]> git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - kernel/tracepoint.c
signals: annotate lock context change on ptrace_stop()
[mirror_ubuntu-artful-kernel.git] / kernel / tracepoint.c
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/sched.h>
28 #include <linux/jump_label.h>
29
30 extern struct tracepoint __start___tracepoints[];
31 extern struct tracepoint __stop___tracepoints[];
32
33 /* Set to 1 to enable tracepoint debug output */
34 static const int tracepoint_debug;
35
36 /*
37 * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
38 * builtin and module tracepoints and the hash table.
39 */
40 static DEFINE_MUTEX(tracepoints_mutex);
41
42 /*
43 * Tracepoint hash table, containing the active tracepoints.
44 * Protected by tracepoints_mutex.
45 */
46 #define TRACEPOINT_HASH_BITS 6
47 #define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
48 static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
49
50 /*
51 * Note about RCU :
52 * It is used to delay the free of multiple probes array until a quiescent
53 * state is reached.
54 * Tracepoint entries modifications are protected by the tracepoints_mutex.
55 */
56 struct tracepoint_entry {
57 struct hlist_node hlist;
58 struct tracepoint_func *funcs;
59 int refcount; /* Number of times armed. 0 if disarmed. */
60 char name[0];
61 };
62
63 struct tp_probes {
64 union {
65 struct rcu_head rcu;
66 struct list_head list;
67 } u;
68 struct tracepoint_func probes[0];
69 };
70
71 static inline void *allocate_probes(int count)
72 {
73 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
74 + sizeof(struct tp_probes), GFP_KERNEL);
75 return p == NULL ? NULL : p->probes;
76 }
77
78 static void rcu_free_old_probes(struct rcu_head *head)
79 {
80 kfree(container_of(head, struct tp_probes, u.rcu));
81 }
82
83 static inline void release_probes(struct tracepoint_func *old)
84 {
85 if (old) {
86 struct tp_probes *tp_probes = container_of(old,
87 struct tp_probes, probes[0]);
88 call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
89 }
90 }
91
92 static void debug_print_probes(struct tracepoint_entry *entry)
93 {
94 int i;
95
96 if (!tracepoint_debug || !entry->funcs)
97 return;
98
99 for (i = 0; entry->funcs[i].func; i++)
100 printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
101 }
102
103 static struct tracepoint_func *
104 tracepoint_entry_add_probe(struct tracepoint_entry *entry,
105 void *probe, void *data)
106 {
107 int nr_probes = 0;
108 struct tracepoint_func *old, *new;
109
110 WARN_ON(!probe);
111
112 debug_print_probes(entry);
113 old = entry->funcs;
114 if (old) {
115 /* (N -> N+1), (N != 0, 1) probes */
116 for (nr_probes = 0; old[nr_probes].func; nr_probes++)
117 if (old[nr_probes].func == probe &&
118 old[nr_probes].data == data)
119 return ERR_PTR(-EEXIST);
120 }
121 /* + 2 : one for new probe, one for NULL func */
122 new = allocate_probes(nr_probes + 2);
123 if (new == NULL)
124 return ERR_PTR(-ENOMEM);
125 if (old)
126 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
127 new[nr_probes].func = probe;
128 new[nr_probes].data = data;
129 new[nr_probes + 1].func = NULL;
130 entry->refcount = nr_probes + 1;
131 entry->funcs = new;
132 debug_print_probes(entry);
133 return old;
134 }
135
136 static void *
137 tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
138 void *probe, void *data)
139 {
140 int nr_probes = 0, nr_del = 0, i;
141 struct tracepoint_func *old, *new;
142
143 old = entry->funcs;
144
145 if (!old)
146 return ERR_PTR(-ENOENT);
147
148 debug_print_probes(entry);
149 /* (N -> M), (N > 1, M >= 0) probes */
150 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
151 if (!probe ||
152 (old[nr_probes].func == probe &&
153 old[nr_probes].data == data))
154 nr_del++;
155 }
156
157 if (nr_probes - nr_del == 0) {
158 /* N -> 0, (N > 1) */
159 entry->funcs = NULL;
160 entry->refcount = 0;
161 debug_print_probes(entry);
162 return old;
163 } else {
164 int j = 0;
165 /* N -> M, (N > 1, M > 0) */
166 /* + 1 for NULL */
167 new = allocate_probes(nr_probes - nr_del + 1);
168 if (new == NULL)
169 return ERR_PTR(-ENOMEM);
170 for (i = 0; old[i].func; i++)
171 if (probe &&
172 (old[i].func != probe || old[i].data != data))
173 new[j++] = old[i];
174 new[nr_probes - nr_del].func = NULL;
175 entry->refcount = nr_probes - nr_del;
176 entry->funcs = new;
177 }
178 debug_print_probes(entry);
179 return old;
180 }
181
182 /*
183 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
184 * Must be called with tracepoints_mutex held.
185 * Returns NULL if not present.
186 */
187 static struct tracepoint_entry *get_tracepoint(const char *name)
188 {
189 struct hlist_head *head;
190 struct hlist_node *node;
191 struct tracepoint_entry *e;
192 u32 hash = jhash(name, strlen(name), 0);
193
194 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
195 hlist_for_each_entry(e, node, head, hlist) {
196 if (!strcmp(name, e->name))
197 return e;
198 }
199 return NULL;
200 }
201
202 /*
203 * Add the tracepoint to the tracepoint hash table. Must be called with
204 * tracepoints_mutex held.
205 */
206 static struct tracepoint_entry *add_tracepoint(const char *name)
207 {
208 struct hlist_head *head;
209 struct hlist_node *node;
210 struct tracepoint_entry *e;
211 size_t name_len = strlen(name) + 1;
212 u32 hash = jhash(name, name_len-1, 0);
213
214 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
215 hlist_for_each_entry(e, node, head, hlist) {
216 if (!strcmp(name, e->name)) {
217 printk(KERN_NOTICE
218 "tracepoint %s busy\n", name);
219 return ERR_PTR(-EEXIST); /* Already there */
220 }
221 }
222 /*
223 * Using kmalloc here to allocate a variable length element. Could
224 * cause some memory fragmentation if overused.
225 */
226 e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
227 if (!e)
228 return ERR_PTR(-ENOMEM);
229 memcpy(&e->name[0], name, name_len);
230 e->funcs = NULL;
231 e->refcount = 0;
232 hlist_add_head(&e->hlist, head);
233 return e;
234 }
235
236 /*
237 * Remove the tracepoint from the tracepoint hash table. Must be called with
238 * mutex_lock held.
239 */
240 static inline void remove_tracepoint(struct tracepoint_entry *e)
241 {
242 hlist_del(&e->hlist);
243 kfree(e);
244 }
245
246 /*
247 * Sets the probe callback corresponding to one tracepoint.
248 */
249 static void set_tracepoint(struct tracepoint_entry **entry,
250 struct tracepoint *elem, int active)
251 {
252 WARN_ON(strcmp((*entry)->name, elem->name) != 0);
253
254 if (elem->regfunc && !elem->state && active)
255 elem->regfunc();
256 else if (elem->unregfunc && elem->state && !active)
257 elem->unregfunc();
258
259 /*
260 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
261 * probe callbacks array is consistent before setting a pointer to it.
262 * This array is referenced by __DO_TRACE from
263 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
264 * is used.
265 */
266 rcu_assign_pointer(elem->funcs, (*entry)->funcs);
267 if (!elem->state && active) {
268 jump_label_enable(&elem->state);
269 elem->state = active;
270 } else if (elem->state && !active) {
271 jump_label_disable(&elem->state);
272 elem->state = active;
273 }
274 }
275
276 /*
277 * Disable a tracepoint and its probe callback.
278 * Note: only waiting an RCU period after setting elem->call to the empty
279 * function insures that the original callback is not used anymore. This insured
280 * by preempt_disable around the call site.
281 */
282 static void disable_tracepoint(struct tracepoint *elem)
283 {
284 if (elem->unregfunc && elem->state)
285 elem->unregfunc();
286
287 if (elem->state) {
288 jump_label_disable(&elem->state);
289 elem->state = 0;
290 }
291 rcu_assign_pointer(elem->funcs, NULL);
292 }
293
294 /**
295 * tracepoint_update_probe_range - Update a probe range
296 * @begin: beginning of the range
297 * @end: end of the range
298 *
299 * Updates the probe callback corresponding to a range of tracepoints.
300 */
301 void
302 tracepoint_update_probe_range(struct tracepoint *begin, struct tracepoint *end)
303 {
304 struct tracepoint *iter;
305 struct tracepoint_entry *mark_entry;
306
307 if (!begin)
308 return;
309
310 mutex_lock(&tracepoints_mutex);
311 for (iter = begin; iter < end; iter++) {
312 mark_entry = get_tracepoint(iter->name);
313 if (mark_entry) {
314 set_tracepoint(&mark_entry, iter,
315 !!mark_entry->refcount);
316 } else {
317 disable_tracepoint(iter);
318 }
319 }
320 mutex_unlock(&tracepoints_mutex);
321 }
322
323 /*
324 * Update probes, removing the faulty probes.
325 */
326 static void tracepoint_update_probes(void)
327 {
328 /* Core kernel tracepoints */
329 tracepoint_update_probe_range(__start___tracepoints,
330 __stop___tracepoints);
331 /* tracepoints in modules. */
332 module_update_tracepoints();
333 }
334
335 static struct tracepoint_func *
336 tracepoint_add_probe(const char *name, void *probe, void *data)
337 {
338 struct tracepoint_entry *entry;
339 struct tracepoint_func *old;
340
341 entry = get_tracepoint(name);
342 if (!entry) {
343 entry = add_tracepoint(name);
344 if (IS_ERR(entry))
345 return (struct tracepoint_func *)entry;
346 }
347 old = tracepoint_entry_add_probe(entry, probe, data);
348 if (IS_ERR(old) && !entry->refcount)
349 remove_tracepoint(entry);
350 return old;
351 }
352
353 /**
354 * tracepoint_probe_register - Connect a probe to a tracepoint
355 * @name: tracepoint name
356 * @probe: probe handler
357 *
358 * Returns 0 if ok, error value on error.
359 * The probe address must at least be aligned on the architecture pointer size.
360 */
361 int tracepoint_probe_register(const char *name, void *probe, void *data)
362 {
363 struct tracepoint_func *old;
364
365 mutex_lock(&tracepoints_mutex);
366 old = tracepoint_add_probe(name, probe, data);
367 mutex_unlock(&tracepoints_mutex);
368 if (IS_ERR(old))
369 return PTR_ERR(old);
370
371 tracepoint_update_probes(); /* may update entry */
372 release_probes(old);
373 return 0;
374 }
375 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
376
377 static struct tracepoint_func *
378 tracepoint_remove_probe(const char *name, void *probe, void *data)
379 {
380 struct tracepoint_entry *entry;
381 struct tracepoint_func *old;
382
383 entry = get_tracepoint(name);
384 if (!entry)
385 return ERR_PTR(-ENOENT);
386 old = tracepoint_entry_remove_probe(entry, probe, data);
387 if (IS_ERR(old))
388 return old;
389 if (!entry->refcount)
390 remove_tracepoint(entry);
391 return old;
392 }
393
394 /**
395 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
396 * @name: tracepoint name
397 * @probe: probe function pointer
398 *
399 * We do not need to call a synchronize_sched to make sure the probes have
400 * finished running before doing a module unload, because the module unload
401 * itself uses stop_machine(), which insures that every preempt disabled section
402 * have finished.
403 */
404 int tracepoint_probe_unregister(const char *name, void *probe, void *data)
405 {
406 struct tracepoint_func *old;
407
408 mutex_lock(&tracepoints_mutex);
409 old = tracepoint_remove_probe(name, probe, data);
410 mutex_unlock(&tracepoints_mutex);
411 if (IS_ERR(old))
412 return PTR_ERR(old);
413
414 tracepoint_update_probes(); /* may update entry */
415 release_probes(old);
416 return 0;
417 }
418 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
419
420 static LIST_HEAD(old_probes);
421 static int need_update;
422
423 static void tracepoint_add_old_probes(void *old)
424 {
425 need_update = 1;
426 if (old) {
427 struct tp_probes *tp_probes = container_of(old,
428 struct tp_probes, probes[0]);
429 list_add(&tp_probes->u.list, &old_probes);
430 }
431 }
432
433 /**
434 * tracepoint_probe_register_noupdate - register a probe but not connect
435 * @name: tracepoint name
436 * @probe: probe handler
437 *
438 * caller must call tracepoint_probe_update_all()
439 */
440 int tracepoint_probe_register_noupdate(const char *name, void *probe,
441 void *data)
442 {
443 struct tracepoint_func *old;
444
445 mutex_lock(&tracepoints_mutex);
446 old = tracepoint_add_probe(name, probe, data);
447 if (IS_ERR(old)) {
448 mutex_unlock(&tracepoints_mutex);
449 return PTR_ERR(old);
450 }
451 tracepoint_add_old_probes(old);
452 mutex_unlock(&tracepoints_mutex);
453 return 0;
454 }
455 EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
456
457 /**
458 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
459 * @name: tracepoint name
460 * @probe: probe function pointer
461 *
462 * caller must call tracepoint_probe_update_all()
463 */
464 int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
465 void *data)
466 {
467 struct tracepoint_func *old;
468
469 mutex_lock(&tracepoints_mutex);
470 old = tracepoint_remove_probe(name, probe, data);
471 if (IS_ERR(old)) {
472 mutex_unlock(&tracepoints_mutex);
473 return PTR_ERR(old);
474 }
475 tracepoint_add_old_probes(old);
476 mutex_unlock(&tracepoints_mutex);
477 return 0;
478 }
479 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
480
481 /**
482 * tracepoint_probe_update_all - update tracepoints
483 */
484 void tracepoint_probe_update_all(void)
485 {
486 LIST_HEAD(release_probes);
487 struct tp_probes *pos, *next;
488
489 mutex_lock(&tracepoints_mutex);
490 if (!need_update) {
491 mutex_unlock(&tracepoints_mutex);
492 return;
493 }
494 if (!list_empty(&old_probes))
495 list_replace_init(&old_probes, &release_probes);
496 need_update = 0;
497 mutex_unlock(&tracepoints_mutex);
498
499 tracepoint_update_probes();
500 list_for_each_entry_safe(pos, next, &release_probes, u.list) {
501 list_del(&pos->u.list);
502 call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
503 }
504 }
505 EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
506
507 /**
508 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
509 * @tracepoint: current tracepoints (in), next tracepoint (out)
510 * @begin: beginning of the range
511 * @end: end of the range
512 *
513 * Returns whether a next tracepoint has been found (1) or not (0).
514 * Will return the first tracepoint in the range if the input tracepoint is
515 * NULL.
516 */
517 int tracepoint_get_iter_range(struct tracepoint **tracepoint,
518 struct tracepoint *begin, struct tracepoint *end)
519 {
520 if (!*tracepoint && begin != end) {
521 *tracepoint = begin;
522 return 1;
523 }
524 if (*tracepoint >= begin && *tracepoint < end)
525 return 1;
526 return 0;
527 }
528 EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
529
530 static void tracepoint_get_iter(struct tracepoint_iter *iter)
531 {
532 int found = 0;
533
534 /* Core kernel tracepoints */
535 if (!iter->module) {
536 found = tracepoint_get_iter_range(&iter->tracepoint,
537 __start___tracepoints, __stop___tracepoints);
538 if (found)
539 goto end;
540 }
541 /* tracepoints in modules. */
542 found = module_get_iter_tracepoints(iter);
543 end:
544 if (!found)
545 tracepoint_iter_reset(iter);
546 }
547
548 void tracepoint_iter_start(struct tracepoint_iter *iter)
549 {
550 tracepoint_get_iter(iter);
551 }
552 EXPORT_SYMBOL_GPL(tracepoint_iter_start);
553
554 void tracepoint_iter_next(struct tracepoint_iter *iter)
555 {
556 iter->tracepoint++;
557 /*
558 * iter->tracepoint may be invalid because we blindly incremented it.
559 * Make sure it is valid by marshalling on the tracepoints, getting the
560 * tracepoints from following modules if necessary.
561 */
562 tracepoint_get_iter(iter);
563 }
564 EXPORT_SYMBOL_GPL(tracepoint_iter_next);
565
566 void tracepoint_iter_stop(struct tracepoint_iter *iter)
567 {
568 }
569 EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
570
571 void tracepoint_iter_reset(struct tracepoint_iter *iter)
572 {
573 iter->module = NULL;
574 iter->tracepoint = NULL;
575 }
576 EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
577
578 #ifdef CONFIG_MODULES
579
580 int tracepoint_module_notify(struct notifier_block *self,
581 unsigned long val, void *data)
582 {
583 struct module *mod = data;
584
585 switch (val) {
586 case MODULE_STATE_COMING:
587 case MODULE_STATE_GOING:
588 tracepoint_update_probe_range(mod->tracepoints,
589 mod->tracepoints + mod->num_tracepoints);
590 break;
591 }
592 return 0;
593 }
594
595 struct notifier_block tracepoint_module_nb = {
596 .notifier_call = tracepoint_module_notify,
597 .priority = 0,
598 };
599
600 static int init_tracepoints(void)
601 {
602 return register_module_notifier(&tracepoint_module_nb);
603 }
604 __initcall(init_tracepoints);
605
606 #endif /* CONFIG_MODULES */
607
608 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
609
610 /* NB: reg/unreg are called while guarded with the tracepoints_mutex */
611 static int sys_tracepoint_refcount;
612
613 void syscall_regfunc(void)
614 {
615 unsigned long flags;
616 struct task_struct *g, *t;
617
618 if (!sys_tracepoint_refcount) {
619 read_lock_irqsave(&tasklist_lock, flags);
620 do_each_thread(g, t) {
621 /* Skip kernel threads. */
622 if (t->mm)
623 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
624 } while_each_thread(g, t);
625 read_unlock_irqrestore(&tasklist_lock, flags);
626 }
627 sys_tracepoint_refcount++;
628 }
629
630 void syscall_unregfunc(void)
631 {
632 unsigned long flags;
633 struct task_struct *g, *t;
634
635 sys_tracepoint_refcount--;
636 if (!sys_tracepoint_refcount) {
637 read_lock_irqsave(&tasklist_lock, flags);
638 do_each_thread(g, t) {
639 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
640 } while_each_thread(g, t);
641 read_unlock_irqrestore(&tasklist_lock, flags);
642 }
643 }
644 #endif