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