?  search:
summary | log | graphiclog1 | graphiclog2 | commit | commitdiff | tree | refs | edit | fork
blame | history | raw | HEAD
staging: vboxvideo: Atomic phase 2: Wire up state object handlers
[linux/fpc-iii.git] / fs / select.c
blob4a6b6e4b21cb91aecdf40492c4763f09bf4ccc3f
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * This file contains the procedures for the handling of select and poll
4 *
5 * Created for Linux based loosely upon Mathius Lattner's minix
6 * patches by Peter MacDonald. Heavily edited by Linus.
7 *
8 * 4 February 1994
9 * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
10 * flag set in its personality we do *not* modify the given timeout
11 * parameter to reflect time remaining.
12 *
13 * 24 January 2000
14 * Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
15 * of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
16 */
17
18 #include <linux/kernel.h>
19 #include <linux/sched/signal.h>
20 #include <linux/sched/rt.h>
21 #include <linux/syscalls.h>
22 #include <linux/export.h>
23 #include <linux/slab.h>
24 #include <linux/poll.h>
25 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
26 #include <linux/file.h>
27 #include <linux/fdtable.h>
28 #include <linux/fs.h>
29 #include <linux/rcupdate.h>
30 #include <linux/hrtimer.h>
31 #include <linux/freezer.h>
32 #include <net/busy_poll.h>
33 #include <linux/vmalloc.h>
34
35 #include <linux/uaccess.h>
36
37
38 /*
39 * Estimate expected accuracy in ns from a timeval.
40 *
41 * After quite a bit of churning around, we've settled on
42 * a simple thing of taking 0.1% of the timeout as the
43 * slack, with a cap of 100 msec.
44 * "nice" tasks get a 0.5% slack instead.
45 *
46 * Consider this comment an open invitation to come up with even
47 * better solutions..
48 */
49
50 #define MAX_SLACK (100 * NSEC_PER_MSEC)
51
52 static long __estimate_accuracy(struct timespec64 *tv)
53 {
54 long slack;
55 int divfactor = 1000;
56
57 if (tv->tv_sec < 0)
58 return 0;
59
60 if (task_nice(current) > 0)
61 divfactor = divfactor / 5;
62
63 if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
64 return MAX_SLACK;
65
66 slack = tv->tv_nsec / divfactor;
67 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
68
69 if (slack > MAX_SLACK)
70 return MAX_SLACK;
71
72 return slack;
73 }
74
75 u64 select_estimate_accuracy(struct timespec64 *tv)
76 {
77 u64 ret;
78 struct timespec64 now;
79
80 /*
81 * Realtime tasks get a slack of 0 for obvious reasons.
82 */
83
84 if (rt_task(current))
85 return 0;
86
87 ktime_get_ts64(&now);
88 now = timespec64_sub(*tv, now);
89 ret = __estimate_accuracy(&now);
90 if (ret < current->timer_slack_ns)
91 return current->timer_slack_ns;
92 return ret;
93 }
94
95
96
97 struct poll_table_page {
98 struct poll_table_page * next;
99 struct poll_table_entry * entry;
100 struct poll_table_entry entries[0];
101 };
102
103 #define POLL_TABLE_FULL(table) \
104 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
105
106 /*
107 * Ok, Peter made a complicated, but straightforward multiple_wait() function.
108 * I have rewritten this, taking some shortcuts: This code may not be easy to
109 * follow, but it should be free of race-conditions, and it's practical. If you
110 * understand what I'm doing here, then you understand how the linux
111 * sleep/wakeup mechanism works.
112 *
113 * Two very simple procedures, poll_wait() and poll_freewait() make all the
114 * work. poll_wait() is an inline-function defined in <linux/poll.h>,
115 * as all select/poll functions have to call it to add an entry to the
116 * poll table.
117 */
118 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
119 poll_table *p);
120
121 void poll_initwait(struct poll_wqueues *pwq)
122 {
123 init_poll_funcptr(&pwq->pt, __pollwait);
124 pwq->polling_task = current;
125 pwq->triggered = 0;
126 pwq->error = 0;
127 pwq->table = NULL;
128 pwq->inline_index = 0;
129 }
130 EXPORT_SYMBOL(poll_initwait);
131
132 static void free_poll_entry(struct poll_table_entry *entry)
133 {
134 remove_wait_queue(entry->wait_address, &entry->wait);
135 fput(entry->filp);
136 }
137
138 void poll_freewait(struct poll_wqueues *pwq)
139 {
140 struct poll_table_page * p = pwq->table;
141 int i;
142 for (i = 0; i < pwq->inline_index; i++)
143 free_poll_entry(pwq->inline_entries + i);
144 while (p) {
145 struct poll_table_entry * entry;
146 struct poll_table_page *old;
147
148 entry = p->entry;
149 do {
150 entry--;
151 free_poll_entry(entry);
152 } while (entry > p->entries);
153 old = p;
154 p = p->next;
155 free_page((unsigned long) old);
156 }
157 }
158 EXPORT_SYMBOL(poll_freewait);
159
160 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
161 {
162 struct poll_table_page *table = p->table;
163
164 if (p->inline_index < N_INLINE_POLL_ENTRIES)
165 return p->inline_entries + p->inline_index++;
166
167 if (!table || POLL_TABLE_FULL(table)) {
168 struct poll_table_page *new_table;
169
170 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
171 if (!new_table) {
172 p->error = -ENOMEM;
173 return NULL;
174 }
175 new_table->entry = new_table->entries;
176 new_table->next = table;
177 p->table = new_table;
178 table = new_table;
179 }
180
181 return table->entry++;
182 }
183
184 static int __pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
185 {
186 struct poll_wqueues *pwq = wait->private;
187 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
188
189 /*
190 * Although this function is called under waitqueue lock, LOCK
191 * doesn't imply write barrier and the users expect write
192 * barrier semantics on wakeup functions. The following
193 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
194 * and is paired with smp_store_mb() in poll_schedule_timeout.
195 */
196 smp_wmb();
197 pwq->triggered = 1;
198
199 /*
200 * Perform the default wake up operation using a dummy
201 * waitqueue.
202 *
203 * TODO: This is hacky but there currently is no interface to
204 * pass in @sync. @sync is scheduled to be removed and once
205 * that happens, wake_up_process() can be used directly.
206 */
207 return default_wake_function(&dummy_wait, mode, sync, key);
208 }
209
210 static int pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
211 {
212 struct poll_table_entry *entry;
213
214 entry = container_of(wait, struct poll_table_entry, wait);
215 if (key && !(key_to_poll(key) & entry->key))
216 return 0;
217 return __pollwake(wait, mode, sync, key);
218 }
219
220 /* Add a new entry */
221 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
222 poll_table *p)
223 {
224 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
225 struct poll_table_entry *entry = poll_get_entry(pwq);
226 if (!entry)
227 return;
228 entry->filp = get_file(filp);
229 entry->wait_address = wait_address;
230 entry->key = p->_key;
231 init_waitqueue_func_entry(&entry->wait, pollwake);
232 entry->wait.private = pwq;
233 add_wait_queue(wait_address, &entry->wait);
234 }
235
236 static int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
237 ktime_t *expires, unsigned long slack)
238 {
239 int rc = -EINTR;
240
241 set_current_state(state);
242 if (!pwq->triggered)
243 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
244 __set_current_state(TASK_RUNNING);
245
246 /*
247 * Prepare for the next iteration.
248 *
249 * The following smp_store_mb() serves two purposes. First, it's
250 * the counterpart rmb of the wmb in pollwake() such that data
251 * written before wake up is always visible after wake up.
252 * Second, the full barrier guarantees that triggered clearing
253 * doesn't pass event check of the next iteration. Note that
254 * this problem doesn't exist for the first iteration as
255 * add_wait_queue() has full barrier semantics.
256 */
257 smp_store_mb(pwq->triggered, 0);
258
259 return rc;
260 }
261
262 /**
263 * poll_select_set_timeout - helper function to setup the timeout value
264 * @to: pointer to timespec64 variable for the final timeout
265 * @sec: seconds (from user space)
266 * @nsec: nanoseconds (from user space)
267 *
268 * Note, we do not use a timespec for the user space value here, That
269 * way we can use the function for timeval and compat interfaces as well.
270 *
271 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
272 */
273 int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec)
274 {
275 struct timespec64 ts = {.tv_sec = sec, .tv_nsec = nsec};
276
277 if (!timespec64_valid(&ts))
278 return -EINVAL;
279
280 /* Optimize for the zero timeout value here */
281 if (!sec && !nsec) {
282 to->tv_sec = to->tv_nsec = 0;
283 } else {
284 ktime_get_ts64(to);
285 *to = timespec64_add_safe(*to, ts);
286 }
287 return 0;
288 }
289
290 static int poll_select_copy_remaining(struct timespec64 *end_time,
291 void __user *p,
292 int timeval, int ret)
293 {
294 struct timespec64 rts;
295 struct timeval rtv;
296
297 if (!p)
298 return ret;
299
300 if (current->personality & STICKY_TIMEOUTS)
301 goto sticky;
302
303 /* No update for zero timeout */
304 if (!end_time->tv_sec && !end_time->tv_nsec)
305 return ret;
306
307 ktime_get_ts64(&rts);
308 rts = timespec64_sub(*end_time, rts);
309 if (rts.tv_sec < 0)
310 rts.tv_sec = rts.tv_nsec = 0;
311
312
313 if (timeval) {
314 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
315 memset(&rtv, 0, sizeof(rtv));
316 rtv.tv_sec = rts.tv_sec;
317 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
318
319 if (!copy_to_user(p, &rtv, sizeof(rtv)))
320 return ret;
321
322 } else if (!put_timespec64(&rts, p))
323 return ret;
324
325 /*
326 * If an application puts its timeval in read-only memory, we
327 * don't want the Linux-specific update to the timeval to
328 * cause a fault after the select has completed
329 * successfully. However, because we're not updating the
330 * timeval, we can't restart the system call.
331 */
332
333 sticky:
334 if (ret == -ERESTARTNOHAND)
335 ret = -EINTR;
336 return ret;
337 }
338
339 /*
340 * Scalable version of the fd_set.
341 */
342
343 typedef struct {
344 unsigned long *in, *out, *ex;
345 unsigned long *res_in, *res_out, *res_ex;
346 } fd_set_bits;
347
348 /*
349 * How many longwords for "nr" bits?
350 */
351 #define FDS_BITPERLONG (8*sizeof(long))
352 #define FDS_LONGS(nr) (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG)
353 #define FDS_BYTES(nr) (FDS_LONGS(nr)*sizeof(long))
354
355 /*
356 * We do a VERIFY_WRITE here even though we are only reading this time:
357 * we'll write to it eventually..
358 *
359 * Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
360 */
361 static inline
362 int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
363 {
364 nr = FDS_BYTES(nr);
365 if (ufdset)
366 return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0;
367
368 memset(fdset, 0, nr);
369 return 0;
370 }
371
372 static inline unsigned long __must_check
373 set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
374 {
375 if (ufdset)
376 return __copy_to_user(ufdset, fdset, FDS_BYTES(nr));
377 return 0;
378 }
379
380 static inline
381 void zero_fd_set(unsigned long nr, unsigned long *fdset)
382 {
383 memset(fdset, 0, FDS_BYTES(nr));
384 }
385
386 #define FDS_IN(fds, n) (fds->in + n)
387 #define FDS_OUT(fds, n) (fds->out + n)
388 #define FDS_EX(fds, n) (fds->ex + n)
389
390 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
391
392 static int max_select_fd(unsigned long n, fd_set_bits *fds)
393 {
394 unsigned long *open_fds;
395 unsigned long set;
396 int max;
397 struct fdtable *fdt;
398
399 /* handle last in-complete long-word first */
400 set = ~(~0UL << (n & (BITS_PER_LONG-1)));
401 n /= BITS_PER_LONG;
402 fdt = files_fdtable(current->files);
403 open_fds = fdt->open_fds + n;
404 max = 0;
405 if (set) {
406 set &= BITS(fds, n);
407 if (set) {
408 if (!(set & ~*open_fds))
409 goto get_max;
410 return -EBADF;
411 }
412 }
413 while (n) {
414 open_fds--;
415 n--;
416 set = BITS(fds, n);
417 if (!set)
418 continue;
419 if (set & ~*open_fds)
420 return -EBADF;
421 if (max)
422 continue;
423 get_max:
424 do {
425 max++;
426 set >>= 1;
427 } while (set);
428 max += n * BITS_PER_LONG;
429 }
430
431 return max;
432 }
433
434 #define POLLIN_SET (EPOLLRDNORM | EPOLLRDBAND | EPOLLIN | EPOLLHUP | EPOLLERR)
435 #define POLLOUT_SET (EPOLLWRBAND | EPOLLWRNORM | EPOLLOUT | EPOLLERR)
436 #define POLLEX_SET (EPOLLPRI)
437
438 static inline void wait_key_set(poll_table *wait, unsigned long in,
439 unsigned long out, unsigned long bit,
440 __poll_t ll_flag)
441 {
442 wait->_key = POLLEX_SET | ll_flag;
443 if (in & bit)
444 wait->_key |= POLLIN_SET;
445 if (out & bit)
446 wait->_key |= POLLOUT_SET;
447 }
448
449 static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
450 {
451 ktime_t expire, *to = NULL;
452 struct poll_wqueues table;
453 poll_table *wait;
454 int retval, i, timed_out = 0;
455 u64 slack = 0;
456 __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
457 unsigned long busy_start = 0;
458
459 rcu_read_lock();
460 retval = max_select_fd(n, fds);
461 rcu_read_unlock();
462
463 if (retval < 0)
464 return retval;
465 n = retval;
466
467 poll_initwait(&table);
468 wait = &table.pt;
469 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
470 wait->_qproc = NULL;
471 timed_out = 1;
472 }
473
474 if (end_time && !timed_out)
475 slack = select_estimate_accuracy(end_time);
476
477 retval = 0;
478 for (;;) {
479 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
480 bool can_busy_loop = false;
481
482 inp = fds->in; outp = fds->out; exp = fds->ex;
483 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
484
485 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
486 unsigned long in, out, ex, all_bits, bit = 1, j;
487 unsigned long res_in = 0, res_out = 0, res_ex = 0;
488 __poll_t mask;
489
490 in = *inp++; out = *outp++; ex = *exp++;
491 all_bits = in | out | ex;
492 if (all_bits == 0) {
493 i += BITS_PER_LONG;
494 continue;
495 }
496
497 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
498 struct fd f;
499 if (i >= n)
500 break;
501 if (!(bit & all_bits))
502 continue;
503 f = fdget(i);
504 if (f.file) {
505 wait_key_set(wait, in, out, bit,
506 busy_flag);
507 mask = vfs_poll(f.file, wait);
508
509 fdput(f);
510 if ((mask & POLLIN_SET) && (in & bit)) {
511 res_in |= bit;
512 retval++;
513 wait->_qproc = NULL;
514 }
515 if ((mask & POLLOUT_SET) && (out & bit)) {
516 res_out |= bit;
517 retval++;
518 wait->_qproc = NULL;
519 }
520 if ((mask & POLLEX_SET) && (ex & bit)) {
521 res_ex |= bit;
522 retval++;
523 wait->_qproc = NULL;
524 }
525 /* got something, stop busy polling */
526 if (retval) {
527 can_busy_loop = false;
528 busy_flag = 0;
529
530 /*
531 * only remember a returned
532 * POLL_BUSY_LOOP if we asked for it
533 */
534 } else if (busy_flag & mask)
535 can_busy_loop = true;
536
537 }
538 }
539 if (res_in)
540 *rinp = res_in;
541 if (res_out)
542 *routp = res_out;
543 if (res_ex)
544 *rexp = res_ex;
545 cond_resched();
546 }
547 wait->_qproc = NULL;
548 if (retval || timed_out || signal_pending(current))
549 break;
550 if (table.error) {
551 retval = table.error;
552 break;
553 }
554
555 /* only if found POLL_BUSY_LOOP sockets && not out of time */
556 if (can_busy_loop && !need_resched()) {
557 if (!busy_start) {
558 busy_start = busy_loop_current_time();
559 continue;
560 }
561 if (!busy_loop_timeout(busy_start))
562 continue;
563 }
564 busy_flag = 0;
565
566 /*
567 * If this is the first loop and we have a timeout
568 * given, then we convert to ktime_t and set the to
569 * pointer to the expiry value.
570 */
571 if (end_time && !to) {
572 expire = timespec64_to_ktime(*end_time);
573 to = &expire;
574 }
575
576 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
577 to, slack))
578 timed_out = 1;
579 }
580
581 poll_freewait(&table);
582
583 return retval;
584 }
585
586 /*
587 * We can actually return ERESTARTSYS instead of EINTR, but I'd
588 * like to be certain this leads to no problems. So I return
589 * EINTR just for safety.
590 *
591 * Update: ERESTARTSYS breaks at least the xview clock binary, so
592 * I'm trying ERESTARTNOHAND which restart only when you want to.
593 */
594 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
595 fd_set __user *exp, struct timespec64 *end_time)
596 {
597 fd_set_bits fds;
598 void *bits;
599 int ret, max_fds;
600 size_t size, alloc_size;
601 struct fdtable *fdt;
602 /* Allocate small arguments on the stack to save memory and be faster */
603 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
604
605 ret = -EINVAL;
606 if (n < 0)
607 goto out_nofds;
608
609 /* max_fds can increase, so grab it once to avoid race */
610 rcu_read_lock();
611 fdt = files_fdtable(current->files);
612 max_fds = fdt->max_fds;
613 rcu_read_unlock();
614 if (n > max_fds)
615 n = max_fds;
616
617 /*
618 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
619 * since we used fdset we need to allocate memory in units of
620 * long-words.
621 */
622 size = FDS_BYTES(n);
623 bits = stack_fds;
624 if (size > sizeof(stack_fds) / 6) {
625 /* Not enough space in on-stack array; must use kmalloc */
626 ret = -ENOMEM;
627 if (size > (SIZE_MAX / 6))
628 goto out_nofds;
629
630 alloc_size = 6 * size;
631 bits = kvmalloc(alloc_size, GFP_KERNEL);
632 if (!bits)
633 goto out_nofds;
634 }
635 fds.in = bits;
636 fds.out = bits + size;
637 fds.ex = bits + 2*size;
638 fds.res_in = bits + 3*size;
639 fds.res_out = bits + 4*size;
640 fds.res_ex = bits + 5*size;
641
642 if ((ret = get_fd_set(n, inp, fds.in)) ||
643 (ret = get_fd_set(n, outp, fds.out)) ||
644 (ret = get_fd_set(n, exp, fds.ex)))
645 goto out;
646 zero_fd_set(n, fds.res_in);
647 zero_fd_set(n, fds.res_out);
648 zero_fd_set(n, fds.res_ex);
649
650 ret = do_select(n, &fds, end_time);
651
652 if (ret < 0)
653 goto out;
654 if (!ret) {
655 ret = -ERESTARTNOHAND;
656 if (signal_pending(current))
657 goto out;
658 ret = 0;
659 }
660
661 if (set_fd_set(n, inp, fds.res_in) ||
662 set_fd_set(n, outp, fds.res_out) ||
663 set_fd_set(n, exp, fds.res_ex))
664 ret = -EFAULT;
665
666 out:
667 if (bits != stack_fds)
668 kvfree(bits);
669 out_nofds:
670 return ret;
671 }
672
673 static int kern_select(int n, fd_set __user *inp, fd_set __user *outp,
674 fd_set __user *exp, struct timeval __user *tvp)
675 {
676 struct timespec64 end_time, *to = NULL;
677 struct timeval tv;
678 int ret;
679
680 if (tvp) {
681 if (copy_from_user(&tv, tvp, sizeof(tv)))
682 return -EFAULT;
683
684 to = &end_time;
685 if (poll_select_set_timeout(to,
686 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
687 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
688 return -EINVAL;
689 }
690
691 ret = core_sys_select(n, inp, outp, exp, to);
692 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
693
694 return ret;
695 }
696
697 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
698 fd_set __user *, exp, struct timeval __user *, tvp)
699 {
700 return kern_select(n, inp, outp, exp, tvp);
701 }
702
703 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
704 fd_set __user *exp, struct timespec __user *tsp,
705 const sigset_t __user *sigmask, size_t sigsetsize)
706 {
707 sigset_t ksigmask, sigsaved;
708 struct timespec64 ts, end_time, *to = NULL;
709 int ret;
710
711 if (tsp) {
712 if (get_timespec64(&ts, tsp))
713 return -EFAULT;
714
715 to = &end_time;
716 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
717 return -EINVAL;
718 }
719
720 if (sigmask) {
721 /* XXX: Don't preclude handling different sized sigset_t's. */
722 if (sigsetsize != sizeof(sigset_t))
723 return -EINVAL;
724 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
725 return -EFAULT;
726
727 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
728 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
729 }
730
731 ret = core_sys_select(n, inp, outp, exp, to);
732 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
733
734 if (ret == -ERESTARTNOHAND) {
735 /*
736 * Don't restore the signal mask yet. Let do_signal() deliver
737 * the signal on the way back to userspace, before the signal
738 * mask is restored.
739 */
740 if (sigmask) {
741 memcpy(&current->saved_sigmask, &sigsaved,
742 sizeof(sigsaved));
743 set_restore_sigmask();
744 }
745 } else if (sigmask)
746 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
747
748 return ret;
749 }
750
751 /*
752 * Most architectures can't handle 7-argument syscalls. So we provide a
753 * 6-argument version where the sixth argument is a pointer to a structure
754 * which has a pointer to the sigset_t itself followed by a size_t containing
755 * the sigset size.
756 */
757 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
758 fd_set __user *, exp, struct timespec __user *, tsp,
759 void __user *, sig)
760 {
761 size_t sigsetsize = 0;
762 sigset_t __user *up = NULL;
763
764 if (sig) {
765 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
766 || __get_user(up, (sigset_t __user * __user *)sig)
767 || __get_user(sigsetsize,
768 (size_t __user *)(sig+sizeof(void *))))
769 return -EFAULT;
770 }
771
772 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
773 }
774
775 #ifdef __ARCH_WANT_SYS_OLD_SELECT
776 struct sel_arg_struct {
777 unsigned long n;
778 fd_set __user *inp, *outp, *exp;
779 struct timeval __user *tvp;
780 };
781
782 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
783 {
784 struct sel_arg_struct a;
785
786 if (copy_from_user(&a, arg, sizeof(a)))
787 return -EFAULT;
788 return kern_select(a.n, a.inp, a.outp, a.exp, a.tvp);
789 }
790 #endif
791
792 struct poll_list {
793 struct poll_list *next;
794 int len;
795 struct pollfd entries[0];
796 };
797
798 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
799
800 /*
801 * Fish for pollable events on the pollfd->fd file descriptor. We're only
802 * interested in events matching the pollfd->events mask, and the result
803 * matching that mask is both recorded in pollfd->revents and returned. The
804 * pwait poll_table will be used by the fd-provided poll handler for waiting,
805 * if pwait->_qproc is non-NULL.
806 */
807 static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
808 bool *can_busy_poll,
809 __poll_t busy_flag)
810 {
811 int fd = pollfd->fd;
812 __poll_t mask = 0, filter;
813 struct fd f;
814
815 if (fd < 0)
816 goto out;
817 mask = EPOLLNVAL;
818 f = fdget(fd);
819 if (!f.file)
820 goto out;
821
822 /* userland u16 ->events contains POLL... bitmap */
823 filter = demangle_poll(pollfd->events) | EPOLLERR | EPOLLHUP;
824 pwait->_key = filter | busy_flag;
825 mask = vfs_poll(f.file, pwait);
826 if (mask & busy_flag)
827 *can_busy_poll = true;
828 mask &= filter; /* Mask out unneeded events. */
829 fdput(f);
830
831 out:
832 /* ... and so does ->revents */
833 pollfd->revents = mangle_poll(mask);
834 return mask;
835 }
836
837 static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
838 struct timespec64 *end_time)
839 {
840 poll_table* pt = &wait->pt;
841 ktime_t expire, *to = NULL;
842 int timed_out = 0, count = 0;
843 u64 slack = 0;
844 __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
845 unsigned long busy_start = 0;
846
847 /* Optimise the no-wait case */
848 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
849 pt->_qproc = NULL;
850 timed_out = 1;
851 }
852
853 if (end_time && !timed_out)
854 slack = select_estimate_accuracy(end_time);
855
856 for (;;) {
857 struct poll_list *walk;
858 bool can_busy_loop = false;
859
860 for (walk = list; walk != NULL; walk = walk->next) {
861 struct pollfd * pfd, * pfd_end;
862
863 pfd = walk->entries;
864 pfd_end = pfd + walk->len;
865 for (; pfd != pfd_end; pfd++) {
866 /*
867 * Fish for events. If we found one, record it
868 * and kill poll_table->_qproc, so we don't
869 * needlessly register any other waiters after
870 * this. They'll get immediately deregistered
871 * when we break out and return.
872 */
873 if (do_pollfd(pfd, pt, &can_busy_loop,
874 busy_flag)) {
875 count++;
876 pt->_qproc = NULL;
877 /* found something, stop busy polling */
878 busy_flag = 0;
879 can_busy_loop = false;
880 }
881 }
882 }
883 /*
884 * All waiters have already been registered, so don't provide
885 * a poll_table->_qproc to them on the next loop iteration.
886 */
887 pt->_qproc = NULL;
888 if (!count) {
889 count = wait->error;
890 if (signal_pending(current))
891 count = -EINTR;
892 }
893 if (count || timed_out)
894 break;
895
896 /* only if found POLL_BUSY_LOOP sockets && not out of time */
897 if (can_busy_loop && !need_resched()) {
898 if (!busy_start) {
899 busy_start = busy_loop_current_time();
900 continue;
901 }
902 if (!busy_loop_timeout(busy_start))
903 continue;
904 }
905 busy_flag = 0;
906
907 /*
908 * If this is the first loop and we have a timeout
909 * given, then we convert to ktime_t and set the to
910 * pointer to the expiry value.
911 */
912 if (end_time && !to) {
913 expire = timespec64_to_ktime(*end_time);
914 to = &expire;
915 }
916
917 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
918 timed_out = 1;
919 }
920 return count;
921 }
922
923 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \
924 sizeof(struct pollfd))
925
926 static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
927 struct timespec64 *end_time)
928 {
929 struct poll_wqueues table;
930 int err = -EFAULT, fdcount, len, size;
931 /* Allocate small arguments on the stack to save memory and be
932 faster - use long to make sure the buffer is aligned properly
933 on 64 bit archs to avoid unaligned access */
934 long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
935 struct poll_list *const head = (struct poll_list *)stack_pps;
936 struct poll_list *walk = head;
937 unsigned long todo = nfds;
938
939 if (nfds > rlimit(RLIMIT_NOFILE))
940 return -EINVAL;
941
942 len = min_t(unsigned int, nfds, N_STACK_PPS);
943 for (;;) {
944 walk->next = NULL;
945 walk->len = len;
946 if (!len)
947 break;
948
949 if (copy_from_user(walk->entries, ufds + nfds-todo,
950 sizeof(struct pollfd) * walk->len))
951 goto out_fds;
952
953 todo -= walk->len;
954 if (!todo)
955 break;
956
957 len = min(todo, POLLFD_PER_PAGE);
958 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
959 walk = walk->next = kmalloc(size, GFP_KERNEL);
960 if (!walk) {
961 err = -ENOMEM;
962 goto out_fds;
963 }
964 }
965
966 poll_initwait(&table);
967 fdcount = do_poll(head, &table, end_time);
968 poll_freewait(&table);
969
970 for (walk = head; walk; walk = walk->next) {
971 struct pollfd *fds = walk->entries;
972 int j;
973
974 for (j = 0; j < walk->len; j++, ufds++)
975 if (__put_user(fds[j].revents, &ufds->revents))
976 goto out_fds;
977 }
978
979 err = fdcount;
980 out_fds:
981 walk = head->next;
982 while (walk) {
983 struct poll_list *pos = walk;
984 walk = walk->next;
985 kfree(pos);
986 }
987
988 return err;
989 }
990
991 static long do_restart_poll(struct restart_block *restart_block)
992 {
993 struct pollfd __user *ufds = restart_block->poll.ufds;
994 int nfds = restart_block->poll.nfds;
995 struct timespec64 *to = NULL, end_time;
996 int ret;
997
998 if (restart_block->poll.has_timeout) {
999 end_time.tv_sec = restart_block->poll.tv_sec;
1000 end_time.tv_nsec = restart_block->poll.tv_nsec;
1001 to = &end_time;
1002 }
1003
1004 ret = do_sys_poll(ufds, nfds, to);
1005
1006 if (ret == -EINTR) {
1007 restart_block->fn = do_restart_poll;
1008 ret = -ERESTART_RESTARTBLOCK;
1009 }
1010 return ret;
1011 }
1012
1013 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
1014 int, timeout_msecs)
1015 {
1016 struct timespec64 end_time, *to = NULL;
1017 int ret;
1018
1019 if (timeout_msecs >= 0) {
1020 to = &end_time;
1021 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
1022 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
1023 }
1024
1025 ret = do_sys_poll(ufds, nfds, to);
1026
1027 if (ret == -EINTR) {
1028 struct restart_block *restart_block;
1029
1030 restart_block = &current->restart_block;
1031 restart_block->fn = do_restart_poll;
1032 restart_block->poll.ufds = ufds;
1033 restart_block->poll.nfds = nfds;
1034
1035 if (timeout_msecs >= 0) {
1036 restart_block->poll.tv_sec = end_time.tv_sec;
1037 restart_block->poll.tv_nsec = end_time.tv_nsec;
1038 restart_block->poll.has_timeout = 1;
1039 } else
1040 restart_block->poll.has_timeout = 0;
1041
1042 ret = -ERESTART_RESTARTBLOCK;
1043 }
1044 return ret;
1045 }
1046
1047 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
1048 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
1049 size_t, sigsetsize)
1050 {
1051 sigset_t ksigmask, sigsaved;
1052 struct timespec64 ts, end_time, *to = NULL;
1053 int ret;
1054
1055 if (tsp) {
1056 if (get_timespec64(&ts, tsp))
1057 return -EFAULT;
1058
1059 to = &end_time;
1060 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1061 return -EINVAL;
1062 }
1063
1064 if (sigmask) {
1065 /* XXX: Don't preclude handling different sized sigset_t's. */
1066 if (sigsetsize != sizeof(sigset_t))
1067 return -EINVAL;
1068 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1069 return -EFAULT;
1070
1071 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1072 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1073 }
1074
1075 ret = do_sys_poll(ufds, nfds, to);
1076
1077 /* We can restart this syscall, usually */
1078 if (ret == -EINTR) {
1079 /*
1080 * Don't restore the signal mask yet. Let do_signal() deliver
1081 * the signal on the way back to userspace, before the signal
1082 * mask is restored.
1083 */
1084 if (sigmask) {
1085 memcpy(&current->saved_sigmask, &sigsaved,
1086 sizeof(sigsaved));
1087 set_restore_sigmask();
1088 }
1089 ret = -ERESTARTNOHAND;
1090 } else if (sigmask)
1091 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1092
1093 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1094
1095 return ret;
1096 }
1097
1098 #ifdef CONFIG_COMPAT
1099 #define __COMPAT_NFDBITS (8 * sizeof(compat_ulong_t))
1100
1101 static
1102 int compat_poll_select_copy_remaining(struct timespec64 *end_time, void __user *p,
1103 int timeval, int ret)
1104 {
1105 struct timespec64 ts;
1106
1107 if (!p)
1108 return ret;
1109
1110 if (current->personality & STICKY_TIMEOUTS)
1111 goto sticky;
1112
1113 /* No update for zero timeout */
1114 if (!end_time->tv_sec && !end_time->tv_nsec)
1115 return ret;
1116
1117 ktime_get_ts64(&ts);
1118 ts = timespec64_sub(*end_time, ts);
1119 if (ts.tv_sec < 0)
1120 ts.tv_sec = ts.tv_nsec = 0;
1121
1122 if (timeval) {
1123 struct compat_timeval rtv;
1124
1125 rtv.tv_sec = ts.tv_sec;
1126 rtv.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
1127
1128 if (!copy_to_user(p, &rtv, sizeof(rtv)))
1129 return ret;
1130 } else {
1131 if (!compat_put_timespec64(&ts, p))
1132 return ret;
1133 }
1134 /*
1135 * If an application puts its timeval in read-only memory, we
1136 * don't want the Linux-specific update to the timeval to
1137 * cause a fault after the select has completed
1138 * successfully. However, because we're not updating the
1139 * timeval, we can't restart the system call.
1140 */
1141
1142 sticky:
1143 if (ret == -ERESTARTNOHAND)
1144 ret = -EINTR;
1145 return ret;
1146 }
1147
1148 /*
1149 * Ooo, nasty. We need here to frob 32-bit unsigned longs to
1150 * 64-bit unsigned longs.
1151 */
1152 static
1153 int compat_get_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
1154 unsigned long *fdset)
1155 {
1156 if (ufdset) {
1157 return compat_get_bitmap(fdset, ufdset, nr);
1158 } else {
1159 zero_fd_set(nr, fdset);
1160 return 0;
1161 }
1162 }
1163
1164 static
1165 int compat_set_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
1166 unsigned long *fdset)
1167 {
1168 if (!ufdset)
1169 return 0;
1170 return compat_put_bitmap(ufdset, fdset, nr);
1171 }
1172
1173
1174 /*
1175 * This is a virtual copy of sys_select from fs/select.c and probably
1176 * should be compared to it from time to time
1177 */
1178
1179 /*
1180 * We can actually return ERESTARTSYS instead of EINTR, but I'd
1181 * like to be certain this leads to no problems. So I return
1182 * EINTR just for safety.
1183 *
1184 * Update: ERESTARTSYS breaks at least the xview clock binary, so
1185 * I'm trying ERESTARTNOHAND which restart only when you want to.
1186 */
1187 static int compat_core_sys_select(int n, compat_ulong_t __user *inp,
1188 compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1189 struct timespec64 *end_time)
1190 {
1191 fd_set_bits fds;
1192 void *bits;
1193 int size, max_fds, ret = -EINVAL;
1194 struct fdtable *fdt;
1195 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
1196
1197 if (n < 0)
1198 goto out_nofds;
1199
1200 /* max_fds can increase, so grab it once to avoid race */
1201 rcu_read_lock();
1202 fdt = files_fdtable(current->files);
1203 max_fds = fdt->max_fds;
1204 rcu_read_unlock();
1205 if (n > max_fds)
1206 n = max_fds;
1207
1208 /*
1209 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
1210 * since we used fdset we need to allocate memory in units of
1211 * long-words.
1212 */
1213 size = FDS_BYTES(n);
1214 bits = stack_fds;
1215 if (size > sizeof(stack_fds) / 6) {
1216 bits = kmalloc_array(6, size, GFP_KERNEL);
1217 ret = -ENOMEM;
1218 if (!bits)
1219 goto out_nofds;
1220 }
1221 fds.in = (unsigned long *) bits;
1222 fds.out = (unsigned long *) (bits + size);
1223 fds.ex = (unsigned long *) (bits + 2*size);
1224 fds.res_in = (unsigned long *) (bits + 3*size);
1225 fds.res_out = (unsigned long *) (bits + 4*size);
1226 fds.res_ex = (unsigned long *) (bits + 5*size);
1227
1228 if ((ret = compat_get_fd_set(n, inp, fds.in)) ||
1229 (ret = compat_get_fd_set(n, outp, fds.out)) ||
1230 (ret = compat_get_fd_set(n, exp, fds.ex)))
1231 goto out;
1232 zero_fd_set(n, fds.res_in);
1233 zero_fd_set(n, fds.res_out);
1234 zero_fd_set(n, fds.res_ex);
1235
1236 ret = do_select(n, &fds, end_time);
1237
1238 if (ret < 0)
1239 goto out;
1240 if (!ret) {
1241 ret = -ERESTARTNOHAND;
1242 if (signal_pending(current))
1243 goto out;
1244 ret = 0;
1245 }
1246
1247 if (compat_set_fd_set(n, inp, fds.res_in) ||
1248 compat_set_fd_set(n, outp, fds.res_out) ||
1249 compat_set_fd_set(n, exp, fds.res_ex))
1250 ret = -EFAULT;
1251 out:
1252 if (bits != stack_fds)
1253 kfree(bits);
1254 out_nofds:
1255 return ret;
1256 }
1257
1258 static int do_compat_select(int n, compat_ulong_t __user *inp,
1259 compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1260 struct compat_timeval __user *tvp)
1261 {
1262 struct timespec64 end_time, *to = NULL;
1263 struct compat_timeval tv;
1264 int ret;
1265
1266 if (tvp) {
1267 if (copy_from_user(&tv, tvp, sizeof(tv)))
1268 return -EFAULT;
1269
1270 to = &end_time;
1271 if (poll_select_set_timeout(to,
1272 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
1273 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
1274 return -EINVAL;
1275 }
1276
1277 ret = compat_core_sys_select(n, inp, outp, exp, to);
1278 ret = compat_poll_select_copy_remaining(&end_time, tvp, 1, ret);
1279
1280 return ret;
1281 }
1282
1283 COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp,
1284 compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
1285 struct compat_timeval __user *, tvp)
1286 {
1287 return do_compat_select(n, inp, outp, exp, tvp);
1288 }
1289
1290 struct compat_sel_arg_struct {
1291 compat_ulong_t n;
1292 compat_uptr_t inp;
1293 compat_uptr_t outp;
1294 compat_uptr_t exp;
1295 compat_uptr_t tvp;
1296 };
1297
1298 COMPAT_SYSCALL_DEFINE1(old_select, struct compat_sel_arg_struct __user *, arg)
1299 {
1300 struct compat_sel_arg_struct a;
1301
1302 if (copy_from_user(&a, arg, sizeof(a)))
1303 return -EFAULT;
1304 return do_compat_select(a.n, compat_ptr(a.inp), compat_ptr(a.outp),
1305 compat_ptr(a.exp), compat_ptr(a.tvp));
1306 }
1307
1308 static long do_compat_pselect(int n, compat_ulong_t __user *inp,
1309 compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1310 struct compat_timespec __user *tsp, compat_sigset_t __user *sigmask,
1311 compat_size_t sigsetsize)
1312 {
1313 sigset_t ksigmask, sigsaved;
1314 struct timespec64 ts, end_time, *to = NULL;
1315 int ret;
1316
1317 if (tsp) {
1318 if (compat_get_timespec64(&ts, tsp))
1319 return -EFAULT;
1320
1321 to = &end_time;
1322 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1323 return -EINVAL;
1324 }
1325
1326 if (sigmask) {
1327 if (sigsetsize != sizeof(compat_sigset_t))
1328 return -EINVAL;
1329 if (get_compat_sigset(&ksigmask, sigmask))
1330 return -EFAULT;
1331
1332 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1333 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1334 }
1335
1336 ret = compat_core_sys_select(n, inp, outp, exp, to);
1337 ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
1338
1339 if (ret == -ERESTARTNOHAND) {
1340 /*
1341 * Don't restore the signal mask yet. Let do_signal() deliver
1342 * the signal on the way back to userspace, before the signal
1343 * mask is restored.
1344 */
1345 if (sigmask) {
1346 memcpy(&current->saved_sigmask, &sigsaved,
1347 sizeof(sigsaved));
1348 set_restore_sigmask();
1349 }
1350 } else if (sigmask)
1351 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1352
1353 return ret;
1354 }
1355
1356 COMPAT_SYSCALL_DEFINE6(pselect6, int, n, compat_ulong_t __user *, inp,
1357 compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
1358 struct compat_timespec __user *, tsp, void __user *, sig)
1359 {
1360 compat_size_t sigsetsize = 0;
1361 compat_uptr_t up = 0;
1362
1363 if (sig) {
1364 if (!access_ok(VERIFY_READ, sig,
1365 sizeof(compat_uptr_t)+sizeof(compat_size_t)) ||
1366 __get_user(up, (compat_uptr_t __user *)sig) ||
1367 __get_user(sigsetsize,
1368 (compat_size_t __user *)(sig+sizeof(up))))
1369 return -EFAULT;
1370 }
1371 return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(up),
1372 sigsetsize);
1373 }
1374
1375 COMPAT_SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds,
1376 unsigned int, nfds, struct compat_timespec __user *, tsp,
1377 const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize)
1378 {
1379 sigset_t ksigmask, sigsaved;
1380 struct timespec64 ts, end_time, *to = NULL;
1381 int ret;
1382
1383 if (tsp) {
1384 if (compat_get_timespec64(&ts, tsp))
1385 return -EFAULT;
1386
1387 to = &end_time;
1388 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1389 return -EINVAL;
1390 }
1391
1392 if (sigmask) {
1393 if (sigsetsize != sizeof(compat_sigset_t))
1394 return -EINVAL;
1395 if (get_compat_sigset(&ksigmask, sigmask))
1396 return -EFAULT;
1397
1398 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1399 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1400 }
1401
1402 ret = do_sys_poll(ufds, nfds, to);
1403
1404 /* We can restart this syscall, usually */
1405 if (ret == -EINTR) {
1406 /*
1407 * Don't restore the signal mask yet. Let do_signal() deliver
1408 * the signal on the way back to userspace, before the signal
1409 * mask is restored.
1410 */
1411 if (sigmask) {
1412 memcpy(&current->saved_sigmask, &sigsaved,
1413 sizeof(sigsaved));
1414 set_restore_sigmask();
1415 }
1416 ret = -ERESTARTNOHAND;
1417 } else if (sigmask)
1418 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1419
1420 ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
1421
1422 return ret;
1423 }
1424 #endif
Linux with added FPC-III support