1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/kdebug.h>
3 #include <linux/kprobes.h>
4 #include <linux/export.h>
5 #include <linux/notifier.h>
6 #include <linux/rcupdate.h>
7 #include <linux/vmalloc.h>
8 #include <linux/reboot.h>
9
10 #define CREATE_TRACE_POINTS
11 #include <trace/events/notifier.h>
12
13 /*
14 * Notifier list for kernel code which wants to be called
15 * at shutdown. This is used to stop any idling DMA operations
16 * and the like.
17 */
18 BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
19
20 /*
21 * Notifier chain core routines. The exported routines below
22 * are layered on top of these, with appropriate locking added.
23 */
24
25 static int notifier_chain_register(struct notifier_block **nl,
26 struct notifier_block *n,
27 bool unique_priority)
28 {
29 while ((*nl) != NULL) {
30 if (unlikely((*nl) == n)) {
31 WARN(1, "notifier callback %ps already registered",
32 n->notifier_call);
33 return -EEXIST;
34 }
35 if (n->priority > (*nl)->priority)
36 break;
37 if (n->priority == (*nl)->priority && unique_priority)
38 return -EBUSY;
39 nl = &((*nl)->next);
40 }
41 n->next = *nl;
42 rcu_assign_pointer(*nl, n);
43 trace_notifier_register((void *)n->notifier_call);
44 return 0;
45 }
46
47 static int notifier_chain_unregister(struct notifier_block **nl,
48 struct notifier_block *n)
49 {
50 while ((*nl) != NULL) {
51 if ((*nl) == n) {
52 rcu_assign_pointer(*nl, n->next);
53 trace_notifier_unregister((void *)n->notifier_call);
54 return 0;
55 }
56 nl = &((*nl)->next);
57 }
58 return -ENOENT;
59 }
60
61 /**
62 * notifier_call_chain - Informs the registered notifiers about an event.
63 * @nl: Pointer to head of the blocking notifier chain
64 * @val: Value passed unmodified to notifier function
65 * @v: Pointer passed unmodified to notifier function
66 * @nr_to_call: Number of notifier functions to be called. Don't care
67 * value of this parameter is -1.
68 * @nr_calls: Records the number of notifications sent. Don't care
69 * value of this field is NULL.
70 * Return: notifier_call_chain returns the value returned by the
71 * last notifier function called.
72 */
73 static int notifier_call_chain(struct notifier_block **nl,
74 unsigned long val, void *v,
75 int nr_to_call, int *nr_calls)
76 {
77 int ret = NOTIFY_DONE;
78 struct notifier_block *nb, *next_nb;
79
80 nb = rcu_dereference_raw(*nl);
81
82 while (nb && nr_to_call) {
83 next_nb = rcu_dereference_raw(nb->next);
84
85 #ifdef CONFIG_DEBUG_NOTIFIERS
86 if (unlikely(!func_ptr_is_kernel_text(nb->notifier_call))) {
87 WARN(1, "Invalid notifier called!");
88 nb = next_nb;
89 continue;
90 }
91 #endif
92 trace_notifier_run((void *)nb->notifier_call);
93 ret = nb->notifier_call(nb, val, v);
94
95 if (nr_calls)
96 (*nr_calls)++;
97
98 if (ret & NOTIFY_STOP_MASK)
99 break;
100 nb = next_nb;
101 nr_to_call--;
102 }
103 return ret;
104 }
105 NOKPROBE_SYMBOL(notifier_call_chain);
106
107 /**
108 * notifier_call_chain_robust - Inform the registered notifiers about an event
109 * and rollback on error.
110 * @nl: Pointer to head of the blocking notifier chain
111 * @val_up: Value passed unmodified to the notifier function
112 * @val_down: Value passed unmodified to the notifier function when recovering
113 * from an error on @val_up
114 * @v: Pointer passed unmodified to the notifier function
115 *
116 * NOTE: It is important the @nl chain doesn't change between the two
117 * invocations of notifier_call_chain() such that we visit the
118 * exact same notifier callbacks; this rules out any RCU usage.
119 *
120 * Return: the return value of the @val_up call.
121 */
122 static int notifier_call_chain_robust(struct notifier_block **nl,
123 unsigned long val_up, unsigned long val_down,
124 void *v)
125 {
126 int ret, nr = 0;
127
128 ret = notifier_call_chain(nl, val_up, v, -1, &nr);
129 if (ret & NOTIFY_STOP_MASK)
130 notifier_call_chain(nl, val_down, v, nr-1, NULL);
131
132 return ret;
133 }
134
135 /*
136 * Atomic notifier chain routines. Registration and unregistration
137 * use a spinlock, and call_chain is synchronized by RCU (no locks).
138 */
139
140 /**
141 * atomic_notifier_chain_register - Add notifier to an atomic notifier chain
142 * @nh: Pointer to head of the atomic notifier chain
143 * @n: New entry in notifier chain
144 *
145 * Adds a notifier to an atomic notifier chain.
146 *
147 * Returns 0 on success, %-EEXIST on error.
148 */
149 int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
150 struct notifier_block *n)
151 {
152 unsigned long flags;
153 int ret;
154
155 spin_lock_irqsave(&nh->lock, flags);
156 ret = notifier_chain_register(&nh->head, n, false);
157 spin_unlock_irqrestore(&nh->lock, flags);
158 return ret;
159 }
160 EXPORT_SYMBOL_GPL(atomic_notifier_chain_register);
161
162 /**
163 * atomic_notifier_chain_register_unique_prio - Add notifier to an atomic notifier chain
164 * @nh: Pointer to head of the atomic notifier chain
165 * @n: New entry in notifier chain
166 *
167 * Adds a notifier to an atomic notifier chain if there is no other
168 * notifier registered using the same priority.
169 *
170 * Returns 0 on success, %-EEXIST or %-EBUSY on error.
171 */
172 int atomic_notifier_chain_register_unique_prio(struct atomic_notifier_head *nh,
173 struct notifier_block *n)
174 {
175 unsigned long flags;
176 int ret;
177
178 spin_lock_irqsave(&nh->lock, flags);
179 ret = notifier_chain_register(&nh->head, n, true);
180 spin_unlock_irqrestore(&nh->lock, flags);
181 return ret;
182 }
183 EXPORT_SYMBOL_GPL(atomic_notifier_chain_register_unique_prio);
184
185 /**
186 * atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
187 * @nh: Pointer to head of the atomic notifier chain
188 * @n: Entry to remove from notifier chain
189 *
190 * Removes a notifier from an atomic notifier chain.
191 *
192 * Returns zero on success or %-ENOENT on failure.
193 */
194 int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
195 struct notifier_block *n)
196 {
197 unsigned long flags;
198 int ret;
199
200 spin_lock_irqsave(&nh->lock, flags);
201 ret = notifier_chain_unregister(&nh->head, n);
202 spin_unlock_irqrestore(&nh->lock, flags);
203 synchronize_rcu();
204 return ret;
205 }
206 EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
207
208 /**
209 * atomic_notifier_call_chain - Call functions in an atomic notifier chain
210 * @nh: Pointer to head of the atomic notifier chain
211 * @val: Value passed unmodified to notifier function
212 * @v: Pointer passed unmodified to notifier function
213 *
214 * Calls each function in a notifier chain in turn. The functions
215 * run in an atomic context, so they must not block.
216 * This routine uses RCU to synchronize with changes to the chain.
217 *
218 * If the return value of the notifier can be and'ed
219 * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
220 * will return immediately, with the return value of
221 * the notifier function which halted execution.
222 * Otherwise the return value is the return value
223 * of the last notifier function called.
224 */
225 int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
226 unsigned long val, void *v)
227 {
228 int ret;
229
230 rcu_read_lock();
231 ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
232 rcu_read_unlock();
233
234 return ret;
235 }
236 EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
237 NOKPROBE_SYMBOL(atomic_notifier_call_chain);
238
239 /**
240 * atomic_notifier_call_chain_is_empty - Check whether notifier chain is empty
241 * @nh: Pointer to head of the atomic notifier chain
242 *
243 * Checks whether notifier chain is empty.
244 *
245 * Returns true is notifier chain is empty, false otherwise.
246 */
247 bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh)
248 {
249 return !rcu_access_pointer(nh->head);
250 }
251
252 /*
253 * Blocking notifier chain routines. All access to the chain is
254 * synchronized by an rwsem.
255 */
256
257 static int __blocking_notifier_chain_register(struct blocking_notifier_head *nh,
258 struct notifier_block *n,
259 bool unique_priority)
260 {
261 int ret;
262
263 /*
264 * This code gets used during boot-up, when task switching is
265 * not yet working and interrupts must remain disabled. At
266 * such times we must not call down_write().
267 */
268 if (unlikely(system_state == SYSTEM_BOOTING))
269 return notifier_chain_register(&nh->head, n, unique_priority);
270
271 down_write(&nh->rwsem);
272 ret = notifier_chain_register(&nh->head, n, unique_priority);
273 up_write(&nh->rwsem);
274 return ret;
275 }
276
277 /**
278 * blocking_notifier_chain_register - Add notifier to a blocking notifier chain
279 * @nh: Pointer to head of the blocking notifier chain
280 * @n: New entry in notifier chain
281 *
282 * Adds a notifier to a blocking notifier chain.
283 * Must be called in process context.
284 *
285 * Returns 0 on success, %-EEXIST on error.
286 */
287 int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
288 struct notifier_block *n)
289 {
290 return __blocking_notifier_chain_register(nh, n, false);
291 }
292 EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
293
294 /**
295 * blocking_notifier_chain_register_unique_prio - Add notifier to a blocking notifier chain
296 * @nh: Pointer to head of the blocking notifier chain
297 * @n: New entry in notifier chain
298 *
299 * Adds a notifier to an blocking notifier chain if there is no other
300 * notifier registered using the same priority.
301 *
302 * Returns 0 on success, %-EEXIST or %-EBUSY on error.
303 */
304 int blocking_notifier_chain_register_unique_prio(struct blocking_notifier_head *nh,
305 struct notifier_block *n)
306 {
307 return __blocking_notifier_chain_register(nh, n, true);
308 }
309 EXPORT_SYMBOL_GPL(blocking_notifier_chain_register_unique_prio);
310
311 /**
312 * blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
313 * @nh: Pointer to head of the blocking notifier chain
314 * @n: Entry to remove from notifier chain
315 *
316 * Removes a notifier from a blocking notifier chain.
317 * Must be called from process context.
318 *
319 * Returns zero on success or %-ENOENT on failure.
320 */
321 int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
322 struct notifier_block *n)
323 {
324 int ret;
325
326 /*
327 * This code gets used during boot-up, when task switching is
328 * not yet working and interrupts must remain disabled. At
329 * such times we must not call down_write().
330 */
331 if (unlikely(system_state == SYSTEM_BOOTING))
332 return notifier_chain_unregister(&nh->head, n);
333
334 down_write(&nh->rwsem);
335 ret = notifier_chain_unregister(&nh->head, n);
336 up_write(&nh->rwsem);
337 return ret;
338 }
339 EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
340
341 int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
342 unsigned long val_up, unsigned long val_down, void *v)
343 {
344 int ret = NOTIFY_DONE;
345
346 /*
347 * We check the head outside the lock, but if this access is
348 * racy then it does not matter what the result of the test
349 * is, we re-check the list after having taken the lock anyway:
350 */
351 if (rcu_access_pointer(nh->head)) {
352 down_read(&nh->rwsem);
353 ret = notifier_call_chain_robust(&nh->head, val_up, val_down, v);
354 up_read(&nh->rwsem);
355 }
356 return ret;
357 }
358 EXPORT_SYMBOL_GPL(blocking_notifier_call_chain_robust);
359
360 /**
361 * blocking_notifier_call_chain - Call functions in a blocking notifier chain
362 * @nh: Pointer to head of the blocking notifier chain
363 * @val: Value passed unmodified to notifier function
364 * @v: Pointer passed unmodified to notifier function
365 *
366 * Calls each function in a notifier chain in turn. The functions
367 * run in a process context, so they are allowed to block.
368 *
369 * If the return value of the notifier can be and'ed
370 * with %NOTIFY_STOP_MASK then blocking_notifier_call_chain()
371 * will return immediately, with the return value of
372 * the notifier function which halted execution.
373 * Otherwise the return value is the return value
374 * of the last notifier function called.
375 */
376 int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
377 unsigned long val, void *v)
378 {
379 int ret = NOTIFY_DONE;
380
381 /*
382 * We check the head outside the lock, but if this access is
383 * racy then it does not matter what the result of the test
384 * is, we re-check the list after having taken the lock anyway:
385 */
386 if (rcu_access_pointer(nh->head)) {
387 down_read(&nh->rwsem);
388 ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
389 up_read(&nh->rwsem);
390 }
391 return ret;
392 }
393 EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
394
395 /*
396 * Raw notifier chain routines. There is no protection;
397 * the caller must provide it. Use at your own risk!
398 */
399
400 /**
401 * raw_notifier_chain_register - Add notifier to a raw notifier chain
402 * @nh: Pointer to head of the raw notifier chain
403 * @n: New entry in notifier chain
404 *
405 * Adds a notifier to a raw notifier chain.
406 * All locking must be provided by the caller.
407 *
408 * Returns 0 on success, %-EEXIST on error.
409 */
410 int raw_notifier_chain_register(struct raw_notifier_head *nh,
411 struct notifier_block *n)
412 {
413 return notifier_chain_register(&nh->head, n, false);
414 }
415 EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
416
417 /**
418 * raw_notifier_chain_unregister - Remove notifier from a raw notifier chain
419 * @nh: Pointer to head of the raw notifier chain
420 * @n: Entry to remove from notifier chain
421 *
422 * Removes a notifier from a raw notifier chain.
423 * All locking must be provided by the caller.
424 *
425 * Returns zero on success or %-ENOENT on failure.
426 */
427 int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
428 struct notifier_block *n)
429 {
430 return notifier_chain_unregister(&nh->head, n);
431 }
432 EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
433
434 int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
435 unsigned long val_up, unsigned long val_down, void *v)
436 {
437 return notifier_call_chain_robust(&nh->head, val_up, val_down, v);
438 }
439 EXPORT_SYMBOL_GPL(raw_notifier_call_chain_robust);
440
441 /**
442 * raw_notifier_call_chain - Call functions in a raw notifier chain
443 * @nh: Pointer to head of the raw notifier chain
444 * @val: Value passed unmodified to notifier function
445 * @v: Pointer passed unmodified to notifier function
446 *
447 * Calls each function in a notifier chain in turn. The functions
448 * run in an undefined context.
449 * All locking must be provided by the caller.
450 *
451 * If the return value of the notifier can be and'ed
452 * with %NOTIFY_STOP_MASK then raw_notifier_call_chain()
453 * will return immediately, with the return value of
454 * the notifier function which halted execution.
455 * Otherwise the return value is the return value
456 * of the last notifier function called.
457 */
458 int raw_notifier_call_chain(struct raw_notifier_head *nh,
459 unsigned long val, void *v)
460 {
461 return notifier_call_chain(&nh->head, val, v, -1, NULL);
462 }
463 EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
464
465 /*
466 * SRCU notifier chain routines. Registration and unregistration
467 * use a mutex, and call_chain is synchronized by SRCU (no locks).
468 */
469
470 /**
471 * srcu_notifier_chain_register - Add notifier to an SRCU notifier chain
472 * @nh: Pointer to head of the SRCU notifier chain
473 * @n: New entry in notifier chain
474 *
475 * Adds a notifier to an SRCU notifier chain.
476 * Must be called in process context.
477 *
478 * Returns 0 on success, %-EEXIST on error.
479 */
480 int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
481 struct notifier_block *n)
482 {
483 int ret;
484
485 /*
486 * This code gets used during boot-up, when task switching is
487 * not yet working and interrupts must remain disabled. At
488 * such times we must not call mutex_lock().
489 */
490 if (unlikely(system_state == SYSTEM_BOOTING))
491 return notifier_chain_register(&nh->head, n, false);
492
493 mutex_lock(&nh->mutex);
494 ret = notifier_chain_register(&nh->head, n, false);
495 mutex_unlock(&nh->mutex);
496 return ret;
497 }
498 EXPORT_SYMBOL_GPL(srcu_notifier_chain_register);
499
500 /**
501 * srcu_notifier_chain_unregister - Remove notifier from an SRCU notifier chain
502 * @nh: Pointer to head of the SRCU notifier chain
503 * @n: Entry to remove from notifier chain
504 *
505 * Removes a notifier from an SRCU notifier chain.
506 * Must be called from process context.
507 *
508 * Returns zero on success or %-ENOENT on failure.
509 */
510 int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
511 struct notifier_block *n)
512 {
513 int ret;
514
515 /*
516 * This code gets used during boot-up, when task switching is
517 * not yet working and interrupts must remain disabled. At
518 * such times we must not call mutex_lock().
519 */
520 if (unlikely(system_state == SYSTEM_BOOTING))
521 return notifier_chain_unregister(&nh->head, n);
522
523 mutex_lock(&nh->mutex);
524 ret = notifier_chain_unregister(&nh->head, n);
525 mutex_unlock(&nh->mutex);
526 synchronize_srcu(&nh->srcu);
527 return ret;
528 }
529 EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
530
531 /**
532 * srcu_notifier_call_chain - Call functions in an SRCU notifier chain
533 * @nh: Pointer to head of the SRCU notifier chain
534 * @val: Value passed unmodified to notifier function
535 * @v: Pointer passed unmodified to notifier function
536 *
537 * Calls each function in a notifier chain in turn. The functions
538 * run in a process context, so they are allowed to block.
539 *
540 * If the return value of the notifier can be and'ed
541 * with %NOTIFY_STOP_MASK then srcu_notifier_call_chain()
542 * will return immediately, with the return value of
543 * the notifier function which halted execution.
544 * Otherwise the return value is the return value
545 * of the last notifier function called.
546 */
547 int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
548 unsigned long val, void *v)
549 {
550 int ret;
551 int idx;
552
553 idx = srcu_read_lock(&nh->srcu);
554 ret = notifier_call_chain(&nh->head, val, v, -1, NULL);
555 srcu_read_unlock(&nh->srcu, idx);
556 return ret;
557 }
558 EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
559
560 /**
561 * srcu_init_notifier_head - Initialize an SRCU notifier head
562 * @nh: Pointer to head of the srcu notifier chain
563 *
564 * Unlike other sorts of notifier heads, SRCU notifier heads require
565 * dynamic initialization. Be sure to call this routine before
566 * calling any of the other SRCU notifier routines for this head.
567 *
568 * If an SRCU notifier head is deallocated, it must first be cleaned
569 * up by calling srcu_cleanup_notifier_head(). Otherwise the head's
570 * per-cpu data (used by the SRCU mechanism) will leak.
571 */
572 void srcu_init_notifier_head(struct srcu_notifier_head *nh)
573 {
574 mutex_init(&nh->mutex);
575 if (init_srcu_struct(&nh->srcu) < 0)
576 BUG();
577 nh->head = NULL;
578 }
579 EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
580
581 static ATOMIC_NOTIFIER_HEAD(die_chain);
582
583 int notrace notify_die(enum die_val val, const char *str,
584 struct pt_regs *regs, long err, int trap, int sig)
585 {
586 struct die_args args = {
587 .regs = regs,
588 .str = str,
589 .err = err,
590 .trapnr = trap,
591 .signr = sig,
592
593 };
594 RCU_LOCKDEP_WARN(!rcu_is_watching(),
595 "notify_die called but RCU thinks we're quiescent");
596 return atomic_notifier_call_chain(&die_chain, val, &args);
597 }
598 NOKPROBE_SYMBOL(notify_die);
599
600 int register_die_notifier(struct notifier_block *nb)
601 {
602 return atomic_notifier_chain_register(&die_chain, nb);
603 }
604 EXPORT_SYMBOL_GPL(register_die_notifier);
605
606 int unregister_die_notifier(struct notifier_block *nb)
607 {
608 return atomic_notifier_chain_unregister(&die_chain, nb);
609 }
610 EXPORT_SYMBOL_GPL(unregister_die_notifier);
611
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