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Merge tag 'xtensa-20180225' of git://github.com/jcmvbkbc/linux-xtensa
[cris-mirror.git] / fs / select.c
blobb6c36254028ad1f48c5edc79186c52882caf61d1
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 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 EXPORT_SYMBOL(poll_schedule_timeout);
262
263 /**
264 * poll_select_set_timeout - helper function to setup the timeout value
265 * @to: pointer to timespec64 variable for the final timeout
266 * @sec: seconds (from user space)
267 * @nsec: nanoseconds (from user space)
268 *
269 * Note, we do not use a timespec for the user space value here, That
270 * way we can use the function for timeval and compat interfaces as well.
271 *
272 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
273 */
274 int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec)
275 {
276 struct timespec64 ts = {.tv_sec = sec, .tv_nsec = nsec};
277
278 if (!timespec64_valid(&ts))
279 return -EINVAL;
280
281 /* Optimize for the zero timeout value here */
282 if (!sec && !nsec) {
283 to->tv_sec = to->tv_nsec = 0;
284 } else {
285 ktime_get_ts64(to);
286 *to = timespec64_add_safe(*to, ts);
287 }
288 return 0;
289 }
290
291 static int poll_select_copy_remaining(struct timespec64 *end_time,
292 void __user *p,
293 int timeval, int ret)
294 {
295 struct timespec64 rts;
296 struct timeval rtv;
297
298 if (!p)
299 return ret;
300
301 if (current->personality & STICKY_TIMEOUTS)
302 goto sticky;
303
304 /* No update for zero timeout */
305 if (!end_time->tv_sec && !end_time->tv_nsec)
306 return ret;
307
308 ktime_get_ts64(&rts);
309 rts = timespec64_sub(*end_time, rts);
310 if (rts.tv_sec < 0)
311 rts.tv_sec = rts.tv_nsec = 0;
312
313
314 if (timeval) {
315 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
316 memset(&rtv, 0, sizeof(rtv));
317 rtv.tv_sec = rts.tv_sec;
318 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
319
320 if (!copy_to_user(p, &rtv, sizeof(rtv)))
321 return ret;
322
323 } else if (!put_timespec64(&rts, p))
324 return ret;
325
326 /*
327 * If an application puts its timeval in read-only memory, we
328 * don't want the Linux-specific update to the timeval to
329 * cause a fault after the select has completed
330 * successfully. However, because we're not updating the
331 * timeval, we can't restart the system call.
332 */
333
334 sticky:
335 if (ret == -ERESTARTNOHAND)
336 ret = -EINTR;
337 return ret;
338 }
339
340 /*
341 * Scalable version of the fd_set.
342 */
343
344 typedef struct {
345 unsigned long *in, *out, *ex;
346 unsigned long *res_in, *res_out, *res_ex;
347 } fd_set_bits;
348
349 /*
350 * How many longwords for "nr" bits?
351 */
352 #define FDS_BITPERLONG (8*sizeof(long))
353 #define FDS_LONGS(nr) (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG)
354 #define FDS_BYTES(nr) (FDS_LONGS(nr)*sizeof(long))
355
356 /*
357 * We do a VERIFY_WRITE here even though we are only reading this time:
358 * we'll write to it eventually..
359 *
360 * Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
361 */
362 static inline
363 int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
364 {
365 nr = FDS_BYTES(nr);
366 if (ufdset)
367 return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0;
368
369 memset(fdset, 0, nr);
370 return 0;
371 }
372
373 static inline unsigned long __must_check
374 set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
375 {
376 if (ufdset)
377 return __copy_to_user(ufdset, fdset, FDS_BYTES(nr));
378 return 0;
379 }
380
381 static inline
382 void zero_fd_set(unsigned long nr, unsigned long *fdset)
383 {
384 memset(fdset, 0, FDS_BYTES(nr));
385 }
386
387 #define FDS_IN(fds, n) (fds->in + n)
388 #define FDS_OUT(fds, n) (fds->out + n)
389 #define FDS_EX(fds, n) (fds->ex + n)
390
391 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
392
393 static int max_select_fd(unsigned long n, fd_set_bits *fds)
394 {
395 unsigned long *open_fds;
396 unsigned long set;
397 int max;
398 struct fdtable *fdt;
399
400 /* handle last in-complete long-word first */
401 set = ~(~0UL << (n & (BITS_PER_LONG-1)));
402 n /= BITS_PER_LONG;
403 fdt = files_fdtable(current->files);
404 open_fds = fdt->open_fds + n;
405 max = 0;
406 if (set) {
407 set &= BITS(fds, n);
408 if (set) {
409 if (!(set & ~*open_fds))
410 goto get_max;
411 return -EBADF;
412 }
413 }
414 while (n) {
415 open_fds--;
416 n--;
417 set = BITS(fds, n);
418 if (!set)
419 continue;
420 if (set & ~*open_fds)
421 return -EBADF;
422 if (max)
423 continue;
424 get_max:
425 do {
426 max++;
427 set >>= 1;
428 } while (set);
429 max += n * BITS_PER_LONG;
430 }
431
432 return max;
433 }
434
435 #define POLLIN_SET (EPOLLRDNORM | EPOLLRDBAND | EPOLLIN | EPOLLHUP | EPOLLERR)
436 #define POLLOUT_SET (EPOLLWRBAND | EPOLLWRNORM | EPOLLOUT | EPOLLERR)
437 #define POLLEX_SET (EPOLLPRI)
438
439 static inline void wait_key_set(poll_table *wait, unsigned long in,
440 unsigned long out, unsigned long bit,
441 __poll_t ll_flag)
442 {
443 wait->_key = POLLEX_SET | ll_flag;
444 if (in & bit)
445 wait->_key |= POLLIN_SET;
446 if (out & bit)
447 wait->_key |= POLLOUT_SET;
448 }
449
450 static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
451 {
452 ktime_t expire, *to = NULL;
453 struct poll_wqueues table;
454 poll_table *wait;
455 int retval, i, timed_out = 0;
456 u64 slack = 0;
457 __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
458 unsigned long busy_start = 0;
459
460 rcu_read_lock();
461 retval = max_select_fd(n, fds);
462 rcu_read_unlock();
463
464 if (retval < 0)
465 return retval;
466 n = retval;
467
468 poll_initwait(&table);
469 wait = &table.pt;
470 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
471 wait->_qproc = NULL;
472 timed_out = 1;
473 }
474
475 if (end_time && !timed_out)
476 slack = select_estimate_accuracy(end_time);
477
478 retval = 0;
479 for (;;) {
480 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
481 bool can_busy_loop = false;
482
483 inp = fds->in; outp = fds->out; exp = fds->ex;
484 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
485
486 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
487 unsigned long in, out, ex, all_bits, bit = 1, j;
488 unsigned long res_in = 0, res_out = 0, res_ex = 0;
489 __poll_t mask;
490
491 in = *inp++; out = *outp++; ex = *exp++;
492 all_bits = in | out | ex;
493 if (all_bits == 0) {
494 i += BITS_PER_LONG;
495 continue;
496 }
497
498 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
499 struct fd f;
500 if (i >= n)
501 break;
502 if (!(bit & all_bits))
503 continue;
504 f = fdget(i);
505 if (f.file) {
506 const struct file_operations *f_op;
507 f_op = f.file->f_op;
508 mask = DEFAULT_POLLMASK;
509 if (f_op->poll) {
510 wait_key_set(wait, in, out,
511 bit, busy_flag);
512 mask = (*f_op->poll)(f.file, wait);
513 }
514 fdput(f);
515 if ((mask & POLLIN_SET) && (in & bit)) {
516 res_in |= bit;
517 retval++;
518 wait->_qproc = NULL;
519 }
520 if ((mask & POLLOUT_SET) && (out & bit)) {
521 res_out |= bit;
522 retval++;
523 wait->_qproc = NULL;
524 }
525 if ((mask & POLLEX_SET) && (ex & bit)) {
526 res_ex |= bit;
527 retval++;
528 wait->_qproc = NULL;
529 }
530 /* got something, stop busy polling */
531 if (retval) {
532 can_busy_loop = false;
533 busy_flag = 0;
534
535 /*
536 * only remember a returned
537 * POLL_BUSY_LOOP if we asked for it
538 */
539 } else if (busy_flag & mask)
540 can_busy_loop = true;
541
542 }
543 }
544 if (res_in)
545 *rinp = res_in;
546 if (res_out)
547 *routp = res_out;
548 if (res_ex)
549 *rexp = res_ex;
550 cond_resched();
551 }
552 wait->_qproc = NULL;
553 if (retval || timed_out || signal_pending(current))
554 break;
555 if (table.error) {
556 retval = table.error;
557 break;
558 }
559
560 /* only if found POLL_BUSY_LOOP sockets && not out of time */
561 if (can_busy_loop && !need_resched()) {
562 if (!busy_start) {
563 busy_start = busy_loop_current_time();
564 continue;
565 }
566 if (!busy_loop_timeout(busy_start))
567 continue;
568 }
569 busy_flag = 0;
570
571 /*
572 * If this is the first loop and we have a timeout
573 * given, then we convert to ktime_t and set the to
574 * pointer to the expiry value.
575 */
576 if (end_time && !to) {
577 expire = timespec64_to_ktime(*end_time);
578 to = &expire;
579 }
580
581 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
582 to, slack))
583 timed_out = 1;
584 }
585
586 poll_freewait(&table);
587
588 return retval;
589 }
590
591 /*
592 * We can actually return ERESTARTSYS instead of EINTR, but I'd
593 * like to be certain this leads to no problems. So I return
594 * EINTR just for safety.
595 *
596 * Update: ERESTARTSYS breaks at least the xview clock binary, so
597 * I'm trying ERESTARTNOHAND which restart only when you want to.
598 */
599 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
600 fd_set __user *exp, struct timespec64 *end_time)
601 {
602 fd_set_bits fds;
603 void *bits;
604 int ret, max_fds;
605 size_t size, alloc_size;
606 struct fdtable *fdt;
607 /* Allocate small arguments on the stack to save memory and be faster */
608 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
609
610 ret = -EINVAL;
611 if (n < 0)
612 goto out_nofds;
613
614 /* max_fds can increase, so grab it once to avoid race */
615 rcu_read_lock();
616 fdt = files_fdtable(current->files);
617 max_fds = fdt->max_fds;
618 rcu_read_unlock();
619 if (n > max_fds)
620 n = max_fds;
621
622 /*
623 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
624 * since we used fdset we need to allocate memory in units of
625 * long-words.
626 */
627 size = FDS_BYTES(n);
628 bits = stack_fds;
629 if (size > sizeof(stack_fds) / 6) {
630 /* Not enough space in on-stack array; must use kmalloc */
631 ret = -ENOMEM;
632 if (size > (SIZE_MAX / 6))
633 goto out_nofds;
634
635 alloc_size = 6 * size;
636 bits = kvmalloc(alloc_size, GFP_KERNEL);
637 if (!bits)
638 goto out_nofds;
639 }
640 fds.in = bits;
641 fds.out = bits + size;
642 fds.ex = bits + 2*size;
643 fds.res_in = bits + 3*size;
644 fds.res_out = bits + 4*size;
645 fds.res_ex = bits + 5*size;
646
647 if ((ret = get_fd_set(n, inp, fds.in)) ||
648 (ret = get_fd_set(n, outp, fds.out)) ||
649 (ret = get_fd_set(n, exp, fds.ex)))
650 goto out;
651 zero_fd_set(n, fds.res_in);
652 zero_fd_set(n, fds.res_out);
653 zero_fd_set(n, fds.res_ex);
654
655 ret = do_select(n, &fds, end_time);
656
657 if (ret < 0)
658 goto out;
659 if (!ret) {
660 ret = -ERESTARTNOHAND;
661 if (signal_pending(current))
662 goto out;
663 ret = 0;
664 }
665
666 if (set_fd_set(n, inp, fds.res_in) ||
667 set_fd_set(n, outp, fds.res_out) ||
668 set_fd_set(n, exp, fds.res_ex))
669 ret = -EFAULT;
670
671 out:
672 if (bits != stack_fds)
673 kvfree(bits);
674 out_nofds:
675 return ret;
676 }
677
678 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
679 fd_set __user *, exp, struct timeval __user *, tvp)
680 {
681 struct timespec64 end_time, *to = NULL;
682 struct timeval tv;
683 int ret;
684
685 if (tvp) {
686 if (copy_from_user(&tv, tvp, sizeof(tv)))
687 return -EFAULT;
688
689 to = &end_time;
690 if (poll_select_set_timeout(to,
691 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
692 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
693 return -EINVAL;
694 }
695
696 ret = core_sys_select(n, inp, outp, exp, to);
697 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
698
699 return ret;
700 }
701
702 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
703 fd_set __user *exp, struct timespec __user *tsp,
704 const sigset_t __user *sigmask, size_t sigsetsize)
705 {
706 sigset_t ksigmask, sigsaved;
707 struct timespec64 ts, end_time, *to = NULL;
708 int ret;
709
710 if (tsp) {
711 if (get_timespec64(&ts, tsp))
712 return -EFAULT;
713
714 to = &end_time;
715 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
716 return -EINVAL;
717 }
718
719 if (sigmask) {
720 /* XXX: Don't preclude handling different sized sigset_t's. */
721 if (sigsetsize != sizeof(sigset_t))
722 return -EINVAL;
723 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
724 return -EFAULT;
725
726 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
727 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
728 }
729
730 ret = core_sys_select(n, inp, outp, exp, to);
731 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
732
733 if (ret == -ERESTARTNOHAND) {
734 /*
735 * Don't restore the signal mask yet. Let do_signal() deliver
736 * the signal on the way back to userspace, before the signal
737 * mask is restored.
738 */
739 if (sigmask) {
740 memcpy(&current->saved_sigmask, &sigsaved,
741 sizeof(sigsaved));
742 set_restore_sigmask();
743 }
744 } else if (sigmask)
745 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
746
747 return ret;
748 }
749
750 /*
751 * Most architectures can't handle 7-argument syscalls. So we provide a
752 * 6-argument version where the sixth argument is a pointer to a structure
753 * which has a pointer to the sigset_t itself followed by a size_t containing
754 * the sigset size.
755 */
756 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
757 fd_set __user *, exp, struct timespec __user *, tsp,
758 void __user *, sig)
759 {
760 size_t sigsetsize = 0;
761 sigset_t __user *up = NULL;
762
763 if (sig) {
764 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
765 || __get_user(up, (sigset_t __user * __user *)sig)
766 || __get_user(sigsetsize,
767 (size_t __user *)(sig+sizeof(void *))))
768 return -EFAULT;
769 }
770
771 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
772 }
773
774 #ifdef __ARCH_WANT_SYS_OLD_SELECT
775 struct sel_arg_struct {
776 unsigned long n;
777 fd_set __user *inp, *outp, *exp;
778 struct timeval __user *tvp;
779 };
780
781 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
782 {
783 struct sel_arg_struct a;
784
785 if (copy_from_user(&a, arg, sizeof(a)))
786 return -EFAULT;
787 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
788 }
789 #endif
790
791 struct poll_list {
792 struct poll_list *next;
793 int len;
794 struct pollfd entries[0];
795 };
796
797 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
798
799 /*
800 * Fish for pollable events on the pollfd->fd file descriptor. We're only
801 * interested in events matching the pollfd->events mask, and the result
802 * matching that mask is both recorded in pollfd->revents and returned. The
803 * pwait poll_table will be used by the fd-provided poll handler for waiting,
804 * if pwait->_qproc is non-NULL.
805 */
806 static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
807 bool *can_busy_poll,
808 __poll_t busy_flag)
809 {
810 __poll_t mask;
811 int fd;
812
813 mask = 0;
814 fd = pollfd->fd;
815 if (fd >= 0) {
816 struct fd f = fdget(fd);
817 mask = EPOLLNVAL;
818 if (f.file) {
819 /* userland u16 ->events contains POLL... bitmap */
820 __poll_t filter = demangle_poll(pollfd->events) |
821 EPOLLERR | EPOLLHUP;
822 mask = DEFAULT_POLLMASK;
823 if (f.file->f_op->poll) {
824 pwait->_key = filter;
825 pwait->_key |= busy_flag;
826 mask = f.file->f_op->poll(f.file, pwait);
827 if (mask & busy_flag)
828 *can_busy_poll = true;
829 }
830 /* Mask out unneeded events. */
831 mask &= filter;
832 fdput(f);
833 }
834 }
835 /* ... and so does ->revents */
836 pollfd->revents = mangle_poll(mask);
837
838 return mask;
839 }
840
841 static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
842 struct timespec64 *end_time)
843 {
844 poll_table* pt = &wait->pt;
845 ktime_t expire, *to = NULL;
846 int timed_out = 0, count = 0;
847 u64 slack = 0;
848 __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
849 unsigned long busy_start = 0;
850
851 /* Optimise the no-wait case */
852 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
853 pt->_qproc = NULL;
854 timed_out = 1;
855 }
856
857 if (end_time && !timed_out)
858 slack = select_estimate_accuracy(end_time);
859
860 for (;;) {
861 struct poll_list *walk;
862 bool can_busy_loop = false;
863
864 for (walk = list; walk != NULL; walk = walk->next) {
865 struct pollfd * pfd, * pfd_end;
866
867 pfd = walk->entries;
868 pfd_end = pfd + walk->len;
869 for (; pfd != pfd_end; pfd++) {
870 /*
871 * Fish for events. If we found one, record it
872 * and kill poll_table->_qproc, so we don't
873 * needlessly register any other waiters after
874 * this. They'll get immediately deregistered
875 * when we break out and return.
876 */
877 if (do_pollfd(pfd, pt, &can_busy_loop,
878 busy_flag)) {
879 count++;
880 pt->_qproc = NULL;
881 /* found something, stop busy polling */
882 busy_flag = 0;
883 can_busy_loop = false;
884 }
885 }
886 }
887 /*
888 * All waiters have already been registered, so don't provide
889 * a poll_table->_qproc to them on the next loop iteration.
890 */
891 pt->_qproc = NULL;
892 if (!count) {
893 count = wait->error;
894 if (signal_pending(current))
895 count = -EINTR;
896 }
897 if (count || timed_out)
898 break;
899
900 /* only if found POLL_BUSY_LOOP sockets && not out of time */
901 if (can_busy_loop && !need_resched()) {
902 if (!busy_start) {
903 busy_start = busy_loop_current_time();
904 continue;
905 }
906 if (!busy_loop_timeout(busy_start))
907 continue;
908 }
909 busy_flag = 0;
910
911 /*
912 * If this is the first loop and we have a timeout
913 * given, then we convert to ktime_t and set the to
914 * pointer to the expiry value.
915 */
916 if (end_time && !to) {
917 expire = timespec64_to_ktime(*end_time);
918 to = &expire;
919 }
920
921 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
922 timed_out = 1;
923 }
924 return count;
925 }
926
927 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \
928 sizeof(struct pollfd))
929
930 static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
931 struct timespec64 *end_time)
932 {
933 struct poll_wqueues table;
934 int err = -EFAULT, fdcount, len, size;
935 /* Allocate small arguments on the stack to save memory and be
936 faster - use long to make sure the buffer is aligned properly
937 on 64 bit archs to avoid unaligned access */
938 long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
939 struct poll_list *const head = (struct poll_list *)stack_pps;
940 struct poll_list *walk = head;
941 unsigned long todo = nfds;
942
943 if (nfds > rlimit(RLIMIT_NOFILE))
944 return -EINVAL;
945
946 len = min_t(unsigned int, nfds, N_STACK_PPS);
947 for (;;) {
948 walk->next = NULL;
949 walk->len = len;
950 if (!len)
951 break;
952
953 if (copy_from_user(walk->entries, ufds + nfds-todo,
954 sizeof(struct pollfd) * walk->len))
955 goto out_fds;
956
957 todo -= walk->len;
958 if (!todo)
959 break;
960
961 len = min(todo, POLLFD_PER_PAGE);
962 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
963 walk = walk->next = kmalloc(size, GFP_KERNEL);
964 if (!walk) {
965 err = -ENOMEM;
966 goto out_fds;
967 }
968 }
969
970 poll_initwait(&table);
971 fdcount = do_poll(head, &table, end_time);
972 poll_freewait(&table);
973
974 for (walk = head; walk; walk = walk->next) {
975 struct pollfd *fds = walk->entries;
976 int j;
977
978 for (j = 0; j < walk->len; j++, ufds++)
979 if (__put_user(fds[j].revents, &ufds->revents))
980 goto out_fds;
981 }
982
983 err = fdcount;
984 out_fds:
985 walk = head->next;
986 while (walk) {
987 struct poll_list *pos = walk;
988 walk = walk->next;
989 kfree(pos);
990 }
991
992 return err;
993 }
994
995 static long do_restart_poll(struct restart_block *restart_block)
996 {
997 struct pollfd __user *ufds = restart_block->poll.ufds;
998 int nfds = restart_block->poll.nfds;
999 struct timespec64 *to = NULL, end_time;
1000 int ret;
1001
1002 if (restart_block->poll.has_timeout) {
1003 end_time.tv_sec = restart_block->poll.tv_sec;
1004 end_time.tv_nsec = restart_block->poll.tv_nsec;
1005 to = &end_time;
1006 }
1007
1008 ret = do_sys_poll(ufds, nfds, to);
1009
1010 if (ret == -EINTR) {
1011 restart_block->fn = do_restart_poll;
1012 ret = -ERESTART_RESTARTBLOCK;
1013 }
1014 return ret;
1015 }
1016
1017 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
1018 int, timeout_msecs)
1019 {
1020 struct timespec64 end_time, *to = NULL;
1021 int ret;
1022
1023 if (timeout_msecs >= 0) {
1024 to = &end_time;
1025 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
1026 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
1027 }
1028
1029 ret = do_sys_poll(ufds, nfds, to);
1030
1031 if (ret == -EINTR) {
1032 struct restart_block *restart_block;
1033
1034 restart_block = &current->restart_block;
1035 restart_block->fn = do_restart_poll;
1036 restart_block->poll.ufds = ufds;
1037 restart_block->poll.nfds = nfds;
1038
1039 if (timeout_msecs >= 0) {
1040 restart_block->poll.tv_sec = end_time.tv_sec;
1041 restart_block->poll.tv_nsec = end_time.tv_nsec;
1042 restart_block->poll.has_timeout = 1;
1043 } else
1044 restart_block->poll.has_timeout = 0;
1045
1046 ret = -ERESTART_RESTARTBLOCK;
1047 }
1048 return ret;
1049 }
1050
1051 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
1052 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
1053 size_t, sigsetsize)
1054 {
1055 sigset_t ksigmask, sigsaved;
1056 struct timespec64 ts, end_time, *to = NULL;
1057 int ret;
1058
1059 if (tsp) {
1060 if (get_timespec64(&ts, tsp))
1061 return -EFAULT;
1062
1063 to = &end_time;
1064 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1065 return -EINVAL;
1066 }
1067
1068 if (sigmask) {
1069 /* XXX: Don't preclude handling different sized sigset_t's. */
1070 if (sigsetsize != sizeof(sigset_t))
1071 return -EINVAL;
1072 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1073 return -EFAULT;
1074
1075 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1076 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1077 }
1078
1079 ret = do_sys_poll(ufds, nfds, to);
1080
1081 /* We can restart this syscall, usually */
1082 if (ret == -EINTR) {
1083 /*
1084 * Don't restore the signal mask yet. Let do_signal() deliver
1085 * the signal on the way back to userspace, before the signal
1086 * mask is restored.
1087 */
1088 if (sigmask) {
1089 memcpy(&current->saved_sigmask, &sigsaved,
1090 sizeof(sigsaved));
1091 set_restore_sigmask();
1092 }
1093 ret = -ERESTARTNOHAND;
1094 } else if (sigmask)
1095 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1096
1097 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1098
1099 return ret;
1100 }
1101
1102 #ifdef CONFIG_COMPAT
1103 #define __COMPAT_NFDBITS (8 * sizeof(compat_ulong_t))
1104
1105 static
1106 int compat_poll_select_copy_remaining(struct timespec64 *end_time, void __user *p,
1107 int timeval, int ret)
1108 {
1109 struct timespec64 ts;
1110
1111 if (!p)
1112 return ret;
1113
1114 if (current->personality & STICKY_TIMEOUTS)
1115 goto sticky;
1116
1117 /* No update for zero timeout */
1118 if (!end_time->tv_sec && !end_time->tv_nsec)
1119 return ret;
1120
1121 ktime_get_ts64(&ts);
1122 ts = timespec64_sub(*end_time, ts);
1123 if (ts.tv_sec < 0)
1124 ts.tv_sec = ts.tv_nsec = 0;
1125
1126 if (timeval) {
1127 struct compat_timeval rtv;
1128
1129 rtv.tv_sec = ts.tv_sec;
1130 rtv.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
1131
1132 if (!copy_to_user(p, &rtv, sizeof(rtv)))
1133 return ret;
1134 } else {
1135 if (!compat_put_timespec64(&ts, p))
1136 return ret;
1137 }
1138 /*
1139 * If an application puts its timeval in read-only memory, we
1140 * don't want the Linux-specific update to the timeval to
1141 * cause a fault after the select has completed
1142 * successfully. However, because we're not updating the
1143 * timeval, we can't restart the system call.
1144 */
1145
1146 sticky:
1147 if (ret == -ERESTARTNOHAND)
1148 ret = -EINTR;
1149 return ret;
1150 }
1151
1152 /*
1153 * Ooo, nasty. We need here to frob 32-bit unsigned longs to
1154 * 64-bit unsigned longs.
1155 */
1156 static
1157 int compat_get_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
1158 unsigned long *fdset)
1159 {
1160 if (ufdset) {
1161 return compat_get_bitmap(fdset, ufdset, nr);
1162 } else {
1163 zero_fd_set(nr, fdset);
1164 return 0;
1165 }
1166 }
1167
1168 static
1169 int compat_set_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
1170 unsigned long *fdset)
1171 {
1172 if (!ufdset)
1173 return 0;
1174 return compat_put_bitmap(ufdset, fdset, nr);
1175 }
1176
1177
1178 /*
1179 * This is a virtual copy of sys_select from fs/select.c and probably
1180 * should be compared to it from time to time
1181 */
1182
1183 /*
1184 * We can actually return ERESTARTSYS instead of EINTR, but I'd
1185 * like to be certain this leads to no problems. So I return
1186 * EINTR just for safety.
1187 *
1188 * Update: ERESTARTSYS breaks at least the xview clock binary, so
1189 * I'm trying ERESTARTNOHAND which restart only when you want to.
1190 */
1191 static int compat_core_sys_select(int n, compat_ulong_t __user *inp,
1192 compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1193 struct timespec64 *end_time)
1194 {
1195 fd_set_bits fds;
1196 void *bits;
1197 int size, max_fds, ret = -EINVAL;
1198 struct fdtable *fdt;
1199 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
1200
1201 if (n < 0)
1202 goto out_nofds;
1203
1204 /* max_fds can increase, so grab it once to avoid race */
1205 rcu_read_lock();
1206 fdt = files_fdtable(current->files);
1207 max_fds = fdt->max_fds;
1208 rcu_read_unlock();
1209 if (n > max_fds)
1210 n = max_fds;
1211
1212 /*
1213 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
1214 * since we used fdset we need to allocate memory in units of
1215 * long-words.
1216 */
1217 size = FDS_BYTES(n);
1218 bits = stack_fds;
1219 if (size > sizeof(stack_fds) / 6) {
1220 bits = kmalloc(6 * size, GFP_KERNEL);
1221 ret = -ENOMEM;
1222 if (!bits)
1223 goto out_nofds;
1224 }
1225 fds.in = (unsigned long *) bits;
1226 fds.out = (unsigned long *) (bits + size);
1227 fds.ex = (unsigned long *) (bits + 2*size);
1228 fds.res_in = (unsigned long *) (bits + 3*size);
1229 fds.res_out = (unsigned long *) (bits + 4*size);
1230 fds.res_ex = (unsigned long *) (bits + 5*size);
1231
1232 if ((ret = compat_get_fd_set(n, inp, fds.in)) ||
1233 (ret = compat_get_fd_set(n, outp, fds.out)) ||
1234 (ret = compat_get_fd_set(n, exp, fds.ex)))
1235 goto out;
1236 zero_fd_set(n, fds.res_in);
1237 zero_fd_set(n, fds.res_out);
1238 zero_fd_set(n, fds.res_ex);
1239
1240 ret = do_select(n, &fds, end_time);
1241
1242 if (ret < 0)
1243 goto out;
1244 if (!ret) {
1245 ret = -ERESTARTNOHAND;
1246 if (signal_pending(current))
1247 goto out;
1248 ret = 0;
1249 }
1250
1251 if (compat_set_fd_set(n, inp, fds.res_in) ||
1252 compat_set_fd_set(n, outp, fds.res_out) ||
1253 compat_set_fd_set(n, exp, fds.res_ex))
1254 ret = -EFAULT;
1255 out:
1256 if (bits != stack_fds)
1257 kfree(bits);
1258 out_nofds:
1259 return ret;
1260 }
1261
1262 COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp,
1263 compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
1264 struct compat_timeval __user *, tvp)
1265 {
1266 struct timespec64 end_time, *to = NULL;
1267 struct compat_timeval tv;
1268 int ret;
1269
1270 if (tvp) {
1271 if (copy_from_user(&tv, tvp, sizeof(tv)))
1272 return -EFAULT;
1273
1274 to = &end_time;
1275 if (poll_select_set_timeout(to,
1276 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
1277 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
1278 return -EINVAL;
1279 }
1280
1281 ret = compat_core_sys_select(n, inp, outp, exp, to);
1282 ret = compat_poll_select_copy_remaining(&end_time, tvp, 1, ret);
1283
1284 return ret;
1285 }
1286
1287 struct compat_sel_arg_struct {
1288 compat_ulong_t n;
1289 compat_uptr_t inp;
1290 compat_uptr_t outp;
1291 compat_uptr_t exp;
1292 compat_uptr_t tvp;
1293 };
1294
1295 COMPAT_SYSCALL_DEFINE1(old_select, struct compat_sel_arg_struct __user *, arg)
1296 {
1297 struct compat_sel_arg_struct a;
1298
1299 if (copy_from_user(&a, arg, sizeof(a)))
1300 return -EFAULT;
1301 return compat_sys_select(a.n, compat_ptr(a.inp), compat_ptr(a.outp),
1302 compat_ptr(a.exp), compat_ptr(a.tvp));
1303 }
1304
1305 static long do_compat_pselect(int n, compat_ulong_t __user *inp,
1306 compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1307 struct compat_timespec __user *tsp, compat_sigset_t __user *sigmask,
1308 compat_size_t sigsetsize)
1309 {
1310 sigset_t ksigmask, sigsaved;
1311 struct timespec64 ts, end_time, *to = NULL;
1312 int ret;
1313
1314 if (tsp) {
1315 if (compat_get_timespec64(&ts, tsp))
1316 return -EFAULT;
1317
1318 to = &end_time;
1319 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1320 return -EINVAL;
1321 }
1322
1323 if (sigmask) {
1324 if (sigsetsize != sizeof(compat_sigset_t))
1325 return -EINVAL;
1326 if (get_compat_sigset(&ksigmask, sigmask))
1327 return -EFAULT;
1328
1329 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1330 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1331 }
1332
1333 ret = compat_core_sys_select(n, inp, outp, exp, to);
1334 ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
1335
1336 if (ret == -ERESTARTNOHAND) {
1337 /*
1338 * Don't restore the signal mask yet. Let do_signal() deliver
1339 * the signal on the way back to userspace, before the signal
1340 * mask is restored.
1341 */
1342 if (sigmask) {
1343 memcpy(&current->saved_sigmask, &sigsaved,
1344 sizeof(sigsaved));
1345 set_restore_sigmask();
1346 }
1347 } else if (sigmask)
1348 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1349
1350 return ret;
1351 }
1352
1353 COMPAT_SYSCALL_DEFINE6(pselect6, int, n, compat_ulong_t __user *, inp,
1354 compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
1355 struct compat_timespec __user *, tsp, void __user *, sig)
1356 {
1357 compat_size_t sigsetsize = 0;
1358 compat_uptr_t up = 0;
1359
1360 if (sig) {
1361 if (!access_ok(VERIFY_READ, sig,
1362 sizeof(compat_uptr_t)+sizeof(compat_size_t)) ||
1363 __get_user(up, (compat_uptr_t __user *)sig) ||
1364 __get_user(sigsetsize,
1365 (compat_size_t __user *)(sig+sizeof(up))))
1366 return -EFAULT;
1367 }
1368 return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(up),
1369 sigsetsize);
1370 }
1371
1372 COMPAT_SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds,
1373 unsigned int, nfds, struct compat_timespec __user *, tsp,
1374 const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize)
1375 {
1376 sigset_t ksigmask, sigsaved;
1377 struct timespec64 ts, end_time, *to = NULL;
1378 int ret;
1379
1380 if (tsp) {
1381 if (compat_get_timespec64(&ts, tsp))
1382 return -EFAULT;
1383
1384 to = &end_time;
1385 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1386 return -EINVAL;
1387 }
1388
1389 if (sigmask) {
1390 if (sigsetsize != sizeof(compat_sigset_t))
1391 return -EINVAL;
1392 if (get_compat_sigset(&ksigmask, sigmask))
1393 return -EFAULT;
1394
1395 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1396 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1397 }
1398
1399 ret = do_sys_poll(ufds, nfds, to);
1400
1401 /* We can restart this syscall, usually */
1402 if (ret == -EINTR) {
1403 /*
1404 * Don't restore the signal mask yet. Let do_signal() deliver
1405 * the signal on the way back to userspace, before the signal
1406 * mask is restored.
1407 */
1408 if (sigmask) {
1409 memcpy(&current->saved_sigmask, &sigsaved,
1410 sizeof(sigsaved));
1411 set_restore_sigmask();
1412 }
1413 ret = -ERESTARTNOHAND;
1414 } else if (sigmask)
1415 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1416
1417 ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
1418
1419 return ret;
1420 }
1421 #endif
CRIS linux kernel tree