projects/linux·blob v5.9-rc6 · refs

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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 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);