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