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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 */
14 BLOCKING_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
21 static 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
34 static 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
49 static 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 */
74 static 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 }
105 NOKPROBE_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 */
121 int 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 }
132 EXPORT_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 */
143 int 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 }
155 EXPORT_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 */
176 int __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 }
187 EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain);
188 NOKPROBE_SYMBOL(__atomic_notifier_call_chain);
189
190 int 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 }
195 EXPORT_SYMBOL_GPL(atomic_notifier_call_chain);
196 NOKPROBE_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 */
213 int 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 }
231 EXPORT_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 */
244 int 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 }
254 EXPORT_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 */
266 int 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 }
284 EXPORT_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 */
304 int __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 }
323 EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain);
324
325 int 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 }
330 EXPORT_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 */
347 int raw_notifier_chain_register(struct raw_notifier_head *nh,
348 struct notifier_block *n)
349 {
350 return notifier_chain_register(&nh->head, n);
351 }
352 EXPORT_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 */
364 int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
365 struct notifier_block *n)
366 {
367 return notifier_chain_unregister(&nh->head, n);
368 }
369 EXPORT_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 */
390 int __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 }
396 EXPORT_SYMBOL_GPL(__raw_notifier_call_chain);
397
398 int 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 }
403 EXPORT_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 */
421 int 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 }
439 EXPORT_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 */
451 int 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 }
470 EXPORT_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 */
490 int __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 }
502 EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain);
503
504 int 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 }
509 EXPORT_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 */
523 void 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 }
530 EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
531
532 #endif /* CONFIG_SRCU */
533
534 static ATOMIC_NOTIFIER_HEAD(die_chain);
535
536 int 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 return atomic_notifier_call_chain(&die_chain, val, &args);
548 }
549 NOKPROBE_SYMBOL(notify_die);
550
551 int register_die_notifier(struct notifier_block *nb)
552 {
553 vmalloc_sync_all();
554 return atomic_notifier_chain_register(&die_chain, nb);
555 }
556 EXPORT_SYMBOL_GPL(register_die_notifier);
557
558 int unregister_die_notifier(struct notifier_block *nb)
559 {
560 return atomic_notifier_chain_unregister(&die_chain, nb);
561 }
562 EXPORT_SYMBOL_GPL(unregister_die_notifier);