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