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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2008-2014 Mathieu Desnoyers
4 */
5#include <linux/module.h>
6#include <linux/mutex.h>
7#include <linux/types.h>
8#include <linux/jhash.h>
9#include <linux/list.h>
10#include <linux/rcupdate.h>
11#include <linux/tracepoint.h>
12#include <linux/err.h>
13#include <linux/slab.h>
14#include <linux/sched/signal.h>
15#include <linux/sched/task.h>
16#include <linux/static_key.h>
17
18enum tp_func_state {
19 TP_FUNC_0,
20 TP_FUNC_1,
21 TP_FUNC_2,
22 TP_FUNC_N,
23};
24
25extern tracepoint_ptr_t __start___tracepoints_ptrs[];
26extern tracepoint_ptr_t __stop___tracepoints_ptrs[];
27
28enum tp_transition_sync {
29 TP_TRANSITION_SYNC_1_0_1,
30 TP_TRANSITION_SYNC_N_2_1,
31
32 _NR_TP_TRANSITION_SYNC,
33};
34
35struct tp_transition_snapshot {
36 unsigned long rcu;
37 bool ongoing;
38};
39
40/* Protected by tracepoints_mutex */
41static struct tp_transition_snapshot tp_transition_snapshot[_NR_TP_TRANSITION_SYNC];
42
43static void tp_rcu_get_state(enum tp_transition_sync sync)
44{
45 struct tp_transition_snapshot *snapshot = &tp_transition_snapshot[sync];
46
47 /* Keep the latest get_state snapshot. */
48 snapshot->rcu = get_state_synchronize_rcu();
49 snapshot->ongoing = true;
50}
51
52static void tp_rcu_cond_sync(enum tp_transition_sync sync)
53{
54 struct tp_transition_snapshot *snapshot = &tp_transition_snapshot[sync];
55
56 if (!snapshot->ongoing)
57 return;
58 cond_synchronize_rcu(snapshot->rcu);
59 snapshot->ongoing = false;
60}
61
62/* Set to 1 to enable tracepoint debug output */
63static const int tracepoint_debug;
64
65#ifdef CONFIG_MODULES
66/*
67 * Tracepoint module list mutex protects the local module list.
68 */
69static DEFINE_MUTEX(tracepoint_module_list_mutex);
70
71/* Local list of struct tp_module */
72static LIST_HEAD(tracepoint_module_list);
73#endif /* CONFIG_MODULES */
74
75/*
76 * tracepoints_mutex protects the builtin and module tracepoints.
77 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
78 */
79static DEFINE_MUTEX(tracepoints_mutex);
80
81/*
82 * Note about RCU :
83 * It is used to delay the free of multiple probes array until a quiescent
84 * state is reached.
85 */
86struct tp_probes {
87 struct rcu_head rcu;
88 struct tracepoint_func probes[];
89};
90
91/* Called in removal of a func but failed to allocate a new tp_funcs */
92static void tp_stub_func(void)
93{
94 return;
95}
96
97static inline void *allocate_probes(int count)
98{
99 struct tp_probes *p = kmalloc(struct_size(p, probes, count),
100 GFP_KERNEL);
101 return p == NULL ? NULL : p->probes;
102}
103
104static void rcu_free_old_probes(struct rcu_head *head)
105{
106 kfree(container_of(head, struct tp_probes, rcu));
107}
108
109static inline void release_probes(struct tracepoint *tp, struct tracepoint_func *old)
110{
111 if (old) {
112 struct tp_probes *tp_probes = container_of(old,
113 struct tp_probes, probes[0]);
114
115 if (tracepoint_is_faultable(tp))
116 call_rcu_tasks_trace(&tp_probes->rcu, rcu_free_old_probes);
117 else
118 call_rcu(&tp_probes->rcu, rcu_free_old_probes);
119 }
120}
121
122static void debug_print_probes(struct tracepoint_func *funcs)
123{
124 int i;
125
126 if (!tracepoint_debug || !funcs)
127 return;
128
129 for (i = 0; funcs[i].func; i++)
130 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
131}
132
133static struct tracepoint_func *
134func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
135 int prio)
136{
137 struct tracepoint_func *old, *new;
138 int iter_probes; /* Iterate over old probe array. */
139 int nr_probes = 0; /* Counter for probes */
140 int pos = -1; /* Insertion position into new array */
141
142 if (WARN_ON(!tp_func->func))
143 return ERR_PTR(-EINVAL);
144
145 debug_print_probes(*funcs);
146 old = *funcs;
147 if (old) {
148 /* (N -> N+1), (N != 0, 1) probes */
149 for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
150 if (old[iter_probes].func == tp_stub_func)
151 continue; /* Skip stub functions. */
152 if (old[iter_probes].func == tp_func->func &&
153 old[iter_probes].data == tp_func->data)
154 return ERR_PTR(-EEXIST);
155 nr_probes++;
156 }
157 }
158 /* + 2 : one for new probe, one for NULL func */
159 new = allocate_probes(nr_probes + 2);
160 if (new == NULL)
161 return ERR_PTR(-ENOMEM);
162 if (old) {
163 nr_probes = 0;
164 for (iter_probes = 0; old[iter_probes].func; iter_probes++) {
165 if (old[iter_probes].func == tp_stub_func)
166 continue;
167 /* Insert before probes of lower priority */
168 if (pos < 0 && old[iter_probes].prio < prio)
169 pos = nr_probes++;
170 new[nr_probes++] = old[iter_probes];
171 }
172 if (pos < 0)
173 pos = nr_probes++;
174 /* nr_probes now points to the end of the new array */
175 } else {
176 pos = 0;
177 nr_probes = 1; /* must point at end of array */
178 }
179 new[pos] = *tp_func;
180 new[nr_probes].func = NULL;
181 *funcs = new;
182 debug_print_probes(*funcs);
183 return old;
184}
185
186static void *func_remove(struct tracepoint_func **funcs,
187 struct tracepoint_func *tp_func)
188{
189 int nr_probes = 0, nr_del = 0, i;
190 struct tracepoint_func *old, *new;
191
192 old = *funcs;
193
194 if (!old)
195 return ERR_PTR(-ENOENT);
196
197 debug_print_probes(*funcs);
198 /* (N -> M), (N > 1, M >= 0) probes */
199 if (tp_func->func) {
200 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
201 if ((old[nr_probes].func == tp_func->func &&
202 old[nr_probes].data == tp_func->data) ||
203 old[nr_probes].func == tp_stub_func)
204 nr_del++;
205 }
206 }
207
208 /*
209 * If probe is NULL, then nr_probes = nr_del = 0, and then the
210 * entire entry will be removed.
211 */
212 if (nr_probes - nr_del == 0) {
213 /* N -> 0, (N > 1) */
214 *funcs = NULL;
215 debug_print_probes(*funcs);
216 return old;
217 } else {
218 int j = 0;
219 /* N -> M, (N > 1, M > 0) */
220 /* + 1 for NULL */
221 new = allocate_probes(nr_probes - nr_del + 1);
222 if (new) {
223 for (i = 0; old[i].func; i++) {
224 if ((old[i].func != tp_func->func ||
225 old[i].data != tp_func->data) &&
226 old[i].func != tp_stub_func)
227 new[j++] = old[i];
228 }
229 new[nr_probes - nr_del].func = NULL;
230 *funcs = new;
231 } else {
232 /*
233 * Failed to allocate, replace the old function
234 * with calls to tp_stub_func.
235 */
236 for (i = 0; old[i].func; i++) {
237 if (old[i].func == tp_func->func &&
238 old[i].data == tp_func->data)
239 WRITE_ONCE(old[i].func, tp_stub_func);
240 }
241 *funcs = old;
242 }
243 }
244 debug_print_probes(*funcs);
245 return old;
246}
247
248/*
249 * Count the number of functions (enum tp_func_state) in a tp_funcs array.
250 */
251static enum tp_func_state nr_func_state(const struct tracepoint_func *tp_funcs)
252{
253 if (!tp_funcs)
254 return TP_FUNC_0;
255 if (!tp_funcs[1].func)
256 return TP_FUNC_1;
257 if (!tp_funcs[2].func)
258 return TP_FUNC_2;
259 return TP_FUNC_N; /* 3 or more */
260}
261
262static void tracepoint_update_call(struct tracepoint *tp, struct tracepoint_func *tp_funcs)
263{
264 void *func = tp->iterator;
265
266 /* Synthetic events do not have static call sites */
267 if (!tp->static_call_key)
268 return;
269 if (nr_func_state(tp_funcs) == TP_FUNC_1)
270 func = tp_funcs[0].func;
271 __static_call_update(tp->static_call_key, tp->static_call_tramp, func);
272}
273
274/*
275 * Add the probe function to a tracepoint.
276 */
277static int tracepoint_add_func(struct tracepoint *tp,
278 struct tracepoint_func *func, int prio,
279 bool warn)
280{
281 struct tracepoint_func *old, *tp_funcs;
282 int ret;
283
284 if (tp->ext && tp->ext->regfunc && !static_key_enabled(&tp->key)) {
285 ret = tp->ext->regfunc();
286 if (ret < 0)
287 return ret;
288 }
289
290 tp_funcs = rcu_dereference_protected(tp->funcs,
291 lockdep_is_held(&tracepoints_mutex));
292 old = func_add(&tp_funcs, func, prio);
293 if (IS_ERR(old)) {
294 WARN_ON_ONCE(warn && PTR_ERR(old) != -ENOMEM);
295 return PTR_ERR(old);
296 }
297
298 /*
299 * rcu_assign_pointer has as smp_store_release() which makes sure
300 * that the new probe callbacks array is consistent before setting
301 * a pointer to it. This array is referenced by __DO_TRACE from
302 * include/linux/tracepoint.h using rcu_dereference_sched().
303 */
304 switch (nr_func_state(tp_funcs)) {
305 case TP_FUNC_1: /* 0->1 */
306 /*
307 * Make sure new static func never uses old data after a
308 * 1->0->1 transition sequence.
309 */
310 tp_rcu_cond_sync(TP_TRANSITION_SYNC_1_0_1);
311 /* Set static call to first function */
312 tracepoint_update_call(tp, tp_funcs);
313 /* Both iterator and static call handle NULL tp->funcs */
314 rcu_assign_pointer(tp->funcs, tp_funcs);
315 static_branch_enable(&tp->key);
316 break;
317 case TP_FUNC_2: /* 1->2 */
318 /* Set iterator static call */
319 tracepoint_update_call(tp, tp_funcs);
320 /*
321 * Iterator callback installed before updating tp->funcs.
322 * Requires ordering between RCU assign/dereference and
323 * static call update/call.
324 */
325 fallthrough;
326 case TP_FUNC_N: /* N->N+1 (N>1) */
327 rcu_assign_pointer(tp->funcs, tp_funcs);
328 /*
329 * Make sure static func never uses incorrect data after a
330 * N->...->2->1 (N>1) transition sequence.
331 */
332 if (tp_funcs[0].data != old[0].data)
333 tp_rcu_get_state(TP_TRANSITION_SYNC_N_2_1);
334 break;
335 default:
336 WARN_ON_ONCE(1);
337 break;
338 }
339
340 release_probes(tp, old);
341 return 0;
342}
343
344/*
345 * Remove a probe function from a tracepoint.
346 * Note: only waiting an RCU period after setting elem->call to the empty
347 * function insures that the original callback is not used anymore. This insured
348 * by preempt_disable around the call site.
349 */
350static int tracepoint_remove_func(struct tracepoint *tp,
351 struct tracepoint_func *func)
352{
353 struct tracepoint_func *old, *tp_funcs;
354
355 tp_funcs = rcu_dereference_protected(tp->funcs,
356 lockdep_is_held(&tracepoints_mutex));
357 old = func_remove(&tp_funcs, func);
358 if (WARN_ON_ONCE(IS_ERR(old)))
359 return PTR_ERR(old);
360
361 if (tp_funcs == old)
362 /* Failed allocating new tp_funcs, replaced func with stub */
363 return 0;
364
365 switch (nr_func_state(tp_funcs)) {
366 case TP_FUNC_0: /* 1->0 */
367 /* Removed last function */
368 if (tp->ext && tp->ext->unregfunc && static_key_enabled(&tp->key))
369 tp->ext->unregfunc();
370 static_branch_disable(&tp->key);
371 /* Set iterator static call */
372 tracepoint_update_call(tp, tp_funcs);
373 /* Both iterator and static call handle NULL tp->funcs */
374 rcu_assign_pointer(tp->funcs, NULL);
375 /*
376 * Make sure new static func never uses old data after a
377 * 1->0->1 transition sequence.
378 */
379 tp_rcu_get_state(TP_TRANSITION_SYNC_1_0_1);
380 break;
381 case TP_FUNC_1: /* 2->1 */
382 rcu_assign_pointer(tp->funcs, tp_funcs);
383 /*
384 * Make sure static func never uses incorrect data after a
385 * N->...->2->1 (N>2) transition sequence. If the first
386 * element's data has changed, then force the synchronization
387 * to prevent current readers that have loaded the old data
388 * from calling the new function.
389 */
390 if (tp_funcs[0].data != old[0].data)
391 tp_rcu_get_state(TP_TRANSITION_SYNC_N_2_1);
392 tp_rcu_cond_sync(TP_TRANSITION_SYNC_N_2_1);
393 /* Set static call to first function */
394 tracepoint_update_call(tp, tp_funcs);
395 break;
396 case TP_FUNC_2: /* N->N-1 (N>2) */
397 fallthrough;
398 case TP_FUNC_N:
399 rcu_assign_pointer(tp->funcs, tp_funcs);
400 /*
401 * Make sure static func never uses incorrect data after a
402 * N->...->2->1 (N>2) transition sequence.
403 */
404 if (tp_funcs[0].data != old[0].data)
405 tp_rcu_get_state(TP_TRANSITION_SYNC_N_2_1);
406 break;
407 default:
408 WARN_ON_ONCE(1);
409 break;
410 }
411 release_probes(tp, old);
412 return 0;
413}
414
415/**
416 * tracepoint_probe_register_prio_may_exist - Connect a probe to a tracepoint with priority
417 * @tp: tracepoint
418 * @probe: probe handler
419 * @data: tracepoint data
420 * @prio: priority of this function over other registered functions
421 *
422 * Same as tracepoint_probe_register_prio() except that it will not warn
423 * if the tracepoint is already registered.
424 */
425int tracepoint_probe_register_prio_may_exist(struct tracepoint *tp, void *probe,
426 void *data, int prio)
427{
428 struct tracepoint_func tp_func;
429 int ret;
430
431 mutex_lock(&tracepoints_mutex);
432 tp_func.func = probe;
433 tp_func.data = data;
434 tp_func.prio = prio;
435 ret = tracepoint_add_func(tp, &tp_func, prio, false);
436 mutex_unlock(&tracepoints_mutex);
437 return ret;
438}
439EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio_may_exist);
440
441/**
442 * tracepoint_probe_register_prio - Connect a probe to a tracepoint with priority
443 * @tp: tracepoint
444 * @probe: probe handler
445 * @data: tracepoint data
446 * @prio: priority of this function over other registered functions
447 *
448 * Returns 0 if ok, error value on error.
449 * Note: if @tp is within a module, the caller is responsible for
450 * unregistering the probe before the module is gone. This can be
451 * performed either with a tracepoint module going notifier, or from
452 * within module exit functions.
453 */
454int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
455 void *data, int prio)
456{
457 struct tracepoint_func tp_func;
458 int ret;
459
460 mutex_lock(&tracepoints_mutex);
461 tp_func.func = probe;
462 tp_func.data = data;
463 tp_func.prio = prio;
464 ret = tracepoint_add_func(tp, &tp_func, prio, true);
465 mutex_unlock(&tracepoints_mutex);
466 return ret;
467}
468EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio);
469
470/**
471 * tracepoint_probe_register - Connect a probe to a tracepoint
472 * @tp: tracepoint
473 * @probe: probe handler
474 * @data: tracepoint data
475 *
476 * Returns 0 if ok, error value on error.
477 * Note: if @tp is within a module, the caller is responsible for
478 * unregistering the probe before the module is gone. This can be
479 * performed either with a tracepoint module going notifier, or from
480 * within module exit functions.
481 */
482int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
483{
484 return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
485}
486EXPORT_SYMBOL_GPL(tracepoint_probe_register);
487
488/**
489 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
490 * @tp: tracepoint
491 * @probe: probe function pointer
492 * @data: tracepoint data
493 *
494 * Returns 0 if ok, error value on error.
495 */
496int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
497{
498 struct tracepoint_func tp_func;
499 int ret;
500
501 mutex_lock(&tracepoints_mutex);
502 tp_func.func = probe;
503 tp_func.data = data;
504 ret = tracepoint_remove_func(tp, &tp_func);
505 mutex_unlock(&tracepoints_mutex);
506 return ret;
507}
508EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
509
510static void for_each_tracepoint_range(
511 tracepoint_ptr_t *begin, tracepoint_ptr_t *end,
512 void (*fct)(struct tracepoint *tp, void *priv),
513 void *priv)
514{
515 tracepoint_ptr_t *iter;
516
517 if (!begin)
518 return;
519 for (iter = begin; iter < end; iter++)
520 fct(tracepoint_ptr_deref(iter), priv);
521}
522
523#ifdef CONFIG_MODULES
524bool trace_module_has_bad_taint(struct module *mod)
525{
526 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
527 (1 << TAINT_UNSIGNED_MODULE) | (1 << TAINT_TEST) |
528 (1 << TAINT_LIVEPATCH));
529}
530
531static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
532
533/**
534 * register_tracepoint_module_notifier - register tracepoint coming/going notifier
535 * @nb: notifier block
536 *
537 * Notifiers registered with this function are called on module
538 * coming/going with the tracepoint_module_list_mutex held.
539 * The notifier block callback should expect a "struct tp_module" data
540 * pointer.
541 */
542int register_tracepoint_module_notifier(struct notifier_block *nb)
543{
544 struct tp_module *tp_mod;
545 int ret;
546
547 mutex_lock(&tracepoint_module_list_mutex);
548 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
549 if (ret)
550 goto end;
551 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
552 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
553end:
554 mutex_unlock(&tracepoint_module_list_mutex);
555 return ret;
556}
557EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
558
559/**
560 * unregister_tracepoint_module_notifier - unregister tracepoint coming/going notifier
561 * @nb: notifier block
562 *
563 * The notifier block callback should expect a "struct tp_module" data
564 * pointer.
565 */
566int unregister_tracepoint_module_notifier(struct notifier_block *nb)
567{
568 struct tp_module *tp_mod;
569 int ret;
570
571 mutex_lock(&tracepoint_module_list_mutex);
572 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
573 if (ret)
574 goto end;
575 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
576 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
577end:
578 mutex_unlock(&tracepoint_module_list_mutex);
579 return ret;
580
581}
582EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
583
584/*
585 * Ensure the tracer unregistered the module's probes before the module
586 * teardown is performed. Prevents leaks of probe and data pointers.
587 */
588static void tp_module_going_check_quiescent(struct tracepoint *tp, void *priv)
589{
590 WARN_ON_ONCE(tp->funcs);
591}
592
593static int tracepoint_module_coming(struct module *mod)
594{
595 struct tp_module *tp_mod;
596
597 if (!mod->num_tracepoints)
598 return 0;
599
600 /*
601 * We skip modules that taint the kernel, especially those with different
602 * module headers (for forced load), to make sure we don't cause a crash.
603 * Staging, out-of-tree, unsigned GPL, and test modules are fine.
604 */
605 if (trace_module_has_bad_taint(mod))
606 return 0;
607
608 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
609 if (!tp_mod)
610 return -ENOMEM;
611 tp_mod->mod = mod;
612
613 mutex_lock(&tracepoint_module_list_mutex);
614 list_add_tail(&tp_mod->list, &tracepoint_module_list);
615 blocking_notifier_call_chain(&tracepoint_notify_list,
616 MODULE_STATE_COMING, tp_mod);
617 mutex_unlock(&tracepoint_module_list_mutex);
618 return 0;
619}
620
621static void tracepoint_module_going(struct module *mod)
622{
623 struct tp_module *tp_mod;
624
625 if (!mod->num_tracepoints)
626 return;
627
628 mutex_lock(&tracepoint_module_list_mutex);
629 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
630 if (tp_mod->mod == mod) {
631 blocking_notifier_call_chain(&tracepoint_notify_list,
632 MODULE_STATE_GOING, tp_mod);
633 list_del(&tp_mod->list);
634 kfree(tp_mod);
635 /*
636 * Called the going notifier before checking for
637 * quiescence.
638 */
639 for_each_tracepoint_range(mod->tracepoints_ptrs,
640 mod->tracepoints_ptrs + mod->num_tracepoints,
641 tp_module_going_check_quiescent, NULL);
642 break;
643 }
644 }
645 /*
646 * In the case of modules that were tainted at "coming", we'll simply
647 * walk through the list without finding it. We cannot use the "tainted"
648 * flag on "going", in case a module taints the kernel only after being
649 * loaded.
650 */
651 mutex_unlock(&tracepoint_module_list_mutex);
652}
653
654static int tracepoint_module_notify(struct notifier_block *self,
655 unsigned long val, void *data)
656{
657 struct module *mod = data;
658 int ret = 0;
659
660 switch (val) {
661 case MODULE_STATE_COMING:
662 ret = tracepoint_module_coming(mod);
663 break;
664 case MODULE_STATE_LIVE:
665 break;
666 case MODULE_STATE_GOING:
667 tracepoint_module_going(mod);
668 break;
669 case MODULE_STATE_UNFORMED:
670 break;
671 }
672 return notifier_from_errno(ret);
673}
674
675static struct notifier_block tracepoint_module_nb = {
676 .notifier_call = tracepoint_module_notify,
677 .priority = 0,
678};
679
680static __init int init_tracepoints(void)
681{
682 int ret;
683
684 ret = register_module_notifier(&tracepoint_module_nb);
685 if (ret)
686 pr_warn("Failed to register tracepoint module enter notifier\n");
687
688 return ret;
689}
690__initcall(init_tracepoints);
691
692/**
693 * for_each_tracepoint_in_module - iteration on all tracepoints in a module
694 * @mod: module
695 * @fct: callback
696 * @priv: private data
697 */
698void for_each_tracepoint_in_module(struct module *mod,
699 void (*fct)(struct tracepoint *tp,
700 struct module *mod, void *priv),
701 void *priv)
702{
703 tracepoint_ptr_t *begin, *end, *iter;
704
705 lockdep_assert_held(&tracepoint_module_list_mutex);
706
707 if (!mod)
708 return;
709
710 begin = mod->tracepoints_ptrs;
711 end = mod->tracepoints_ptrs + mod->num_tracepoints;
712
713 for (iter = begin; iter < end; iter++)
714 fct(tracepoint_ptr_deref(iter), mod, priv);
715}
716
717/**
718 * for_each_module_tracepoint - iteration on all tracepoints in all modules
719 * @fct: callback
720 * @priv: private data
721 */
722void for_each_module_tracepoint(void (*fct)(struct tracepoint *tp,
723 struct module *mod, void *priv),
724 void *priv)
725{
726 struct tp_module *tp_mod;
727
728 mutex_lock(&tracepoint_module_list_mutex);
729 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
730 for_each_tracepoint_in_module(tp_mod->mod, fct, priv);
731 mutex_unlock(&tracepoint_module_list_mutex);
732}
733#endif /* CONFIG_MODULES */
734
735/**
736 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
737 * @fct: callback
738 * @priv: private data
739 */
740void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
741 void *priv)
742{
743 for_each_tracepoint_range(__start___tracepoints_ptrs,
744 __stop___tracepoints_ptrs, fct, priv);
745}
746EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
747
748#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
749
750/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
751static int sys_tracepoint_refcount;
752
753int syscall_regfunc(void)
754{
755 struct task_struct *p, *t;
756
757 if (!sys_tracepoint_refcount) {
758 read_lock(&tasklist_lock);
759 for_each_process_thread(p, t) {
760 set_task_syscall_work(t, SYSCALL_TRACEPOINT);
761 }
762 read_unlock(&tasklist_lock);
763 }
764 sys_tracepoint_refcount++;
765
766 return 0;
767}
768
769void syscall_unregfunc(void)
770{
771 struct task_struct *p, *t;
772
773 sys_tracepoint_refcount--;
774 if (!sys_tracepoint_refcount) {
775 read_lock(&tasklist_lock);
776 for_each_process_thread(p, t) {
777 clear_task_syscall_work(t, SYSCALL_TRACEPOINT);
778 }
779 read_unlock(&tasklist_lock);
780 }
781}
782#endif
1/*
2 * Copyright (C) 2008-2014 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/static_key.h>
29
30extern struct tracepoint * const __start___tracepoints_ptrs[];
31extern struct tracepoint * const __stop___tracepoints_ptrs[];
32
33/* Set to 1 to enable tracepoint debug output */
34static const int tracepoint_debug;
35
36#ifdef CONFIG_MODULES
37/*
38 * Tracepoint module list mutex protects the local module list.
39 */
40static DEFINE_MUTEX(tracepoint_module_list_mutex);
41
42/* Local list of struct tp_module */
43static LIST_HEAD(tracepoint_module_list);
44#endif /* CONFIG_MODULES */
45
46/*
47 * tracepoints_mutex protects the builtin and module tracepoints.
48 * tracepoints_mutex nests inside tracepoint_module_list_mutex.
49 */
50static DEFINE_MUTEX(tracepoints_mutex);
51
52/*
53 * Note about RCU :
54 * It is used to delay the free of multiple probes array until a quiescent
55 * state is reached.
56 */
57struct tp_probes {
58 struct rcu_head rcu;
59 struct tracepoint_func probes[0];
60};
61
62static inline void *allocate_probes(int count)
63{
64 struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
65 + sizeof(struct tp_probes), GFP_KERNEL);
66 return p == NULL ? NULL : p->probes;
67}
68
69static void rcu_free_old_probes(struct rcu_head *head)
70{
71 kfree(container_of(head, struct tp_probes, rcu));
72}
73
74static inline void release_probes(struct tracepoint_func *old)
75{
76 if (old) {
77 struct tp_probes *tp_probes = container_of(old,
78 struct tp_probes, probes[0]);
79 call_rcu_sched(&tp_probes->rcu, rcu_free_old_probes);
80 }
81}
82
83static void debug_print_probes(struct tracepoint_func *funcs)
84{
85 int i;
86
87 if (!tracepoint_debug || !funcs)
88 return;
89
90 for (i = 0; funcs[i].func; i++)
91 printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
92}
93
94static struct tracepoint_func *
95func_add(struct tracepoint_func **funcs, struct tracepoint_func *tp_func,
96 int prio)
97{
98 struct tracepoint_func *old, *new;
99 int nr_probes = 0;
100 int pos = -1;
101
102 if (WARN_ON(!tp_func->func))
103 return ERR_PTR(-EINVAL);
104
105 debug_print_probes(*funcs);
106 old = *funcs;
107 if (old) {
108 /* (N -> N+1), (N != 0, 1) probes */
109 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
110 /* Insert before probes of lower priority */
111 if (pos < 0 && old[nr_probes].prio < prio)
112 pos = nr_probes;
113 if (old[nr_probes].func == tp_func->func &&
114 old[nr_probes].data == tp_func->data)
115 return ERR_PTR(-EEXIST);
116 }
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 if (pos < 0) {
124 pos = nr_probes;
125 memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
126 } else {
127 /* Copy higher priority probes ahead of the new probe */
128 memcpy(new, old, pos * sizeof(struct tracepoint_func));
129 /* Copy the rest after it. */
130 memcpy(new + pos + 1, old + pos,
131 (nr_probes - pos) * sizeof(struct tracepoint_func));
132 }
133 } else
134 pos = 0;
135 new[pos] = *tp_func;
136 new[nr_probes + 1].func = NULL;
137 *funcs = new;
138 debug_print_probes(*funcs);
139 return old;
140}
141
142static void *func_remove(struct tracepoint_func **funcs,
143 struct tracepoint_func *tp_func)
144{
145 int nr_probes = 0, nr_del = 0, i;
146 struct tracepoint_func *old, *new;
147
148 old = *funcs;
149
150 if (!old)
151 return ERR_PTR(-ENOENT);
152
153 debug_print_probes(*funcs);
154 /* (N -> M), (N > 1, M >= 0) probes */
155 if (tp_func->func) {
156 for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
157 if (old[nr_probes].func == tp_func->func &&
158 old[nr_probes].data == tp_func->data)
159 nr_del++;
160 }
161 }
162
163 /*
164 * If probe is NULL, then nr_probes = nr_del = 0, and then the
165 * entire entry will be removed.
166 */
167 if (nr_probes - nr_del == 0) {
168 /* N -> 0, (N > 1) */
169 *funcs = NULL;
170 debug_print_probes(*funcs);
171 return old;
172 } else {
173 int j = 0;
174 /* N -> M, (N > 1, M > 0) */
175 /* + 1 for NULL */
176 new = allocate_probes(nr_probes - nr_del + 1);
177 if (new == NULL)
178 return ERR_PTR(-ENOMEM);
179 for (i = 0; old[i].func; i++)
180 if (old[i].func != tp_func->func
181 || old[i].data != tp_func->data)
182 new[j++] = old[i];
183 new[nr_probes - nr_del].func = NULL;
184 *funcs = new;
185 }
186 debug_print_probes(*funcs);
187 return old;
188}
189
190/*
191 * Add the probe function to a tracepoint.
192 */
193static int tracepoint_add_func(struct tracepoint *tp,
194 struct tracepoint_func *func, int prio)
195{
196 struct tracepoint_func *old, *tp_funcs;
197 int ret;
198
199 if (tp->regfunc && !static_key_enabled(&tp->key)) {
200 ret = tp->regfunc();
201 if (ret < 0)
202 return ret;
203 }
204
205 tp_funcs = rcu_dereference_protected(tp->funcs,
206 lockdep_is_held(&tracepoints_mutex));
207 old = func_add(&tp_funcs, func, prio);
208 if (IS_ERR(old)) {
209 WARN_ON_ONCE(1);
210 return PTR_ERR(old);
211 }
212
213 /*
214 * rcu_assign_pointer has a smp_wmb() which makes sure that the new
215 * probe callbacks array is consistent before setting a pointer to it.
216 * This array is referenced by __DO_TRACE from
217 * include/linux/tracepoints.h. A matching smp_read_barrier_depends()
218 * is used.
219 */
220 rcu_assign_pointer(tp->funcs, tp_funcs);
221 if (!static_key_enabled(&tp->key))
222 static_key_slow_inc(&tp->key);
223 release_probes(old);
224 return 0;
225}
226
227/*
228 * Remove a probe function from a tracepoint.
229 * Note: only waiting an RCU period after setting elem->call to the empty
230 * function insures that the original callback is not used anymore. This insured
231 * by preempt_disable around the call site.
232 */
233static int tracepoint_remove_func(struct tracepoint *tp,
234 struct tracepoint_func *func)
235{
236 struct tracepoint_func *old, *tp_funcs;
237
238 tp_funcs = rcu_dereference_protected(tp->funcs,
239 lockdep_is_held(&tracepoints_mutex));
240 old = func_remove(&tp_funcs, func);
241 if (IS_ERR(old)) {
242 WARN_ON_ONCE(1);
243 return PTR_ERR(old);
244 }
245
246 if (!tp_funcs) {
247 /* Removed last function */
248 if (tp->unregfunc && static_key_enabled(&tp->key))
249 tp->unregfunc();
250
251 if (static_key_enabled(&tp->key))
252 static_key_slow_dec(&tp->key);
253 }
254 rcu_assign_pointer(tp->funcs, tp_funcs);
255 release_probes(old);
256 return 0;
257}
258
259/**
260 * tracepoint_probe_register - Connect a probe to a tracepoint
261 * @tp: tracepoint
262 * @probe: probe handler
263 * @data: tracepoint data
264 * @prio: priority of this function over other registered functions
265 *
266 * Returns 0 if ok, error value on error.
267 * Note: if @tp is within a module, the caller is responsible for
268 * unregistering the probe before the module is gone. This can be
269 * performed either with a tracepoint module going notifier, or from
270 * within module exit functions.
271 */
272int tracepoint_probe_register_prio(struct tracepoint *tp, void *probe,
273 void *data, int prio)
274{
275 struct tracepoint_func tp_func;
276 int ret;
277
278 mutex_lock(&tracepoints_mutex);
279 tp_func.func = probe;
280 tp_func.data = data;
281 tp_func.prio = prio;
282 ret = tracepoint_add_func(tp, &tp_func, prio);
283 mutex_unlock(&tracepoints_mutex);
284 return ret;
285}
286EXPORT_SYMBOL_GPL(tracepoint_probe_register_prio);
287
288/**
289 * tracepoint_probe_register - Connect a probe to a tracepoint
290 * @tp: tracepoint
291 * @probe: probe handler
292 * @data: tracepoint data
293 * @prio: priority of this function over other registered functions
294 *
295 * Returns 0 if ok, error value on error.
296 * Note: if @tp is within a module, the caller is responsible for
297 * unregistering the probe before the module is gone. This can be
298 * performed either with a tracepoint module going notifier, or from
299 * within module exit functions.
300 */
301int tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data)
302{
303 return tracepoint_probe_register_prio(tp, probe, data, TRACEPOINT_DEFAULT_PRIO);
304}
305EXPORT_SYMBOL_GPL(tracepoint_probe_register);
306
307/**
308 * tracepoint_probe_unregister - Disconnect a probe from a tracepoint
309 * @tp: tracepoint
310 * @probe: probe function pointer
311 * @data: tracepoint data
312 *
313 * Returns 0 if ok, error value on error.
314 */
315int tracepoint_probe_unregister(struct tracepoint *tp, void *probe, void *data)
316{
317 struct tracepoint_func tp_func;
318 int ret;
319
320 mutex_lock(&tracepoints_mutex);
321 tp_func.func = probe;
322 tp_func.data = data;
323 ret = tracepoint_remove_func(tp, &tp_func);
324 mutex_unlock(&tracepoints_mutex);
325 return ret;
326}
327EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
328
329#ifdef CONFIG_MODULES
330bool trace_module_has_bad_taint(struct module *mod)
331{
332 return mod->taints & ~((1 << TAINT_OOT_MODULE) | (1 << TAINT_CRAP) |
333 (1 << TAINT_UNSIGNED_MODULE));
334}
335
336static BLOCKING_NOTIFIER_HEAD(tracepoint_notify_list);
337
338/**
339 * register_tracepoint_notifier - register tracepoint coming/going notifier
340 * @nb: notifier block
341 *
342 * Notifiers registered with this function are called on module
343 * coming/going with the tracepoint_module_list_mutex held.
344 * The notifier block callback should expect a "struct tp_module" data
345 * pointer.
346 */
347int register_tracepoint_module_notifier(struct notifier_block *nb)
348{
349 struct tp_module *tp_mod;
350 int ret;
351
352 mutex_lock(&tracepoint_module_list_mutex);
353 ret = blocking_notifier_chain_register(&tracepoint_notify_list, nb);
354 if (ret)
355 goto end;
356 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
357 (void) nb->notifier_call(nb, MODULE_STATE_COMING, tp_mod);
358end:
359 mutex_unlock(&tracepoint_module_list_mutex);
360 return ret;
361}
362EXPORT_SYMBOL_GPL(register_tracepoint_module_notifier);
363
364/**
365 * unregister_tracepoint_notifier - unregister tracepoint coming/going notifier
366 * @nb: notifier block
367 *
368 * The notifier block callback should expect a "struct tp_module" data
369 * pointer.
370 */
371int unregister_tracepoint_module_notifier(struct notifier_block *nb)
372{
373 struct tp_module *tp_mod;
374 int ret;
375
376 mutex_lock(&tracepoint_module_list_mutex);
377 ret = blocking_notifier_chain_unregister(&tracepoint_notify_list, nb);
378 if (ret)
379 goto end;
380 list_for_each_entry(tp_mod, &tracepoint_module_list, list)
381 (void) nb->notifier_call(nb, MODULE_STATE_GOING, tp_mod);
382end:
383 mutex_unlock(&tracepoint_module_list_mutex);
384 return ret;
385
386}
387EXPORT_SYMBOL_GPL(unregister_tracepoint_module_notifier);
388
389/*
390 * Ensure the tracer unregistered the module's probes before the module
391 * teardown is performed. Prevents leaks of probe and data pointers.
392 */
393static void tp_module_going_check_quiescent(struct tracepoint * const *begin,
394 struct tracepoint * const *end)
395{
396 struct tracepoint * const *iter;
397
398 if (!begin)
399 return;
400 for (iter = begin; iter < end; iter++)
401 WARN_ON_ONCE((*iter)->funcs);
402}
403
404static int tracepoint_module_coming(struct module *mod)
405{
406 struct tp_module *tp_mod;
407 int ret = 0;
408
409 if (!mod->num_tracepoints)
410 return 0;
411
412 /*
413 * We skip modules that taint the kernel, especially those with different
414 * module headers (for forced load), to make sure we don't cause a crash.
415 * Staging, out-of-tree, and unsigned GPL modules are fine.
416 */
417 if (trace_module_has_bad_taint(mod))
418 return 0;
419 mutex_lock(&tracepoint_module_list_mutex);
420 tp_mod = kmalloc(sizeof(struct tp_module), GFP_KERNEL);
421 if (!tp_mod) {
422 ret = -ENOMEM;
423 goto end;
424 }
425 tp_mod->mod = mod;
426 list_add_tail(&tp_mod->list, &tracepoint_module_list);
427 blocking_notifier_call_chain(&tracepoint_notify_list,
428 MODULE_STATE_COMING, tp_mod);
429end:
430 mutex_unlock(&tracepoint_module_list_mutex);
431 return ret;
432}
433
434static void tracepoint_module_going(struct module *mod)
435{
436 struct tp_module *tp_mod;
437
438 if (!mod->num_tracepoints)
439 return;
440
441 mutex_lock(&tracepoint_module_list_mutex);
442 list_for_each_entry(tp_mod, &tracepoint_module_list, list) {
443 if (tp_mod->mod == mod) {
444 blocking_notifier_call_chain(&tracepoint_notify_list,
445 MODULE_STATE_GOING, tp_mod);
446 list_del(&tp_mod->list);
447 kfree(tp_mod);
448 /*
449 * Called the going notifier before checking for
450 * quiescence.
451 */
452 tp_module_going_check_quiescent(mod->tracepoints_ptrs,
453 mod->tracepoints_ptrs + mod->num_tracepoints);
454 break;
455 }
456 }
457 /*
458 * In the case of modules that were tainted at "coming", we'll simply
459 * walk through the list without finding it. We cannot use the "tainted"
460 * flag on "going", in case a module taints the kernel only after being
461 * loaded.
462 */
463 mutex_unlock(&tracepoint_module_list_mutex);
464}
465
466static int tracepoint_module_notify(struct notifier_block *self,
467 unsigned long val, void *data)
468{
469 struct module *mod = data;
470 int ret = 0;
471
472 switch (val) {
473 case MODULE_STATE_COMING:
474 ret = tracepoint_module_coming(mod);
475 break;
476 case MODULE_STATE_LIVE:
477 break;
478 case MODULE_STATE_GOING:
479 tracepoint_module_going(mod);
480 break;
481 case MODULE_STATE_UNFORMED:
482 break;
483 }
484 return ret;
485}
486
487static struct notifier_block tracepoint_module_nb = {
488 .notifier_call = tracepoint_module_notify,
489 .priority = 0,
490};
491
492static __init int init_tracepoints(void)
493{
494 int ret;
495
496 ret = register_module_notifier(&tracepoint_module_nb);
497 if (ret)
498 pr_warn("Failed to register tracepoint module enter notifier\n");
499
500 return ret;
501}
502__initcall(init_tracepoints);
503#endif /* CONFIG_MODULES */
504
505static void for_each_tracepoint_range(struct tracepoint * const *begin,
506 struct tracepoint * const *end,
507 void (*fct)(struct tracepoint *tp, void *priv),
508 void *priv)
509{
510 struct tracepoint * const *iter;
511
512 if (!begin)
513 return;
514 for (iter = begin; iter < end; iter++)
515 fct(*iter, priv);
516}
517
518/**
519 * for_each_kernel_tracepoint - iteration on all kernel tracepoints
520 * @fct: callback
521 * @priv: private data
522 */
523void for_each_kernel_tracepoint(void (*fct)(struct tracepoint *tp, void *priv),
524 void *priv)
525{
526 for_each_tracepoint_range(__start___tracepoints_ptrs,
527 __stop___tracepoints_ptrs, fct, priv);
528}
529EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
530
531#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
532
533/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
534static int sys_tracepoint_refcount;
535
536int syscall_regfunc(void)
537{
538 struct task_struct *p, *t;
539
540 if (!sys_tracepoint_refcount) {
541 read_lock(&tasklist_lock);
542 for_each_process_thread(p, t) {
543 set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
544 }
545 read_unlock(&tasklist_lock);
546 }
547 sys_tracepoint_refcount++;
548
549 return 0;
550}
551
552void syscall_unregfunc(void)
553{
554 struct task_struct *p, *t;
555
556 sys_tracepoint_refcount--;
557 if (!sys_tracepoint_refcount) {
558 read_lock(&tasklist_lock);
559 for_each_process_thread(p, t) {
560 clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
561 }
562 read_unlock(&tasklist_lock);
563 }
564}
565#endif