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fe9d4f57 AD |
1 | #include <linux/kdebug.h> |
2 | #include <linux/kprobes.h> | |
3 | #include <linux/module.h> | |
4 | #include <linux/notifier.h> | |
5 | #include <linux/rcupdate.h> | |
6 | #include <linux/vmalloc.h> | |
c166f23c | 7 | #include <linux/reboot.h> |
fe9d4f57 AD |
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_unregister(struct notifier_block **nl, | |
35 | struct notifier_block *n) | |
36 | { | |
37 | while ((*nl) != NULL) { | |
38 | if ((*nl) == n) { | |
39 | rcu_assign_pointer(*nl, n->next); | |
40 | return 0; | |
41 | } | |
42 | nl = &((*nl)->next); | |
43 | } | |
44 | return -ENOENT; | |
45 | } | |
46 | ||
47 | /** | |
48 | * notifier_call_chain - Informs the registered notifiers about an event. | |
49 | * @nl: Pointer to head of the blocking notifier chain | |
50 | * @val: Value passed unmodified to notifier function | |
51 | * @v: Pointer passed unmodified to notifier function | |
52 | * @nr_to_call: Number of notifier functions to be called. Don't care | |
53 | * value of this parameter is -1. | |
54 | * @nr_calls: Records the number of notifications sent. Don't care | |
55 | * value of this field is NULL. | |
56 | * @returns: notifier_call_chain returns the value returned by the | |
57 | * last notifier function called. | |
58 | */ | |
59 | static int __kprobes notifier_call_chain(struct notifier_block **nl, | |
60 | unsigned long val, void *v, | |
61 | int nr_to_call, int *nr_calls) | |
62 | { | |
63 | int ret = NOTIFY_DONE; | |
64 | struct notifier_block *nb, *next_nb; | |
65 | ||
66 | nb = rcu_dereference(*nl); | |
67 | ||
68 | while (nb && nr_to_call) { | |
69 | next_nb = rcu_dereference(nb->next); | |
70 | ret = nb->notifier_call(nb, val, v); | |
71 | ||
72 | if (nr_calls) | |
73 | (*nr_calls)++; | |
74 | ||
75 | if ((ret & NOTIFY_STOP_MASK) == NOTIFY_STOP_MASK) | |
76 | break; | |
77 | nb = next_nb; | |
78 | nr_to_call--; | |
79 | } | |
80 | return ret; | |
81 | } | |
82 | ||
83 | /* | |
84 | * Atomic notifier chain routines. Registration and unregistration | |
85 | * use a spinlock, and call_chain is synchronized by RCU (no locks). | |
86 | */ | |
87 | ||
88 | /** | |
89 | * atomic_notifier_chain_register - Add notifier to an atomic notifier chain | |
90 | * @nh: Pointer to head of the atomic notifier chain | |
91 | * @n: New entry in notifier chain | |
92 | * | |
93 | * Adds a notifier to an atomic notifier chain. | |
94 | * | |
95 | * Currently always returns zero. | |
96 | */ | |
97 | int atomic_notifier_chain_register(struct atomic_notifier_head *nh, | |
98 | struct notifier_block *n) | |
99 | { | |
100 | unsigned long flags; | |
101 | int ret; | |
102 | ||
103 | spin_lock_irqsave(&nh->lock, flags); | |
104 | ret = notifier_chain_register(&nh->head, n); | |
105 | spin_unlock_irqrestore(&nh->lock, flags); | |
106 | return ret; | |
107 | } | |
108 | EXPORT_SYMBOL_GPL(atomic_notifier_chain_register); | |
109 | ||
110 | /** | |
111 | * atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain | |
112 | * @nh: Pointer to head of the atomic notifier chain | |
113 | * @n: Entry to remove from notifier chain | |
114 | * | |
115 | * Removes a notifier from an atomic notifier chain. | |
116 | * | |
117 | * Returns zero on success or %-ENOENT on failure. | |
118 | */ | |
119 | int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, | |
120 | struct notifier_block *n) | |
121 | { | |
122 | unsigned long flags; | |
123 | int ret; | |
124 | ||
125 | spin_lock_irqsave(&nh->lock, flags); | |
126 | ret = notifier_chain_unregister(&nh->head, n); | |
127 | spin_unlock_irqrestore(&nh->lock, flags); | |
128 | synchronize_rcu(); | |
129 | return ret; | |
130 | } | |
131 | EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister); | |
132 | ||
133 | /** | |
134 | * __atomic_notifier_call_chain - Call functions in an atomic notifier chain | |
135 | * @nh: Pointer to head of the atomic notifier chain | |
136 | * @val: Value passed unmodified to notifier function | |
137 | * @v: Pointer passed unmodified to notifier function | |
138 | * @nr_to_call: See the comment for notifier_call_chain. | |
139 | * @nr_calls: See the comment for notifier_call_chain. | |
140 | * | |
141 | * Calls each function in a notifier chain in turn. The functions | |
142 | * run in an atomic context, so they must not block. | |
143 | * This routine uses RCU to synchronize with changes to the chain. | |
144 | * | |
145 | * If the return value of the notifier can be and'ed | |
146 | * with %NOTIFY_STOP_MASK then atomic_notifier_call_chain() | |
147 | * will return immediately, with the return value of | |
148 | * the notifier function which halted execution. | |
149 | * Otherwise the return value is the return value | |
150 | * of the last notifier function called. | |
151 | */ | |
152 | int __kprobes __atomic_notifier_call_chain(struct atomic_notifier_head *nh, | |
153 | unsigned long val, void *v, | |
154 | int nr_to_call, int *nr_calls) | |
155 | { | |
156 | int ret; | |
157 | ||
158 | rcu_read_lock(); | |
159 | ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls); | |
160 | rcu_read_unlock(); | |
161 | return ret; | |
162 | } | |
163 | EXPORT_SYMBOL_GPL(__atomic_notifier_call_chain); | |
164 | ||
165 | int __kprobes atomic_notifier_call_chain(struct atomic_notifier_head *nh, | |
166 | unsigned long val, void *v) | |
167 | { | |
168 | return __atomic_notifier_call_chain(nh, val, v, -1, NULL); | |
169 | } | |
170 | EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); | |
171 | ||
172 | /* | |
173 | * Blocking notifier chain routines. All access to the chain is | |
174 | * synchronized by an rwsem. | |
175 | */ | |
176 | ||
177 | /** | |
178 | * blocking_notifier_chain_register - Add notifier to a blocking notifier chain | |
179 | * @nh: Pointer to head of the blocking notifier chain | |
180 | * @n: New entry in notifier chain | |
181 | * | |
182 | * Adds a notifier to a blocking notifier chain. | |
183 | * Must be called in process context. | |
184 | * | |
185 | * Currently always returns zero. | |
186 | */ | |
187 | int blocking_notifier_chain_register(struct blocking_notifier_head *nh, | |
188 | struct notifier_block *n) | |
189 | { | |
190 | int ret; | |
191 | ||
192 | /* | |
193 | * This code gets used during boot-up, when task switching is | |
194 | * not yet working and interrupts must remain disabled. At | |
195 | * such times we must not call down_write(). | |
196 | */ | |
197 | if (unlikely(system_state == SYSTEM_BOOTING)) | |
198 | return notifier_chain_register(&nh->head, n); | |
199 | ||
200 | down_write(&nh->rwsem); | |
201 | ret = notifier_chain_register(&nh->head, n); | |
202 | up_write(&nh->rwsem); | |
203 | return ret; | |
204 | } | |
205 | EXPORT_SYMBOL_GPL(blocking_notifier_chain_register); | |
206 | ||
207 | /** | |
208 | * blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain | |
209 | * @nh: Pointer to head of the blocking notifier chain | |
210 | * @n: Entry to remove from notifier chain | |
211 | * | |
212 | * Removes a notifier from a blocking notifier chain. | |
213 | * Must be called from process context. | |
214 | * | |
215 | * Returns zero on success or %-ENOENT on failure. | |
216 | */ | |
217 | int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, | |
218 | struct notifier_block *n) | |
219 | { | |
220 | int ret; | |
221 | ||
222 | /* | |
223 | * This code gets used during boot-up, when task switching is | |
224 | * not yet working and interrupts must remain disabled. At | |
225 | * such times we must not call down_write(). | |
226 | */ | |
227 | if (unlikely(system_state == SYSTEM_BOOTING)) | |
228 | return notifier_chain_unregister(&nh->head, n); | |
229 | ||
230 | down_write(&nh->rwsem); | |
231 | ret = notifier_chain_unregister(&nh->head, n); | |
232 | up_write(&nh->rwsem); | |
233 | return ret; | |
234 | } | |
235 | EXPORT_SYMBOL_GPL(blocking_notifier_chain_unregister); | |
236 | ||
237 | /** | |
238 | * __blocking_notifier_call_chain - Call functions in a blocking notifier chain | |
239 | * @nh: Pointer to head of the blocking notifier chain | |
240 | * @val: Value passed unmodified to notifier function | |
241 | * @v: Pointer passed unmodified to notifier function | |
242 | * @nr_to_call: See comment for notifier_call_chain. | |
243 | * @nr_calls: See comment for notifier_call_chain. | |
244 | * | |
245 | * Calls each function in a notifier chain in turn. The functions | |
246 | * run in a process context, so they are allowed to block. | |
247 | * | |
248 | * If the return value of the notifier can be and'ed | |
249 | * with %NOTIFY_STOP_MASK then blocking_notifier_call_chain() | |
250 | * will return immediately, with the return value of | |
251 | * the notifier function which halted execution. | |
252 | * Otherwise the return value is the return value | |
253 | * of the last notifier function called. | |
254 | */ | |
255 | int __blocking_notifier_call_chain(struct blocking_notifier_head *nh, | |
256 | unsigned long val, void *v, | |
257 | int nr_to_call, int *nr_calls) | |
258 | { | |
259 | int ret = NOTIFY_DONE; | |
260 | ||
261 | /* | |
262 | * We check the head outside the lock, but if this access is | |
263 | * racy then it does not matter what the result of the test | |
264 | * is, we re-check the list after having taken the lock anyway: | |
265 | */ | |
266 | if (rcu_dereference(nh->head)) { | |
267 | down_read(&nh->rwsem); | |
268 | ret = notifier_call_chain(&nh->head, val, v, nr_to_call, | |
269 | nr_calls); | |
270 | up_read(&nh->rwsem); | |
271 | } | |
272 | return ret; | |
273 | } | |
274 | EXPORT_SYMBOL_GPL(__blocking_notifier_call_chain); | |
275 | ||
276 | int blocking_notifier_call_chain(struct blocking_notifier_head *nh, | |
277 | unsigned long val, void *v) | |
278 | { | |
279 | return __blocking_notifier_call_chain(nh, val, v, -1, NULL); | |
280 | } | |
281 | EXPORT_SYMBOL_GPL(blocking_notifier_call_chain); | |
282 | ||
283 | /* | |
284 | * Raw notifier chain routines. There is no protection; | |
285 | * the caller must provide it. Use at your own risk! | |
286 | */ | |
287 | ||
288 | /** | |
289 | * raw_notifier_chain_register - Add notifier to a raw notifier chain | |
290 | * @nh: Pointer to head of the raw notifier chain | |
291 | * @n: New entry in notifier chain | |
292 | * | |
293 | * Adds a notifier to a raw notifier chain. | |
294 | * All locking must be provided by the caller. | |
295 | * | |
296 | * Currently always returns zero. | |
297 | */ | |
298 | int raw_notifier_chain_register(struct raw_notifier_head *nh, | |
299 | struct notifier_block *n) | |
300 | { | |
301 | return notifier_chain_register(&nh->head, n); | |
302 | } | |
303 | EXPORT_SYMBOL_GPL(raw_notifier_chain_register); | |
304 | ||
305 | /** | |
306 | * raw_notifier_chain_unregister - Remove notifier from a raw notifier chain | |
307 | * @nh: Pointer to head of the raw notifier chain | |
308 | * @n: Entry to remove from notifier chain | |
309 | * | |
310 | * Removes a notifier from a raw notifier chain. | |
311 | * All locking must be provided by the caller. | |
312 | * | |
313 | * Returns zero on success or %-ENOENT on failure. | |
314 | */ | |
315 | int raw_notifier_chain_unregister(struct raw_notifier_head *nh, | |
316 | struct notifier_block *n) | |
317 | { | |
318 | return notifier_chain_unregister(&nh->head, n); | |
319 | } | |
320 | EXPORT_SYMBOL_GPL(raw_notifier_chain_unregister); | |
321 | ||
322 | /** | |
323 | * __raw_notifier_call_chain - Call functions in a raw notifier chain | |
324 | * @nh: Pointer to head of the raw notifier chain | |
325 | * @val: Value passed unmodified to notifier function | |
326 | * @v: Pointer passed unmodified to notifier function | |
327 | * @nr_to_call: See comment for notifier_call_chain. | |
328 | * @nr_calls: See comment for notifier_call_chain | |
329 | * | |
330 | * Calls each function in a notifier chain in turn. The functions | |
331 | * run in an undefined context. | |
332 | * All locking must be provided by the caller. | |
333 | * | |
334 | * If the return value of the notifier can be and'ed | |
335 | * with %NOTIFY_STOP_MASK then raw_notifier_call_chain() | |
336 | * will return immediately, with the return value of | |
337 | * the notifier function which halted execution. | |
338 | * Otherwise the return value is the return value | |
339 | * of the last notifier function called. | |
340 | */ | |
341 | int __raw_notifier_call_chain(struct raw_notifier_head *nh, | |
342 | unsigned long val, void *v, | |
343 | int nr_to_call, int *nr_calls) | |
344 | { | |
345 | return notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls); | |
346 | } | |
347 | EXPORT_SYMBOL_GPL(__raw_notifier_call_chain); | |
348 | ||
349 | int raw_notifier_call_chain(struct raw_notifier_head *nh, | |
350 | unsigned long val, void *v) | |
351 | { | |
352 | return __raw_notifier_call_chain(nh, val, v, -1, NULL); | |
353 | } | |
354 | EXPORT_SYMBOL_GPL(raw_notifier_call_chain); | |
355 | ||
356 | /* | |
357 | * SRCU notifier chain routines. Registration and unregistration | |
358 | * use a mutex, and call_chain is synchronized by SRCU (no locks). | |
359 | */ | |
360 | ||
361 | /** | |
362 | * srcu_notifier_chain_register - Add notifier to an SRCU notifier chain | |
363 | * @nh: Pointer to head of the SRCU notifier chain | |
364 | * @n: New entry in notifier chain | |
365 | * | |
366 | * Adds a notifier to an SRCU notifier chain. | |
367 | * Must be called in process context. | |
368 | * | |
369 | * Currently always returns zero. | |
370 | */ | |
371 | int srcu_notifier_chain_register(struct srcu_notifier_head *nh, | |
372 | struct notifier_block *n) | |
373 | { | |
374 | int ret; | |
375 | ||
376 | /* | |
377 | * This code gets used during boot-up, when task switching is | |
378 | * not yet working and interrupts must remain disabled. At | |
379 | * such times we must not call mutex_lock(). | |
380 | */ | |
381 | if (unlikely(system_state == SYSTEM_BOOTING)) | |
382 | return notifier_chain_register(&nh->head, n); | |
383 | ||
384 | mutex_lock(&nh->mutex); | |
385 | ret = notifier_chain_register(&nh->head, n); | |
386 | mutex_unlock(&nh->mutex); | |
387 | return ret; | |
388 | } | |
389 | EXPORT_SYMBOL_GPL(srcu_notifier_chain_register); | |
390 | ||
391 | /** | |
392 | * srcu_notifier_chain_unregister - Remove notifier from an SRCU notifier chain | |
393 | * @nh: Pointer to head of the SRCU notifier chain | |
394 | * @n: Entry to remove from notifier chain | |
395 | * | |
396 | * Removes a notifier from an SRCU notifier chain. | |
397 | * Must be called from process context. | |
398 | * | |
399 | * Returns zero on success or %-ENOENT on failure. | |
400 | */ | |
401 | int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, | |
402 | struct notifier_block *n) | |
403 | { | |
404 | int ret; | |
405 | ||
406 | /* | |
407 | * This code gets used during boot-up, when task switching is | |
408 | * not yet working and interrupts must remain disabled. At | |
409 | * such times we must not call mutex_lock(). | |
410 | */ | |
411 | if (unlikely(system_state == SYSTEM_BOOTING)) | |
412 | return notifier_chain_unregister(&nh->head, n); | |
413 | ||
414 | mutex_lock(&nh->mutex); | |
415 | ret = notifier_chain_unregister(&nh->head, n); | |
416 | mutex_unlock(&nh->mutex); | |
417 | synchronize_srcu(&nh->srcu); | |
418 | return ret; | |
419 | } | |
420 | EXPORT_SYMBOL_GPL(srcu_notifier_chain_unregister); | |
421 | ||
422 | /** | |
423 | * __srcu_notifier_call_chain - Call functions in an SRCU notifier chain | |
424 | * @nh: Pointer to head of the SRCU notifier chain | |
425 | * @val: Value passed unmodified to notifier function | |
426 | * @v: Pointer passed unmodified to notifier function | |
427 | * @nr_to_call: See comment for notifier_call_chain. | |
428 | * @nr_calls: See comment for notifier_call_chain | |
429 | * | |
430 | * Calls each function in a notifier chain in turn. The functions | |
431 | * run in a process context, so they are allowed to block. | |
432 | * | |
433 | * If the return value of the notifier can be and'ed | |
434 | * with %NOTIFY_STOP_MASK then srcu_notifier_call_chain() | |
435 | * will return immediately, with the return value of | |
436 | * the notifier function which halted execution. | |
437 | * Otherwise the return value is the return value | |
438 | * of the last notifier function called. | |
439 | */ | |
440 | int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, | |
441 | unsigned long val, void *v, | |
442 | int nr_to_call, int *nr_calls) | |
443 | { | |
444 | int ret; | |
445 | int idx; | |
446 | ||
447 | idx = srcu_read_lock(&nh->srcu); | |
448 | ret = notifier_call_chain(&nh->head, val, v, nr_to_call, nr_calls); | |
449 | srcu_read_unlock(&nh->srcu, idx); | |
450 | return ret; | |
451 | } | |
452 | EXPORT_SYMBOL_GPL(__srcu_notifier_call_chain); | |
453 | ||
454 | int srcu_notifier_call_chain(struct srcu_notifier_head *nh, | |
455 | unsigned long val, void *v) | |
456 | { | |
457 | return __srcu_notifier_call_chain(nh, val, v, -1, NULL); | |
458 | } | |
459 | EXPORT_SYMBOL_GPL(srcu_notifier_call_chain); | |
460 | ||
461 | /** | |
462 | * srcu_init_notifier_head - Initialize an SRCU notifier head | |
463 | * @nh: Pointer to head of the srcu notifier chain | |
464 | * | |
465 | * Unlike other sorts of notifier heads, SRCU notifier heads require | |
466 | * dynamic initialization. Be sure to call this routine before | |
467 | * calling any of the other SRCU notifier routines for this head. | |
468 | * | |
469 | * If an SRCU notifier head is deallocated, it must first be cleaned | |
470 | * up by calling srcu_cleanup_notifier_head(). Otherwise the head's | |
471 | * per-cpu data (used by the SRCU mechanism) will leak. | |
472 | */ | |
473 | void srcu_init_notifier_head(struct srcu_notifier_head *nh) | |
474 | { | |
475 | mutex_init(&nh->mutex); | |
476 | if (init_srcu_struct(&nh->srcu) < 0) | |
477 | BUG(); | |
478 | nh->head = NULL; | |
479 | } | |
480 | EXPORT_SYMBOL_GPL(srcu_init_notifier_head); | |
481 | ||
482 | /** | |
483 | * register_reboot_notifier - Register function to be called at reboot time | |
484 | * @nb: Info about notifier function to be called | |
485 | * | |
486 | * Registers a function with the list of functions | |
487 | * to be called at reboot time. | |
488 | * | |
489 | * Currently always returns zero, as blocking_notifier_chain_register() | |
490 | * always returns zero. | |
491 | */ | |
492 | int register_reboot_notifier(struct notifier_block *nb) | |
493 | { | |
494 | return blocking_notifier_chain_register(&reboot_notifier_list, nb); | |
495 | } | |
496 | EXPORT_SYMBOL(register_reboot_notifier); | |
497 | ||
498 | /** | |
499 | * unregister_reboot_notifier - Unregister previously registered reboot notifier | |
500 | * @nb: Hook to be unregistered | |
501 | * | |
502 | * Unregisters a previously registered reboot | |
503 | * notifier function. | |
504 | * | |
505 | * Returns zero on success, or %-ENOENT on failure. | |
506 | */ | |
507 | int unregister_reboot_notifier(struct notifier_block *nb) | |
508 | { | |
509 | return blocking_notifier_chain_unregister(&reboot_notifier_list, nb); | |
510 | } | |
511 | EXPORT_SYMBOL(unregister_reboot_notifier); | |
512 | ||
513 | static ATOMIC_NOTIFIER_HEAD(die_chain); | |
514 | ||
515 | int notify_die(enum die_val val, const char *str, | |
516 | struct pt_regs *regs, long err, int trap, int sig) | |
517 | { | |
518 | struct die_args args = { | |
519 | .regs = regs, | |
520 | .str = str, | |
521 | .err = err, | |
522 | .trapnr = trap, | |
523 | .signr = sig, | |
524 | ||
525 | }; | |
526 | return atomic_notifier_call_chain(&die_chain, val, &args); | |
527 | } | |
528 | ||
529 | int register_die_notifier(struct notifier_block *nb) | |
530 | { | |
531 | vmalloc_sync_all(); | |
532 | return atomic_notifier_chain_register(&die_chain, nb); | |
533 | } | |
534 | EXPORT_SYMBOL_GPL(register_die_notifier); | |
535 | ||
536 | int unregister_die_notifier(struct notifier_block *nb) | |
537 | { | |
538 | return atomic_notifier_chain_unregister(&die_chain, nb); | |
539 | } | |
540 | EXPORT_SYMBOL_GPL(unregister_die_notifier); |