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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 * Atomic notifier chain routines. Registration and unregistration
99 * use a spinlock, and call_chain is synchronized by RCU (no locks).
100 */
101
102/**
103 * atomic_notifier_chain_register - Add notifier to an atomic notifier chain
104 * @nh: Pointer to head of the atomic notifier chain
105 * @n: New entry in notifier chain
106 *
107 * Adds a notifier to an atomic notifier chain.
108 *
109 * Currently always returns zero.
110 */
111int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
112 struct notifier_block *n)
113{
114 unsigned long flags;
115 int ret;
116
117 spin_lock_irqsave(&nh->lock, flags);
118 ret = notifier_chain_register(&nh->head, n);
119 spin_unlock_irqrestore(&nh->lock, flags);
120 return ret;
121}
122EXPORT_SYMBOL_GPL(atomic_notifier_chain_register);
123
124/**
125 * atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
126 * @nh: Pointer to head of the atomic notifier chain
127 * @n: Entry to remove from notifier chain
128 *
129 * Removes a notifier from an atomic notifier chain.
130 *
131 * Returns zero on success or %-ENOENT on failure.
132 */
133int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
134 struct notifier_block *n)
135{
136 unsigned long flags;
137 int ret;
138
139 spin_lock_irqsave(&nh->lock, flags);
140 ret = notifier_chain_unregister(&nh->head, n);
141 spin_unlock_irqrestore(&nh->lock, flags);
142 synchronize_rcu();
143 return ret;
144}
145EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
146
147/**
148 * __atomic_notifier_call_chain - Call functions in an atomic notifier chain
149 * @nh: Pointer to head of the atomic notifier chain
150 * @val: Value passed unmodified to notifier function
151 * @v: Pointer passed unmodified to notifier function
152 * @nr_to_call: See the comment for notifier_call_chain.
153 * @nr_calls: See the comment for notifier_call_chain.
154 *
155 * Calls each function in a notifier chain in turn. The functions
156 * run in an atomic context, so they must not block.
157 * This routine uses RCU to synchronize with changes to the chain.
158 *
159 * If the return value of the notifier can be and'ed
160 * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain()
161 * will return immediately, with the return value of
162 * the notifier function which halted execution.
163 * Otherwise the return value is the return value
164 * of the last notifier function called.
165 */
166int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
167 unsigned long val, void *v,
168 int nr_to_call, int *nr_calls)
169{
170 int ret;
171
172 rcu_read_lock();
173 ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
174 rcu_read_unlock();
175 return ret;
176}
177EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
178NOKPROBE_SYMBOL(__atomic_notifier_call_chain);
179
180int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
181 unsigned long val, void *v)
182{
183 return __atomic_notifier_call_chain(nh, val, v, -1, NULL);
184}
185EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
186NOKPROBE_SYMBOL(atomic_notifier_call_chain);
187
188/*
189 * Blocking notifier chain routines. All access to the chain is
190 * synchronized by an rwsem.
191 */
192
193/**
194 * blocking_notifier_chain_register - Add notifier to a blocking notifier chain
195 * @nh: Pointer to head of the blocking notifier chain
196 * @n: New entry in notifier chain
197 *
198 * Adds a notifier to a blocking notifier chain.
199 * Must be called in process context.
200 *
201 * Currently always returns zero.
202 */
203int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
204 struct notifier_block *n)
205{
206 int ret;
207
208 /*
209 * This code gets used during boot-up, when task switching is
210 * not yet working and interrupts must remain disabled. At
211 * such times we must not call down_write().
212 */
213 if (unlikely(system_state == SYSTEM_BOOTING))
214 return notifier_chain_register(&nh->head, n);
215
216 down_write(&nh->rwsem);
217 ret = notifier_chain_register(&nh->head, n);
218 up_write(&nh->rwsem);
219 return ret;
220}
221EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
222
223/**
224 * blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
225 * @nh: Pointer to head of the blocking notifier chain
226 * @n: Entry to remove from notifier chain
227 *
228 * Removes a notifier from a blocking notifier chain.
229 * Must be called from process context.
230 *
231 * Returns zero on success or %-ENOENT on failure.
232 */
233int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
234 struct notifier_block *n)
235{
236 int ret;
237
238 /*
239 * This code gets used during boot-up, when task switching is
240 * not yet working and interrupts must remain disabled. At
241 * such times we must not call down_write().
242 */
243 if (unlikely(system_state == SYSTEM_BOOTING))
244 return notifier_chain_unregister(&nh->head, n);
245
246 down_write(&nh->rwsem);
247 ret = notifier_chain_unregister(&nh->head, n);
248 up_write(&nh->rwsem);
249 return ret;
250}
251EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister);
252
253/**
254 * __blocking_notifier_call_chain - Call functions in a blocking notifier chain
255 * @nh: Pointer to head of the blocking notifier chain
256 * @val: Value passed unmodified to notifier function
257 * @v: Pointer passed unmodified to notifier function
258 * @nr_to_call: See comment for notifier_call_chain.
259 * @nr_calls: See comment for notifier_call_chain.
260 *
261 * Calls each function in a notifier chain in turn. The functions
262 * run in a process context, so they are allowed to block.
263 *
264 * If the return value of the notifier can be and'ed
265 * with %NOTIFY_STOP_MASK then blocking_notifier_call_chain()
266 * will return immediately, with the return value of
267 * the notifier function which halted execution.
268 * Otherwise the return value is the return value
269 * of the last notifier function called.
270 */
271int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
272 unsigned long val, void *v,
273 int nr_to_call, int *nr_calls)
274{
275 int ret = NOTIFY_DONE;
276
277 /*
278 * We check the head outside the lock, but if this access is
279 * racy then it does not matter what the result of the test
280 * is, we re-check the list after having taken the lock anyway:
281 */
282 if (rcu_access_pointer(nh->head)) {
283 down_read(&nh->rwsem);
284 ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
285 nr_calls);
286 up_read(&nh->rwsem);
287 }
288 return ret;
289}
290EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
291
292int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
293 unsigned long val, void *v)
294{
295 return __blocking_notifier_call_chain(nh, val, v, -1, NULL);
296}
297EXPORT_SYMBOL_GPL(blocking_notifier_call_chain);
298
299/*
300 * Raw notifier chain routines. There is no protection;
301 * the caller must provide it. Use at your own risk!
302 */
303
304/**
305 * raw_notifier_chain_register - Add notifier to a raw notifier chain
306 * @nh: Pointer to head of the raw notifier chain
307 * @n: New entry in notifier chain
308 *
309 * Adds a notifier to a raw notifier chain.
310 * All locking must be provided by the caller.
311 *
312 * Currently always returns zero.
313 */
314int raw_notifier_chain_register(struct raw_notifier_head *nh,
315 struct notifier_block *n)
316{
317 return notifier_chain_register(&nh->head, n);
318}
319EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
320
321/**
322 * raw_notifier_chain_unregister - Remove notifier from a raw notifier chain
323 * @nh: Pointer to head of the raw notifier chain
324 * @n: Entry to remove from notifier chain
325 *
326 * Removes a notifier from a raw notifier chain.
327 * All locking must be provided by the caller.
328 *
329 * Returns zero on success or %-ENOENT on failure.
330 */
331int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
332 struct notifier_block *n)
333{
334 return notifier_chain_unregister(&nh->head, n);
335}
336EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister);
337
338/**
339 * __raw_notifier_call_chain - Call functions in a raw notifier chain
340 * @nh: Pointer to head of the raw notifier chain
341 * @val: Value passed unmodified to notifier function
342 * @v: Pointer passed unmodified to notifier function
343 * @nr_to_call: See comment for notifier_call_chain.
344 * @nr_calls: See comment for notifier_call_chain
345 *
346 * Calls each function in a notifier chain in turn. The functions
347 * run in an undefined context.
348 * All locking must be provided by the caller.
349 *
350 * If the return value of the notifier can be and'ed
351 * with %NOTIFY_STOP_MASK then raw_notifier_call_chain()
352 * will return immediately, with the return value of
353 * the notifier function which halted execution.
354 * Otherwise the return value is the return value
355 * of the last notifier function called.
356 */
357int __raw_notifier_call_chain(struct raw_notifier_head *nh,
358 unsigned long val, void *v,
359 int nr_to_call, int *nr_calls)
360{
361 return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
362}
363EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
364
365int raw_notifier_call_chain(struct raw_notifier_head *nh,
366 unsigned long val, void *v)
367{
368 return __raw_notifier_call_chain(nh, val, v, -1, NULL);
369}
370EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
371
372#ifdef CONFIG_SRCU
373/*
374 * SRCU notifier chain routines. Registration and unregistration
375 * use a mutex, and call_chain is synchronized by SRCU (no locks).
376 */
377
378/**
379 * srcu_notifier_chain_register - Add notifier to an SRCU notifier chain
380 * @nh: Pointer to head of the SRCU notifier chain
381 * @n: New entry in notifier chain
382 *
383 * Adds a notifier to an SRCU notifier chain.
384 * Must be called in process context.
385 *
386 * Currently always returns zero.
387 */
388int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
389 struct notifier_block *n)
390{
391 int ret;
392
393 /*
394 * This code gets used during boot-up, when task switching is
395 * not yet working and interrupts must remain disabled. At
396 * such times we must not call mutex_lock().
397 */
398 if (unlikely(system_state == SYSTEM_BOOTING))
399 return notifier_chain_register(&nh->head, n);
400
401 mutex_lock(&nh->mutex);
402 ret = notifier_chain_register(&nh->head, n);
403 mutex_unlock(&nh->mutex);
404 return ret;
405}
406EXPORT_SYMBOL_GPL(srcu_notifier_chain_register);
407
408/**
409 * srcu_notifier_chain_unregister - Remove notifier from an SRCU notifier chain
410 * @nh: Pointer to head of the SRCU notifier chain
411 * @n: Entry to remove from notifier chain
412 *
413 * Removes a notifier from an SRCU notifier chain.
414 * Must be called from process context.
415 *
416 * Returns zero on success or %-ENOENT on failure.
417 */
418int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
419 struct notifier_block *n)
420{
421 int ret;
422
423 /*
424 * This code gets used during boot-up, when task switching is
425 * not yet working and interrupts must remain disabled. At
426 * such times we must not call mutex_lock().
427 */
428 if (unlikely(system_state == SYSTEM_BOOTING))
429 return notifier_chain_unregister(&nh->head, n);
430
431 mutex_lock(&nh->mutex);
432 ret = notifier_chain_unregister(&nh->head, n);
433 mutex_unlock(&nh->mutex);
434 synchronize_srcu(&nh->srcu);
435 return ret;
436}
437EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister);
438
439/**
440 * __srcu_notifier_call_chain - Call functions in an SRCU notifier chain
441 * @nh: Pointer to head of the SRCU notifier chain
442 * @val: Value passed unmodified to notifier function
443 * @v: Pointer passed unmodified to notifier function
444 * @nr_to_call: See comment for notifier_call_chain.
445 * @nr_calls: See comment for notifier_call_chain
446 *
447 * Calls each function in a notifier chain in turn. The functions
448 * run in a process context, so they are allowed to block.
449 *
450 * If the return value of the notifier can be and'ed
451 * with %NOTIFY_STOP_MASK then srcu_notifier_call_chain()
452 * will return immediately, with the return value of
453 * the notifier function which halted execution.
454 * Otherwise the return value is the return value
455 * of the last notifier function called.
456 */
457int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
458 unsigned long val, void *v,
459 int nr_to_call, int *nr_calls)
460{
461 int ret;
462 int idx;
463
464 idx = srcu_read_lock(&nh->srcu);
465 ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls);
466 srcu_read_unlock(&nh->srcu, idx);
467 return ret;
468}
469EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
470
471int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
472 unsigned long val, void *v)
473{
474 return __srcu_notifier_call_chain(nh, val, v, -1, NULL);
475}
476EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
477
478/**
479 * srcu_init_notifier_head - Initialize an SRCU notifier head
480 * @nh: Pointer to head of the srcu notifier chain
481 *
482 * Unlike other sorts of notifier heads, SRCU notifier heads require
483 * dynamic initialization. Be sure to call this routine before
484 * calling any of the other SRCU notifier routines for this head.
485 *
486 * If an SRCU notifier head is deallocated, it must first be cleaned
487 * up by calling srcu_cleanup_notifier_head(). Otherwise the head's
488 * per-cpu data (used by the SRCU mechanism) will leak.
489 */
490void srcu_init_notifier_head(struct srcu_notifier_head *nh)
491{
492 mutex_init(&nh->mutex);
493 if (init_srcu_struct(&nh->srcu) < 0)
494 BUG();
495 nh->head = NULL;
496}
497EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
498
499#endif /* CONFIG_SRCU */
500
501static ATOMIC_NOTIFIER_HEAD(die_chain);
502
503int notrace notify_die(enum die_val val, const char *str,
504 struct pt_regs *regs, long err, int trap, int sig)
505{
506 struct die_args args = {
507 .regs = regs,
508 .str = str,
509 .err = err,
510 .trapnr = trap,
511 .signr = sig,
512
513 };
514 RCU_LOCKDEP_WARN(!rcu_is_watching(),
515 "notify_die called but RCU thinks we're quiescent");
516 return atomic_notifier_call_chain(&die_chain, val, &args);
517}
518NOKPROBE_SYMBOL(notify_die);
519
520int register_die_notifier(struct notifier_block *nb)
521{
522 return atomic_notifier_chain_register(&die_chain, nb);
523}
524EXPORT_SYMBOL_GPL(register_die_notifier);
525
526int unregister_die_notifier(struct notifier_block *nb)
527{
528 return atomic_notifier_chain_unregister(&die_chain, nb);
529}
530EXPORT_SYMBOL_GPL(unregister_die_notifier);