1 /*
2 * This file contains the procedures for the handling of select and poll
3 *
4 * Created for Linux based loosely upon Mathius Lattner's minix
5 * patches by Peter MacDonald. Heavily edited by Linus.
6 *
7 * 4 February 1994
8 * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
9 * flag set in its personality we do *not* modify the given timeout
10 * parameter to reflect time remaining.
11 *
12 * 24 January 2000
13 * Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation
14 * of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
15 */
16
17 #include <linux/kernel.h>
18 #include <linux/syscalls.h>
19 #include <linux/module.h>
20 #include <linux/slab.h>
21 #include <linux/poll.h>
22 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
23 #include <linux/file.h>
24 #include <linux/fdtable.h>
25 #include <linux/fs.h>
26 #include <linux/rcupdate.h>
27 #include <linux/hrtimer.h>
28
29 #include <asm/uaccess.h>
30
31
32 /*
33 * Estimate expected accuracy in ns from a timeval.
34 *
35 * After quite a bit of churning around, we've settled on
36 * a simple thing of taking 0.1% of the timeout as the
37 * slack, with a cap of 100 msec.
38 * "nice" tasks get a 0.5% slack instead.
39 *
40 * Consider this comment an open invitation to come up with even
41 * better solutions..
42 */
43
__estimate_accuracy(struct timespec * tv)44 static long __estimate_accuracy(struct timespec *tv)
45 {
46 long slack;
47 int divfactor = 1000;
48
49 if (task_nice(current) > 0)
50 divfactor = divfactor / 5;
51
52 slack = tv->tv_nsec / divfactor;
53 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
54
55 if (slack > 100 * NSEC_PER_MSEC)
56 slack = 100 * NSEC_PER_MSEC;
57
58 if (slack < 0)
59 slack = 0;
60 return slack;
61 }
62
estimate_accuracy(struct timespec * tv)63 static long estimate_accuracy(struct timespec *tv)
64 {
65 unsigned long ret;
66 struct timespec now;
67
68 /*
69 * Realtime tasks get a slack of 0 for obvious reasons.
70 */
71
72 if (rt_task(current))
73 return 0;
74
75 ktime_get_ts(&now);
76 now = timespec_sub(*tv, now);
77 ret = __estimate_accuracy(&now);
78 if (ret < current->timer_slack_ns)
79 return current->timer_slack_ns;
80 return ret;
81 }
82
83
84
85 struct poll_table_page {
86 struct poll_table_page * next;
87 struct poll_table_entry * entry;
88 struct poll_table_entry entries[0];
89 };
90
91 #define POLL_TABLE_FULL(table) \
92 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
93
94 /*
95 * Ok, Peter made a complicated, but straightforward multiple_wait() function.
96 * I have rewritten this, taking some shortcuts: This code may not be easy to
97 * follow, but it should be free of race-conditions, and it's practical. If you
98 * understand what I'm doing here, then you understand how the linux
99 * sleep/wakeup mechanism works.
100 *
101 * Two very simple procedures, poll_wait() and poll_freewait() make all the
102 * work. poll_wait() is an inline-function defined in <linux/poll.h>,
103 * as all select/poll functions have to call it to add an entry to the
104 * poll table.
105 */
106 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
107 poll_table *p);
108
poll_initwait(struct poll_wqueues * pwq)109 void poll_initwait(struct poll_wqueues *pwq)
110 {
111 init_poll_funcptr(&pwq->pt, __pollwait);
112 pwq->polling_task = current;
113 pwq->error = 0;
114 pwq->table = NULL;
115 pwq->inline_index = 0;
116 }
117 EXPORT_SYMBOL(poll_initwait);
118
free_poll_entry(struct poll_table_entry * entry)119 static void free_poll_entry(struct poll_table_entry *entry)
120 {
121 remove_wait_queue(entry->wait_address, &entry->wait);
122 fput(entry->filp);
123 }
124
poll_freewait(struct poll_wqueues * pwq)125 void poll_freewait(struct poll_wqueues *pwq)
126 {
127 struct poll_table_page * p = pwq->table;
128 int i;
129 for (i = 0; i < pwq->inline_index; i++)
130 free_poll_entry(pwq->inline_entries + i);
131 while (p) {
132 struct poll_table_entry * entry;
133 struct poll_table_page *old;
134
135 entry = p->entry;
136 do {
137 entry--;
138 free_poll_entry(entry);
139 } while (entry > p->entries);
140 old = p;
141 p = p->next;
142 free_page((unsigned long) old);
143 }
144 }
145 EXPORT_SYMBOL(poll_freewait);
146
poll_get_entry(struct poll_wqueues * p)147 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
148 {
149 struct poll_table_page *table = p->table;
150
151 if (p->inline_index < N_INLINE_POLL_ENTRIES)
152 return p->inline_entries + p->inline_index++;
153
154 if (!table || POLL_TABLE_FULL(table)) {
155 struct poll_table_page *new_table;
156
157 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
158 if (!new_table) {
159 p->error = -ENOMEM;
160 return NULL;
161 }
162 new_table->entry = new_table->entries;
163 new_table->next = table;
164 p->table = new_table;
165 table = new_table;
166 }
167
168 return table->entry++;
169 }
170
pollwake(wait_queue_t * wait,unsigned mode,int sync,void * key)171 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
172 {
173 struct poll_wqueues *pwq = wait->private;
174 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
175
176 /*
177 * Although this function is called under waitqueue lock, LOCK
178 * doesn't imply write barrier and the users expect write
179 * barrier semantics on wakeup functions. The following
180 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
181 * and is paired with set_mb() in poll_schedule_timeout.
182 */
183 smp_wmb();
184 pwq->triggered = 1;
185
186 /*
187 * Perform the default wake up operation using a dummy
188 * waitqueue.
189 *
190 * TODO: This is hacky but there currently is no interface to
191 * pass in @sync. @sync is scheduled to be removed and once
192 * that happens, wake_up_process() can be used directly.
193 */
194 return default_wake_function(&dummy_wait, mode, sync, key);
195 }
196
197 /* Add a new entry */
__pollwait(struct file * filp,wait_queue_head_t * wait_address,poll_table * p)198 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
199 poll_table *p)
200 {
201 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
202 struct poll_table_entry *entry = poll_get_entry(pwq);
203 if (!entry)
204 return;
205 get_file(filp);
206 entry->filp = filp;
207 entry->wait_address = wait_address;
208 init_waitqueue_func_entry(&entry->wait, pollwake);
209 entry->wait.private = pwq;
210 add_wait_queue(wait_address, &entry->wait);
211 }
212
poll_schedule_timeout(struct poll_wqueues * pwq,int state,ktime_t * expires,unsigned long slack)213 int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
214 ktime_t *expires, unsigned long slack)
215 {
216 int rc = -EINTR;
217
218 set_current_state(state);
219 if (!pwq->triggered)
220 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
221 __set_current_state(TASK_RUNNING);
222
223 /*
224 * Prepare for the next iteration.
225 *
226 * The following set_mb() serves two purposes. First, it's
227 * the counterpart rmb of the wmb in pollwake() such that data
228 * written before wake up is always visible after wake up.
229 * Second, the full barrier guarantees that triggered clearing
230 * doesn't pass event check of the next iteration. Note that
231 * this problem doesn't exist for the first iteration as
232 * add_wait_queue() has full barrier semantics.
233 */
234 set_mb(pwq->triggered, 0);
235
236 return rc;
237 }
238 EXPORT_SYMBOL(poll_schedule_timeout);
239
240 /**
241 * poll_select_set_timeout - helper function to setup the timeout value
242 * @to: pointer to timespec variable for the final timeout
243 * @sec: seconds (from user space)
244 * @nsec: nanoseconds (from user space)
245 *
246 * Note, we do not use a timespec for the user space value here, That
247 * way we can use the function for timeval and compat interfaces as well.
248 *
249 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
250 */
poll_select_set_timeout(struct timespec * to,long sec,long nsec)251 int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
252 {
253 struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
254
255 if (!timespec_valid(&ts))
256 return -EINVAL;
257
258 /* Optimize for the zero timeout value here */
259 if (!sec && !nsec) {
260 to->tv_sec = to->tv_nsec = 0;
261 } else {
262 ktime_get_ts(to);
263 *to = timespec_add_safe(*to, ts);
264 }
265 return 0;
266 }
267
poll_select_copy_remaining(struct timespec * end_time,void __user * p,int timeval,int ret)268 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
269 int timeval, int ret)
270 {
271 struct timespec rts;
272 struct timeval rtv;
273
274 if (!p)
275 return ret;
276
277 if (current->personality & STICKY_TIMEOUTS)
278 goto sticky;
279
280 /* No update for zero timeout */
281 if (!end_time->tv_sec && !end_time->tv_nsec)
282 return ret;
283
284 ktime_get_ts(&rts);
285 rts = timespec_sub(*end_time, rts);
286 if (rts.tv_sec < 0)
287 rts.tv_sec = rts.tv_nsec = 0;
288
289 if (timeval) {
290 rtv.tv_sec = rts.tv_sec;
291 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
292
293 if (!copy_to_user(p, &rtv, sizeof(rtv)))
294 return ret;
295
296 } else if (!copy_to_user(p, &rts, sizeof(rts)))
297 return ret;
298
299 /*
300 * If an application puts its timeval in read-only memory, we
301 * don't want the Linux-specific update to the timeval to
302 * cause a fault after the select has completed
303 * successfully. However, because we're not updating the
304 * timeval, we can't restart the system call.
305 */
306
307 sticky:
308 if (ret == -ERESTARTNOHAND)
309 ret = -EINTR;
310 return ret;
311 }
312
313 #define FDS_IN(fds, n) (fds->in + n)
314 #define FDS_OUT(fds, n) (fds->out + n)
315 #define FDS_EX(fds, n) (fds->ex + n)
316
317 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
318
max_select_fd(unsigned long n,fd_set_bits * fds)319 static int max_select_fd(unsigned long n, fd_set_bits *fds)
320 {
321 unsigned long *open_fds;
322 unsigned long set;
323 int max;
324 struct fdtable *fdt;
325
326 /* handle last in-complete long-word first */
327 set = ~(~0UL << (n & (__NFDBITS-1)));
328 n /= __NFDBITS;
329 fdt = files_fdtable(current->files);
330 open_fds = fdt->open_fds->fds_bits+n;
331 max = 0;
332 if (set) {
333 set &= BITS(fds, n);
334 if (set) {
335 if (!(set & ~*open_fds))
336 goto get_max;
337 return -EBADF;
338 }
339 }
340 while (n) {
341 open_fds--;
342 n--;
343 set = BITS(fds, n);
344 if (!set)
345 continue;
346 if (set & ~*open_fds)
347 return -EBADF;
348 if (max)
349 continue;
350 get_max:
351 do {
352 max++;
353 set >>= 1;
354 } while (set);
355 max += n * __NFDBITS;
356 }
357
358 return max;
359 }
360
361 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
362 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
363 #define POLLEX_SET (POLLPRI)
364
do_select(int n,fd_set_bits * fds,struct timespec * end_time)365 int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
366 {
367 ktime_t expire, *to = NULL;
368 struct poll_wqueues table;
369 poll_table *wait;
370 int retval, i, timed_out = 0;
371 unsigned long slack = 0;
372
373 rcu_read_lock();
374 retval = max_select_fd(n, fds);
375 rcu_read_unlock();
376
377 if (retval < 0)
378 return retval;
379 n = retval;
380
381 poll_initwait(&table);
382 wait = &table.pt;
383 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
384 wait = NULL;
385 timed_out = 1;
386 }
387
388 if (end_time && !timed_out)
389 slack = estimate_accuracy(end_time);
390
391 retval = 0;
392 for (;;) {
393 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
394
395 inp = fds->in; outp = fds->out; exp = fds->ex;
396 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
397
398 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
399 unsigned long in, out, ex, all_bits, bit = 1, mask, j;
400 unsigned long res_in = 0, res_out = 0, res_ex = 0;
401 const struct file_operations *f_op = NULL;
402 struct file *file = NULL;
403
404 in = *inp++; out = *outp++; ex = *exp++;
405 all_bits = in | out | ex;
406 if (all_bits == 0) {
407 i += __NFDBITS;
408 continue;
409 }
410
411 for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
412 int fput_needed;
413 if (i >= n)
414 break;
415 if (!(bit & all_bits))
416 continue;
417 file = fget_light(i, &fput_needed);
418 if (file) {
419 f_op = file->f_op;
420 mask = DEFAULT_POLLMASK;
421 if (f_op && f_op->poll)
422 mask = (*f_op->poll)(file, retval ? NULL : wait);
423 fput_light(file, fput_needed);
424 if ((mask & POLLIN_SET) && (in & bit)) {
425 res_in |= bit;
426 retval++;
427 }
428 if ((mask & POLLOUT_SET) && (out & bit)) {
429 res_out |= bit;
430 retval++;
431 }
432 if ((mask & POLLEX_SET) && (ex & bit)) {
433 res_ex |= bit;
434 retval++;
435 }
436 }
437 }
438 if (res_in)
439 *rinp = res_in;
440 if (res_out)
441 *routp = res_out;
442 if (res_ex)
443 *rexp = res_ex;
444 cond_resched();
445 }
446 wait = NULL;
447 if (retval || timed_out || signal_pending(current))
448 break;
449 if (table.error) {
450 retval = table.error;
451 break;
452 }
453
454 /*
455 * If this is the first loop and we have a timeout
456 * given, then we convert to ktime_t and set the to
457 * pointer to the expiry value.
458 */
459 if (end_time && !to) {
460 expire = timespec_to_ktime(*end_time);
461 to = &expire;
462 }
463
464 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
465 to, slack))
466 timed_out = 1;
467 }
468
469 poll_freewait(&table);
470
471 return retval;
472 }
473
474 /*
475 * We can actually return ERESTARTSYS instead of EINTR, but I'd
476 * like to be certain this leads to no problems. So I return
477 * EINTR just for safety.
478 *
479 * Update: ERESTARTSYS breaks at least the xview clock binary, so
480 * I'm trying ERESTARTNOHAND which restart only when you want to.
481 */
482 #define MAX_SELECT_SECONDS \
483 ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
484
core_sys_select(int n,fd_set __user * inp,fd_set __user * outp,fd_set __user * exp,struct timespec * end_time)485 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
486 fd_set __user *exp, struct timespec *end_time)
487 {
488 fd_set_bits fds;
489 void *bits;
490 int ret, max_fds;
491 unsigned int size;
492 struct fdtable *fdt;
493 /* Allocate small arguments on the stack to save memory and be faster */
494 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
495
496 ret = -EINVAL;
497 if (n < 0)
498 goto out_nofds;
499
500 /* max_fds can increase, so grab it once to avoid race */
501 rcu_read_lock();
502 fdt = files_fdtable(current->files);
503 max_fds = fdt->max_fds;
504 rcu_read_unlock();
505 if (n > max_fds)
506 n = max_fds;
507
508 /*
509 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
510 * since we used fdset we need to allocate memory in units of
511 * long-words.
512 */
513 size = FDS_BYTES(n);
514 bits = stack_fds;
515 if (size > sizeof(stack_fds) / 6) {
516 /* Not enough space in on-stack array; must use kmalloc */
517 ret = -ENOMEM;
518 bits = kmalloc(6 * size, GFP_KERNEL);
519 if (!bits)
520 goto out_nofds;
521 }
522 fds.in = bits;
523 fds.out = bits + size;
524 fds.ex = bits + 2*size;
525 fds.res_in = bits + 3*size;
526 fds.res_out = bits + 4*size;
527 fds.res_ex = bits + 5*size;
528
529 if ((ret = get_fd_set(n, inp, fds.in)) ||
530 (ret = get_fd_set(n, outp, fds.out)) ||
531 (ret = get_fd_set(n, exp, fds.ex)))
532 goto out;
533 zero_fd_set(n, fds.res_in);
534 zero_fd_set(n, fds.res_out);
535 zero_fd_set(n, fds.res_ex);
536
537 ret = do_select(n, &fds, end_time);
538
539 if (ret < 0)
540 goto out;
541 if (!ret) {
542 ret = -ERESTARTNOHAND;
543 if (signal_pending(current))
544 goto out;
545 ret = 0;
546 }
547
548 if (set_fd_set(n, inp, fds.res_in) ||
549 set_fd_set(n, outp, fds.res_out) ||
550 set_fd_set(n, exp, fds.res_ex))
551 ret = -EFAULT;
552
553 out:
554 if (bits != stack_fds)
555 kfree(bits);
556 out_nofds:
557 return ret;
558 }
559
SYSCALL_DEFINE5(select,int,n,fd_set __user *,inp,fd_set __user *,outp,fd_set __user *,exp,struct timeval __user *,tvp)560 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
561 fd_set __user *, exp, struct timeval __user *, tvp)
562 {
563 struct timespec end_time, *to = NULL;
564 struct timeval tv;
565 int ret;
566
567 if (tvp) {
568 if (copy_from_user(&tv, tvp, sizeof(tv)))
569 return -EFAULT;
570
571 to = &end_time;
572 if (poll_select_set_timeout(to,
573 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
574 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
575 return -EINVAL;
576 }
577
578 ret = core_sys_select(n, inp, outp, exp, to);
579 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
580
581 return ret;
582 }
583
584 #ifdef HAVE_SET_RESTORE_SIGMASK
do_pselect(int n,fd_set __user * inp,fd_set __user * outp,fd_set __user * exp,struct timespec __user * tsp,const sigset_t __user * sigmask,size_t sigsetsize)585 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
586 fd_set __user *exp, struct timespec __user *tsp,
587 const sigset_t __user *sigmask, size_t sigsetsize)
588 {
589 sigset_t ksigmask, sigsaved;
590 struct timespec ts, end_time, *to = NULL;
591 int ret;
592
593 if (tsp) {
594 if (copy_from_user(&ts, tsp, sizeof(ts)))
595 return -EFAULT;
596
597 to = &end_time;
598 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
599 return -EINVAL;
600 }
601
602 if (sigmask) {
603 /* XXX: Don't preclude handling different sized sigset_t's. */
604 if (sigsetsize != sizeof(sigset_t))
605 return -EINVAL;
606 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
607 return -EFAULT;
608
609 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
610 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
611 }
612
613 ret = core_sys_select(n, inp, outp, exp, to);
614 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
615
616 if (ret == -ERESTARTNOHAND) {
617 /*
618 * Don't restore the signal mask yet. Let do_signal() deliver
619 * the signal on the way back to userspace, before the signal
620 * mask is restored.
621 */
622 if (sigmask) {
623 memcpy(¤t->saved_sigmask, &sigsaved,
624 sizeof(sigsaved));
625 set_restore_sigmask();
626 }
627 } else if (sigmask)
628 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
629
630 return ret;
631 }
632
633 /*
634 * Most architectures can't handle 7-argument syscalls. So we provide a
635 * 6-argument version where the sixth argument is a pointer to a structure
636 * which has a pointer to the sigset_t itself followed by a size_t containing
637 * the sigset size.
638 */
SYSCALL_DEFINE6(pselect6,int,n,fd_set __user *,inp,fd_set __user *,outp,fd_set __user *,exp,struct timespec __user *,tsp,void __user *,sig)639 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
640 fd_set __user *, exp, struct timespec __user *, tsp,
641 void __user *, sig)
642 {
643 size_t sigsetsize = 0;
644 sigset_t __user *up = NULL;
645
646 if (sig) {
647 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
648 || __get_user(up, (sigset_t __user * __user *)sig)
649 || __get_user(sigsetsize,
650 (size_t __user *)(sig+sizeof(void *))))
651 return -EFAULT;
652 }
653
654 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
655 }
656 #endif /* HAVE_SET_RESTORE_SIGMASK */
657
658 struct poll_list {
659 struct poll_list *next;
660 int len;
661 struct pollfd entries[0];
662 };
663
664 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
665
666 /*
667 * Fish for pollable events on the pollfd->fd file descriptor. We're only
668 * interested in events matching the pollfd->events mask, and the result
669 * matching that mask is both recorded in pollfd->revents and returned. The
670 * pwait poll_table will be used by the fd-provided poll handler for waiting,
671 * if non-NULL.
672 */
do_pollfd(struct pollfd * pollfd,poll_table * pwait)673 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
674 {
675 unsigned int mask;
676 int fd;
677
678 mask = 0;
679 fd = pollfd->fd;
680 if (fd >= 0) {
681 int fput_needed;
682 struct file * file;
683
684 file = fget_light(fd, &fput_needed);
685 mask = POLLNVAL;
686 if (file != NULL) {
687 mask = DEFAULT_POLLMASK;
688 if (file->f_op && file->f_op->poll)
689 mask = file->f_op->poll(file, pwait);
690 /* Mask out unneeded events. */
691 mask &= pollfd->events | POLLERR | POLLHUP;
692 fput_light(file, fput_needed);
693 }
694 }
695 pollfd->revents = mask;
696
697 return mask;
698 }
699
do_poll(unsigned int nfds,struct poll_list * list,struct poll_wqueues * wait,struct timespec * end_time)700 static int do_poll(unsigned int nfds, struct poll_list *list,
701 struct poll_wqueues *wait, struct timespec *end_time)
702 {
703 poll_table* pt = &wait->pt;
704 ktime_t expire, *to = NULL;
705 int timed_out = 0, count = 0;
706 unsigned long slack = 0;
707
708 /* Optimise the no-wait case */
709 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
710 pt = NULL;
711 timed_out = 1;
712 }
713
714 if (end_time && !timed_out)
715 slack = estimate_accuracy(end_time);
716
717 for (;;) {
718 struct poll_list *walk;
719
720 for (walk = list; walk != NULL; walk = walk->next) {
721 struct pollfd * pfd, * pfd_end;
722
723 pfd = walk->entries;
724 pfd_end = pfd + walk->len;
725 for (; pfd != pfd_end; pfd++) {
726 /*
727 * Fish for events. If we found one, record it
728 * and kill the poll_table, so we don't
729 * needlessly register any other waiters after
730 * this. They'll get immediately deregistered
731 * when we break out and return.
732 */
733 if (do_pollfd(pfd, pt)) {
734 count++;
735 pt = NULL;
736 }
737 }
738 }
739 /*
740 * All waiters have already been registered, so don't provide
741 * a poll_table to them on the next loop iteration.
742 */
743 pt = NULL;
744 if (!count) {
745 count = wait->error;
746 if (signal_pending(current))
747 count = -EINTR;
748 }
749 if (count || timed_out)
750 break;
751
752 /*
753 * If this is the first loop and we have a timeout
754 * given, then we convert to ktime_t and set the to
755 * pointer to the expiry value.
756 */
757 if (end_time && !to) {
758 expire = timespec_to_ktime(*end_time);
759 to = &expire;
760 }
761
762 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
763 timed_out = 1;
764 }
765 return count;
766 }
767
768 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \
769 sizeof(struct pollfd))
770
do_sys_poll(struct pollfd __user * ufds,unsigned int nfds,struct timespec * end_time)771 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
772 struct timespec *end_time)
773 {
774 struct poll_wqueues table;
775 int err = -EFAULT, fdcount, len, size;
776 /* Allocate small arguments on the stack to save memory and be
777 faster - use long to make sure the buffer is aligned properly
778 on 64 bit archs to avoid unaligned access */
779 long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
780 struct poll_list *const head = (struct poll_list *)stack_pps;
781 struct poll_list *walk = head;
782 unsigned long todo = nfds;
783
784 if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
785 return -EINVAL;
786
787 len = min_t(unsigned int, nfds, N_STACK_PPS);
788 for (;;) {
789 walk->next = NULL;
790 walk->len = len;
791 if (!len)
792 break;
793
794 if (copy_from_user(walk->entries, ufds + nfds-todo,
795 sizeof(struct pollfd) * walk->len))
796 goto out_fds;
797
798 todo -= walk->len;
799 if (!todo)
800 break;
801
802 len = min(todo, POLLFD_PER_PAGE);
803 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
804 walk = walk->next = kmalloc(size, GFP_KERNEL);
805 if (!walk) {
806 err = -ENOMEM;
807 goto out_fds;
808 }
809 }
810
811 poll_initwait(&table);
812 fdcount = do_poll(nfds, head, &table, end_time);
813 poll_freewait(&table);
814
815 for (walk = head; walk; walk = walk->next) {
816 struct pollfd *fds = walk->entries;
817 int j;
818
819 for (j = 0; j < walk->len; j++, ufds++)
820 if (__put_user(fds[j].revents, &ufds->revents))
821 goto out_fds;
822 }
823
824 err = fdcount;
825 out_fds:
826 walk = head->next;
827 while (walk) {
828 struct poll_list *pos = walk;
829 walk = walk->next;
830 kfree(pos);
831 }
832
833 return err;
834 }
835
do_restart_poll(struct restart_block * restart_block)836 static long do_restart_poll(struct restart_block *restart_block)
837 {
838 struct pollfd __user *ufds = restart_block->poll.ufds;
839 int nfds = restart_block->poll.nfds;
840 struct timespec *to = NULL, end_time;
841 int ret;
842
843 if (restart_block->poll.has_timeout) {
844 end_time.tv_sec = restart_block->poll.tv_sec;
845 end_time.tv_nsec = restart_block->poll.tv_nsec;
846 to = &end_time;
847 }
848
849 ret = do_sys_poll(ufds, nfds, to);
850
851 if (ret == -EINTR) {
852 restart_block->fn = do_restart_poll;
853 ret = -ERESTART_RESTARTBLOCK;
854 }
855 return ret;
856 }
857
SYSCALL_DEFINE3(poll,struct pollfd __user *,ufds,unsigned int,nfds,long,timeout_msecs)858 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
859 long, timeout_msecs)
860 {
861 struct timespec end_time, *to = NULL;
862 int ret;
863
864 if (timeout_msecs >= 0) {
865 to = &end_time;
866 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
867 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
868 }
869
870 ret = do_sys_poll(ufds, nfds, to);
871
872 if (ret == -EINTR) {
873 struct restart_block *restart_block;
874
875 restart_block = ¤t_thread_info()->restart_block;
876 restart_block->fn = do_restart_poll;
877 restart_block->poll.ufds = ufds;
878 restart_block->poll.nfds = nfds;
879
880 if (timeout_msecs >= 0) {
881 restart_block->poll.tv_sec = end_time.tv_sec;
882 restart_block->poll.tv_nsec = end_time.tv_nsec;
883 restart_block->poll.has_timeout = 1;
884 } else
885 restart_block->poll.has_timeout = 0;
886
887 ret = -ERESTART_RESTARTBLOCK;
888 }
889 return ret;
890 }
891
892 #ifdef HAVE_SET_RESTORE_SIGMASK
SYSCALL_DEFINE5(ppoll,struct pollfd __user *,ufds,unsigned int,nfds,struct timespec __user *,tsp,const sigset_t __user *,sigmask,size_t,sigsetsize)893 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
894 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
895 size_t, sigsetsize)
896 {
897 sigset_t ksigmask, sigsaved;
898 struct timespec ts, end_time, *to = NULL;
899 int ret;
900
901 if (tsp) {
902 if (copy_from_user(&ts, tsp, sizeof(ts)))
903 return -EFAULT;
904
905 to = &end_time;
906 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
907 return -EINVAL;
908 }
909
910 if (sigmask) {
911 /* XXX: Don't preclude handling different sized sigset_t's. */
912 if (sigsetsize != sizeof(sigset_t))
913 return -EINVAL;
914 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
915 return -EFAULT;
916
917 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
918 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
919 }
920
921 ret = do_sys_poll(ufds, nfds, to);
922
923 /* We can restart this syscall, usually */
924 if (ret == -EINTR) {
925 /*
926 * Don't restore the signal mask yet. Let do_signal() deliver
927 * the signal on the way back to userspace, before the signal
928 * mask is restored.
929 */
930 if (sigmask) {
931 memcpy(¤t->saved_sigmask, &sigsaved,
932 sizeof(sigsaved));
933 set_restore_sigmask();
934 }
935 ret = -ERESTARTNOHAND;
936 } else if (sigmask)
937 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
938
939 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
940
941 return ret;
942 }
943 #endif /* HAVE_SET_RESTORE_SIGMASK */
944