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Mathieu Desnoyers97e1c182008-07-18 12:16:16 -04001/*
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
28extern struct tracepoint __start___tracepoints[];
29extern struct tracepoint __stop___tracepoints[];
30
31/* Set to 1 to enable tracepoint debug output */
32static const int tracepoint_debug;
33
34/*
35 * tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
36 * builtin and module tracepoints and the hash table.
37 */
38static DEFINE_MUTEX(tracepoints_mutex);
39
40/*
41 * Tracepoint hash table, containing the active tracepoints.
42 * Protected by tracepoints_mutex.
43 */
44#define TRACEPOINT_HASH_BITS 6
45#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
Lai Jiangshan19dba332008-10-28 10:51:49 +080046static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040047
48/*
49 * Note about RCU :
50 * It is used to to delay the free of multiple probes array until a quiescent
51 * state is reached.
52 * Tracepoint entries modifications are protected by the tracepoints_mutex.
53 */
54struct tracepoint_entry {
55 struct hlist_node hlist;
56 void **funcs;
57 int refcount; /* Number of times armed. 0 if disarmed. */
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040058 char name[0];
59};
60
Lai Jiangshan19dba332008-10-28 10:51:49 +080061struct tp_probes {
Lai Jiangshan127cafb2008-10-28 10:51:53 +080062 union {
63 struct rcu_head rcu;
64 struct list_head list;
65 } u;
Lai Jiangshan19dba332008-10-28 10:51:49 +080066 void *probes[0];
67};
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040068
Lai Jiangshan19dba332008-10-28 10:51:49 +080069static inline void *allocate_probes(int count)
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040070{
Lai Jiangshan19dba332008-10-28 10:51:49 +080071 struct tp_probes *p = kmalloc(count * sizeof(void *)
72 + sizeof(struct tp_probes), GFP_KERNEL);
73 return p == NULL ? NULL : p->probes;
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040074}
75
Lai Jiangshan19dba332008-10-28 10:51:49 +080076static void rcu_free_old_probes(struct rcu_head *head)
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040077{
Lai Jiangshan127cafb2008-10-28 10:51:53 +080078 kfree(container_of(head, struct tp_probes, u.rcu));
Lai Jiangshan19dba332008-10-28 10:51:49 +080079}
80
81static inline void release_probes(void *old)
82{
83 if (old) {
84 struct tp_probes *tp_probes = container_of(old,
85 struct tp_probes, probes[0]);
Lai Jiangshan127cafb2008-10-28 10:51:53 +080086 call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
Lai Jiangshan19dba332008-10-28 10:51:49 +080087 }
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040088}
89
90static void debug_print_probes(struct tracepoint_entry *entry)
91{
92 int i;
93
Lai Jiangshan19dba332008-10-28 10:51:49 +080094 if (!tracepoint_debug || !entry->funcs)
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -040095 return;
96
97 for (i = 0; entry->funcs[i]; i++)
98 printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i]);
99}
100
101static void *
102tracepoint_entry_add_probe(struct tracepoint_entry *entry, void *probe)
103{
104 int nr_probes = 0;
105 void **old, **new;
106
107 WARN_ON(!probe);
108
109 debug_print_probes(entry);
110 old = entry->funcs;
111 if (old) {
112 /* (N -> N+1), (N != 0, 1) probes */
113 for (nr_probes = 0; old[nr_probes]; nr_probes++)
114 if (old[nr_probes] == probe)
115 return ERR_PTR(-EEXIST);
116 }
117 /* + 2 : one for new probe, one for NULL func */
Lai Jiangshan19dba332008-10-28 10:51:49 +0800118 new = allocate_probes(nr_probes + 2);
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400119 if (new == NULL)
120 return ERR_PTR(-ENOMEM);
121 if (old)
122 memcpy(new, old, nr_probes * sizeof(void *));
123 new[nr_probes] = probe;
Lai Jiangshan19dba332008-10-28 10:51:49 +0800124 new[nr_probes + 1] = NULL;
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400125 entry->refcount = nr_probes + 1;
126 entry->funcs = new;
127 debug_print_probes(entry);
128 return old;
129}
130
131static void *
132tracepoint_entry_remove_probe(struct tracepoint_entry *entry, void *probe)
133{
134 int nr_probes = 0, nr_del = 0, i;
135 void **old, **new;
136
137 old = entry->funcs;
138
Frederic Weisbeckerf66af452008-10-22 19:14:55 +0200139 if (!old)
Lai Jiangshan19dba332008-10-28 10:51:49 +0800140 return ERR_PTR(-ENOENT);
Frederic Weisbeckerf66af452008-10-22 19:14:55 +0200141
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400142 debug_print_probes(entry);
143 /* (N -> M), (N > 1, M >= 0) probes */
144 for (nr_probes = 0; old[nr_probes]; nr_probes++) {
145 if ((!probe || old[nr_probes] == probe))
146 nr_del++;
147 }
148
149 if (nr_probes - nr_del == 0) {
150 /* N -> 0, (N > 1) */
151 entry->funcs = NULL;
152 entry->refcount = 0;
153 debug_print_probes(entry);
154 return old;
155 } else {
156 int j = 0;
157 /* N -> M, (N > 1, M > 0) */
158 /* + 1 for NULL */
Lai Jiangshan19dba332008-10-28 10:51:49 +0800159 new = allocate_probes(nr_probes - nr_del + 1);
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400160 if (new == NULL)
161 return ERR_PTR(-ENOMEM);
162 for (i = 0; old[i]; i++)
163 if ((probe && old[i] != probe))
164 new[j++] = old[i];
Lai Jiangshan19dba332008-10-28 10:51:49 +0800165 new[nr_probes - nr_del] = NULL;
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400166 entry->refcount = nr_probes - nr_del;
167 entry->funcs = new;
168 }
169 debug_print_probes(entry);
170 return old;
171}
172
173/*
174 * Get tracepoint if the tracepoint is present in the tracepoint hash table.
175 * Must be called with tracepoints_mutex held.
176 * Returns NULL if not present.
177 */
178static struct tracepoint_entry *get_tracepoint(const char *name)
179{
180 struct hlist_head *head;
181 struct hlist_node *node;
182 struct tracepoint_entry *e;
183 u32 hash = jhash(name, strlen(name), 0);
184
Mathieu Desnoyers97953022008-07-24 16:37:23 -0400185 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400186 hlist_for_each_entry(e, node, head, hlist) {
187 if (!strcmp(name, e->name))
188 return e;
189 }
190 return NULL;
191}
192
193/*
194 * Add the tracepoint to the tracepoint hash table. Must be called with
195 * tracepoints_mutex held.
196 */
197static struct tracepoint_entry *add_tracepoint(const char *name)
198{
199 struct hlist_head *head;
200 struct hlist_node *node;
201 struct tracepoint_entry *e;
202 size_t name_len = strlen(name) + 1;
203 u32 hash = jhash(name, name_len-1, 0);
204
Mathieu Desnoyers97953022008-07-24 16:37:23 -0400205 head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400206 hlist_for_each_entry(e, node, head, hlist) {
207 if (!strcmp(name, e->name)) {
208 printk(KERN_NOTICE
209 "tracepoint %s busy\n", name);
210 return ERR_PTR(-EEXIST); /* Already there */
211 }
212 }
213 /*
214 * Using kmalloc here to allocate a variable length element. Could
215 * cause some memory fragmentation if overused.
216 */
217 e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
218 if (!e)
219 return ERR_PTR(-ENOMEM);
220 memcpy(&e->name[0], name, name_len);
221 e->funcs = NULL;
222 e->refcount = 0;
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400223 hlist_add_head(&e->hlist, head);
224 return e;
225}
226
227/*
228 * Remove the tracepoint from the tracepoint hash table. Must be called with
229 * mutex_lock held.
230 */
Lai Jiangshan19dba332008-10-28 10:51:49 +0800231static inline void remove_tracepoint(struct tracepoint_entry *e)
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400232{
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400233 hlist_del(&e->hlist);
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400234 kfree(e);
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400235}
236
237/*
238 * Sets the probe callback corresponding to one tracepoint.
239 */
240static void set_tracepoint(struct tracepoint_entry **entry,
241 struct tracepoint *elem, int active)
242{
243 WARN_ON(strcmp((*entry)->name, elem->name) != 0);
244
245 /*
246 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
247 * probe callbacks array is consistent before setting a pointer to it.
248 * This array is referenced by __DO_TRACE from
249 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
250 * is used.
251 */
252 rcu_assign_pointer(elem->funcs, (*entry)->funcs);
253 elem->state = active;
254}
255
256/*
257 * Disable a tracepoint and its probe callback.
258 * Note: only waiting an RCU period after setting elem->call to the empty
259 * function insures that the original callback is not used anymore. This insured
260 * by preempt_disable around the call site.
261 */
262static void disable_tracepoint(struct tracepoint *elem)
263{
264 elem->state = 0;
Mathieu Desnoyersde0baf92008-11-14 17:47:42 -0500265 rcu_assign_pointer(elem->funcs, NULL);
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400266}
267
268/**
269 * tracepoint_update_probe_range - Update a probe range
270 * @begin: beginning of the range
271 * @end: end of the range
272 *
273 * Updates the probe callback corresponding to a range of tracepoints.
274 */
Jaswinder Singh Rajput09933a12009-03-18 22:18:56 +0530275void
276tracepoint_update_probe_range(struct tracepoint *begin, struct tracepoint *end)
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400277{
278 struct tracepoint *iter;
279 struct tracepoint_entry *mark_entry;
280
Ingo Molnarec625cb2009-03-18 19:54:04 +0100281 if (!begin)
Jaswinder Singh Rajput09933a12009-03-18 22:18:56 +0530282 return;
Jaswinder Singh Rajput09933a12009-03-18 22:18:56 +0530283
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400284 mutex_lock(&tracepoints_mutex);
285 for (iter = begin; iter < end; iter++) {
286 mark_entry = get_tracepoint(iter->name);
287 if (mark_entry) {
288 set_tracepoint(&mark_entry, iter,
289 !!mark_entry->refcount);
290 } else {
291 disable_tracepoint(iter);
292 }
293 }
294 mutex_unlock(&tracepoints_mutex);
295}
296
297/*
298 * Update probes, removing the faulty probes.
299 */
300static void tracepoint_update_probes(void)
301{
302 /* Core kernel tracepoints */
303 tracepoint_update_probe_range(__start___tracepoints,
304 __stop___tracepoints);
305 /* tracepoints in modules. */
306 module_update_tracepoints();
307}
308
Lai Jiangshan127cafb2008-10-28 10:51:53 +0800309static void *tracepoint_add_probe(const char *name, void *probe)
310{
311 struct tracepoint_entry *entry;
312 void *old;
313
314 entry = get_tracepoint(name);
315 if (!entry) {
316 entry = add_tracepoint(name);
317 if (IS_ERR(entry))
318 return entry;
319 }
320 old = tracepoint_entry_add_probe(entry, probe);
321 if (IS_ERR(old) && !entry->refcount)
322 remove_tracepoint(entry);
323 return old;
324}
325
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400326/**
327 * tracepoint_probe_register - Connect a probe to a tracepoint
328 * @name: tracepoint name
329 * @probe: probe handler
330 *
331 * Returns 0 if ok, error value on error.
332 * The probe address must at least be aligned on the architecture pointer size.
333 */
334int tracepoint_probe_register(const char *name, void *probe)
335{
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400336 void *old;
337
338 mutex_lock(&tracepoints_mutex);
Lai Jiangshan127cafb2008-10-28 10:51:53 +0800339 old = tracepoint_add_probe(name, probe);
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400340 mutex_unlock(&tracepoints_mutex);
Lai Jiangshan127cafb2008-10-28 10:51:53 +0800341 if (IS_ERR(old))
342 return PTR_ERR(old);
343
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400344 tracepoint_update_probes(); /* may update entry */
Lai Jiangshan19dba332008-10-28 10:51:49 +0800345 release_probes(old);
346 return 0;
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400347}
348EXPORT_SYMBOL_GPL(tracepoint_probe_register);
349
Lai Jiangshan127cafb2008-10-28 10:51:53 +0800350static void *tracepoint_remove_probe(const char *name, void *probe)
351{
352 struct tracepoint_entry *entry;
353 void *old;
354
355 entry = get_tracepoint(name);
356 if (!entry)
357 return ERR_PTR(-ENOENT);
358 old = tracepoint_entry_remove_probe(entry, probe);
359 if (IS_ERR(old))
360 return old;
361 if (!entry->refcount)
362 remove_tracepoint(entry);
363 return old;
364}
365
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400366/**
367 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
368 * @name: tracepoint name
369 * @probe: probe function pointer
370 *
371 * We do not need to call a synchronize_sched to make sure the probes have
372 * finished running before doing a module unload, because the module unload
373 * itself uses stop_machine(), which insures that every preempt disabled section
374 * have finished.
375 */
376int tracepoint_probe_unregister(const char *name, void *probe)
377{
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400378 void *old;
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400379
380 mutex_lock(&tracepoints_mutex);
Lai Jiangshan127cafb2008-10-28 10:51:53 +0800381 old = tracepoint_remove_probe(name, probe);
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400382 mutex_unlock(&tracepoints_mutex);
Lai Jiangshan127cafb2008-10-28 10:51:53 +0800383 if (IS_ERR(old))
384 return PTR_ERR(old);
385
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400386 tracepoint_update_probes(); /* may update entry */
Lai Jiangshan19dba332008-10-28 10:51:49 +0800387 release_probes(old);
388 return 0;
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400389}
390EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
391
Lai Jiangshan127cafb2008-10-28 10:51:53 +0800392static LIST_HEAD(old_probes);
393static int need_update;
394
395static void tracepoint_add_old_probes(void *old)
396{
397 need_update = 1;
398 if (old) {
399 struct tp_probes *tp_probes = container_of(old,
400 struct tp_probes, probes[0]);
401 list_add(&tp_probes->u.list, &old_probes);
402 }
403}
404
405/**
406 * tracepoint_probe_register_noupdate - register a probe but not connect
407 * @name: tracepoint name
408 * @probe: probe handler
409 *
410 * caller must call tracepoint_probe_update_all()
411 */
412int tracepoint_probe_register_noupdate(const char *name, void *probe)
413{
414 void *old;
415
416 mutex_lock(&tracepoints_mutex);
417 old = tracepoint_add_probe(name, probe);
418 if (IS_ERR(old)) {
419 mutex_unlock(&tracepoints_mutex);
420 return PTR_ERR(old);
421 }
422 tracepoint_add_old_probes(old);
423 mutex_unlock(&tracepoints_mutex);
424 return 0;
425}
426EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
427
428/**
429 * tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
430 * @name: tracepoint name
431 * @probe: probe function pointer
432 *
433 * caller must call tracepoint_probe_update_all()
434 */
435int tracepoint_probe_unregister_noupdate(const char *name, void *probe)
436{
437 void *old;
438
439 mutex_lock(&tracepoints_mutex);
440 old = tracepoint_remove_probe(name, probe);
441 if (IS_ERR(old)) {
442 mutex_unlock(&tracepoints_mutex);
443 return PTR_ERR(old);
444 }
445 tracepoint_add_old_probes(old);
446 mutex_unlock(&tracepoints_mutex);
447 return 0;
448}
449EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
450
451/**
452 * tracepoint_probe_update_all - update tracepoints
453 */
454void tracepoint_probe_update_all(void)
455{
456 LIST_HEAD(release_probes);
457 struct tp_probes *pos, *next;
458
459 mutex_lock(&tracepoints_mutex);
460 if (!need_update) {
461 mutex_unlock(&tracepoints_mutex);
462 return;
463 }
464 if (!list_empty(&old_probes))
465 list_replace_init(&old_probes, &release_probes);
466 need_update = 0;
467 mutex_unlock(&tracepoints_mutex);
468
469 tracepoint_update_probes();
470 list_for_each_entry_safe(pos, next, &release_probes, u.list) {
471 list_del(&pos->u.list);
472 call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
473 }
474}
475EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
476
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400477/**
478 * tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
479 * @tracepoint: current tracepoints (in), next tracepoint (out)
480 * @begin: beginning of the range
481 * @end: end of the range
482 *
483 * Returns whether a next tracepoint has been found (1) or not (0).
484 * Will return the first tracepoint in the range if the input tracepoint is
485 * NULL.
486 */
487int tracepoint_get_iter_range(struct tracepoint **tracepoint,
488 struct tracepoint *begin, struct tracepoint *end)
489{
490 if (!*tracepoint && begin != end) {
491 *tracepoint = begin;
492 return 1;
493 }
494 if (*tracepoint >= begin && *tracepoint < end)
495 return 1;
496 return 0;
497}
498EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
499
500static void tracepoint_get_iter(struct tracepoint_iter *iter)
501{
502 int found = 0;
503
504 /* Core kernel tracepoints */
505 if (!iter->module) {
506 found = tracepoint_get_iter_range(&iter->tracepoint,
507 __start___tracepoints, __stop___tracepoints);
508 if (found)
509 goto end;
510 }
511 /* tracepoints in modules. */
512 found = module_get_iter_tracepoints(iter);
513end:
514 if (!found)
515 tracepoint_iter_reset(iter);
516}
517
518void tracepoint_iter_start(struct tracepoint_iter *iter)
519{
520 tracepoint_get_iter(iter);
521}
522EXPORT_SYMBOL_GPL(tracepoint_iter_start);
523
524void tracepoint_iter_next(struct tracepoint_iter *iter)
525{
526 iter->tracepoint++;
527 /*
528 * iter->tracepoint may be invalid because we blindly incremented it.
529 * Make sure it is valid by marshalling on the tracepoints, getting the
530 * tracepoints from following modules if necessary.
531 */
532 tracepoint_get_iter(iter);
533}
534EXPORT_SYMBOL_GPL(tracepoint_iter_next);
535
536void tracepoint_iter_stop(struct tracepoint_iter *iter)
537{
538}
539EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
540
541void tracepoint_iter_reset(struct tracepoint_iter *iter)
542{
543 iter->module = NULL;
544 iter->tracepoint = NULL;
545}
546EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
Mathieu Desnoyers32f85742008-11-14 17:47:46 -0500547
Ingo Molnar227a8372008-11-16 09:50:34 +0100548#ifdef CONFIG_MODULES
549
Mathieu Desnoyers32f85742008-11-14 17:47:46 -0500550int tracepoint_module_notify(struct notifier_block *self,
551 unsigned long val, void *data)
552{
553 struct module *mod = data;
554
555 switch (val) {
556 case MODULE_STATE_COMING:
557 tracepoint_update_probe_range(mod->tracepoints,
558 mod->tracepoints + mod->num_tracepoints);
559 break;
560 case MODULE_STATE_GOING:
561 tracepoint_update_probe_range(mod->tracepoints,
562 mod->tracepoints + mod->num_tracepoints);
563 break;
564 }
565 return 0;
566}
567
568struct notifier_block tracepoint_module_nb = {
569 .notifier_call = tracepoint_module_notify,
570 .priority = 0,
571};
572
573static int init_tracepoints(void)
574{
575 return register_module_notifier(&tracepoint_module_nb);
576}
577__initcall(init_tracepoints);
Ingo Molnar227a8372008-11-16 09:50:34 +0100578
579#endif /* CONFIG_MODULES */