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