1 // SPDX-License-Identifier: GPL-2.0-or-later 1
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
18 enum tp_func_state {
19 TP_FUNC_0,
20 TP_FUNC_1,
21 TP_FUNC_2,
22 TP_FUNC_N,
23 };
24
25 extern tracepoint_ptr_t __start___tracepoints_
26 extern tracepoint_ptr_t __stop___tracepoints_p
27
28 DEFINE_SRCU(tracepoint_srcu);
29 EXPORT_SYMBOL_GPL(tracepoint_srcu);
30
31 enum tp_transition_sync {
32 TP_TRANSITION_SYNC_1_0_1,
33 TP_TRANSITION_SYNC_N_2_1,
34
35 _NR_TP_TRANSITION_SYNC,
36 };
37
38 struct tp_transition_snapshot {
39 unsigned long rcu;
40 unsigned long srcu;
41 bool ongoing;
42 };
43
44 /* Protected by tracepoints_mutex */
45 static struct tp_transition_snapshot tp_transi
46
47 static void tp_rcu_get_state(enum tp_transitio
48 {
49 struct tp_transition_snapshot *snapsho
50
51 /* Keep the latest get_state snapshot.
52 snapshot->rcu = get_state_synchronize_
53 snapshot->srcu = start_poll_synchroniz
54 snapshot->ongoing = true;
55 }
56
57 static void tp_rcu_cond_sync(enum tp_transitio
58 {
59 struct tp_transition_snapshot *snapsho
60
61 if (!snapshot->ongoing)
62 return;
63 cond_synchronize_rcu(snapshot->rcu);
64 if (!poll_state_synchronize_srcu(&trac
65 synchronize_srcu(&tracepoint_s
66 snapshot->ongoing = false;
67 }
68
69 /* Set to 1 to enable tracepoint debug output
70 static const int tracepoint_debug;
71
72 #ifdef CONFIG_MODULES
73 /*
74 * Tracepoint module list mutex protects the l
75 */
76 static DEFINE_MUTEX(tracepoint_module_list_mut
77
78 /* Local list of struct tp_module */
79 static LIST_HEAD(tracepoint_module_list);
80 #endif /* CONFIG_MODULES */
81
82 /*
83 * tracepoints_mutex protects the builtin and
84 * tracepoints_mutex nests inside tracepoint_m
85 */
86 static DEFINE_MUTEX(tracepoints_mutex);
87
88 static struct rcu_head *early_probes;
89 static bool ok_to_free_tracepoints;
90
91 /*
92 * Note about RCU :
93 * It is used to delay the free of multiple pr
94 * state is reached.
95 */
96 struct tp_probes {
97 struct rcu_head rcu;
98 struct tracepoint_func probes[];
99 };
100
101 /* Called in removal of a func but failed to a
102 static void tp_stub_func(void)
103 {
104 return;
105 }
106
107 static inline void *allocate_probes(int count)
108 {
109 struct tp_probes *p = kmalloc(struct_
110 GFP_KER
111 return p == NULL ? NULL : p->probes;
112 }
113
114 static void srcu_free_old_probes(struct rcu_he
115 {
116 kfree(container_of(head, struct tp_pro
117 }
118
119 static void rcu_free_old_probes(struct rcu_hea
120 {
121 call_srcu(&tracepoint_srcu, head, srcu
122 }
123
124 static __init int release_early_probes(void)
125 {
126 struct rcu_head *tmp;
127
128 ok_to_free_tracepoints = true;
129
130 while (early_probes) {
131 tmp = early_probes;
132 early_probes = tmp->next;
133 call_rcu(tmp, rcu_free_old_pro
134 }
135
136 return 0;
137 }
138
139 /* SRCU is initialized at core_initcall */
140 postcore_initcall(release_early_probes);
141
142 static inline void release_probes(struct trace
143 {
144 if (old) {
145 struct tp_probes *tp_probes =
146 struct tp_probes, prob
147
148 /*
149 * We can't free probes if SRC
150 * Postpone the freeing till a
151 */
152 if (unlikely(!ok_to_free_trace
153 tp_probes->rcu.next =
154 early_probes = &tp_pro
155 return;
156 }
157
158 /*
159 * Tracepoint probes are prote
160 * by calling the SRCU callbac
161 * cover both cases. So let us
162 * callbacks to wait for both
163 */
164 call_rcu(&tp_probes->rcu, rcu_
165 }
166 }
167
168 static void debug_print_probes(struct tracepoi
169 {
170 int i;
171
172 if (!tracepoint_debug || !funcs)
173 return;
174
175 for (i = 0; funcs[i].func; i++)
176 printk(KERN_DEBUG "Probe %d :
177 }
178
179 static struct tracepoint_func *
180 func_add(struct tracepoint_func **funcs, struc
181 int prio)
182 {
183 struct tracepoint_func *old, *new;
184 int iter_probes; /* Iterate ove
185 int nr_probes = 0; /* Counter for
186 int pos = -1; /* Insertion p
187
188 if (WARN_ON(!tp_func->func))
189 return ERR_PTR(-EINVAL);
190
191 debug_print_probes(*funcs);
192 old = *funcs;
193 if (old) {
194 /* (N -> N+1), (N != 0, 1) pro
195 for (iter_probes = 0; old[iter
196 if (old[iter_probes].f
197 continue;
198 if (old[iter_probes].f
199 old[iter_probes].d
200 return ERR_PTR
201 nr_probes++;
202 }
203 }
204 /* + 2 : one for new probe, one for NU
205 new = allocate_probes(nr_probes + 2);
206 if (new == NULL)
207 return ERR_PTR(-ENOMEM);
208 if (old) {
209 nr_probes = 0;
210 for (iter_probes = 0; old[iter
211 if (old[iter_probes].f
212 continue;
213 /* Insert before probe
214 if (pos < 0 && old[ite
215 pos = nr_probe
216 new[nr_probes++] = old
217 }
218 if (pos < 0)
219 pos = nr_probes++;
220 /* nr_probes now points to the
221 } else {
222 pos = 0;
223 nr_probes = 1; /* must point a
224 }
225 new[pos] = *tp_func;
226 new[nr_probes].func = NULL;
227 *funcs = new;
228 debug_print_probes(*funcs);
229 return old;
230 }
231
232 static void *func_remove(struct tracepoint_fun
233 struct tracepoint_func *tp_fun
234 {
235 int nr_probes = 0, nr_del = 0, i;
236 struct tracepoint_func *old, *new;
237
238 old = *funcs;
239
240 if (!old)
241 return ERR_PTR(-ENOENT);
242
243 debug_print_probes(*funcs);
244 /* (N -> M), (N > 1, M >= 0) probes */
245 if (tp_func->func) {
246 for (nr_probes = 0; old[nr_pro
247 if ((old[nr_probes].fu
248 old[nr_probes].da
249 old[nr_probes].fun
250 nr_del++;
251 }
252 }
253
254 /*
255 * If probe is NULL, then nr_probes =
256 * entire entry will be removed.
257 */
258 if (nr_probes - nr_del == 0) {
259 /* N -> 0, (N > 1) */
260 *funcs = NULL;
261 debug_print_probes(*funcs);
262 return old;
263 } else {
264 int j = 0;
265 /* N -> M, (N > 1, M > 0) */
266 /* + 1 for NULL */
267 new = allocate_probes(nr_probe
268 if (new) {
269 for (i = 0; old[i].fun
270 if ((old[i].fu
271 old[i].da
272 old[i].fun
273 new[j+
274 }
275 new[nr_probes - nr_del
276 *funcs = new;
277 } else {
278 /*
279 * Failed to allocate,
280 * with calls to tp_st
281 */
282 for (i = 0; old[i].fun
283 if (old[i].fun
284 old[i].dat
285 WRITE_
286 }
287 *funcs = old;
288 }
289 }
290 debug_print_probes(*funcs);
291 return old;
292 }
293
294 /*
295 * Count the number of functions (enum tp_func
296 */
297 static enum tp_func_state nr_func_state(const
298 {
299 if (!tp_funcs)
300 return TP_FUNC_0;
301 if (!tp_funcs[1].func)
302 return TP_FUNC_1;
303 if (!tp_funcs[2].func)
304 return TP_FUNC_2;
305 return TP_FUNC_N; /* 3 or more *
306 }
307
308 static void tracepoint_update_call(struct trac
309 {
310 void *func = tp->iterator;
311
312 /* Synthetic events do not have static
313 if (!tp->static_call_key)
314 return;
315 if (nr_func_state(tp_funcs) == TP_FUNC
316 func = tp_funcs[0].func;
317 __static_call_update(tp->static_call_k
318 }
319
320 /*
321 * Add the probe function to a tracepoint.
322 */
323 static int tracepoint_add_func(struct tracepoi
324 struct tracepoi
325 bool warn)
326 {
327 struct tracepoint_func *old, *tp_funcs
328 int ret;
329
330 if (tp->regfunc && !static_key_enabled
331 ret = tp->regfunc();
332 if (ret < 0)
333 return ret;
334 }
335
336 tp_funcs = rcu_dereference_protected(t
337 lockdep_is_held(&trace
338 old = func_add(&tp_funcs, func, prio);
339 if (IS_ERR(old)) {
340 WARN_ON_ONCE(warn && PTR_ERR(o
341 return PTR_ERR(old);
342 }
343
344 /*
345 * rcu_assign_pointer has as smp_store
346 * that the new probe callbacks array
347 * a pointer to it. This array is ref
348 * include/linux/tracepoint.h using rc
349 */
350 switch (nr_func_state(tp_funcs)) {
351 case TP_FUNC_1: /* 0->1 */
352 /*
353 * Make sure new static func n
354 * 1->0->1 transition sequence
355 */
356 tp_rcu_cond_sync(TP_TRANSITION
357 /* Set static call to first fu
358 tracepoint_update_call(tp, tp_
359 /* Both iterator and static ca
360 rcu_assign_pointer(tp->funcs,
361 static_key_enable(&tp->key);
362 break;
363 case TP_FUNC_2: /* 1->2 */
364 /* Set iterator static call */
365 tracepoint_update_call(tp, tp_
366 /*
367 * Iterator callback installed
368 * Requires ordering between R
369 * static call update/call.
370 */
371 fallthrough;
372 case TP_FUNC_N: /* N->N+1 (N>1
373 rcu_assign_pointer(tp->funcs,
374 /*
375 * Make sure static func never
376 * N->...->2->1 (N>1) transiti
377 */
378 if (tp_funcs[0].data != old[0]
379 tp_rcu_get_state(TP_TR
380 break;
381 default:
382 WARN_ON_ONCE(1);
383 break;
384 }
385
386 release_probes(old);
387 return 0;
388 }
389
390 /*
391 * Remove a probe function from a tracepoint.
392 * Note: only waiting an RCU period after sett
393 * function insures that the original callback
394 * by preempt_disable around the call site.
395 */
396 static int tracepoint_remove_func(struct trace
397 struct tracepoint_func *func)
398 {
399 struct tracepoint_func *old, *tp_funcs
400
401 tp_funcs = rcu_dereference_protected(t
402 lockdep_is_held(&trace
403 old = func_remove(&tp_funcs, func);
404 if (WARN_ON_ONCE(IS_ERR(old)))
405 return PTR_ERR(old);
406
407 if (tp_funcs == old)
408 /* Failed allocating new tp_fu
409 return 0;
410
411 switch (nr_func_state(tp_funcs)) {
412 case TP_FUNC_0: /* 1->0 */
413 /* Removed last function */
414 if (tp->unregfunc && static_ke
415 tp->unregfunc();
416
417 static_key_disable(&tp->key);
418 /* Set iterator static call */
419 tracepoint_update_call(tp, tp_
420 /* Both iterator and static ca
421 rcu_assign_pointer(tp->funcs,
422 /*
423 * Make sure new static func n
424 * 1->0->1 transition sequence
425 */
426 tp_rcu_get_state(TP_TRANSITION
427 break;
428 case TP_FUNC_1: /* 2->1 */
429 rcu_assign_pointer(tp->funcs,
430 /*
431 * Make sure static func never
432 * N->...->2->1 (N>2) transiti
433 * element's data has changed,
434 * to prevent current readers
435 * from calling the new functi
436 */
437 if (tp_funcs[0].data != old[0]
438 tp_rcu_get_state(TP_TR
439 tp_rcu_cond_sync(TP_TRANSITION
440 /* Set static call to first fu
441 tracepoint_update_call(tp, tp_
442 break;
443 case TP_FUNC_2: /* N->N-1 (N>2
444 fallthrough;
445 case TP_FUNC_N:
446 rcu_assign_pointer(tp->funcs,
447 /*
448 * Make sure static func never
449 * N->...->2->1 (N>2) transiti
450 */
451 if (tp_funcs[0].data != old[0]
452 tp_rcu_get_state(TP_TR
453 break;
454 default:
455 WARN_ON_ONCE(1);
456 break;
457 }
458 release_probes(old);
459 return 0;
460 }
461
462 /**
463 * tracepoint_probe_register_prio_may_exist -
464 * @tp: tracepoint
465 * @probe: probe handler
466 * @data: tracepoint data
467 * @prio: priority of this function over other
468 *
469 * Same as tracepoint_probe_register_prio() ex
470 * if the tracepoint is already registered.
471 */
472 int tracepoint_probe_register_prio_may_exist(s
473 v
474 {
475 struct tracepoint_func tp_func;
476 int ret;
477
478 mutex_lock(&tracepoints_mutex);
479 tp_func.func = probe;
480 tp_func.data = data;
481 tp_func.prio = prio;
482 ret = tracepoint_add_func(tp, &tp_func
483 mutex_unlock(&tracepoints_mutex);
484 return ret;
485 }
486 EXPORT_SYMBOL_GPL(tracepoint_probe_register_pr
487
488 /**
489 * tracepoint_probe_register_prio - Connect a
490 * @tp: tracepoint
491 * @probe: probe handler
492 * @data: tracepoint data
493 * @prio: priority of this function over other
494 *
495 * Returns 0 if ok, error value on error.
496 * Note: if @tp is within a module, the caller
497 * unregistering the probe before the module i
498 * performed either with a tracepoint module g
499 * within module exit functions.
500 */
501 int tracepoint_probe_register_prio(struct trac
502 void *data,
503 {
504 struct tracepoint_func tp_func;
505 int ret;
506
507 mutex_lock(&tracepoints_mutex);
508 tp_func.func = probe;
509 tp_func.data = data;
510 tp_func.prio = prio;
511 ret = tracepoint_add_func(tp, &tp_func
512 mutex_unlock(&tracepoints_mutex);
513 return ret;
514 }
515 EXPORT_SYMBOL_GPL(tracepoint_probe_register_pr
516
517 /**
518 * tracepoint_probe_register - Connect a prob
519 * @tp: tracepoint
520 * @probe: probe handler
521 * @data: tracepoint data
522 *
523 * Returns 0 if ok, error value on error.
524 * Note: if @tp is within a module, the caller
525 * unregistering the probe before the module i
526 * performed either with a tracepoint module g
527 * within module exit functions.
528 */
529 int tracepoint_probe_register(struct tracepoin
530 {
531 return tracepoint_probe_register_prio(
532 }
533 EXPORT_SYMBOL_GPL(tracepoint_probe_register);
534
535 /**
536 * tracepoint_probe_unregister - Disconnect a
537 * @tp: tracepoint
538 * @probe: probe function pointer
539 * @data: tracepoint data
540 *
541 * Returns 0 if ok, error value on error.
542 */
543 int tracepoint_probe_unregister(struct tracepo
544 {
545 struct tracepoint_func tp_func;
546 int ret;
547
548 mutex_lock(&tracepoints_mutex);
549 tp_func.func = probe;
550 tp_func.data = data;
551 ret = tracepoint_remove_func(tp, &tp_f
552 mutex_unlock(&tracepoints_mutex);
553 return ret;
554 }
555 EXPORT_SYMBOL_GPL(tracepoint_probe_unregister)
556
557 static void for_each_tracepoint_range(
558 tracepoint_ptr_t *begin, trace
559 void (*fct)(struct tracepoint
560 void *priv)
561 {
562 tracepoint_ptr_t *iter;
563
564 if (!begin)
565 return;
566 for (iter = begin; iter < end; iter++)
567 fct(tracepoint_ptr_deref(iter)
568 }
569
570 #ifdef CONFIG_MODULES
571 bool trace_module_has_bad_taint(struct module
572 {
573 return mod->taints & ~((1 << TAINT_OOT
574 (1 << TAINT_UN
575 (1 << TAINT_LI
576 }
577
578 static BLOCKING_NOTIFIER_HEAD(tracepoint_notif
579
580 /**
581 * register_tracepoint_module_notifier - regis
582 * @nb: notifier block
583 *
584 * Notifiers registered with this function are
585 * coming/going with the tracepoint_module_lis
586 * The notifier block callback should expect a
587 * pointer.
588 */
589 int register_tracepoint_module_notifier(struct
590 {
591 struct tp_module *tp_mod;
592 int ret;
593
594 mutex_lock(&tracepoint_module_list_mut
595 ret = blocking_notifier_chain_register
596 if (ret)
597 goto end;
598 list_for_each_entry(tp_mod, &tracepoin
599 (void) nb->notifier_call(nb, M
600 end:
601 mutex_unlock(&tracepoint_module_list_m
602 return ret;
603 }
604 EXPORT_SYMBOL_GPL(register_tracepoint_module_n
605
606 /**
607 * unregister_tracepoint_module_notifier - unr
608 * @nb: notifier block
609 *
610 * The notifier block callback should expect a
611 * pointer.
612 */
613 int unregister_tracepoint_module_notifier(stru
614 {
615 struct tp_module *tp_mod;
616 int ret;
617
618 mutex_lock(&tracepoint_module_list_mut
619 ret = blocking_notifier_chain_unregist
620 if (ret)
621 goto end;
622 list_for_each_entry(tp_mod, &tracepoin
623 (void) nb->notifier_call(nb, M
624 end:
625 mutex_unlock(&tracepoint_module_list_m
626 return ret;
627
628 }
629 EXPORT_SYMBOL_GPL(unregister_tracepoint_module
630
631 /*
632 * Ensure the tracer unregistered the module's
633 * teardown is performed. Prevents leaks of pr
634 */
635 static void tp_module_going_check_quiescent(st
636 {
637 WARN_ON_ONCE(tp->funcs);
638 }
639
640 static int tracepoint_module_coming(struct mod
641 {
642 struct tp_module *tp_mod;
643
644 if (!mod->num_tracepoints)
645 return 0;
646
647 /*
648 * We skip modules that taint the kern
649 * module headers (for forced load), t
650 * Staging, out-of-tree, unsigned GPL,
651 */
652 if (trace_module_has_bad_taint(mod))
653 return 0;
654
655 tp_mod = kmalloc(sizeof(struct tp_modu
656 if (!tp_mod)
657 return -ENOMEM;
658 tp_mod->mod = mod;
659
660 mutex_lock(&tracepoint_module_list_mut
661 list_add_tail(&tp_mod->list, &tracepoi
662 blocking_notifier_call_chain(&tracepoi
663 MODULE_STATE_COMING, t
664 mutex_unlock(&tracepoint_module_list_m
665 return 0;
666 }
667
668 static void tracepoint_module_going(struct mod
669 {
670 struct tp_module *tp_mod;
671
672 if (!mod->num_tracepoints)
673 return;
674
675 mutex_lock(&tracepoint_module_list_mut
676 list_for_each_entry(tp_mod, &tracepoin
677 if (tp_mod->mod == mod) {
678 blocking_notifier_call
679 MODULE
680 list_del(&tp_mod->list
681 kfree(tp_mod);
682 /*
683 * Called the going no
684 * quiescence.
685 */
686 for_each_tracepoint_ra
687 mod->tracepoin
688 tp_module_goin
689 break;
690 }
691 }
692 /*
693 * In the case of modules that were ta
694 * walk through the list without findi
695 * flag on "going", in case a module t
696 * loaded.
697 */
698 mutex_unlock(&tracepoint_module_list_m
699 }
700
701 static int tracepoint_module_notify(struct not
702 unsigned long val, void *data)
703 {
704 struct module *mod = data;
705 int ret = 0;
706
707 switch (val) {
708 case MODULE_STATE_COMING:
709 ret = tracepoint_module_coming
710 break;
711 case MODULE_STATE_LIVE:
712 break;
713 case MODULE_STATE_GOING:
714 tracepoint_module_going(mod);
715 break;
716 case MODULE_STATE_UNFORMED:
717 break;
718 }
719 return notifier_from_errno(ret);
720 }
721
722 static struct notifier_block tracepoint_module
723 .notifier_call = tracepoint_module_not
724 .priority = 0,
725 };
726
727 static __init int init_tracepoints(void)
728 {
729 int ret;
730
731 ret = register_module_notifier(&tracep
732 if (ret)
733 pr_warn("Failed to register tr
734
735 return ret;
736 }
737 __initcall(init_tracepoints);
738 #endif /* CONFIG_MODULES */
739
740 /**
741 * for_each_kernel_tracepoint - iteration on a
742 * @fct: callback
743 * @priv: private data
744 */
745 void for_each_kernel_tracepoint(void (*fct)(st
746 void *priv)
747 {
748 for_each_tracepoint_range(__start___tr
749 __stop___tracepoints_ptrs, fct
750 }
751 EXPORT_SYMBOL_GPL(for_each_kernel_tracepoint);
752
753 #ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
754
755 /* NB: reg/unreg are called while guarded with
756 static int sys_tracepoint_refcount;
757
758 int syscall_regfunc(void)
759 {
760 struct task_struct *p, *t;
761
762 if (!sys_tracepoint_refcount) {
763 read_lock(&tasklist_lock);
764 for_each_process_thread(p, t)
765 set_task_syscall_work(
766 }
767 read_unlock(&tasklist_lock);
768 }
769 sys_tracepoint_refcount++;
770
771 return 0;
772 }
773
774 void syscall_unregfunc(void)
775 {
776 struct task_struct *p, *t;
777
778 sys_tracepoint_refcount--;
779 if (!sys_tracepoint_refcount) {
780 read_lock(&tasklist_lock);
781 for_each_process_thread(p, t)
782 clear_task_syscall_wor
783 }
784 read_unlock(&tasklist_lock);
785 }
786 }
787 #endif
788
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