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/sched.h>
19 #include <linux/syscalls.h>
20 #include <linux/export.h>
21 #include <linux/slab.h>
22 #include <linux/poll.h>
23 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
24 #include <linux/file.h>
25 #include <linux/fdtable.h>
26 #include <linux/fs.h>
27 #include <linux/rcupdate.h>
28 #include <linux/hrtimer.h>
29 #include <linux/sched/rt.h>
30 #include <linux/freezer.h>
31 #include <net/busy_poll.h>
32 #include <linux/vmalloc.h>
33
34 #include <asm/uaccess.h>
35
36
37 /*
38 * Estimate expected accuracy in ns from a timeval.
39 *
40 * After quite a bit of churning around, we've settled on
41 * a simple thing of taking 0.1% of the timeout as the
42 * slack, with a cap of 100 msec.
43 * "nice" tasks get a 0.5% slack instead.
44 *
45 * Consider this comment an open invitation to come up with even
46 * better solutions..
47 */
48
49 #define MAX_SLACK (100 * NSEC_PER_MSEC)
50
__estimate_accuracy(struct timespec * tv)51 static long __estimate_accuracy(struct timespec *tv)
52 {
53 long slack;
54 int divfactor = 1000;
55
56 if (tv->tv_sec < 0)
57 return 0;
58
59 if (task_nice(current) > 0)
60 divfactor = divfactor / 5;
61
62 if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
63 return MAX_SLACK;
64
65 slack = tv->tv_nsec / divfactor;
66 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
67
68 if (slack > MAX_SLACK)
69 return MAX_SLACK;
70
71 return slack;
72 }
73
select_estimate_accuracy(struct timespec * tv)74 u64 select_estimate_accuracy(struct timespec *tv)
75 {
76 u64 ret;
77 struct timespec now;
78
79 /*
80 * Realtime tasks get a slack of 0 for obvious reasons.
81 */
82
83 if (rt_task(current))
84 return 0;
85
86 ktime_get_ts(&now);
87 now = timespec_sub(*tv, now);
88 ret = __estimate_accuracy(&now);
89 if (ret < current->timer_slack_ns)
90 return current->timer_slack_ns;
91 return ret;
92 }
93
94
95
96 struct poll_table_page {
97 struct poll_table_page * next;
98 struct poll_table_entry * entry;
99 struct poll_table_entry entries[0];
100 };
101
102 #define POLL_TABLE_FULL(table) \
103 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
104
105 /*
106 * Ok, Peter made a complicated, but straightforward multiple_wait() function.
107 * I have rewritten this, taking some shortcuts: This code may not be easy to
108 * follow, but it should be free of race-conditions, and it's practical. If you
109 * understand what I'm doing here, then you understand how the linux
110 * sleep/wakeup mechanism works.
111 *
112 * Two very simple procedures, poll_wait() and poll_freewait() make all the
113 * work. poll_wait() is an inline-function defined in <linux/poll.h>,
114 * as all select/poll functions have to call it to add an entry to the
115 * poll table.
116 */
117 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
118 poll_table *p);
119
poll_initwait(struct poll_wqueues * pwq)120 void poll_initwait(struct poll_wqueues *pwq)
121 {
122 init_poll_funcptr(&pwq->pt, __pollwait);
123 pwq->polling_task = current;
124 pwq->triggered = 0;
125 pwq->error = 0;
126 pwq->table = NULL;
127 pwq->inline_index = 0;
128 }
129 EXPORT_SYMBOL(poll_initwait);
130
free_poll_entry(struct poll_table_entry * entry)131 static void free_poll_entry(struct poll_table_entry *entry)
132 {
133 remove_wait_queue(entry->wait_address, &entry->wait);
134 fput(entry->filp);
135 }
136
poll_freewait(struct poll_wqueues * pwq)137 void poll_freewait(struct poll_wqueues *pwq)
138 {
139 struct poll_table_page * p = pwq->table;
140 int i;
141 for (i = 0; i < pwq->inline_index; i++)
142 free_poll_entry(pwq->inline_entries + i);
143 while (p) {
144 struct poll_table_entry * entry;
145 struct poll_table_page *old;
146
147 entry = p->entry;
148 do {
149 entry--;
150 free_poll_entry(entry);
151 } while (entry > p->entries);
152 old = p;
153 p = p->next;
154 free_page((unsigned long) old);
155 }
156 }
157 EXPORT_SYMBOL(poll_freewait);
158
poll_get_entry(struct poll_wqueues * p)159 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
160 {
161 struct poll_table_page *table = p->table;
162
163 if (p->inline_index < N_INLINE_POLL_ENTRIES)
164 return p->inline_entries + p->inline_index++;
165
166 if (!table || POLL_TABLE_FULL(table)) {
167 struct poll_table_page *new_table;
168
169 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
170 if (!new_table) {
171 p->error = -ENOMEM;
172 return NULL;
173 }
174 new_table->entry = new_table->entries;
175 new_table->next = table;
176 p->table = new_table;
177 table = new_table;
178 }
179
180 return table->entry++;
181 }
182
__pollwake(wait_queue_t * wait,unsigned mode,int sync,void * key)183 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
184 {
185 struct poll_wqueues *pwq = wait->private;
186 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
187
188 /*
189 * Although this function is called under waitqueue lock, LOCK
190 * doesn't imply write barrier and the users expect write
191 * barrier semantics on wakeup functions. The following
192 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
193 * and is paired with smp_store_mb() in poll_schedule_timeout.
194 */
195 smp_wmb();
196 pwq->triggered = 1;
197
198 /*
199 * Perform the default wake up operation using a dummy
200 * waitqueue.
201 *
202 * TODO: This is hacky but there currently is no interface to
203 * pass in @sync. @sync is scheduled to be removed and once
204 * that happens, wake_up_process() can be used directly.
205 */
206 return default_wake_function(&dummy_wait, mode, sync, key);
207 }
208
pollwake(wait_queue_t * wait,unsigned mode,int sync,void * key)209 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
210 {
211 struct poll_table_entry *entry;
212
213 entry = container_of(wait, struct poll_table_entry, wait);
214 if (key && !((unsigned long)key & entry->key))
215 return 0;
216 return __pollwake(wait, mode, sync, key);
217 }
218
219 /* Add a new entry */
__pollwait(struct file * filp,wait_queue_head_t * wait_address,poll_table * p)220 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
221 poll_table *p)
222 {
223 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
224 struct poll_table_entry *entry = poll_get_entry(pwq);
225 if (!entry)
226 return;
227 entry->filp = get_file(filp);
228 entry->wait_address = wait_address;
229 entry->key = p->_key;
230 init_waitqueue_func_entry(&entry->wait, pollwake);
231 entry->wait.private = pwq;
232 add_wait_queue(wait_address, &entry->wait);
233 }
234
poll_schedule_timeout(struct poll_wqueues * pwq,int state,ktime_t * expires,unsigned long slack)235 int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
236 ktime_t *expires, unsigned long slack)
237 {
238 int rc = -EINTR;
239
240 set_current_state(state);
241 if (!pwq->triggered)
242 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
243 __set_current_state(TASK_RUNNING);
244
245 /*
246 * Prepare for the next iteration.
247 *
248 * The following smp_store_mb() serves two purposes. First, it's
249 * the counterpart rmb of the wmb in pollwake() such that data
250 * written before wake up is always visible after wake up.
251 * Second, the full barrier guarantees that triggered clearing
252 * doesn't pass event check of the next iteration. Note that
253 * this problem doesn't exist for the first iteration as
254 * add_wait_queue() has full barrier semantics.
255 */
256 smp_store_mb(pwq->triggered, 0);
257
258 return rc;
259 }
260 EXPORT_SYMBOL(poll_schedule_timeout);
261
262 /**
263 * poll_select_set_timeout - helper function to setup the timeout value
264 * @to: pointer to timespec 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 */
poll_select_set_timeout(struct timespec * to,long sec,long nsec)273 int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
274 {
275 struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
276
277 if (!timespec_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_ts(to);
285 *to = timespec_add_safe(*to, ts);
286 }
287 return 0;
288 }
289
poll_select_copy_remaining(struct timespec * end_time,void __user * p,int timeval,int ret)290 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
291 int timeval, int ret)
292 {
293 struct timespec rts;
294 struct timeval rtv;
295
296 if (!p)
297 return ret;
298
299 if (current->personality & STICKY_TIMEOUTS)
300 goto sticky;
301
302 /* No update for zero timeout */
303 if (!end_time->tv_sec && !end_time->tv_nsec)
304 return ret;
305
306 ktime_get_ts(&rts);
307 rts = timespec_sub(*end_time, rts);
308 if (rts.tv_sec < 0)
309 rts.tv_sec = rts.tv_nsec = 0;
310
311 if (timeval) {
312 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
313 memset(&rtv, 0, sizeof(rtv));
314 rtv.tv_sec = rts.tv_sec;
315 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
316
317 if (!copy_to_user(p, &rtv, sizeof(rtv)))
318 return ret;
319
320 } else if (!copy_to_user(p, &rts, sizeof(rts)))
321 return ret;
322
323 /*
324 * If an application puts its timeval in read-only memory, we
325 * don't want the Linux-specific update to the timeval to
326 * cause a fault after the select has completed
327 * successfully. However, because we're not updating the
328 * timeval, we can't restart the system call.
329 */
330
331 sticky:
332 if (ret == -ERESTARTNOHAND)
333 ret = -EINTR;
334 return ret;
335 }
336
337 #define FDS_IN(fds, n) (fds->in + n)
338 #define FDS_OUT(fds, n) (fds->out + n)
339 #define FDS_EX(fds, n) (fds->ex + n)
340
341 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
342
max_select_fd(unsigned long n,fd_set_bits * fds)343 static int max_select_fd(unsigned long n, fd_set_bits *fds)
344 {
345 unsigned long *open_fds;
346 unsigned long set;
347 int max;
348 struct fdtable *fdt;
349
350 /* handle last in-complete long-word first */
351 set = ~(~0UL << (n & (BITS_PER_LONG-1)));
352 n /= BITS_PER_LONG;
353 fdt = files_fdtable(current->files);
354 open_fds = fdt->open_fds + n;
355 max = 0;
356 if (set) {
357 set &= BITS(fds, n);
358 if (set) {
359 if (!(set & ~*open_fds))
360 goto get_max;
361 return -EBADF;
362 }
363 }
364 while (n) {
365 open_fds--;
366 n--;
367 set = BITS(fds, n);
368 if (!set)
369 continue;
370 if (set & ~*open_fds)
371 return -EBADF;
372 if (max)
373 continue;
374 get_max:
375 do {
376 max++;
377 set >>= 1;
378 } while (set);
379 max += n * BITS_PER_LONG;
380 }
381
382 return max;
383 }
384
385 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
386 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
387 #define POLLEX_SET (POLLPRI)
388
wait_key_set(poll_table * wait,unsigned long in,unsigned long out,unsigned long bit,unsigned int ll_flag)389 static inline void wait_key_set(poll_table *wait, unsigned long in,
390 unsigned long out, unsigned long bit,
391 unsigned int ll_flag)
392 {
393 wait->_key = POLLEX_SET | ll_flag;
394 if (in & bit)
395 wait->_key |= POLLIN_SET;
396 if (out & bit)
397 wait->_key |= POLLOUT_SET;
398 }
399
do_select(int n,fd_set_bits * fds,struct timespec * end_time)400 int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
401 {
402 ktime_t expire, *to = NULL;
403 struct poll_wqueues table;
404 poll_table *wait;
405 int retval, i, timed_out = 0;
406 u64 slack = 0;
407 unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
408 unsigned long busy_end = 0;
409
410 rcu_read_lock();
411 retval = max_select_fd(n, fds);
412 rcu_read_unlock();
413
414 if (retval < 0)
415 return retval;
416 n = retval;
417
418 poll_initwait(&table);
419 wait = &table.pt;
420 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
421 wait->_qproc = NULL;
422 timed_out = 1;
423 }
424
425 if (end_time && !timed_out)
426 slack = select_estimate_accuracy(end_time);
427
428 retval = 0;
429 for (;;) {
430 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
431 bool can_busy_loop = false;
432
433 inp = fds->in; outp = fds->out; exp = fds->ex;
434 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
435
436 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
437 unsigned long in, out, ex, all_bits, bit = 1, mask, j;
438 unsigned long res_in = 0, res_out = 0, res_ex = 0;
439
440 in = *inp++; out = *outp++; ex = *exp++;
441 all_bits = in | out | ex;
442 if (all_bits == 0) {
443 i += BITS_PER_LONG;
444 continue;
445 }
446
447 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
448 struct fd f;
449 if (i >= n)
450 break;
451 if (!(bit & all_bits))
452 continue;
453 f = fdget(i);
454 if (f.file) {
455 const struct file_operations *f_op;
456 f_op = f.file->f_op;
457 mask = DEFAULT_POLLMASK;
458 if (f_op->poll) {
459 wait_key_set(wait, in, out,
460 bit, busy_flag);
461 mask = (*f_op->poll)(f.file, wait);
462 }
463 fdput(f);
464 if ((mask & POLLIN_SET) && (in & bit)) {
465 res_in |= bit;
466 retval++;
467 wait->_qproc = NULL;
468 }
469 if ((mask & POLLOUT_SET) && (out & bit)) {
470 res_out |= bit;
471 retval++;
472 wait->_qproc = NULL;
473 }
474 if ((mask & POLLEX_SET) && (ex & bit)) {
475 res_ex |= bit;
476 retval++;
477 wait->_qproc = NULL;
478 }
479 /* got something, stop busy polling */
480 if (retval) {
481 can_busy_loop = false;
482 busy_flag = 0;
483
484 /*
485 * only remember a returned
486 * POLL_BUSY_LOOP if we asked for it
487 */
488 } else if (busy_flag & mask)
489 can_busy_loop = true;
490
491 }
492 }
493 if (res_in)
494 *rinp = res_in;
495 if (res_out)
496 *routp = res_out;
497 if (res_ex)
498 *rexp = res_ex;
499 cond_resched();
500 }
501 wait->_qproc = NULL;
502 if (retval || timed_out || signal_pending(current))
503 break;
504 if (table.error) {
505 retval = table.error;
506 break;
507 }
508
509 /* only if found POLL_BUSY_LOOP sockets && not out of time */
510 if (can_busy_loop && !need_resched()) {
511 if (!busy_end) {
512 busy_end = busy_loop_end_time();
513 continue;
514 }
515 if (!busy_loop_timeout(busy_end))
516 continue;
517 }
518 busy_flag = 0;
519
520 /*
521 * If this is the first loop and we have a timeout
522 * given, then we convert to ktime_t and set the to
523 * pointer to the expiry value.
524 */
525 if (end_time && !to) {
526 expire = timespec_to_ktime(*end_time);
527 to = &expire;
528 }
529
530 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
531 to, slack))
532 timed_out = 1;
533 }
534
535 poll_freewait(&table);
536
537 return retval;
538 }
539
540 /*
541 * We can actually return ERESTARTSYS instead of EINTR, but I'd
542 * like to be certain this leads to no problems. So I return
543 * EINTR just for safety.
544 *
545 * Update: ERESTARTSYS breaks at least the xview clock binary, so
546 * I'm trying ERESTARTNOHAND which restart only when you want to.
547 */
core_sys_select(int n,fd_set __user * inp,fd_set __user * outp,fd_set __user * exp,struct timespec * end_time)548 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
549 fd_set __user *exp, struct timespec *end_time)
550 {
551 fd_set_bits fds;
552 void *bits;
553 int ret, max_fds;
554 size_t size, alloc_size;
555 struct fdtable *fdt;
556 /* Allocate small arguments on the stack to save memory and be faster */
557 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
558
559 ret = -EINVAL;
560 if (n < 0)
561 goto out_nofds;
562
563 /* max_fds can increase, so grab it once to avoid race */
564 rcu_read_lock();
565 fdt = files_fdtable(current->files);
566 max_fds = fdt->max_fds;
567 rcu_read_unlock();
568 if (n > max_fds)
569 n = max_fds;
570
571 /*
572 * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
573 * since we used fdset we need to allocate memory in units of
574 * long-words.
575 */
576 size = FDS_BYTES(n);
577 bits = stack_fds;
578 if (size > sizeof(stack_fds) / 6) {
579 /* Not enough space in on-stack array; must use kmalloc */
580 ret = -ENOMEM;
581 if (size > (SIZE_MAX / 6))
582 goto out_nofds;
583
584 alloc_size = 6 * size;
585 bits = kmalloc(alloc_size, GFP_KERNEL|__GFP_NOWARN);
586 if (!bits && alloc_size > PAGE_SIZE)
587 bits = vmalloc(alloc_size);
588
589 if (!bits)
590 goto out_nofds;
591 }
592 fds.in = bits;
593 fds.out = bits + size;
594 fds.ex = bits + 2*size;
595 fds.res_in = bits + 3*size;
596 fds.res_out = bits + 4*size;
597 fds.res_ex = bits + 5*size;
598
599 if ((ret = get_fd_set(n, inp, fds.in)) ||
600 (ret = get_fd_set(n, outp, fds.out)) ||
601 (ret = get_fd_set(n, exp, fds.ex)))
602 goto out;
603 zero_fd_set(n, fds.res_in);
604 zero_fd_set(n, fds.res_out);
605 zero_fd_set(n, fds.res_ex);
606
607 ret = do_select(n, &fds, end_time);
608
609 if (ret < 0)
610 goto out;
611 if (!ret) {
612 ret = -ERESTARTNOHAND;
613 if (signal_pending(current))
614 goto out;
615 ret = 0;
616 }
617
618 if (set_fd_set(n, inp, fds.res_in) ||
619 set_fd_set(n, outp, fds.res_out) ||
620 set_fd_set(n, exp, fds.res_ex))
621 ret = -EFAULT;
622
623 out:
624 if (bits != stack_fds)
625 kvfree(bits);
626 out_nofds:
627 return ret;
628 }
629
SYSCALL_DEFINE5(select,int,n,fd_set __user *,inp,fd_set __user *,outp,fd_set __user *,exp,struct timeval __user *,tvp)630 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
631 fd_set __user *, exp, struct timeval __user *, tvp)
632 {
633 struct timespec end_time, *to = NULL;
634 struct timeval tv;
635 int ret;
636
637 if (tvp) {
638 if (copy_from_user(&tv, tvp, sizeof(tv)))
639 return -EFAULT;
640
641 to = &end_time;
642 if (poll_select_set_timeout(to,
643 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
644 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
645 return -EINVAL;
646 }
647
648 ret = core_sys_select(n, inp, outp, exp, to);
649 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
650
651 return ret;
652 }
653
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)654 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
655 fd_set __user *exp, struct timespec __user *tsp,
656 const sigset_t __user *sigmask, size_t sigsetsize)
657 {
658 sigset_t ksigmask, sigsaved;
659 struct timespec ts, end_time, *to = NULL;
660 int ret;
661
662 if (tsp) {
663 if (copy_from_user(&ts, tsp, sizeof(ts)))
664 return -EFAULT;
665
666 to = &end_time;
667 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
668 return -EINVAL;
669 }
670
671 if (sigmask) {
672 /* XXX: Don't preclude handling different sized sigset_t's. */
673 if (sigsetsize != sizeof(sigset_t))
674 return -EINVAL;
675 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
676 return -EFAULT;
677
678 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
679 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
680 }
681
682 ret = core_sys_select(n, inp, outp, exp, to);
683 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
684
685 if (ret == -ERESTARTNOHAND) {
686 /*
687 * Don't restore the signal mask yet. Let do_signal() deliver
688 * the signal on the way back to userspace, before the signal
689 * mask is restored.
690 */
691 if (sigmask) {
692 memcpy(¤t->saved_sigmask, &sigsaved,
693 sizeof(sigsaved));
694 set_restore_sigmask();
695 }
696 } else if (sigmask)
697 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
698
699 return ret;
700 }
701
702 /*
703 * Most architectures can't handle 7-argument syscalls. So we provide a
704 * 6-argument version where the sixth argument is a pointer to a structure
705 * which has a pointer to the sigset_t itself followed by a size_t containing
706 * the sigset size.
707 */
SYSCALL_DEFINE6(pselect6,int,n,fd_set __user *,inp,fd_set __user *,outp,fd_set __user *,exp,struct timespec __user *,tsp,void __user *,sig)708 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
709 fd_set __user *, exp, struct timespec __user *, tsp,
710 void __user *, sig)
711 {
712 size_t sigsetsize = 0;
713 sigset_t __user *up = NULL;
714
715 if (sig) {
716 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
717 || __get_user(up, (sigset_t __user * __user *)sig)
718 || __get_user(sigsetsize,
719 (size_t __user *)(sig+sizeof(void *))))
720 return -EFAULT;
721 }
722
723 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
724 }
725
726 #ifdef __ARCH_WANT_SYS_OLD_SELECT
727 struct sel_arg_struct {
728 unsigned long n;
729 fd_set __user *inp, *outp, *exp;
730 struct timeval __user *tvp;
731 };
732
SYSCALL_DEFINE1(old_select,struct sel_arg_struct __user *,arg)733 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
734 {
735 struct sel_arg_struct a;
736
737 if (copy_from_user(&a, arg, sizeof(a)))
738 return -EFAULT;
739 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
740 }
741 #endif
742
743 struct poll_list {
744 struct poll_list *next;
745 int len;
746 struct pollfd entries[0];
747 };
748
749 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
750
751 /*
752 * Fish for pollable events on the pollfd->fd file descriptor. We're only
753 * interested in events matching the pollfd->events mask, and the result
754 * matching that mask is both recorded in pollfd->revents and returned. The
755 * pwait poll_table will be used by the fd-provided poll handler for waiting,
756 * if pwait->_qproc is non-NULL.
757 */
do_pollfd(struct pollfd * pollfd,poll_table * pwait,bool * can_busy_poll,unsigned int busy_flag)758 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
759 bool *can_busy_poll,
760 unsigned int busy_flag)
761 {
762 unsigned int mask;
763 int fd;
764
765 mask = 0;
766 fd = pollfd->fd;
767 if (fd >= 0) {
768 struct fd f = fdget(fd);
769 mask = POLLNVAL;
770 if (f.file) {
771 mask = DEFAULT_POLLMASK;
772 if (f.file->f_op->poll) {
773 pwait->_key = pollfd->events|POLLERR|POLLHUP;
774 pwait->_key |= busy_flag;
775 mask = f.file->f_op->poll(f.file, pwait);
776 if (mask & busy_flag)
777 *can_busy_poll = true;
778 }
779 /* Mask out unneeded events. */
780 mask &= pollfd->events | POLLERR | POLLHUP;
781 fdput(f);
782 }
783 }
784 pollfd->revents = mask;
785
786 return mask;
787 }
788
do_poll(unsigned int nfds,struct poll_list * list,struct poll_wqueues * wait,struct timespec * end_time)789 static int do_poll(unsigned int nfds, struct poll_list *list,
790 struct poll_wqueues *wait, struct timespec *end_time)
791 {
792 poll_table* pt = &wait->pt;
793 ktime_t expire, *to = NULL;
794 int timed_out = 0, count = 0;
795 u64 slack = 0;
796 unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
797 unsigned long busy_end = 0;
798
799 /* Optimise the no-wait case */
800 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
801 pt->_qproc = NULL;
802 timed_out = 1;
803 }
804
805 if (end_time && !timed_out)
806 slack = select_estimate_accuracy(end_time);
807
808 for (;;) {
809 struct poll_list *walk;
810 bool can_busy_loop = false;
811
812 for (walk = list; walk != NULL; walk = walk->next) {
813 struct pollfd * pfd, * pfd_end;
814
815 pfd = walk->entries;
816 pfd_end = pfd + walk->len;
817 for (; pfd != pfd_end; pfd++) {
818 /*
819 * Fish for events. If we found one, record it
820 * and kill poll_table->_qproc, so we don't
821 * needlessly register any other waiters after
822 * this. They'll get immediately deregistered
823 * when we break out and return.
824 */
825 if (do_pollfd(pfd, pt, &can_busy_loop,
826 busy_flag)) {
827 count++;
828 pt->_qproc = NULL;
829 /* found something, stop busy polling */
830 busy_flag = 0;
831 can_busy_loop = false;
832 }
833 }
834 }
835 /*
836 * All waiters have already been registered, so don't provide
837 * a poll_table->_qproc to them on the next loop iteration.
838 */
839 pt->_qproc = NULL;
840 if (!count) {
841 count = wait->error;
842 if (signal_pending(current))
843 count = -EINTR;
844 }
845 if (count || timed_out)
846 break;
847
848 /* only if found POLL_BUSY_LOOP sockets && not out of time */
849 if (can_busy_loop && !need_resched()) {
850 if (!busy_end) {
851 busy_end = busy_loop_end_time();
852 continue;
853 }
854 if (!busy_loop_timeout(busy_end))
855 continue;
856 }
857 busy_flag = 0;
858
859 /*
860 * If this is the first loop and we have a timeout
861 * given, then we convert to ktime_t and set the to
862 * pointer to the expiry value.
863 */
864 if (end_time && !to) {
865 expire = timespec_to_ktime(*end_time);
866 to = &expire;
867 }
868
869 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
870 timed_out = 1;
871 }
872 return count;
873 }
874
875 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \
876 sizeof(struct pollfd))
877
do_sys_poll(struct pollfd __user * ufds,unsigned int nfds,struct timespec * end_time)878 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
879 struct timespec *end_time)
880 {
881 struct poll_wqueues table;
882 int err = -EFAULT, fdcount, len, size;
883 /* Allocate small arguments on the stack to save memory and be
884 faster - use long to make sure the buffer is aligned properly
885 on 64 bit archs to avoid unaligned access */
886 long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
887 struct poll_list *const head = (struct poll_list *)stack_pps;
888 struct poll_list *walk = head;
889 unsigned long todo = nfds;
890
891 if (nfds > rlimit(RLIMIT_NOFILE))
892 return -EINVAL;
893
894 len = min_t(unsigned int, nfds, N_STACK_PPS);
895 for (;;) {
896 walk->next = NULL;
897 walk->len = len;
898 if (!len)
899 break;
900
901 if (copy_from_user(walk->entries, ufds + nfds-todo,
902 sizeof(struct pollfd) * walk->len))
903 goto out_fds;
904
905 todo -= walk->len;
906 if (!todo)
907 break;
908
909 len = min(todo, POLLFD_PER_PAGE);
910 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
911 walk = walk->next = kmalloc(size, GFP_KERNEL);
912 if (!walk) {
913 err = -ENOMEM;
914 goto out_fds;
915 }
916 }
917
918 poll_initwait(&table);
919 fdcount = do_poll(nfds, head, &table, end_time);
920 poll_freewait(&table);
921
922 for (walk = head; walk; walk = walk->next) {
923 struct pollfd *fds = walk->entries;
924 int j;
925
926 for (j = 0; j < walk->len; j++, ufds++)
927 if (__put_user(fds[j].revents, &ufds->revents))
928 goto out_fds;
929 }
930
931 err = fdcount;
932 out_fds:
933 walk = head->next;
934 while (walk) {
935 struct poll_list *pos = walk;
936 walk = walk->next;
937 kfree(pos);
938 }
939
940 return err;
941 }
942
do_restart_poll(struct restart_block * restart_block)943 static long do_restart_poll(struct restart_block *restart_block)
944 {
945 struct pollfd __user *ufds = restart_block->poll.ufds;
946 int nfds = restart_block->poll.nfds;
947 struct timespec *to = NULL, end_time;
948 int ret;
949
950 if (restart_block->poll.has_timeout) {
951 end_time.tv_sec = restart_block->poll.tv_sec;
952 end_time.tv_nsec = restart_block->poll.tv_nsec;
953 to = &end_time;
954 }
955
956 ret = do_sys_poll(ufds, nfds, to);
957
958 if (ret == -EINTR) {
959 restart_block->fn = do_restart_poll;
960 ret = -ERESTART_RESTARTBLOCK;
961 }
962 return ret;
963 }
964
SYSCALL_DEFINE3(poll,struct pollfd __user *,ufds,unsigned int,nfds,int,timeout_msecs)965 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
966 int, timeout_msecs)
967 {
968 struct timespec end_time, *to = NULL;
969 int ret;
970
971 if (timeout_msecs >= 0) {
972 to = &end_time;
973 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
974 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
975 }
976
977 ret = do_sys_poll(ufds, nfds, to);
978
979 if (ret == -EINTR) {
980 struct restart_block *restart_block;
981
982 restart_block = ¤t->restart_block;
983 restart_block->fn = do_restart_poll;
984 restart_block->poll.ufds = ufds;
985 restart_block->poll.nfds = nfds;
986
987 if (timeout_msecs >= 0) {
988 restart_block->poll.tv_sec = end_time.tv_sec;
989 restart_block->poll.tv_nsec = end_time.tv_nsec;
990 restart_block->poll.has_timeout = 1;
991 } else
992 restart_block->poll.has_timeout = 0;
993
994 ret = -ERESTART_RESTARTBLOCK;
995 }
996 return ret;
997 }
998
SYSCALL_DEFINE5(ppoll,struct pollfd __user *,ufds,unsigned int,nfds,struct timespec __user *,tsp,const sigset_t __user *,sigmask,size_t,sigsetsize)999 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
1000 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
1001 size_t, sigsetsize)
1002 {
1003 sigset_t ksigmask, sigsaved;
1004 struct timespec ts, end_time, *to = NULL;
1005 int ret;
1006
1007 if (tsp) {
1008 if (copy_from_user(&ts, tsp, sizeof(ts)))
1009 return -EFAULT;
1010
1011 to = &end_time;
1012 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1013 return -EINVAL;
1014 }
1015
1016 if (sigmask) {
1017 /* XXX: Don't preclude handling different sized sigset_t's. */
1018 if (sigsetsize != sizeof(sigset_t))
1019 return -EINVAL;
1020 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1021 return -EFAULT;
1022
1023 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1024 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1025 }
1026
1027 ret = do_sys_poll(ufds, nfds, to);
1028
1029 /* We can restart this syscall, usually */
1030 if (ret == -EINTR) {
1031 /*
1032 * Don't restore the signal mask yet. Let do_signal() deliver
1033 * the signal on the way back to userspace, before the signal
1034 * mask is restored.
1035 */
1036 if (sigmask) {
1037 memcpy(¤t->saved_sigmask, &sigsaved,
1038 sizeof(sigsaved));
1039 set_restore_sigmask();
1040 }
1041 ret = -ERESTARTNOHAND;
1042 } else if (sigmask)
1043 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1044
1045 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1046
1047 return ret;
1048 }
1049