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1 | /* |
2 | * fs/eventpoll.c (Efficient event retrieval implementation) |
3 | * Copyright (C) 2001,...,2009 Davide Libenzi |
4 | * |
5 | * This program is free software; you can redistribute it and/or modify |
6 | * it under the terms of the GNU General Public License as published by |
7 | * the Free Software Foundation; either version 2 of the License, or |
8 | * (at your option) any later version. |
9 | * |
10 | * Davide Libenzi <davidel@xmailserver.org> |
11 | * |
12 | */ |
13 | |
14 | #include <linux/init.h> |
15 | #include <linux/kernel.h> |
16 | #include <linux/sched.h> |
17 | #include <linux/fs.h> |
18 | #include <linux/file.h> |
19 | #include <linux/signal.h> |
20 | #include <linux/errno.h> |
21 | #include <linux/mm.h> |
22 | #include <linux/slab.h> |
23 | #include <linux/poll.h> |
24 | #include <linux/string.h> |
25 | #include <linux/list.h> |
26 | #include <linux/hash.h> |
27 | #include <linux/spinlock.h> |
28 | #include <linux/syscalls.h> |
29 | #include <linux/rbtree.h> |
30 | #include <linux/wait.h> |
31 | #include <linux/eventpoll.h> |
32 | #include <linux/mount.h> |
33 | #include <linux/bitops.h> |
34 | #include <linux/mutex.h> |
35 | #include <linux/anon_inodes.h> |
36 | #include <linux/device.h> |
37 | #include <asm/uaccess.h> |
38 | #include <asm/io.h> |
39 | #include <asm/mman.h> |
40 | #include <linux/atomic.h> |
41 | #include <linux/proc_fs.h> |
42 | #include <linux/seq_file.h> |
43 | #include <linux/compat.h> |
44 | #include <linux/rculist.h> |
45 | |
46 | /* |
47 | * LOCKING: |
48 | * There are three level of locking required by epoll : |
49 | * |
50 | * 1) epmutex (mutex) |
51 | * 2) ep->mtx (mutex) |
52 | * 3) ep->lock (spinlock) |
53 | * |
54 | * The acquire order is the one listed above, from 1 to 3. |
55 | * We need a spinlock (ep->lock) because we manipulate objects |
56 | * from inside the poll callback, that might be triggered from |
57 | * a wake_up() that in turn might be called from IRQ context. |
58 | * So we can't sleep inside the poll callback and hence we need |
59 | * a spinlock. During the event transfer loop (from kernel to |
60 | * user space) we could end up sleeping due a copy_to_user(), so |
61 | * we need a lock that will allow us to sleep. This lock is a |
62 | * mutex (ep->mtx). It is acquired during the event transfer loop, |
63 | * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file(). |
64 | * Then we also need a global mutex to serialize eventpoll_release_file() |
65 | * and ep_free(). |
66 | * This mutex is acquired by ep_free() during the epoll file |
67 | * cleanup path and it is also acquired by eventpoll_release_file() |
68 | * if a file has been pushed inside an epoll set and it is then |
69 | * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). |
70 | * It is also acquired when inserting an epoll fd onto another epoll |
71 | * fd. We do this so that we walk the epoll tree and ensure that this |
72 | * insertion does not create a cycle of epoll file descriptors, which |
73 | * could lead to deadlock. We need a global mutex to prevent two |
74 | * simultaneous inserts (A into B and B into A) from racing and |
75 | * constructing a cycle without either insert observing that it is |
76 | * going to. |
77 | * It is necessary to acquire multiple "ep->mtx"es at once in the |
78 | * case when one epoll fd is added to another. In this case, we |
79 | * always acquire the locks in the order of nesting (i.e. after |
80 | * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired |
81 | * before e2->mtx). Since we disallow cycles of epoll file |
82 | * descriptors, this ensures that the mutexes are well-ordered. In |
83 | * order to communicate this nesting to lockdep, when walking a tree |
84 | * of epoll file descriptors, we use the current recursion depth as |
85 | * the lockdep subkey. |
86 | * It is possible to drop the "ep->mtx" and to use the global |
87 | * mutex "epmutex" (together with "ep->lock") to have it working, |
88 | * but having "ep->mtx" will make the interface more scalable. |
89 | * Events that require holding "epmutex" are very rare, while for |
90 | * normal operations the epoll private "ep->mtx" will guarantee |
91 | * a better scalability. |
92 | */ |
93 | |
94 | /* Epoll private bits inside the event mask */ |
95 | #define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET) |
96 | |
97 | /* Maximum number of nesting allowed inside epoll sets */ |
98 | #define EP_MAX_NESTS 4 |
99 | |
100 | #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
101 | |
102 | #define EP_UNACTIVE_PTR ((void *) -1L) |
103 | |
104 | #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
105 | |
106 | struct epoll_filefd { |
107 | struct file *file; |
108 | int fd; |
109 | } __packed; |
110 | |
111 | /* |
112 | * Structure used to track possible nested calls, for too deep recursions |
113 | * and loop cycles. |
114 | */ |
115 | struct nested_call_node { |
116 | struct list_head llink; |
117 | void *cookie; |
118 | void *ctx; |
119 | }; |
120 | |
121 | /* |
122 | * This structure is used as collector for nested calls, to check for |
123 | * maximum recursion dept and loop cycles. |
124 | */ |
125 | struct nested_calls { |
126 | struct list_head tasks_call_list; |
127 | spinlock_t lock; |
128 | }; |
129 | |
130 | /* |
131 | * Each file descriptor added to the eventpoll interface will |
132 | * have an entry of this type linked to the "rbr" RB tree. |
133 | * Avoid increasing the size of this struct, there can be many thousands |
134 | * of these on a server and we do not want this to take another cache line. |
135 | */ |
136 | struct epitem { |
137 | union { |
138 | /* RB tree node links this structure to the eventpoll RB tree */ |
139 | struct rb_node rbn; |
140 | /* Used to free the struct epitem */ |
141 | struct rcu_head rcu; |
142 | }; |
143 | |
144 | /* List header used to link this structure to the eventpoll ready list */ |
145 | struct list_head rdllink; |
146 | |
147 | /* |
148 | * Works together "struct eventpoll"->ovflist in keeping the |
149 | * single linked chain of items. |
150 | */ |
151 | struct epitem *next; |
152 | |
153 | /* The file descriptor information this item refers to */ |
154 | struct epoll_filefd ffd; |
155 | |
156 | /* Number of active wait queue attached to poll operations */ |
157 | int nwait; |
158 | |
159 | /* List containing poll wait queues */ |
160 | struct list_head pwqlist; |
161 | |
162 | /* The "container" of this item */ |
163 | struct eventpoll *ep; |
164 | |
165 | /* List header used to link this item to the "struct file" items list */ |
166 | struct list_head fllink; |
167 | |
168 | /* wakeup_source used when EPOLLWAKEUP is set */ |
169 | struct wakeup_source __rcu *ws; |
170 | |
171 | /* The structure that describe the interested events and the source fd */ |
172 | struct epoll_event event; |
173 | }; |
174 | |
175 | /* |
176 | * This structure is stored inside the "private_data" member of the file |
177 | * structure and represents the main data structure for the eventpoll |
178 | * interface. |
179 | */ |
180 | struct eventpoll { |
181 | /* Protect the access to this structure */ |
182 | spinlock_t lock; |
183 | |
184 | /* |
185 | * This mutex is used to ensure that files are not removed |
186 | * while epoll is using them. This is held during the event |
187 | * collection loop, the file cleanup path, the epoll file exit |
188 | * code and the ctl operations. |
189 | */ |
190 | struct mutex mtx; |
191 | |
192 | /* Wait queue used by sys_epoll_wait() */ |
193 | wait_queue_head_t wq; |
194 | |
195 | /* Wait queue used by file->poll() */ |
196 | wait_queue_head_t poll_wait; |
197 | |
198 | /* List of ready file descriptors */ |
199 | struct list_head rdllist; |
200 | |
201 | /* RB tree root used to store monitored fd structs */ |
202 | struct rb_root rbr; |
203 | |
204 | /* |
205 | * This is a single linked list that chains all the "struct epitem" that |
206 | * happened while transferring ready events to userspace w/out |
207 | * holding ->lock. |
208 | */ |
209 | struct epitem *ovflist; |
210 | |
211 | /* wakeup_source used when ep_scan_ready_list is running */ |
212 | struct wakeup_source *ws; |
213 | |
214 | /* The user that created the eventpoll descriptor */ |
215 | struct user_struct *user; |
216 | |
217 | struct file *file; |
218 | |
219 | /* used to optimize loop detection check */ |
220 | int visited; |
221 | struct list_head visited_list_link; |
222 | }; |
223 | |
224 | /* Wait structure used by the poll hooks */ |
225 | struct eppoll_entry { |
226 | /* List header used to link this structure to the "struct epitem" */ |
227 | struct list_head llink; |
228 | |
229 | /* The "base" pointer is set to the container "struct epitem" */ |
230 | struct epitem *base; |
231 | |
232 | /* |
233 | * Wait queue item that will be linked to the target file wait |
234 | * queue head. |
235 | */ |
236 | wait_queue_t wait; |
237 | |
238 | /* The wait queue head that linked the "wait" wait queue item */ |
239 | wait_queue_head_t *whead; |
240 | }; |
241 | |
242 | /* Wrapper struct used by poll queueing */ |
243 | struct ep_pqueue { |
244 | poll_table pt; |
245 | struct epitem *epi; |
246 | }; |
247 | |
248 | /* Used by the ep_send_events() function as callback private data */ |
249 | struct ep_send_events_data { |
250 | int maxevents; |
251 | struct epoll_event __user *events; |
252 | }; |
253 | |
254 | /* |
255 | * Configuration options available inside /proc/sys/fs/epoll/ |
256 | */ |
257 | /* Maximum number of epoll watched descriptors, per user */ |
258 | static long max_user_watches __read_mostly; |
259 | |
260 | /* |
261 | * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
262 | */ |
263 | static DEFINE_MUTEX(epmutex); |
264 | |
265 | /* Used to check for epoll file descriptor inclusion loops */ |
266 | static struct nested_calls poll_loop_ncalls; |
267 | |
268 | /* Used for safe wake up implementation */ |
269 | static struct nested_calls poll_safewake_ncalls; |
270 | |
271 | /* Used to call file's f_op->poll() under the nested calls boundaries */ |
272 | static struct nested_calls poll_readywalk_ncalls; |
273 | |
274 | /* Slab cache used to allocate "struct epitem" */ |
275 | static struct kmem_cache *epi_cache __read_mostly; |
276 | |
277 | /* Slab cache used to allocate "struct eppoll_entry" */ |
278 | static struct kmem_cache *pwq_cache __read_mostly; |
279 | |
280 | /* Visited nodes during ep_loop_check(), so we can unset them when we finish */ |
281 | static LIST_HEAD(visited_list); |
282 | |
283 | /* |
284 | * List of files with newly added links, where we may need to limit the number |
285 | * of emanating paths. Protected by the epmutex. |
286 | */ |
287 | static LIST_HEAD(tfile_check_list); |
288 | |
289 | #ifdef CONFIG_SYSCTL |
290 | |
291 | #include <linux/sysctl.h> |
292 | |
293 | static long zero; |
294 | static long long_max = LONG_MAX; |
295 | |
296 | struct ctl_table epoll_table[] = { |
297 | { |
298 | .procname = "max_user_watches", |
299 | .data = &max_user_watches, |
300 | .maxlen = sizeof(max_user_watches), |
301 | .mode = 0644, |
302 | .proc_handler = proc_doulongvec_minmax, |
303 | .extra1 = &zero, |
304 | .extra2 = &long_max, |
305 | }, |
306 | { } |
307 | }; |
308 | #endif /* CONFIG_SYSCTL */ |
309 | |
310 | static const struct file_operations eventpoll_fops; |
311 | |
312 | static inline int is_file_epoll(struct file *f) |
313 | { |
314 | return f->f_op == &eventpoll_fops; |
315 | } |
316 | |
317 | /* Setup the structure that is used as key for the RB tree */ |
318 | static inline void ep_set_ffd(struct epoll_filefd *ffd, |
319 | struct file *file, int fd) |
320 | { |
321 | ffd->file = file; |
322 | ffd->fd = fd; |
323 | } |
324 | |
325 | /* Compare RB tree keys */ |
326 | static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
327 | struct epoll_filefd *p2) |
328 | { |
329 | return (p1->file > p2->file ? +1: |
330 | (p1->file < p2->file ? -1 : p1->fd - p2->fd)); |
331 | } |
332 | |
333 | /* Tells us if the item is currently linked */ |
334 | static inline int ep_is_linked(struct list_head *p) |
335 | { |
336 | return !list_empty(p); |
337 | } |
338 | |
339 | static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p) |
340 | { |
341 | return container_of(p, struct eppoll_entry, wait); |
342 | } |
343 | |
344 | /* Get the "struct epitem" from a wait queue pointer */ |
345 | static inline struct epitem *ep_item_from_wait(wait_queue_t *p) |
346 | { |
347 | return container_of(p, struct eppoll_entry, wait)->base; |
348 | } |
349 | |
350 | /* Get the "struct epitem" from an epoll queue wrapper */ |
351 | static inline struct epitem *ep_item_from_epqueue(poll_table *p) |
352 | { |
353 | return container_of(p, struct ep_pqueue, pt)->epi; |
354 | } |
355 | |
356 | /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ |
357 | static inline int ep_op_has_event(int op) |
358 | { |
359 | return op != EPOLL_CTL_DEL; |
360 | } |
361 | |
362 | /* Initialize the poll safe wake up structure */ |
363 | static void ep_nested_calls_init(struct nested_calls *ncalls) |
364 | { |
365 | INIT_LIST_HEAD(&ncalls->tasks_call_list); |
366 | spin_lock_init(&ncalls->lock); |
367 | } |
368 | |
369 | /** |
370 | * ep_events_available - Checks if ready events might be available. |
371 | * |
372 | * @ep: Pointer to the eventpoll context. |
373 | * |
374 | * Returns: Returns a value different than zero if ready events are available, |
375 | * or zero otherwise. |
376 | */ |
377 | static inline int ep_events_available(struct eventpoll *ep) |
378 | { |
379 | return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR; |
380 | } |
381 | |
382 | /** |
383 | * ep_call_nested - Perform a bound (possibly) nested call, by checking |
384 | * that the recursion limit is not exceeded, and that |
385 | * the same nested call (by the meaning of same cookie) is |
386 | * no re-entered. |
387 | * |
388 | * @ncalls: Pointer to the nested_calls structure to be used for this call. |
389 | * @max_nests: Maximum number of allowed nesting calls. |
390 | * @nproc: Nested call core function pointer. |
391 | * @priv: Opaque data to be passed to the @nproc callback. |
392 | * @cookie: Cookie to be used to identify this nested call. |
393 | * @ctx: This instance context. |
394 | * |
395 | * Returns: Returns the code returned by the @nproc callback, or -1 if |
396 | * the maximum recursion limit has been exceeded. |
397 | */ |
398 | static int ep_call_nested(struct nested_calls *ncalls, int max_nests, |
399 | int (*nproc)(void *, void *, int), void *priv, |
400 | void *cookie, void *ctx) |
401 | { |
402 | int error, call_nests = 0; |
403 | unsigned long flags; |
404 | struct list_head *lsthead = &ncalls->tasks_call_list; |
405 | struct nested_call_node *tncur; |
406 | struct nested_call_node tnode; |
407 | |
408 | spin_lock_irqsave(&ncalls->lock, flags); |
409 | |
410 | /* |
411 | * Try to see if the current task is already inside this wakeup call. |
412 | * We use a list here, since the population inside this set is always |
413 | * very much limited. |
414 | */ |
415 | list_for_each_entry(tncur, lsthead, llink) { |
416 | if (tncur->ctx == ctx && |
417 | (tncur->cookie == cookie || ++call_nests > max_nests)) { |
418 | /* |
419 | * Ops ... loop detected or maximum nest level reached. |
420 | * We abort this wake by breaking the cycle itself. |
421 | */ |
422 | error = -1; |
423 | goto out_unlock; |
424 | } |
425 | } |
426 | |
427 | /* Add the current task and cookie to the list */ |
428 | tnode.ctx = ctx; |
429 | tnode.cookie = cookie; |
430 | list_add(&tnode.llink, lsthead); |
431 | |
432 | spin_unlock_irqrestore(&ncalls->lock, flags); |
433 | |
434 | /* Call the nested function */ |
435 | error = (*nproc)(priv, cookie, call_nests); |
436 | |
437 | /* Remove the current task from the list */ |
438 | spin_lock_irqsave(&ncalls->lock, flags); |
439 | list_del(&tnode.llink); |
440 | out_unlock: |
441 | spin_unlock_irqrestore(&ncalls->lock, flags); |
442 | |
443 | return error; |
444 | } |
445 | |
446 | /* |
447 | * As described in commit 0ccf831cb lockdep: annotate epoll |
448 | * the use of wait queues used by epoll is done in a very controlled |
449 | * manner. Wake ups can nest inside each other, but are never done |
450 | * with the same locking. For example: |
451 | * |
452 | * dfd = socket(...); |
453 | * efd1 = epoll_create(); |
454 | * efd2 = epoll_create(); |
455 | * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...); |
456 | * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...); |
457 | * |
458 | * When a packet arrives to the device underneath "dfd", the net code will |
459 | * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a |
460 | * callback wakeup entry on that queue, and the wake_up() performed by the |
461 | * "dfd" net code will end up in ep_poll_callback(). At this point epoll |
462 | * (efd1) notices that it may have some event ready, so it needs to wake up |
463 | * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake() |
464 | * that ends up in another wake_up(), after having checked about the |
465 | * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to |
466 | * avoid stack blasting. |
467 | * |
468 | * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle |
469 | * this special case of epoll. |
470 | */ |
471 | #ifdef CONFIG_DEBUG_LOCK_ALLOC |
472 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, |
473 | unsigned long events, int subclass) |
474 | { |
475 | unsigned long flags; |
476 | |
477 | spin_lock_irqsave_nested(&wqueue->lock, flags, subclass); |
478 | wake_up_locked_poll(wqueue, events); |
479 | spin_unlock_irqrestore(&wqueue->lock, flags); |
480 | } |
481 | #else |
482 | static inline void ep_wake_up_nested(wait_queue_head_t *wqueue, |
483 | unsigned long events, int subclass) |
484 | { |
485 | wake_up_poll(wqueue, events); |
486 | } |
487 | #endif |
488 | |
489 | static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests) |
490 | { |
491 | ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN, |
492 | 1 + call_nests); |
493 | return 0; |
494 | } |
495 | |
496 | /* |
497 | * Perform a safe wake up of the poll wait list. The problem is that |
498 | * with the new callback'd wake up system, it is possible that the |
499 | * poll callback is reentered from inside the call to wake_up() done |
500 | * on the poll wait queue head. The rule is that we cannot reenter the |
501 | * wake up code from the same task more than EP_MAX_NESTS times, |
502 | * and we cannot reenter the same wait queue head at all. This will |
503 | * enable to have a hierarchy of epoll file descriptor of no more than |
504 | * EP_MAX_NESTS deep. |
505 | */ |
506 | static void ep_poll_safewake(wait_queue_head_t *wq) |
507 | { |
508 | int this_cpu = get_cpu(); |
509 | |
510 | ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS, |
511 | ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu); |
512 | |
513 | put_cpu(); |
514 | } |
515 | |
516 | static void ep_remove_wait_queue(struct eppoll_entry *pwq) |
517 | { |
518 | wait_queue_head_t *whead; |
519 | |
520 | rcu_read_lock(); |
521 | /* If it is cleared by POLLFREE, it should be rcu-safe */ |
522 | whead = rcu_dereference(pwq->whead); |
523 | if (whead) |
524 | remove_wait_queue(whead, &pwq->wait); |
525 | rcu_read_unlock(); |
526 | } |
527 | |
528 | /* |
529 | * This function unregisters poll callbacks from the associated file |
530 | * descriptor. Must be called with "mtx" held (or "epmutex" if called from |
531 | * ep_free). |
532 | */ |
533 | static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
534 | { |
535 | struct list_head *lsthead = &epi->pwqlist; |
536 | struct eppoll_entry *pwq; |
537 | |
538 | while (!list_empty(lsthead)) { |
539 | pwq = list_first_entry(lsthead, struct eppoll_entry, llink); |
540 | |
541 | list_del(&pwq->llink); |
542 | ep_remove_wait_queue(pwq); |
543 | kmem_cache_free(pwq_cache, pwq); |
544 | } |
545 | } |
546 | |
547 | /* call only when ep->mtx is held */ |
548 | static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi) |
549 | { |
550 | return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx)); |
551 | } |
552 | |
553 | /* call only when ep->mtx is held */ |
554 | static inline void ep_pm_stay_awake(struct epitem *epi) |
555 | { |
556 | struct wakeup_source *ws = ep_wakeup_source(epi); |
557 | |
558 | if (ws) |
559 | __pm_stay_awake(ws); |
560 | } |
561 | |
562 | static inline bool ep_has_wakeup_source(struct epitem *epi) |
563 | { |
564 | return rcu_access_pointer(epi->ws) ? true : false; |
565 | } |
566 | |
567 | /* call when ep->mtx cannot be held (ep_poll_callback) */ |
568 | static inline void ep_pm_stay_awake_rcu(struct epitem *epi) |
569 | { |
570 | struct wakeup_source *ws; |
571 | |
572 | rcu_read_lock(); |
573 | ws = rcu_dereference(epi->ws); |
574 | if (ws) |
575 | __pm_stay_awake(ws); |
576 | rcu_read_unlock(); |
577 | } |
578 | |
579 | /** |
580 | * ep_scan_ready_list - Scans the ready list in a way that makes possible for |
581 | * the scan code, to call f_op->poll(). Also allows for |
582 | * O(NumReady) performance. |
583 | * |
584 | * @ep: Pointer to the epoll private data structure. |
585 | * @sproc: Pointer to the scan callback. |
586 | * @priv: Private opaque data passed to the @sproc callback. |
587 | * @depth: The current depth of recursive f_op->poll calls. |
588 | * @ep_locked: caller already holds ep->mtx |
589 | * |
590 | * Returns: The same integer error code returned by the @sproc callback. |
591 | */ |
592 | static int ep_scan_ready_list(struct eventpoll *ep, |
593 | int (*sproc)(struct eventpoll *, |
594 | struct list_head *, void *), |
595 | void *priv, int depth, bool ep_locked) |
596 | { |
597 | int error, pwake = 0; |
598 | unsigned long flags; |
599 | struct epitem *epi, *nepi; |
600 | LIST_HEAD(txlist); |
601 | |
602 | /* |
603 | * We need to lock this because we could be hit by |
604 | * eventpoll_release_file() and epoll_ctl(). |
605 | */ |
606 | |
607 | if (!ep_locked) |
608 | mutex_lock_nested(&ep->mtx, depth); |
609 | |
610 | /* |
611 | * Steal the ready list, and re-init the original one to the |
612 | * empty list. Also, set ep->ovflist to NULL so that events |
613 | * happening while looping w/out locks, are not lost. We cannot |
614 | * have the poll callback to queue directly on ep->rdllist, |
615 | * because we want the "sproc" callback to be able to do it |
616 | * in a lockless way. |
617 | */ |
618 | spin_lock_irqsave(&ep->lock, flags); |
619 | list_splice_init(&ep->rdllist, &txlist); |
620 | ep->ovflist = NULL; |
621 | spin_unlock_irqrestore(&ep->lock, flags); |
622 | |
623 | /* |
624 | * Now call the callback function. |
625 | */ |
626 | error = (*sproc)(ep, &txlist, priv); |
627 | |
628 | spin_lock_irqsave(&ep->lock, flags); |
629 | /* |
630 | * During the time we spent inside the "sproc" callback, some |
631 | * other events might have been queued by the poll callback. |
632 | * We re-insert them inside the main ready-list here. |
633 | */ |
634 | for (nepi = ep->ovflist; (epi = nepi) != NULL; |
635 | nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { |
636 | /* |
637 | * We need to check if the item is already in the list. |
638 | * During the "sproc" callback execution time, items are |
639 | * queued into ->ovflist but the "txlist" might already |
640 | * contain them, and the list_splice() below takes care of them. |
641 | */ |
642 | if (!ep_is_linked(&epi->rdllink)) { |
643 | list_add_tail(&epi->rdllink, &ep->rdllist); |
644 | ep_pm_stay_awake(epi); |
645 | } |
646 | } |
647 | /* |
648 | * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after |
649 | * releasing the lock, events will be queued in the normal way inside |
650 | * ep->rdllist. |
651 | */ |
652 | ep->ovflist = EP_UNACTIVE_PTR; |
653 | |
654 | /* |
655 | * Quickly re-inject items left on "txlist". |
656 | */ |
657 | list_splice(&txlist, &ep->rdllist); |
658 | __pm_relax(ep->ws); |
659 | |
660 | if (!list_empty(&ep->rdllist)) { |
661 | /* |
662 | * Wake up (if active) both the eventpoll wait list and |
663 | * the ->poll() wait list (delayed after we release the lock). |
664 | */ |
665 | if (waitqueue_active(&ep->wq)) |
666 | wake_up_locked(&ep->wq); |
667 | if (waitqueue_active(&ep->poll_wait)) |
668 | pwake++; |
669 | } |
670 | spin_unlock_irqrestore(&ep->lock, flags); |
671 | |
672 | if (!ep_locked) |
673 | mutex_unlock(&ep->mtx); |
674 | |
675 | /* We have to call this outside the lock */ |
676 | if (pwake) |
677 | ep_poll_safewake(&ep->poll_wait); |
678 | |
679 | return error; |
680 | } |
681 | |
682 | static void epi_rcu_free(struct rcu_head *head) |
683 | { |
684 | struct epitem *epi = container_of(head, struct epitem, rcu); |
685 | kmem_cache_free(epi_cache, epi); |
686 | } |
687 | |
688 | /* |
689 | * Removes a "struct epitem" from the eventpoll RB tree and deallocates |
690 | * all the associated resources. Must be called with "mtx" held. |
691 | */ |
692 | static int ep_remove(struct eventpoll *ep, struct epitem *epi) |
693 | { |
694 | unsigned long flags; |
695 | struct file *file = epi->ffd.file; |
696 | |
697 | /* |
698 | * Removes poll wait queue hooks. We _have_ to do this without holding |
699 | * the "ep->lock" otherwise a deadlock might occur. This because of the |
700 | * sequence of the lock acquisition. Here we do "ep->lock" then the wait |
701 | * queue head lock when unregistering the wait queue. The wakeup callback |
702 | * will run by holding the wait queue head lock and will call our callback |
703 | * that will try to get "ep->lock". |
704 | */ |
705 | ep_unregister_pollwait(ep, epi); |
706 | |
707 | /* Remove the current item from the list of epoll hooks */ |
708 | spin_lock(&file->f_lock); |
709 | list_del_rcu(&epi->fllink); |
710 | spin_unlock(&file->f_lock); |
711 | |
712 | rb_erase(&epi->rbn, &ep->rbr); |
713 | |
714 | spin_lock_irqsave(&ep->lock, flags); |
715 | if (ep_is_linked(&epi->rdllink)) |
716 | list_del_init(&epi->rdllink); |
717 | spin_unlock_irqrestore(&ep->lock, flags); |
718 | |
719 | wakeup_source_unregister(ep_wakeup_source(epi)); |
720 | /* |
721 | * At this point it is safe to free the eventpoll item. Use the union |
722 | * field epi->rcu, since we are trying to minimize the size of |
723 | * 'struct epitem'. The 'rbn' field is no longer in use. Protected by |
724 | * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make |
725 | * use of the rbn field. |
726 | */ |
727 | call_rcu(&epi->rcu, epi_rcu_free); |
728 | |
729 | atomic_long_dec(&ep->user->epoll_watches); |
730 | |
731 | return 0; |
732 | } |
733 | |
734 | static void ep_free(struct eventpoll *ep) |
735 | { |
736 | struct rb_node *rbp; |
737 | struct epitem *epi; |
738 | |
739 | /* We need to release all tasks waiting for these file */ |
740 | if (waitqueue_active(&ep->poll_wait)) |
741 | ep_poll_safewake(&ep->poll_wait); |
742 | |
743 | /* |
744 | * We need to lock this because we could be hit by |
745 | * eventpoll_release_file() while we're freeing the "struct eventpoll". |
746 | * We do not need to hold "ep->mtx" here because the epoll file |
747 | * is on the way to be removed and no one has references to it |
748 | * anymore. The only hit might come from eventpoll_release_file() but |
749 | * holding "epmutex" is sufficient here. |
750 | */ |
751 | mutex_lock(&epmutex); |
752 | |
753 | /* |
754 | * Walks through the whole tree by unregistering poll callbacks. |
755 | */ |
756 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
757 | epi = rb_entry(rbp, struct epitem, rbn); |
758 | |
759 | ep_unregister_pollwait(ep, epi); |
760 | cond_resched(); |
761 | } |
762 | |
763 | /* |
764 | * Walks through the whole tree by freeing each "struct epitem". At this |
765 | * point we are sure no poll callbacks will be lingering around, and also by |
766 | * holding "epmutex" we can be sure that no file cleanup code will hit |
767 | * us during this operation. So we can avoid the lock on "ep->lock". |
768 | * We do not need to lock ep->mtx, either, we only do it to prevent |
769 | * a lockdep warning. |
770 | */ |
771 | mutex_lock(&ep->mtx); |
772 | while ((rbp = rb_first(&ep->rbr)) != NULL) { |
773 | epi = rb_entry(rbp, struct epitem, rbn); |
774 | ep_remove(ep, epi); |
775 | cond_resched(); |
776 | } |
777 | mutex_unlock(&ep->mtx); |
778 | |
779 | mutex_unlock(&epmutex); |
780 | mutex_destroy(&ep->mtx); |
781 | free_uid(ep->user); |
782 | wakeup_source_unregister(ep->ws); |
783 | kfree(ep); |
784 | } |
785 | |
786 | static int ep_eventpoll_release(struct inode *inode, struct file *file) |
787 | { |
788 | struct eventpoll *ep = file->private_data; |
789 | |
790 | if (ep) |
791 | ep_free(ep); |
792 | |
793 | return 0; |
794 | } |
795 | |
796 | static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt) |
797 | { |
798 | pt->_key = epi->event.events; |
799 | |
800 | return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events; |
801 | } |
802 | |
803 | static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head, |
804 | void *priv) |
805 | { |
806 | struct epitem *epi, *tmp; |
807 | poll_table pt; |
808 | |
809 | init_poll_funcptr(&pt, NULL); |
810 | |
811 | list_for_each_entry_safe(epi, tmp, head, rdllink) { |
812 | if (ep_item_poll(epi, &pt)) |
813 | return POLLIN | POLLRDNORM; |
814 | else { |
815 | /* |
816 | * Item has been dropped into the ready list by the poll |
817 | * callback, but it's not actually ready, as far as |
818 | * caller requested events goes. We can remove it here. |
819 | */ |
820 | __pm_relax(ep_wakeup_source(epi)); |
821 | list_del_init(&epi->rdllink); |
822 | } |
823 | } |
824 | |
825 | return 0; |
826 | } |
827 | |
828 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
829 | poll_table *pt); |
830 | |
831 | struct readyevents_arg { |
832 | struct eventpoll *ep; |
833 | bool locked; |
834 | }; |
835 | |
836 | static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests) |
837 | { |
838 | struct readyevents_arg *arg = priv; |
839 | |
840 | return ep_scan_ready_list(arg->ep, ep_read_events_proc, NULL, |
841 | call_nests + 1, arg->locked); |
842 | } |
843 | |
844 | static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait) |
845 | { |
846 | int pollflags; |
847 | struct eventpoll *ep = file->private_data; |
848 | struct readyevents_arg arg; |
849 | |
850 | /* |
851 | * During ep_insert() we already hold the ep->mtx for the tfile. |
852 | * Prevent re-aquisition. |
853 | */ |
854 | arg.locked = wait && (wait->_qproc == ep_ptable_queue_proc); |
855 | arg.ep = ep; |
856 | |
857 | /* Insert inside our poll wait queue */ |
858 | poll_wait(file, &ep->poll_wait, wait); |
859 | |
860 | /* |
861 | * Proceed to find out if wanted events are really available inside |
862 | * the ready list. This need to be done under ep_call_nested() |
863 | * supervision, since the call to f_op->poll() done on listed files |
864 | * could re-enter here. |
865 | */ |
866 | pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS, |
867 | ep_poll_readyevents_proc, &arg, ep, current); |
868 | |
869 | return pollflags != -1 ? pollflags : 0; |
870 | } |
871 | |
872 | #ifdef CONFIG_PROC_FS |
873 | static int ep_show_fdinfo(struct seq_file *m, struct file *f) |
874 | { |
875 | struct eventpoll *ep = f->private_data; |
876 | struct rb_node *rbp; |
877 | int ret = 0; |
878 | |
879 | mutex_lock(&ep->mtx); |
880 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
881 | struct epitem *epi = rb_entry(rbp, struct epitem, rbn); |
882 | |
883 | ret = seq_printf(m, "tfd: %8d events: %8x data: %16llx\n", |
884 | epi->ffd.fd, epi->event.events, |
885 | (long long)epi->event.data); |
886 | if (ret) |
887 | break; |
888 | } |
889 | mutex_unlock(&ep->mtx); |
890 | |
891 | return ret; |
892 | } |
893 | #endif |
894 | |
895 | /* File callbacks that implement the eventpoll file behaviour */ |
896 | static const struct file_operations eventpoll_fops = { |
897 | #ifdef CONFIG_PROC_FS |
898 | .show_fdinfo = ep_show_fdinfo, |
899 | #endif |
900 | .release = ep_eventpoll_release, |
901 | .poll = ep_eventpoll_poll, |
902 | .llseek = noop_llseek, |
903 | }; |
904 | |
905 | /* |
906 | * This is called from eventpoll_release() to unlink files from the eventpoll |
907 | * interface. We need to have this facility to cleanup correctly files that are |
908 | * closed without being removed from the eventpoll interface. |
909 | */ |
910 | void eventpoll_release_file(struct file *file) |
911 | { |
912 | struct eventpoll *ep; |
913 | struct epitem *epi, *next; |
914 | |
915 | /* |
916 | * We don't want to get "file->f_lock" because it is not |
917 | * necessary. It is not necessary because we're in the "struct file" |
918 | * cleanup path, and this means that no one is using this file anymore. |
919 | * So, for example, epoll_ctl() cannot hit here since if we reach this |
920 | * point, the file counter already went to zero and fget() would fail. |
921 | * The only hit might come from ep_free() but by holding the mutex |
922 | * will correctly serialize the operation. We do need to acquire |
923 | * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
924 | * from anywhere but ep_free(). |
925 | * |
926 | * Besides, ep_remove() acquires the lock, so we can't hold it here. |
927 | */ |
928 | mutex_lock(&epmutex); |
929 | list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { |
930 | ep = epi->ep; |
931 | mutex_lock_nested(&ep->mtx, 0); |
932 | ep_remove(ep, epi); |
933 | mutex_unlock(&ep->mtx); |
934 | } |
935 | mutex_unlock(&epmutex); |
936 | } |
937 | |
938 | static int ep_alloc(struct eventpoll **pep) |
939 | { |
940 | int error; |
941 | struct user_struct *user; |
942 | struct eventpoll *ep; |
943 | |
944 | user = get_current_user(); |
945 | error = -ENOMEM; |
946 | ep = kzalloc(sizeof(*ep), GFP_KERNEL); |
947 | if (unlikely(!ep)) |
948 | goto free_uid; |
949 | |
950 | spin_lock_init(&ep->lock); |
951 | mutex_init(&ep->mtx); |
952 | init_waitqueue_head(&ep->wq); |
953 | init_waitqueue_head(&ep->poll_wait); |
954 | INIT_LIST_HEAD(&ep->rdllist); |
955 | ep->rbr = RB_ROOT; |
956 | ep->ovflist = EP_UNACTIVE_PTR; |
957 | ep->user = user; |
958 | |
959 | *pep = ep; |
960 | |
961 | return 0; |
962 | |
963 | free_uid: |
964 | free_uid(user); |
965 | return error; |
966 | } |
967 | |
968 | /* |
969 | * Search the file inside the eventpoll tree. The RB tree operations |
970 | * are protected by the "mtx" mutex, and ep_find() must be called with |
971 | * "mtx" held. |
972 | */ |
973 | static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) |
974 | { |
975 | int kcmp; |
976 | struct rb_node *rbp; |
977 | struct epitem *epi, *epir = NULL; |
978 | struct epoll_filefd ffd; |
979 | |
980 | ep_set_ffd(&ffd, file, fd); |
981 | for (rbp = ep->rbr.rb_node; rbp; ) { |
982 | epi = rb_entry(rbp, struct epitem, rbn); |
983 | kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
984 | if (kcmp > 0) |
985 | rbp = rbp->rb_right; |
986 | else if (kcmp < 0) |
987 | rbp = rbp->rb_left; |
988 | else { |
989 | epir = epi; |
990 | break; |
991 | } |
992 | } |
993 | |
994 | return epir; |
995 | } |
996 | |
997 | /* |
998 | * This is the callback that is passed to the wait queue wakeup |
999 | * mechanism. It is called by the stored file descriptors when they |
1000 | * have events to report. |
1001 | */ |
1002 | static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key) |
1003 | { |
1004 | int pwake = 0; |
1005 | unsigned long flags; |
1006 | struct epitem *epi = ep_item_from_wait(wait); |
1007 | struct eventpoll *ep = epi->ep; |
1008 | |
1009 | if ((unsigned long)key & POLLFREE) { |
1010 | ep_pwq_from_wait(wait)->whead = NULL; |
1011 | /* |
1012 | * whead = NULL above can race with ep_remove_wait_queue() |
1013 | * which can do another remove_wait_queue() after us, so we |
1014 | * can't use __remove_wait_queue(). whead->lock is held by |
1015 | * the caller. |
1016 | */ |
1017 | list_del_init(&wait->task_list); |
1018 | } |
1019 | |
1020 | spin_lock_irqsave(&ep->lock, flags); |
1021 | |
1022 | /* |
1023 | * If the event mask does not contain any poll(2) event, we consider the |
1024 | * descriptor to be disabled. This condition is likely the effect of the |
1025 | * EPOLLONESHOT bit that disables the descriptor when an event is received, |
1026 | * until the next EPOLL_CTL_MOD will be issued. |
1027 | */ |
1028 | if (!(epi->event.events & ~EP_PRIVATE_BITS)) |
1029 | goto out_unlock; |
1030 | |
1031 | /* |
1032 | * Check the events coming with the callback. At this stage, not |
1033 | * every device reports the events in the "key" parameter of the |
1034 | * callback. We need to be able to handle both cases here, hence the |
1035 | * test for "key" != NULL before the event match test. |
1036 | */ |
1037 | if (key && !((unsigned long) key & epi->event.events)) |
1038 | goto out_unlock; |
1039 | |
1040 | /* |
1041 | * If we are transferring events to userspace, we can hold no locks |
1042 | * (because we're accessing user memory, and because of linux f_op->poll() |
1043 | * semantics). All the events that happen during that period of time are |
1044 | * chained in ep->ovflist and requeued later on. |
1045 | */ |
1046 | if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) { |
1047 | if (epi->next == EP_UNACTIVE_PTR) { |
1048 | epi->next = ep->ovflist; |
1049 | ep->ovflist = epi; |
1050 | if (epi->ws) { |
1051 | /* |
1052 | * Activate ep->ws since epi->ws may get |
1053 | * deactivated at any time. |
1054 | */ |
1055 | __pm_stay_awake(ep->ws); |
1056 | } |
1057 | |
1058 | } |
1059 | goto out_unlock; |
1060 | } |
1061 | |
1062 | /* If this file is already in the ready list we exit soon */ |
1063 | if (!ep_is_linked(&epi->rdllink)) { |
1064 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1065 | ep_pm_stay_awake_rcu(epi); |
1066 | } |
1067 | |
1068 | /* |
1069 | * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
1070 | * wait list. |
1071 | */ |
1072 | if (waitqueue_active(&ep->wq)) |
1073 | wake_up_locked(&ep->wq); |
1074 | if (waitqueue_active(&ep->poll_wait)) |
1075 | pwake++; |
1076 | |
1077 | out_unlock: |
1078 | spin_unlock_irqrestore(&ep->lock, flags); |
1079 | |
1080 | /* We have to call this outside the lock */ |
1081 | if (pwake) |
1082 | ep_poll_safewake(&ep->poll_wait); |
1083 | |
1084 | return 1; |
1085 | } |
1086 | |
1087 | /* |
1088 | * This is the callback that is used to add our wait queue to the |
1089 | * target file wakeup lists. |
1090 | */ |
1091 | static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
1092 | poll_table *pt) |
1093 | { |
1094 | struct epitem *epi = ep_item_from_epqueue(pt); |
1095 | struct eppoll_entry *pwq; |
1096 | |
1097 | if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) { |
1098 | init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
1099 | pwq->whead = whead; |
1100 | pwq->base = epi; |
1101 | add_wait_queue(whead, &pwq->wait); |
1102 | list_add_tail(&pwq->llink, &epi->pwqlist); |
1103 | epi->nwait++; |
1104 | } else { |
1105 | /* We have to signal that an error occurred */ |
1106 | epi->nwait = -1; |
1107 | } |
1108 | } |
1109 | |
1110 | static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
1111 | { |
1112 | int kcmp; |
1113 | struct rb_node **p = &ep->rbr.rb_node, *parent = NULL; |
1114 | struct epitem *epic; |
1115 | |
1116 | while (*p) { |
1117 | parent = *p; |
1118 | epic = rb_entry(parent, struct epitem, rbn); |
1119 | kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
1120 | if (kcmp > 0) |
1121 | p = &parent->rb_right; |
1122 | else |
1123 | p = &parent->rb_left; |
1124 | } |
1125 | rb_link_node(&epi->rbn, parent, p); |
1126 | rb_insert_color(&epi->rbn, &ep->rbr); |
1127 | } |
1128 | |
1129 | |
1130 | |
1131 | #define PATH_ARR_SIZE 5 |
1132 | /* |
1133 | * These are the number paths of length 1 to 5, that we are allowing to emanate |
1134 | * from a single file of interest. For example, we allow 1000 paths of length |
1135 | * 1, to emanate from each file of interest. This essentially represents the |
1136 | * potential wakeup paths, which need to be limited in order to avoid massive |
1137 | * uncontrolled wakeup storms. The common use case should be a single ep which |
1138 | * is connected to n file sources. In this case each file source has 1 path |
1139 | * of length 1. Thus, the numbers below should be more than sufficient. These |
1140 | * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify |
1141 | * and delete can't add additional paths. Protected by the epmutex. |
1142 | */ |
1143 | static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 }; |
1144 | static int path_count[PATH_ARR_SIZE]; |
1145 | |
1146 | static int path_count_inc(int nests) |
1147 | { |
1148 | /* Allow an arbitrary number of depth 1 paths */ |
1149 | if (nests == 0) |
1150 | return 0; |
1151 | |
1152 | if (++path_count[nests] > path_limits[nests]) |
1153 | return -1; |
1154 | return 0; |
1155 | } |
1156 | |
1157 | static void path_count_init(void) |
1158 | { |
1159 | int i; |
1160 | |
1161 | for (i = 0; i < PATH_ARR_SIZE; i++) |
1162 | path_count[i] = 0; |
1163 | } |
1164 | |
1165 | static int reverse_path_check_proc(void *priv, void *cookie, int call_nests) |
1166 | { |
1167 | int error = 0; |
1168 | struct file *file = priv; |
1169 | struct file *child_file; |
1170 | struct epitem *epi; |
1171 | |
1172 | /* CTL_DEL can remove links here, but that can't increase our count */ |
1173 | rcu_read_lock(); |
1174 | list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) { |
1175 | child_file = epi->ep->file; |
1176 | if (is_file_epoll(child_file)) { |
1177 | if (list_empty(&child_file->f_ep_links)) { |
1178 | if (path_count_inc(call_nests)) { |
1179 | error = -1; |
1180 | break; |
1181 | } |
1182 | } else { |
1183 | error = ep_call_nested(&poll_loop_ncalls, |
1184 | EP_MAX_NESTS, |
1185 | reverse_path_check_proc, |
1186 | child_file, child_file, |
1187 | current); |
1188 | } |
1189 | if (error != 0) |
1190 | break; |
1191 | } else { |
1192 | printk(KERN_ERR "reverse_path_check_proc: " |
1193 | "file is not an ep!\n"); |
1194 | } |
1195 | } |
1196 | rcu_read_unlock(); |
1197 | return error; |
1198 | } |
1199 | |
1200 | /** |
1201 | * reverse_path_check - The tfile_check_list is list of file *, which have |
1202 | * links that are proposed to be newly added. We need to |
1203 | * make sure that those added links don't add too many |
1204 | * paths such that we will spend all our time waking up |
1205 | * eventpoll objects. |
1206 | * |
1207 | * Returns: Returns zero if the proposed links don't create too many paths, |
1208 | * -1 otherwise. |
1209 | */ |
1210 | static int reverse_path_check(void) |
1211 | { |
1212 | int error = 0; |
1213 | struct file *current_file; |
1214 | |
1215 | /* let's call this for all tfiles */ |
1216 | list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) { |
1217 | path_count_init(); |
1218 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
1219 | reverse_path_check_proc, current_file, |
1220 | current_file, current); |
1221 | if (error) |
1222 | break; |
1223 | } |
1224 | return error; |
1225 | } |
1226 | |
1227 | static int ep_create_wakeup_source(struct epitem *epi) |
1228 | { |
1229 | const char *name; |
1230 | struct wakeup_source *ws; |
1231 | |
1232 | if (!epi->ep->ws) { |
1233 | epi->ep->ws = wakeup_source_register("eventpoll"); |
1234 | if (!epi->ep->ws) |
1235 | return -ENOMEM; |
1236 | } |
1237 | |
1238 | name = epi->ffd.file->f_path.dentry->d_name.name; |
1239 | ws = wakeup_source_register(name); |
1240 | |
1241 | if (!ws) |
1242 | return -ENOMEM; |
1243 | rcu_assign_pointer(epi->ws, ws); |
1244 | |
1245 | return 0; |
1246 | } |
1247 | |
1248 | /* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */ |
1249 | static noinline void ep_destroy_wakeup_source(struct epitem *epi) |
1250 | { |
1251 | struct wakeup_source *ws = ep_wakeup_source(epi); |
1252 | |
1253 | RCU_INIT_POINTER(epi->ws, NULL); |
1254 | |
1255 | /* |
1256 | * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is |
1257 | * used internally by wakeup_source_remove, too (called by |
1258 | * wakeup_source_unregister), so we cannot use call_rcu |
1259 | */ |
1260 | synchronize_rcu(); |
1261 | wakeup_source_unregister(ws); |
1262 | } |
1263 | |
1264 | /* |
1265 | * Must be called with "mtx" held. |
1266 | */ |
1267 | static int ep_insert(struct eventpoll *ep, struct epoll_event *event, |
1268 | struct file *tfile, int fd, int full_check) |
1269 | { |
1270 | int error, revents, pwake = 0; |
1271 | unsigned long flags; |
1272 | long user_watches; |
1273 | struct epitem *epi; |
1274 | struct ep_pqueue epq; |
1275 | |
1276 | user_watches = atomic_long_read(&ep->user->epoll_watches); |
1277 | if (unlikely(user_watches >= max_user_watches)) |
1278 | return -ENOSPC; |
1279 | if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL))) |
1280 | return -ENOMEM; |
1281 | |
1282 | /* Item initialization follow here ... */ |
1283 | INIT_LIST_HEAD(&epi->rdllink); |
1284 | INIT_LIST_HEAD(&epi->fllink); |
1285 | INIT_LIST_HEAD(&epi->pwqlist); |
1286 | epi->ep = ep; |
1287 | ep_set_ffd(&epi->ffd, tfile, fd); |
1288 | epi->event = *event; |
1289 | epi->nwait = 0; |
1290 | epi->next = EP_UNACTIVE_PTR; |
1291 | if (epi->event.events & EPOLLWAKEUP) { |
1292 | error = ep_create_wakeup_source(epi); |
1293 | if (error) |
1294 | goto error_create_wakeup_source; |
1295 | } else { |
1296 | RCU_INIT_POINTER(epi->ws, NULL); |
1297 | } |
1298 | |
1299 | /* Initialize the poll table using the queue callback */ |
1300 | epq.epi = epi; |
1301 | init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); |
1302 | |
1303 | /* |
1304 | * Attach the item to the poll hooks and get current event bits. |
1305 | * We can safely use the file* here because its usage count has |
1306 | * been increased by the caller of this function. Note that after |
1307 | * this operation completes, the poll callback can start hitting |
1308 | * the new item. |
1309 | */ |
1310 | revents = ep_item_poll(epi, &epq.pt); |
1311 | |
1312 | /* |
1313 | * We have to check if something went wrong during the poll wait queue |
1314 | * install process. Namely an allocation for a wait queue failed due |
1315 | * high memory pressure. |
1316 | */ |
1317 | error = -ENOMEM; |
1318 | if (epi->nwait < 0) |
1319 | goto error_unregister; |
1320 | |
1321 | /* Add the current item to the list of active epoll hook for this file */ |
1322 | spin_lock(&tfile->f_lock); |
1323 | list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links); |
1324 | spin_unlock(&tfile->f_lock); |
1325 | |
1326 | /* |
1327 | * Add the current item to the RB tree. All RB tree operations are |
1328 | * protected by "mtx", and ep_insert() is called with "mtx" held. |
1329 | */ |
1330 | ep_rbtree_insert(ep, epi); |
1331 | |
1332 | /* now check if we've created too many backpaths */ |
1333 | error = -EINVAL; |
1334 | if (full_check && reverse_path_check()) |
1335 | goto error_remove_epi; |
1336 | |
1337 | /* We have to drop the new item inside our item list to keep track of it */ |
1338 | spin_lock_irqsave(&ep->lock, flags); |
1339 | |
1340 | /* If the file is already "ready" we drop it inside the ready list */ |
1341 | if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) { |
1342 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1343 | ep_pm_stay_awake(epi); |
1344 | |
1345 | /* Notify waiting tasks that events are available */ |
1346 | if (waitqueue_active(&ep->wq)) |
1347 | wake_up_locked(&ep->wq); |
1348 | if (waitqueue_active(&ep->poll_wait)) |
1349 | pwake++; |
1350 | } |
1351 | |
1352 | spin_unlock_irqrestore(&ep->lock, flags); |
1353 | |
1354 | atomic_long_inc(&ep->user->epoll_watches); |
1355 | |
1356 | /* We have to call this outside the lock */ |
1357 | if (pwake) |
1358 | ep_poll_safewake(&ep->poll_wait); |
1359 | |
1360 | return 0; |
1361 | |
1362 | error_remove_epi: |
1363 | spin_lock(&tfile->f_lock); |
1364 | list_del_rcu(&epi->fllink); |
1365 | spin_unlock(&tfile->f_lock); |
1366 | |
1367 | rb_erase(&epi->rbn, &ep->rbr); |
1368 | |
1369 | error_unregister: |
1370 | ep_unregister_pollwait(ep, epi); |
1371 | |
1372 | /* |
1373 | * We need to do this because an event could have been arrived on some |
1374 | * allocated wait queue. Note that we don't care about the ep->ovflist |
1375 | * list, since that is used/cleaned only inside a section bound by "mtx". |
1376 | * And ep_insert() is called with "mtx" held. |
1377 | */ |
1378 | spin_lock_irqsave(&ep->lock, flags); |
1379 | if (ep_is_linked(&epi->rdllink)) |
1380 | list_del_init(&epi->rdllink); |
1381 | spin_unlock_irqrestore(&ep->lock, flags); |
1382 | |
1383 | wakeup_source_unregister(ep_wakeup_source(epi)); |
1384 | |
1385 | error_create_wakeup_source: |
1386 | kmem_cache_free(epi_cache, epi); |
1387 | |
1388 | return error; |
1389 | } |
1390 | |
1391 | /* |
1392 | * Modify the interest event mask by dropping an event if the new mask |
1393 | * has a match in the current file status. Must be called with "mtx" held. |
1394 | */ |
1395 | static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event) |
1396 | { |
1397 | int pwake = 0; |
1398 | unsigned int revents; |
1399 | poll_table pt; |
1400 | |
1401 | init_poll_funcptr(&pt, NULL); |
1402 | |
1403 | /* |
1404 | * Set the new event interest mask before calling f_op->poll(); |
1405 | * otherwise we might miss an event that happens between the |
1406 | * f_op->poll() call and the new event set registering. |
1407 | */ |
1408 | epi->event.events = event->events; /* need barrier below */ |
1409 | epi->event.data = event->data; /* protected by mtx */ |
1410 | if (epi->event.events & EPOLLWAKEUP) { |
1411 | if (!ep_has_wakeup_source(epi)) |
1412 | ep_create_wakeup_source(epi); |
1413 | } else if (ep_has_wakeup_source(epi)) { |
1414 | ep_destroy_wakeup_source(epi); |
1415 | } |
1416 | |
1417 | /* |
1418 | * The following barrier has two effects: |
1419 | * |
1420 | * 1) Flush epi changes above to other CPUs. This ensures |
1421 | * we do not miss events from ep_poll_callback if an |
1422 | * event occurs immediately after we call f_op->poll(). |
1423 | * We need this because we did not take ep->lock while |
1424 | * changing epi above (but ep_poll_callback does take |
1425 | * ep->lock). |
1426 | * |
1427 | * 2) We also need to ensure we do not miss _past_ events |
1428 | * when calling f_op->poll(). This barrier also |
1429 | * pairs with the barrier in wq_has_sleeper (see |
1430 | * comments for wq_has_sleeper). |
1431 | * |
1432 | * This barrier will now guarantee ep_poll_callback or f_op->poll |
1433 | * (or both) will notice the readiness of an item. |
1434 | */ |
1435 | smp_mb(); |
1436 | |
1437 | /* |
1438 | * Get current event bits. We can safely use the file* here because |
1439 | * its usage count has been increased by the caller of this function. |
1440 | */ |
1441 | revents = ep_item_poll(epi, &pt); |
1442 | |
1443 | /* |
1444 | * If the item is "hot" and it is not registered inside the ready |
1445 | * list, push it inside. |
1446 | */ |
1447 | if (revents & event->events) { |
1448 | spin_lock_irq(&ep->lock); |
1449 | if (!ep_is_linked(&epi->rdllink)) { |
1450 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1451 | ep_pm_stay_awake(epi); |
1452 | |
1453 | /* Notify waiting tasks that events are available */ |
1454 | if (waitqueue_active(&ep->wq)) |
1455 | wake_up_locked(&ep->wq); |
1456 | if (waitqueue_active(&ep->poll_wait)) |
1457 | pwake++; |
1458 | } |
1459 | spin_unlock_irq(&ep->lock); |
1460 | } |
1461 | |
1462 | /* We have to call this outside the lock */ |
1463 | if (pwake) |
1464 | ep_poll_safewake(&ep->poll_wait); |
1465 | |
1466 | return 0; |
1467 | } |
1468 | |
1469 | static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head, |
1470 | void *priv) |
1471 | { |
1472 | struct ep_send_events_data *esed = priv; |
1473 | int eventcnt; |
1474 | unsigned int revents; |
1475 | struct epitem *epi; |
1476 | struct epoll_event __user *uevent; |
1477 | struct wakeup_source *ws; |
1478 | poll_table pt; |
1479 | |
1480 | init_poll_funcptr(&pt, NULL); |
1481 | |
1482 | /* |
1483 | * We can loop without lock because we are passed a task private list. |
1484 | * Items cannot vanish during the loop because ep_scan_ready_list() is |
1485 | * holding "mtx" during this call. |
1486 | */ |
1487 | for (eventcnt = 0, uevent = esed->events; |
1488 | !list_empty(head) && eventcnt < esed->maxevents;) { |
1489 | epi = list_first_entry(head, struct epitem, rdllink); |
1490 | |
1491 | /* |
1492 | * Activate ep->ws before deactivating epi->ws to prevent |
1493 | * triggering auto-suspend here (in case we reactive epi->ws |
1494 | * below). |
1495 | * |
1496 | * This could be rearranged to delay the deactivation of epi->ws |
1497 | * instead, but then epi->ws would temporarily be out of sync |
1498 | * with ep_is_linked(). |
1499 | */ |
1500 | ws = ep_wakeup_source(epi); |
1501 | if (ws) { |
1502 | if (ws->active) |
1503 | __pm_stay_awake(ep->ws); |
1504 | __pm_relax(ws); |
1505 | } |
1506 | |
1507 | list_del_init(&epi->rdllink); |
1508 | |
1509 | revents = ep_item_poll(epi, &pt); |
1510 | |
1511 | /* |
1512 | * If the event mask intersect the caller-requested one, |
1513 | * deliver the event to userspace. Again, ep_scan_ready_list() |
1514 | * is holding "mtx", so no operations coming from userspace |
1515 | * can change the item. |
1516 | */ |
1517 | if (revents) { |
1518 | if (__put_user(revents, &uevent->events) || |
1519 | __put_user(epi->event.data, &uevent->data)) { |
1520 | list_add(&epi->rdllink, head); |
1521 | ep_pm_stay_awake(epi); |
1522 | return eventcnt ? eventcnt : -EFAULT; |
1523 | } |
1524 | eventcnt++; |
1525 | uevent++; |
1526 | if (epi->event.events & EPOLLONESHOT) |
1527 | epi->event.events &= EP_PRIVATE_BITS; |
1528 | else if (!(epi->event.events & EPOLLET)) { |
1529 | /* |
1530 | * If this file has been added with Level |
1531 | * Trigger mode, we need to insert back inside |
1532 | * the ready list, so that the next call to |
1533 | * epoll_wait() will check again the events |
1534 | * availability. At this point, no one can insert |
1535 | * into ep->rdllist besides us. The epoll_ctl() |
1536 | * callers are locked out by |
1537 | * ep_scan_ready_list() holding "mtx" and the |
1538 | * poll callback will queue them in ep->ovflist. |
1539 | */ |
1540 | list_add_tail(&epi->rdllink, &ep->rdllist); |
1541 | ep_pm_stay_awake(epi); |
1542 | } |
1543 | } |
1544 | } |
1545 | |
1546 | return eventcnt; |
1547 | } |
1548 | |
1549 | static int ep_send_events(struct eventpoll *ep, |
1550 | struct epoll_event __user *events, int maxevents) |
1551 | { |
1552 | struct ep_send_events_data esed; |
1553 | |
1554 | esed.maxevents = maxevents; |
1555 | esed.events = events; |
1556 | |
1557 | return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false); |
1558 | } |
1559 | |
1560 | static inline struct timespec ep_set_mstimeout(long ms) |
1561 | { |
1562 | struct timespec now, ts = { |
1563 | .tv_sec = ms / MSEC_PER_SEC, |
1564 | .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC), |
1565 | }; |
1566 | |
1567 | ktime_get_ts(&now); |
1568 | return timespec_add_safe(now, ts); |
1569 | } |
1570 | |
1571 | /** |
1572 | * ep_poll - Retrieves ready events, and delivers them to the caller supplied |
1573 | * event buffer. |
1574 | * |
1575 | * @ep: Pointer to the eventpoll context. |
1576 | * @events: Pointer to the userspace buffer where the ready events should be |
1577 | * stored. |
1578 | * @maxevents: Size (in terms of number of events) of the caller event buffer. |
1579 | * @timeout: Maximum timeout for the ready events fetch operation, in |
1580 | * milliseconds. If the @timeout is zero, the function will not block, |
1581 | * while if the @timeout is less than zero, the function will block |
1582 | * until at least one event has been retrieved (or an error |
1583 | * occurred). |
1584 | * |
1585 | * Returns: Returns the number of ready events which have been fetched, or an |
1586 | * error code, in case of error. |
1587 | */ |
1588 | static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
1589 | int maxevents, long timeout) |
1590 | { |
1591 | int res = 0, eavail, timed_out = 0; |
1592 | unsigned long flags; |
1593 | long slack = 0; |
1594 | wait_queue_t wait; |
1595 | ktime_t expires, *to = NULL; |
1596 | |
1597 | if (timeout > 0) { |
1598 | struct timespec end_time = ep_set_mstimeout(timeout); |
1599 | |
1600 | slack = select_estimate_accuracy(&end_time); |
1601 | to = &expires; |
1602 | *to = timespec_to_ktime(end_time); |
1603 | } else if (timeout == 0) { |
1604 | /* |
1605 | * Avoid the unnecessary trip to the wait queue loop, if the |
1606 | * caller specified a non blocking operation. |
1607 | */ |
1608 | timed_out = 1; |
1609 | spin_lock_irqsave(&ep->lock, flags); |
1610 | goto check_events; |
1611 | } |
1612 | |
1613 | fetch_events: |
1614 | spin_lock_irqsave(&ep->lock, flags); |
1615 | |
1616 | if (!ep_events_available(ep)) { |
1617 | /* |
1618 | * We don't have any available event to return to the caller. |
1619 | * We need to sleep here, and we will be wake up by |
1620 | * ep_poll_callback() when events will become available. |
1621 | */ |
1622 | init_waitqueue_entry(&wait, current); |
1623 | __add_wait_queue_exclusive(&ep->wq, &wait); |
1624 | |
1625 | for (;;) { |
1626 | /* |
1627 | * We don't want to sleep if the ep_poll_callback() sends us |
1628 | * a wakeup in between. That's why we set the task state |
1629 | * to TASK_INTERRUPTIBLE before doing the checks. |
1630 | */ |
1631 | set_current_state(TASK_INTERRUPTIBLE); |
1632 | if (ep_events_available(ep) || timed_out) |
1633 | break; |
1634 | if (signal_pending(current)) { |
1635 | res = -EINTR; |
1636 | break; |
1637 | } |
1638 | |
1639 | spin_unlock_irqrestore(&ep->lock, flags); |
1640 | if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS)) |
1641 | timed_out = 1; |
1642 | |
1643 | spin_lock_irqsave(&ep->lock, flags); |
1644 | } |
1645 | __remove_wait_queue(&ep->wq, &wait); |
1646 | |
1647 | set_current_state(TASK_RUNNING); |
1648 | } |
1649 | check_events: |
1650 | /* Is it worth to try to dig for events ? */ |
1651 | eavail = ep_events_available(ep); |
1652 | |
1653 | spin_unlock_irqrestore(&ep->lock, flags); |
1654 | |
1655 | /* |
1656 | * Try to transfer events to user space. In case we get 0 events and |
1657 | * there's still timeout left over, we go trying again in search of |
1658 | * more luck. |
1659 | */ |
1660 | if (!res && eavail && |
1661 | !(res = ep_send_events(ep, events, maxevents)) && !timed_out) |
1662 | goto fetch_events; |
1663 | |
1664 | return res; |
1665 | } |
1666 | |
1667 | /** |
1668 | * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested() |
1669 | * API, to verify that adding an epoll file inside another |
1670 | * epoll structure, does not violate the constraints, in |
1671 | * terms of closed loops, or too deep chains (which can |
1672 | * result in excessive stack usage). |
1673 | * |
1674 | * @priv: Pointer to the epoll file to be currently checked. |
1675 | * @cookie: Original cookie for this call. This is the top-of-the-chain epoll |
1676 | * data structure pointer. |
1677 | * @call_nests: Current dept of the @ep_call_nested() call stack. |
1678 | * |
1679 | * Returns: Returns zero if adding the epoll @file inside current epoll |
1680 | * structure @ep does not violate the constraints, or -1 otherwise. |
1681 | */ |
1682 | static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) |
1683 | { |
1684 | int error = 0; |
1685 | struct file *file = priv; |
1686 | struct eventpoll *ep = file->private_data; |
1687 | struct eventpoll *ep_tovisit; |
1688 | struct rb_node *rbp; |
1689 | struct epitem *epi; |
1690 | |
1691 | mutex_lock_nested(&ep->mtx, call_nests + 1); |
1692 | ep->visited = 1; |
1693 | list_add(&ep->visited_list_link, &visited_list); |
1694 | for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
1695 | epi = rb_entry(rbp, struct epitem, rbn); |
1696 | if (unlikely(is_file_epoll(epi->ffd.file))) { |
1697 | ep_tovisit = epi->ffd.file->private_data; |
1698 | if (ep_tovisit->visited) |
1699 | continue; |
1700 | error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
1701 | ep_loop_check_proc, epi->ffd.file, |
1702 | ep_tovisit, current); |
1703 | if (error != 0) |
1704 | break; |
1705 | } else { |
1706 | /* |
1707 | * If we've reached a file that is not associated with |
1708 | * an ep, then we need to check if the newly added |
1709 | * links are going to add too many wakeup paths. We do |
1710 | * this by adding it to the tfile_check_list, if it's |
1711 | * not already there, and calling reverse_path_check() |
1712 | * during ep_insert(). |
1713 | */ |
1714 | if (list_empty(&epi->ffd.file->f_tfile_llink)) |
1715 | list_add(&epi->ffd.file->f_tfile_llink, |
1716 | &tfile_check_list); |
1717 | } |
1718 | } |
1719 | mutex_unlock(&ep->mtx); |
1720 | |
1721 | return error; |
1722 | } |
1723 | |
1724 | /** |
1725 | * ep_loop_check - Performs a check to verify that adding an epoll file (@file) |
1726 | * another epoll file (represented by @ep) does not create |
1727 | * closed loops or too deep chains. |
1728 | * |
1729 | * @ep: Pointer to the epoll private data structure. |
1730 | * @file: Pointer to the epoll file to be checked. |
1731 | * |
1732 | * Returns: Returns zero if adding the epoll @file inside current epoll |
1733 | * structure @ep does not violate the constraints, or -1 otherwise. |
1734 | */ |
1735 | static int ep_loop_check(struct eventpoll *ep, struct file *file) |
1736 | { |
1737 | int ret; |
1738 | struct eventpoll *ep_cur, *ep_next; |
1739 | |
1740 | ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS, |
1741 | ep_loop_check_proc, file, ep, current); |
1742 | /* clear visited list */ |
1743 | list_for_each_entry_safe(ep_cur, ep_next, &visited_list, |
1744 | visited_list_link) { |
1745 | ep_cur->visited = 0; |
1746 | list_del(&ep_cur->visited_list_link); |
1747 | } |
1748 | return ret; |
1749 | } |
1750 | |
1751 | static void clear_tfile_check_list(void) |
1752 | { |
1753 | struct file *file; |
1754 | |
1755 | /* first clear the tfile_check_list */ |
1756 | while (!list_empty(&tfile_check_list)) { |
1757 | file = list_first_entry(&tfile_check_list, struct file, |
1758 | f_tfile_llink); |
1759 | list_del_init(&file->f_tfile_llink); |
1760 | } |
1761 | INIT_LIST_HEAD(&tfile_check_list); |
1762 | } |
1763 | |
1764 | /* |
1765 | * Open an eventpoll file descriptor. |
1766 | */ |
1767 | SYSCALL_DEFINE1(epoll_create1, int, flags) |
1768 | { |
1769 | int error, fd; |
1770 | struct eventpoll *ep = NULL; |
1771 | struct file *file; |
1772 | |
1773 | /* Check the EPOLL_* constant for consistency. */ |
1774 | BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); |
1775 | |
1776 | if (flags & ~EPOLL_CLOEXEC) |
1777 | return -EINVAL; |
1778 | /* |
1779 | * Create the internal data structure ("struct eventpoll"). |
1780 | */ |
1781 | error = ep_alloc(&ep); |
1782 | if (error < 0) |
1783 | return error; |
1784 | /* |
1785 | * Creates all the items needed to setup an eventpoll file. That is, |
1786 | * a file structure and a free file descriptor. |
1787 | */ |
1788 | fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC)); |
1789 | if (fd < 0) { |
1790 | error = fd; |
1791 | goto out_free_ep; |
1792 | } |
1793 | file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep, |
1794 | O_RDWR | (flags & O_CLOEXEC)); |
1795 | if (IS_ERR(file)) { |
1796 | error = PTR_ERR(file); |
1797 | goto out_free_fd; |
1798 | } |
1799 | ep->file = file; |
1800 | fd_install(fd, file); |
1801 | return fd; |
1802 | |
1803 | out_free_fd: |
1804 | put_unused_fd(fd); |
1805 | out_free_ep: |
1806 | ep_free(ep); |
1807 | return error; |
1808 | } |
1809 | |
1810 | SYSCALL_DEFINE1(epoll_create, int, size) |
1811 | { |
1812 | if (size <= 0) |
1813 | return -EINVAL; |
1814 | |
1815 | return sys_epoll_create1(0); |
1816 | } |
1817 | |
1818 | /* |
1819 | * The following function implements the controller interface for |
1820 | * the eventpoll file that enables the insertion/removal/change of |
1821 | * file descriptors inside the interest set. |
1822 | */ |
1823 | SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
1824 | struct epoll_event __user *, event) |
1825 | { |
1826 | int error; |
1827 | int full_check = 0; |
1828 | struct fd f, tf; |
1829 | struct eventpoll *ep; |
1830 | struct epitem *epi; |
1831 | struct epoll_event epds; |
1832 | struct eventpoll *tep = NULL; |
1833 | |
1834 | error = -EFAULT; |
1835 | if (ep_op_has_event(op) && |
1836 | copy_from_user(&epds, event, sizeof(struct epoll_event))) |
1837 | goto error_return; |
1838 | |
1839 | error = -EBADF; |
1840 | f = fdget(epfd); |
1841 | if (!f.file) |
1842 | goto error_return; |
1843 | |
1844 | /* Get the "struct file *" for the target file */ |
1845 | tf = fdget(fd); |
1846 | if (!tf.file) |
1847 | goto error_fput; |
1848 | |
1849 | /* The target file descriptor must support poll */ |
1850 | error = -EPERM; |
1851 | if (!tf.file->f_op->poll) |
1852 | goto error_tgt_fput; |
1853 | |
1854 | /* Check if EPOLLWAKEUP is allowed */ |
1855 | if (ep_op_has_event(op)) |
1856 | ep_take_care_of_epollwakeup(&epds); |
1857 | |
1858 | /* |
1859 | * We have to check that the file structure underneath the file descriptor |
1860 | * the user passed to us _is_ an eventpoll file. And also we do not permit |
1861 | * adding an epoll file descriptor inside itself. |
1862 | */ |
1863 | error = -EINVAL; |
1864 | if (f.file == tf.file || !is_file_epoll(f.file)) |
1865 | goto error_tgt_fput; |
1866 | |
1867 | /* |
1868 | * At this point it is safe to assume that the "private_data" contains |
1869 | * our own data structure. |
1870 | */ |
1871 | ep = f.file->private_data; |
1872 | |
1873 | /* |
1874 | * When we insert an epoll file descriptor, inside another epoll file |
1875 | * descriptor, there is the change of creating closed loops, which are |
1876 | * better be handled here, than in more critical paths. While we are |
1877 | * checking for loops we also determine the list of files reachable |
1878 | * and hang them on the tfile_check_list, so we can check that we |
1879 | * haven't created too many possible wakeup paths. |
1880 | * |
1881 | * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when |
1882 | * the epoll file descriptor is attaching directly to a wakeup source, |
1883 | * unless the epoll file descriptor is nested. The purpose of taking the |
1884 | * 'epmutex' on add is to prevent complex toplogies such as loops and |
1885 | * deep wakeup paths from forming in parallel through multiple |
1886 | * EPOLL_CTL_ADD operations. |
1887 | */ |
1888 | mutex_lock_nested(&ep->mtx, 0); |
1889 | if (op == EPOLL_CTL_ADD) { |
1890 | if (!list_empty(&f.file->f_ep_links) || |
1891 | is_file_epoll(tf.file)) { |
1892 | full_check = 1; |
1893 | mutex_unlock(&ep->mtx); |
1894 | mutex_lock(&epmutex); |
1895 | if (is_file_epoll(tf.file)) { |
1896 | error = -ELOOP; |
1897 | if (ep_loop_check(ep, tf.file) != 0) { |
1898 | clear_tfile_check_list(); |
1899 | goto error_tgt_fput; |
1900 | } |
1901 | } else |
1902 | list_add(&tf.file->f_tfile_llink, |
1903 | &tfile_check_list); |
1904 | mutex_lock_nested(&ep->mtx, 0); |
1905 | if (is_file_epoll(tf.file)) { |
1906 | tep = tf.file->private_data; |
1907 | mutex_lock_nested(&tep->mtx, 1); |
1908 | } |
1909 | } |
1910 | } |
1911 | |
1912 | /* |
1913 | * Try to lookup the file inside our RB tree, Since we grabbed "mtx" |
1914 | * above, we can be sure to be able to use the item looked up by |
1915 | * ep_find() till we release the mutex. |
1916 | */ |
1917 | epi = ep_find(ep, tf.file, fd); |
1918 | |
1919 | error = -EINVAL; |
1920 | switch (op) { |
1921 | case EPOLL_CTL_ADD: |
1922 | if (!epi) { |
1923 | epds.events |= POLLERR | POLLHUP; |
1924 | error = ep_insert(ep, &epds, tf.file, fd, full_check); |
1925 | } else |
1926 | error = -EEXIST; |
1927 | if (full_check) |
1928 | clear_tfile_check_list(); |
1929 | break; |
1930 | case EPOLL_CTL_DEL: |
1931 | if (epi) |
1932 | error = ep_remove(ep, epi); |
1933 | else |
1934 | error = -ENOENT; |
1935 | break; |
1936 | case EPOLL_CTL_MOD: |
1937 | if (epi) { |
1938 | epds.events |= POLLERR | POLLHUP; |
1939 | error = ep_modify(ep, epi, &epds); |
1940 | } else |
1941 | error = -ENOENT; |
1942 | break; |
1943 | } |
1944 | if (tep != NULL) |
1945 | mutex_unlock(&tep->mtx); |
1946 | mutex_unlock(&ep->mtx); |
1947 | |
1948 | error_tgt_fput: |
1949 | if (full_check) |
1950 | mutex_unlock(&epmutex); |
1951 | |
1952 | fdput(tf); |
1953 | error_fput: |
1954 | fdput(f); |
1955 | error_return: |
1956 | |
1957 | return error; |
1958 | } |
1959 | |
1960 | /* |
1961 | * Implement the event wait interface for the eventpoll file. It is the kernel |
1962 | * part of the user space epoll_wait(2). |
1963 | */ |
1964 | SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
1965 | int, maxevents, int, timeout) |
1966 | { |
1967 | int error; |
1968 | struct fd f; |
1969 | struct eventpoll *ep; |
1970 | |
1971 | /* The maximum number of event must be greater than zero */ |
1972 | if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) |
1973 | return -EINVAL; |
1974 | |
1975 | /* Verify that the area passed by the user is writeable */ |
1976 | if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) |
1977 | return -EFAULT; |
1978 | |
1979 | /* Get the "struct file *" for the eventpoll file */ |
1980 | f = fdget(epfd); |
1981 | if (!f.file) |
1982 | return -EBADF; |
1983 | |
1984 | /* |
1985 | * We have to check that the file structure underneath the fd |
1986 | * the user passed to us _is_ an eventpoll file. |
1987 | */ |
1988 | error = -EINVAL; |
1989 | if (!is_file_epoll(f.file)) |
1990 | goto error_fput; |
1991 | |
1992 | /* |
1993 | * At this point it is safe to assume that the "private_data" contains |
1994 | * our own data structure. |
1995 | */ |
1996 | ep = f.file->private_data; |
1997 | |
1998 | /* Time to fish for events ... */ |
1999 | error = ep_poll(ep, events, maxevents, timeout); |
2000 | |
2001 | error_fput: |
2002 | fdput(f); |
2003 | return error; |
2004 | } |
2005 | |
2006 | /* |
2007 | * Implement the event wait interface for the eventpoll file. It is the kernel |
2008 | * part of the user space epoll_pwait(2). |
2009 | */ |
2010 | SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
2011 | int, maxevents, int, timeout, const sigset_t __user *, sigmask, |
2012 | size_t, sigsetsize) |
2013 | { |
2014 | int error; |
2015 | sigset_t ksigmask, sigsaved; |
2016 | |
2017 | /* |
2018 | * If the caller wants a certain signal mask to be set during the wait, |
2019 | * we apply it here. |
2020 | */ |
2021 | if (sigmask) { |
2022 | if (sigsetsize != sizeof(sigset_t)) |
2023 | return -EINVAL; |
2024 | if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) |
2025 | return -EFAULT; |
2026 | sigsaved = current->blocked; |
2027 | set_current_blocked(&ksigmask); |
2028 | } |
2029 | |
2030 | error = sys_epoll_wait(epfd, events, maxevents, timeout); |
2031 | |
2032 | /* |
2033 | * If we changed the signal mask, we need to restore the original one. |
2034 | * In case we've got a signal while waiting, we do not restore the |
2035 | * signal mask yet, and we allow do_signal() to deliver the signal on |
2036 | * the way back to userspace, before the signal mask is restored. |
2037 | */ |
2038 | if (sigmask) { |
2039 | if (error == -EINTR) { |
2040 | memcpy(¤t->saved_sigmask, &sigsaved, |
2041 | sizeof(sigsaved)); |
2042 | set_restore_sigmask(); |
2043 | } else |
2044 | set_current_blocked(&sigsaved); |
2045 | } |
2046 | |
2047 | return error; |
2048 | } |
2049 | |
2050 | #ifdef CONFIG_COMPAT |
2051 | COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd, |
2052 | struct epoll_event __user *, events, |
2053 | int, maxevents, int, timeout, |
2054 | const compat_sigset_t __user *, sigmask, |
2055 | compat_size_t, sigsetsize) |
2056 | { |
2057 | long err; |
2058 | compat_sigset_t csigmask; |
2059 | sigset_t ksigmask, sigsaved; |
2060 | |
2061 | /* |
2062 | * If the caller wants a certain signal mask to be set during the wait, |
2063 | * we apply it here. |
2064 | */ |
2065 | if (sigmask) { |
2066 | if (sigsetsize != sizeof(compat_sigset_t)) |
2067 | return -EINVAL; |
2068 | if (copy_from_user(&csigmask, sigmask, sizeof(csigmask))) |
2069 | return -EFAULT; |
2070 | sigset_from_compat(&ksigmask, &csigmask); |
2071 | sigsaved = current->blocked; |
2072 | set_current_blocked(&ksigmask); |
2073 | } |
2074 | |
2075 | err = sys_epoll_wait(epfd, events, maxevents, timeout); |
2076 | |
2077 | /* |
2078 | * If we changed the signal mask, we need to restore the original one. |
2079 | * In case we've got a signal while waiting, we do not restore the |
2080 | * signal mask yet, and we allow do_signal() to deliver the signal on |
2081 | * the way back to userspace, before the signal mask is restored. |
2082 | */ |
2083 | if (sigmask) { |
2084 | if (err == -EINTR) { |
2085 | memcpy(¤t->saved_sigmask, &sigsaved, |
2086 | sizeof(sigsaved)); |
2087 | set_restore_sigmask(); |
2088 | } else |
2089 | set_current_blocked(&sigsaved); |
2090 | } |
2091 | |
2092 | return err; |
2093 | } |
2094 | #endif |
2095 | |
2096 | static int __init eventpoll_init(void) |
2097 | { |
2098 | struct sysinfo si; |
2099 | |
2100 | si_meminfo(&si); |
2101 | /* |
2102 | * Allows top 4% of lomem to be allocated for epoll watches (per user). |
2103 | */ |
2104 | max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / |
2105 | EP_ITEM_COST; |
2106 | BUG_ON(max_user_watches < 0); |
2107 | |
2108 | /* |
2109 | * Initialize the structure used to perform epoll file descriptor |
2110 | * inclusion loops checks. |
2111 | */ |
2112 | ep_nested_calls_init(&poll_loop_ncalls); |
2113 | |
2114 | /* Initialize the structure used to perform safe poll wait head wake ups */ |
2115 | ep_nested_calls_init(&poll_safewake_ncalls); |
2116 | |
2117 | /* Initialize the structure used to perform file's f_op->poll() calls */ |
2118 | ep_nested_calls_init(&poll_readywalk_ncalls); |
2119 | |
2120 | /* |
2121 | * We can have many thousands of epitems, so prevent this from |
2122 | * using an extra cache line on 64-bit (and smaller) CPUs |
2123 | */ |
2124 | BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128); |
2125 | |
2126 | /* Allocates slab cache used to allocate "struct epitem" items */ |
2127 | epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
2128 | 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); |
2129 | |
2130 | /* Allocates slab cache used to allocate "struct eppoll_entry" */ |
2131 | pwq_cache = kmem_cache_create("eventpoll_pwq", |
2132 | sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL); |
2133 | |
2134 | return 0; |
2135 | } |
2136 | fs_initcall(eventpoll_init); |
2137 |
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