem, int active) | |
243 | { | |
244 | WARN_ON(strcmp((*entry)->name, elem->name) != 0); | |
245 | ||
246 | /* | |
247 | * rcu_assign_pointer has a smp_wmb() which makes sure that the new | |
248 | * probe callbacks array is consistent before setting a pointer to it. | |
249 | * This array is referenced by __DO_TRACE from | |
250 | * include/linux/tracepoints.h. A matching smp_read_barrier_depends() | |
251 | * is used. | |
252 | */ | |
253 | rcu_assign_pointer(elem->funcs, (*entry)->funcs); | |
254 | elem->state__imv = active; | |
255 | } | |
256 | ||
257 | /* | |
258 | * Disable a tracepoint and its probe callback. | |
259 | * Note: only waiting an RCU period after setting elem->call to the empty | |
260 | * function insures that the original callback is not used anymore. This insured | |
261 | * by preempt_disable around the call site. | |
262 | */ | |
263 | static void disable_tracepoint(struct tracepoint *elem) | |
264 | { | |
265 | elem->state__imv = 0; | |
266 | rcu_assign_pointer(elem->funcs, NULL); | |
267 | } | |
268 | ||
269 | /** | |
270 | * tracepoint_update_probe_range - Update a probe range | |
271 | * @begin: beginning of the range | |
272 | * @end: end of the range | |
273 | * | |
274 | * Updates the probe callback corresponding to a range of tracepoints. | |
275 | */ | |
276 | void tracepoint_update_probe_range(struct tracepoint *begin, | |
277 | struct tracepoint *end) | |
278 | { | |
279 | struct tracepoint *iter; | |
280 | struct tracepoint_entry *mark_entry; | |
281 | ||
282 | mutex_lock(&tracepoints_mutex); | |
283 | for (iter = begin; iter < end; iter++) { | |
284 | mark_entry = get_tracepoint(iter->name); | |
285 | if (mark_entry) { | |
286 | set_tracepoint(&mark_entry, iter, | |
287 | !!mark_entry->refcount); | |
288 | } else { | |
289 | disable_tracepoint(iter); | |
290 | } | |
291 | } | |
292 | mutex_unlock(&tracepoints_mutex); | |
293 | } | |
294 | ||
295 | /* | |
296 | * Update probes, removing the faulty probes. | |
297 | */ | |
298 | static void tracepoint_update_probes(void) | |
299 | { | |
300 | /* Core kernel tracepoints */ | |
301 | tracepoint_update_probe_range(__start___tracepoints, | |
302 | __stop___tracepoints); | |
303 | /* tracepoints in modules. */ | |
304 | module_update_tracepoints(); | |
305 | /* Update immediate values */ | |
306 | core_imv_update(); | |
307 | module_imv_update(); | |
308 | } | |
309 | ||
310 | static void *tracepoint_add_probe(const char *name, void *probe) | |
311 | { | |
312 | struct tracepoint_entry *entry; | |
313 | void *old; | |
314 | ||
315 | entry = get_tracepoint(name); | |
316 | if (!entry) { | |
317 | entry = add_tracepoint(name); | |
318 | if (IS_ERR(entry)) | |
319 | return entry; | |
320 | } | |
321 | old = tracepoint_entry_add_probe(entry, probe); | |
322 | if (IS_ERR(old) && !entry->refcount) | |
323 | remove_tracepoint(entry); | |
324 | return old; | |
325 | } | |
326 | ||
327 | /** | |
328 | * tracepoint_probe_register - Connect a probe to a tracepoint | |
329 | * @name: tracepoint name | |
330 | * @probe: probe handler | |
331 | * | |
332 | * Returns 0 if ok, error value on error. | |
333 | * The probe address must at least be aligned on the architecture pointer size. | |
334 | */ | |
335 | int tracepoint_probe_register(const char *name, void *probe) | |
336 | { | |
337 | void *old; | |
338 | ||
339 | mutex_lock(&tracepoints_mutex); | |
340 | old = tracepoint_add_probe(name, probe); | |
341 | mutex_unlock(&tracepoints_mutex); | |
342 | if (IS_ERR(old)) | |
343 | return PTR_ERR(old); | |
344 | ||
345 | tracepoint_update_probes(); /* may update entry */ | |
346 | release_probes(old); | |
347 | return 0; | |
348 | } | |
349 | EXPORT_SYMBOL_GPL(tracepoint_probe_register); | |
350 | ||
351 | static void *tracepoint_remove_probe(const char *name, void *probe) | |
352 | { | |
353 | struct tracepoint_entry *entry; | |
354 | void *old; | |
355 | ||
356 | entry = get_tracepoint(name); | |
357 | if (!entry) | |
358 | return ERR_PTR(-ENOENT); | |
359 | old = tracepoint_entry_remove_probe(entry, probe); | |
360 | if (IS_ERR(old)) | |
361 | return old; | |
362 | if (!entry->refcount) | |
363 | remove_tracepoint(entry); | |
364 | return old; | |
365 | } | |
366 | ||
367 | /** | |
368 | * tracepoint_probe_unregister - Disconnect a probe from a tracepoint | |
369 | * @name: tracepoint name | |
370 | * @probe: probe function pointer | |
371 | * | |
372 | * We do not need to call a synchronize_sched to make sure the probes have | |
373 | * finished running before doing a module unload, because the module unload | |
374 | * itself uses stop_machine(), which insures that every preempt disabled section | |
375 | * have finished. | |
376 | */ | |
377 | int tracepoint_probe_unregister(const char *name, void *probe) | |
378 | { | |
379 | void *old; | |
380 | ||
381 | mutex_lock(&tracepoints_mutex); | |
382 | old = tracepoint_remove_probe(name, probe); | |
383 | mutex_unlock(&tracepoints_mutex); | |
384 | if (IS_ERR(old)) | |
385 | return PTR_ERR(old); | |
386 | ||
387 | tracepoint_update_probes(); /* may update entry */ | |
388 | release_probes(old); | |
389 | return 0; | |
390 | } | |
391 | EXPORT_SYMBOL_GPL(tracepoint_probe_unregister); | |
392 | ||
393 | static LIST_HEAD(old_probes); | |
394 | static int need_update; | |
395 | ||
396 | static void tracepoint_add_old_probes(void *old) | |
397 | { | |
398 | need_update = 1; | |
399 | if (old) { | |
400 | struct tp_probes *tp_probes = container_of(old, | |
401 | struct tp_probes, probes[0]); | |
402 | list_add(&tp_probes->u.list, &old_probes); | |
403 | } | |
404 | } | |
405 | ||
406 | /** | |
407 | * tracepoint_probe_register_noupdate - register a probe but not connect | |
408 | * @name: tracepoint name | |
409 | * @probe: probe handler | |
410 | * | |
411 | * caller must call tracepoint_probe_update_all() | |
412 | */ | |
413 | int tracepoint_probe_register_noupdate(const char *name, void *probe) | |
414 | { | |
415 | void *old; | |
416 | ||
417 | mutex_lock(&tracepoints_mutex); | |
418 | old = tracepoint_add_probe(name, probe); | |
419 | if (IS_ERR(old)) { | |
420 | mutex_unlock(&tracepoints_mutex); | |
421 | return PTR_ERR(old); | |
422 | } | |
423 | tracepoint_add_old_probes(old); | |
424 | mutex_unlock(&tracepoints_mutex); | |
425 | return 0; | |
426 | } | |
427 | EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate); | |
428 | ||
429 | /** | |
430 | * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect | |
431 | * @name: tracepoint name | |
432 | * @probe: probe function pointer | |
433 | * | |
434 | * caller must call tracepoint_probe_update_all() | |
435 | */ | |
436 | int tracepoint_probe_unregister_noupdate(const char *name, void *probe) | |
437 | { | |
438 | void *old; | |
439 | ||
440 | mutex_lock(&tracepoints_mutex); | |
441 | old = tracepoint_remove_probe(name, probe); | |
442 | if (IS_ERR(old)) { | |
443 | mutex_unlock(&tracepoints_mutex); | |
444 | return PTR_ERR(old); | |
445 | } | |
446 | tracepoint_add_old_probes(old); | |
447 | mutex_unlock(&tracepoints_mutex); | |
448 | return 0; | |
449 | } | |
450 | EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate); | |
451 | ||
452 | /** | |
453 | * tracepoint_probe_update_all - update tracepoints | |
454 | */ | |
455 | void tracepoint_probe_update_all(void) | |
456 | { | |
457 | LIST_HEAD(release_probes); | |
458 | struct tp_probes *pos, *next; | |
459 | ||
460 | mutex_lock(&tracepoints_mutex); | |
461 | if (!need_update) { | |
462 | mutex_unlock(&tracepoints_mutex); | |
463 | return; | |
464 | } | |
465 | if (!list_empty(&old_probes)) | |
466 | list_replace_init(&old_probes, &release_probes); | |
467 | need_update = 0; | |
468 | mutex_unlock(&tracepoints_mutex); | |
469 | ||
470 | tracepoint_update_probes(); | |
471 | list_for_each_entry_safe(pos, next, &release_probes, u.list) { | |
472 | list_del(&pos->u.list); | |
473 | call_rcu_sched(&pos->u.rcu, rcu_free_old_probes); | |
474 | } | |
475 | } | |
476 | EXPORT_SYMBOL_GPL(tracepoint_probe_update_all); | |
477 | ||
478 | /** | |
479 | * tracepoint_get_iter_range - Get a next tracepoint iterator given a range. | |
480 | * @tracepoint: current tracepoints (in), next tracepoint (out) | |
481 | * @begin: beginning of the range | |
482 | * @end: end of the range | |
483 | * | |
484 | * Returns whether a next tracepoint has been found (1) or not (0). | |
485 | * Will return the first tracepoint in the range if the input tracepoint is | |
486 | * NULL. | |
487 | */ | |
488 | int tracepoint_get_iter_range(struct tracepoint **tracepoint, | |
489 | struct tracepoint *begin, struct tracepoint *end) | |
490 | { | |
491 | if (!*tracepoint && begin != end) { | |
492 | *tracepoint = begin; | |
493 | return 1; | |
494 | } | |
495 | if (*tracepoint >= begin && *tracepoint < end) | |
496 | return 1; | |
497 | return 0; | |
498 | } | |
499 | EXPORT_SYMBOL_GPL(tracepoint_get_iter_range); | |
500 | ||
501 | static void tracepoint_get_iter(struct tracepoint_iter *iter) | |
502 | { | |
503 | int found = 0; | |
504 | ||
505 | /* Core kernel tracepoints */ | |
506 | if (!iter->module) { | |
507 | found = tracepoint_get_iter_range(&iter->tracepoint, | |
508 | __start___tracepoints, __stop___tracepoints); | |
509 | if (found) | |
510 | goto end; | |
511 | } | |
512 | /* tracepoints in modules. */ | |
513 | found = module_get_iter_tracepoints(iter); | |
514 | end: | |
515 | if (!found) | |
516 | tracepoint_iter_reset(iter); | |
517 | } | |
518 | ||
519 | void tracepoint_iter_start(struct tracepoint_iter *iter) | |
520 | { | |
521 | tracepoint_get_iter(iter); | |
522 | } | |
523 | EXPORT_SYMBOL_GPL(tracepoint_iter_start); | |
524 | ||
525 | void tracepoint_iter_next(struct tracepoint_iter *iter) | |
526 | { | |
527 | iter->tracepoint++; | |
528 | /* | |
529 | * iter->tracepoint may be invalid because we blindly incremented it. | |
530 | * Make sure it is valid by marshalling on the tracepoints, getting the | |
531 | * tracepoints from following modules if necessary. | |
532 | */ | |
533 | tracepoint_get_iter(iter); | |
534 | } | |
535 | EXPORT_SYMBOL_GPL(tracepoint_iter_next); | |
536 | ||
537 | void tracepoint_iter_stop(struct tracepoint_iter *iter) | |
538 | { | |
539 | } | |
540 | EXPORT_SYMBOL_GPL(tracepoint_iter_stop); | |
541 | ||
542 | void tracepoint_iter_reset(struct tracepoint_iter *iter) | |
543 | { | |
544 | iter->module = NULL; | |
545 | iter->tracepoint = NULL; | |
546 | } | |
547 | EXPORT_SYMBOL_GPL(tracepoint_iter_reset); | |
548 | ||
549 | #ifdef CONFIG_MODULES | |
550 | ||
551 | int tracepoint_module_notify(struct notifier_block *self, | |
552 | unsigned long val, void *data) | |
553 | { | |
554 | struct module *mod = data; | |
555 | ||
556 | switch (val) { | |
557 | case MODULE_STATE_COMING: | |
558 | tracepoint_update_probe_range(mod->tracepoints, | |
559 | mod->tracepoints + mod->num_tracepoints); | |
560 | break; | |
561 | case MODULE_STATE_GOING: | |
562 | tracepoint_update_probe_range(mod->tracepoints, | |
563 | mod->tracepoints + mod->num_tracepoints); | |
564 | break; | |
565 | } | |
566 | return 0; | |
567 | } | |
568 | ||
569 | struct notifier_block tracepoint_module_nb = { | |
570 | .notifier_call = tracepoint_module_notify, | |
571 | .priority = 0, | |
572 | }; | |
573 | ||
574 | static int init_tracepoints(void) | |
575 | { | |
576 | return register_module_notifier(&tracepoint_module_nb); | |
577 | } | |
578 | __initcall(init_tracepoints); | |
579 | ||
580 | #endif /* CONFIG_MODULES */ |