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TOMOYO Linux Cross Reference
Linux/fs/select.c

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  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 
 33 #include <asm/uaccess.h>
 34 
 35 
 36 /*
 37  * Estimate expected accuracy in ns from a timeval.
 38  *
 39  * After quite a bit of churning around, we've settled on
 40  * a simple thing of taking 0.1% of the timeout as the
 41  * slack, with a cap of 100 msec.
 42  * "nice" tasks get a 0.5% slack instead.
 43  *
 44  * Consider this comment an open invitation to come up with even
 45  * better solutions..
 46  */
 47 
 48 #define MAX_SLACK       (100 * NSEC_PER_MSEC)
 49 
 50 static long __estimate_accuracy(struct timespec *tv)
 51 {
 52         long slack;
 53         int divfactor = 1000;
 54 
 55         if (tv->tv_sec < 0)
 56                 return 0;
 57 
 58         if (task_nice(current) > 0)
 59                 divfactor = divfactor / 5;
 60 
 61         if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
 62                 return MAX_SLACK;
 63 
 64         slack = tv->tv_nsec / divfactor;
 65         slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
 66 
 67         if (slack > MAX_SLACK)
 68                 return MAX_SLACK;
 69 
 70         return slack;
 71 }
 72 
 73 long select_estimate_accuracy(struct timespec *tv)
 74 {
 75         unsigned long ret;
 76         struct timespec now;
 77 
 78         /*
 79          * Realtime tasks get a slack of 0 for obvious reasons.
 80          */
 81 
 82         if (rt_task(current))
 83                 return 0;
 84 
 85         ktime_get_ts(&now);
 86         now = timespec_sub(*tv, now);
 87         ret = __estimate_accuracy(&now);
 88         if (ret < current->timer_slack_ns)
 89                 return current->timer_slack_ns;
 90         return ret;
 91 }
 92 
 93 
 94 
 95 struct poll_table_page {
 96         struct poll_table_page * next;
 97         struct poll_table_entry * entry;
 98         struct poll_table_entry entries[0];
 99 };
100 
101 #define POLL_TABLE_FULL(table) \
102         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
103 
104 /*
105  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
106  * I have rewritten this, taking some shortcuts: This code may not be easy to
107  * follow, but it should be free of race-conditions, and it's practical. If you
108  * understand what I'm doing here, then you understand how the linux
109  * sleep/wakeup mechanism works.
110  *
111  * Two very simple procedures, poll_wait() and poll_freewait() make all the
112  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
113  * as all select/poll functions have to call it to add an entry to the
114  * poll table.
115  */
116 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
117                        poll_table *p);
118 
119 void poll_initwait(struct poll_wqueues *pwq)
120 {
121         init_poll_funcptr(&pwq->pt, __pollwait);
122         pwq->polling_task = current;
123         pwq->triggered = 0;
124         pwq->error = 0;
125         pwq->table = NULL;
126         pwq->inline_index = 0;
127 }
128 EXPORT_SYMBOL(poll_initwait);
129 
130 static void free_poll_entry(struct poll_table_entry *entry)
131 {
132         remove_wait_queue(entry->wait_address, &entry->wait);
133         fput(entry->filp);
134 }
135 
136 void poll_freewait(struct poll_wqueues *pwq)
137 {
138         struct poll_table_page * p = pwq->table;
139         int i;
140         for (i = 0; i < pwq->inline_index; i++)
141                 free_poll_entry(pwq->inline_entries + i);
142         while (p) {
143                 struct poll_table_entry * entry;
144                 struct poll_table_page *old;
145 
146                 entry = p->entry;
147                 do {
148                         entry--;
149                         free_poll_entry(entry);
150                 } while (entry > p->entries);
151                 old = p;
152                 p = p->next;
153                 free_page((unsigned long) old);
154         }
155 }
156 EXPORT_SYMBOL(poll_freewait);
157 
158 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
159 {
160         struct poll_table_page *table = p->table;
161 
162         if (p->inline_index < N_INLINE_POLL_ENTRIES)
163                 return p->inline_entries + p->inline_index++;
164 
165         if (!table || POLL_TABLE_FULL(table)) {
166                 struct poll_table_page *new_table;
167 
168                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
169                 if (!new_table) {
170                         p->error = -ENOMEM;
171                         return NULL;
172                 }
173                 new_table->entry = new_table->entries;
174                 new_table->next = table;
175                 p->table = new_table;
176                 table = new_table;
177         }
178 
179         return table->entry++;
180 }
181 
182 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
183 {
184         struct poll_wqueues *pwq = wait->private;
185         DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
186 
187         /*
188          * Although this function is called under waitqueue lock, LOCK
189          * doesn't imply write barrier and the users expect write
190          * barrier semantics on wakeup functions.  The following
191          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
192          * and is paired with set_mb() in poll_schedule_timeout.
193          */
194         smp_wmb();
195         pwq->triggered = 1;
196 
197         /*
198          * Perform the default wake up operation using a dummy
199          * waitqueue.
200          *
201          * TODO: This is hacky but there currently is no interface to
202          * pass in @sync.  @sync is scheduled to be removed and once
203          * that happens, wake_up_process() can be used directly.
204          */
205         return default_wake_function(&dummy_wait, mode, sync, key);
206 }
207 
208 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key)
209 {
210         struct poll_table_entry *entry;
211 
212         entry = container_of(wait, struct poll_table_entry, wait);
213         if (key && !((unsigned long)key & entry->key))
214                 return 0;
215         return __pollwake(wait, mode, sync, key);
216 }
217 
218 /* Add a new entry */
219 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
220                                 poll_table *p)
221 {
222         struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
223         struct poll_table_entry *entry = poll_get_entry(pwq);
224         if (!entry)
225                 return;
226         entry->filp = get_file(filp);
227         entry->wait_address = wait_address;
228         entry->key = p->_key;
229         init_waitqueue_func_entry(&entry->wait, pollwake);
230         entry->wait.private = pwq;
231         add_wait_queue(wait_address, &entry->wait);
232 }
233 
234 int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
235                           ktime_t *expires, unsigned long slack)
236 {
237         int rc = -EINTR;
238 
239         set_current_state(state);
240         if (!pwq->triggered)
241                 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
242         __set_current_state(TASK_RUNNING);
243 
244         /*
245          * Prepare for the next iteration.
246          *
247          * The following set_mb() serves two purposes.  First, it's
248          * the counterpart rmb of the wmb in pollwake() such that data
249          * written before wake up is always visible after wake up.
250          * Second, the full barrier guarantees that triggered clearing
251          * doesn't pass event check of the next iteration.  Note that
252          * this problem doesn't exist for the first iteration as
253          * add_wait_queue() has full barrier semantics.
254          */
255         set_mb(pwq->triggered, 0);
256 
257         return rc;
258 }
259 EXPORT_SYMBOL(poll_schedule_timeout);
260 
261 /**
262  * poll_select_set_timeout - helper function to setup the timeout value
263  * @to:         pointer to timespec variable for the final timeout
264  * @sec:        seconds (from user space)
265  * @nsec:       nanoseconds (from user space)
266  *
267  * Note, we do not use a timespec for the user space value here, That
268  * way we can use the function for timeval and compat interfaces as well.
269  *
270  * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
271  */
272 int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
273 {
274         struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
275 
276         if (!timespec_valid(&ts))
277                 return -EINVAL;
278 
279         /* Optimize for the zero timeout value here */
280         if (!sec && !nsec) {
281                 to->tv_sec = to->tv_nsec = 0;
282         } else {
283                 ktime_get_ts(to);
284                 *to = timespec_add_safe(*to, ts);
285         }
286         return 0;
287 }
288 
289 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
290                                       int timeval, int ret)
291 {
292         struct timespec rts;
293         struct timeval rtv;
294 
295         if (!p)
296                 return ret;
297 
298         if (current->personality & STICKY_TIMEOUTS)
299                 goto sticky;
300 
301         /* No update for zero timeout */
302         if (!end_time->tv_sec && !end_time->tv_nsec)
303                 return ret;
304 
305         ktime_get_ts(&rts);
306         rts = timespec_sub(*end_time, rts);
307         if (rts.tv_sec < 0)
308                 rts.tv_sec = rts.tv_nsec = 0;
309 
310         if (timeval) {
311                 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
312                         memset(&rtv, 0, sizeof(rtv));
313                 rtv.tv_sec = rts.tv_sec;
314                 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
315 
316                 if (!copy_to_user(p, &rtv, sizeof(rtv)))
317                         return ret;
318 
319         } else if (!copy_to_user(p, &rts, sizeof(rts)))
320                 return ret;
321 
322         /*
323          * If an application puts its timeval in read-only memory, we
324          * don't want the Linux-specific update to the timeval to
325          * cause a fault after the select has completed
326          * successfully. However, because we're not updating the
327          * timeval, we can't restart the system call.
328          */
329 
330 sticky:
331         if (ret == -ERESTARTNOHAND)
332                 ret = -EINTR;
333         return ret;
334 }
335 
336 #define FDS_IN(fds, n)          (fds->in + n)
337 #define FDS_OUT(fds, n)         (fds->out + n)
338 #define FDS_EX(fds, n)          (fds->ex + n)
339 
340 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
341 
342 static int max_select_fd(unsigned long n, fd_set_bits *fds)
343 {
344         unsigned long *open_fds;
345         unsigned long set;
346         int max;
347         struct fdtable *fdt;
348 
349         /* handle last in-complete long-word first */
350         set = ~(~0UL << (n & (BITS_PER_LONG-1)));
351         n /= BITS_PER_LONG;
352         fdt = files_fdtable(current->files);
353         open_fds = fdt->open_fds + n;
354         max = 0;
355         if (set) {
356                 set &= BITS(fds, n);
357                 if (set) {
358                         if (!(set & ~*open_fds))
359                                 goto get_max;
360                         return -EBADF;
361                 }
362         }
363         while (n) {
364                 open_fds--;
365                 n--;
366                 set = BITS(fds, n);
367                 if (!set)
368                         continue;
369                 if (set & ~*open_fds)
370                         return -EBADF;
371                 if (max)
372                         continue;
373 get_max:
374                 do {
375                         max++;
376                         set >>= 1;
377                 } while (set);
378                 max += n * BITS_PER_LONG;
379         }
380 
381         return max;
382 }
383 
384 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
385 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
386 #define POLLEX_SET (POLLPRI)
387 
388 static inline void wait_key_set(poll_table *wait, unsigned long in,
389                                 unsigned long out, unsigned long bit,
390                                 unsigned int ll_flag)
391 {
392         wait->_key = POLLEX_SET | ll_flag;
393         if (in & bit)
394                 wait->_key |= POLLIN_SET;
395         if (out & bit)
396                 wait->_key |= POLLOUT_SET;
397 }
398 
399 int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
400 {
401         ktime_t expire, *to = NULL;
402         struct poll_wqueues table;
403         poll_table *wait;
404         int retval, i, timed_out = 0;
405         unsigned long slack = 0;
406         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
407         unsigned long busy_end = 0;
408 
409         rcu_read_lock();
410         retval = max_select_fd(n, fds);
411         rcu_read_unlock();
412 
413         if (retval < 0)
414                 return retval;
415         n = retval;
416 
417         poll_initwait(&table);
418         wait = &table.pt;
419         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
420                 wait->_qproc = NULL;
421                 timed_out = 1;
422         }
423 
424         if (end_time && !timed_out)
425                 slack = select_estimate_accuracy(end_time);
426 
427         retval = 0;
428         for (;;) {
429                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
430                 bool can_busy_loop = false;
431 
432                 inp = fds->in; outp = fds->out; exp = fds->ex;
433                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
434 
435                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
436                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
437                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
438 
439                         in = *inp++; out = *outp++; ex = *exp++;
440                         all_bits = in | out | ex;
441                         if (all_bits == 0) {
442                                 i += BITS_PER_LONG;
443                                 continue;
444                         }
445 
446                         for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
447                                 struct fd f;
448                                 if (i >= n)
449                                         break;
450                                 if (!(bit & all_bits))
451                                         continue;
452                                 f = fdget(i);
453                                 if (f.file) {
454                                         const struct file_operations *f_op;
455                                         f_op = f.file->f_op;
456                                         mask = DEFAULT_POLLMASK;
457                                         if (f_op && f_op->poll) {
458                                                 wait_key_set(wait, in, out,
459                                                              bit, busy_flag);
460                                                 mask = (*f_op->poll)(f.file, wait);
461                                         }
462                                         fdput(f);
463                                         if ((mask & POLLIN_SET) && (in & bit)) {
464                                                 res_in |= bit;
465                                                 retval++;
466                                                 wait->_qproc = NULL;
467                                         }
468                                         if ((mask & POLLOUT_SET) && (out & bit)) {
469                                                 res_out |= bit;
470                                                 retval++;
471                                                 wait->_qproc = NULL;
472                                         }
473                                         if ((mask & POLLEX_SET) && (ex & bit)) {
474                                                 res_ex |= bit;
475                                                 retval++;
476                                                 wait->_qproc = NULL;
477                                         }
478                                         /* got something, stop busy polling */
479                                         if (retval) {
480                                                 can_busy_loop = false;
481                                                 busy_flag = 0;
482 
483                                         /*
484                                          * only remember a returned
485                                          * POLL_BUSY_LOOP if we asked for it
486                                          */
487                                         } else if (busy_flag & mask)
488                                                 can_busy_loop = true;
489 
490                                 }
491                         }
492                         if (res_in)
493                                 *rinp = res_in;
494                         if (res_out)
495                                 *routp = res_out;
496                         if (res_ex)
497                                 *rexp = res_ex;
498                         cond_resched();
499                 }
500                 wait->_qproc = NULL;
501                 if (retval || timed_out || signal_pending(current))
502                         break;
503                 if (table.error) {
504                         retval = table.error;
505                         break;
506                 }
507 
508                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
509                 if (can_busy_loop && !need_resched()) {
510                         if (!busy_end) {
511                                 busy_end = busy_loop_end_time();
512                                 continue;
513                         }
514                         if (!busy_loop_timeout(busy_end))
515                                 continue;
516                 }
517                 busy_flag = 0;
518 
519                 /*
520                  * If this is the first loop and we have a timeout
521                  * given, then we convert to ktime_t and set the to
522                  * pointer to the expiry value.
523                  */
524                 if (end_time && !to) {
525                         expire = timespec_to_ktime(*end_time);
526                         to = &expire;
527                 }
528 
529                 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
530                                            to, slack))
531                         timed_out = 1;
532         }
533 
534         poll_freewait(&table);
535 
536         return retval;
537 }
538 
539 /*
540  * We can actually return ERESTARTSYS instead of EINTR, but I'd
541  * like to be certain this leads to no problems. So I return
542  * EINTR just for safety.
543  *
544  * Update: ERESTARTSYS breaks at least the xview clock binary, so
545  * I'm trying ERESTARTNOHAND which restart only when you want to.
546  */
547 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
548                            fd_set __user *exp, struct timespec *end_time)
549 {
550         fd_set_bits fds;
551         void *bits;
552         int ret, max_fds;
553         unsigned int size;
554         struct fdtable *fdt;
555         /* Allocate small arguments on the stack to save memory and be faster */
556         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
557 
558         ret = -EINVAL;
559         if (n < 0)
560                 goto out_nofds;
561 
562         /* max_fds can increase, so grab it once to avoid race */
563         rcu_read_lock();
564         fdt = files_fdtable(current->files);
565         max_fds = fdt->max_fds;
566         rcu_read_unlock();
567         if (n > max_fds)
568                 n = max_fds;
569 
570         /*
571          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
572          * since we used fdset we need to allocate memory in units of
573          * long-words. 
574          */
575         size = FDS_BYTES(n);
576         bits = stack_fds;
577         if (size > sizeof(stack_fds) / 6) {
578                 /* Not enough space in on-stack array; must use kmalloc */
579                 ret = -ENOMEM;
580                 bits = kmalloc(6 * size, GFP_KERNEL);
581                 if (!bits)
582                         goto out_nofds;
583         }
584         fds.in      = bits;
585         fds.out     = bits +   size;
586         fds.ex      = bits + 2*size;
587         fds.res_in  = bits + 3*size;
588         fds.res_out = bits + 4*size;
589         fds.res_ex  = bits + 5*size;
590 
591         if ((ret = get_fd_set(n, inp, fds.in)) ||
592             (ret = get_fd_set(n, outp, fds.out)) ||
593             (ret = get_fd_set(n, exp, fds.ex)))
594                 goto out;
595         zero_fd_set(n, fds.res_in);
596         zero_fd_set(n, fds.res_out);
597         zero_fd_set(n, fds.res_ex);
598 
599         ret = do_select(n, &fds, end_time);
600 
601         if (ret < 0)
602                 goto out;
603         if (!ret) {
604                 ret = -ERESTARTNOHAND;
605                 if (signal_pending(current))
606                         goto out;
607                 ret = 0;
608         }
609 
610         if (set_fd_set(n, inp, fds.res_in) ||
611             set_fd_set(n, outp, fds.res_out) ||
612             set_fd_set(n, exp, fds.res_ex))
613                 ret = -EFAULT;
614 
615 out:
616         if (bits != stack_fds)
617                 kfree(bits);
618 out_nofds:
619         return ret;
620 }
621 
622 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
623                 fd_set __user *, exp, struct timeval __user *, tvp)
624 {
625         struct timespec end_time, *to = NULL;
626         struct timeval tv;
627         int ret;
628 
629         if (tvp) {
630                 if (copy_from_user(&tv, tvp, sizeof(tv)))
631                         return -EFAULT;
632 
633                 to = &end_time;
634                 if (poll_select_set_timeout(to,
635                                 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
636                                 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
637                         return -EINVAL;
638         }
639 
640         ret = core_sys_select(n, inp, outp, exp, to);
641         ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
642 
643         return ret;
644 }
645 
646 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
647                        fd_set __user *exp, struct timespec __user *tsp,
648                        const sigset_t __user *sigmask, size_t sigsetsize)
649 {
650         sigset_t ksigmask, sigsaved;
651         struct timespec ts, end_time, *to = NULL;
652         int ret;
653 
654         if (tsp) {
655                 if (copy_from_user(&ts, tsp, sizeof(ts)))
656                         return -EFAULT;
657 
658                 to = &end_time;
659                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
660                         return -EINVAL;
661         }
662 
663         if (sigmask) {
664                 /* XXX: Don't preclude handling different sized sigset_t's.  */
665                 if (sigsetsize != sizeof(sigset_t))
666                         return -EINVAL;
667                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
668                         return -EFAULT;
669 
670                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
671                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
672         }
673 
674         ret = core_sys_select(n, inp, outp, exp, to);
675         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
676 
677         if (ret == -ERESTARTNOHAND) {
678                 /*
679                  * Don't restore the signal mask yet. Let do_signal() deliver
680                  * the signal on the way back to userspace, before the signal
681                  * mask is restored.
682                  */
683                 if (sigmask) {
684                         memcpy(&current->saved_sigmask, &sigsaved,
685                                         sizeof(sigsaved));
686                         set_restore_sigmask();
687                 }
688         } else if (sigmask)
689                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
690 
691         return ret;
692 }
693 
694 /*
695  * Most architectures can't handle 7-argument syscalls. So we provide a
696  * 6-argument version where the sixth argument is a pointer to a structure
697  * which has a pointer to the sigset_t itself followed by a size_t containing
698  * the sigset size.
699  */
700 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
701                 fd_set __user *, exp, struct timespec __user *, tsp,
702                 void __user *, sig)
703 {
704         size_t sigsetsize = 0;
705         sigset_t __user *up = NULL;
706 
707         if (sig) {
708                 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
709                     || __get_user(up, (sigset_t __user * __user *)sig)
710                     || __get_user(sigsetsize,
711                                 (size_t __user *)(sig+sizeof(void *))))
712                         return -EFAULT;
713         }
714 
715         return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
716 }
717 
718 #ifdef __ARCH_WANT_SYS_OLD_SELECT
719 struct sel_arg_struct {
720         unsigned long n;
721         fd_set __user *inp, *outp, *exp;
722         struct timeval __user *tvp;
723 };
724 
725 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
726 {
727         struct sel_arg_struct a;
728 
729         if (copy_from_user(&a, arg, sizeof(a)))
730                 return -EFAULT;
731         return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp);
732 }
733 #endif
734 
735 struct poll_list {
736         struct poll_list *next;
737         int len;
738         struct pollfd entries[0];
739 };
740 
741 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
742 
743 /*
744  * Fish for pollable events on the pollfd->fd file descriptor. We're only
745  * interested in events matching the pollfd->events mask, and the result
746  * matching that mask is both recorded in pollfd->revents and returned. The
747  * pwait poll_table will be used by the fd-provided poll handler for waiting,
748  * if pwait->_qproc is non-NULL.
749  */
750 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait,
751                                      bool *can_busy_poll,
752                                      unsigned int busy_flag)
753 {
754         unsigned int mask;
755         int fd;
756 
757         mask = 0;
758         fd = pollfd->fd;
759         if (fd >= 0) {
760                 struct fd f = fdget(fd);
761                 mask = POLLNVAL;
762                 if (f.file) {
763                         mask = DEFAULT_POLLMASK;
764                         if (f.file->f_op && f.file->f_op->poll) {
765                                 pwait->_key = pollfd->events|POLLERR|POLLHUP;
766                                 pwait->_key |= busy_flag;
767                                 mask = f.file->f_op->poll(f.file, pwait);
768                                 if (mask & busy_flag)
769                                         *can_busy_poll = true;
770                         }
771                         /* Mask out unneeded events. */
772                         mask &= pollfd->events | POLLERR | POLLHUP;
773                         fdput(f);
774                 }
775         }
776         pollfd->revents = mask;
777 
778         return mask;
779 }
780 
781 static int do_poll(unsigned int nfds,  struct poll_list *list,
782                    struct poll_wqueues *wait, struct timespec *end_time)
783 {
784         poll_table* pt = &wait->pt;
785         ktime_t expire, *to = NULL;
786         int timed_out = 0, count = 0;
787         unsigned long slack = 0;
788         unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
789         unsigned long busy_end = 0;
790 
791         /* Optimise the no-wait case */
792         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
793                 pt->_qproc = NULL;
794                 timed_out = 1;
795         }
796 
797         if (end_time && !timed_out)
798                 slack = select_estimate_accuracy(end_time);
799 
800         for (;;) {
801                 struct poll_list *walk;
802                 bool can_busy_loop = false;
803 
804                 for (walk = list; walk != NULL; walk = walk->next) {
805                         struct pollfd * pfd, * pfd_end;
806 
807                         pfd = walk->entries;
808                         pfd_end = pfd + walk->len;
809                         for (; pfd != pfd_end; pfd++) {
810                                 /*
811                                  * Fish for events. If we found one, record it
812                                  * and kill poll_table->_qproc, so we don't
813                                  * needlessly register any other waiters after
814                                  * this. They'll get immediately deregistered
815                                  * when we break out and return.
816                                  */
817                                 if (do_pollfd(pfd, pt, &can_busy_loop,
818                                               busy_flag)) {
819                                         count++;
820                                         pt->_qproc = NULL;
821                                         /* found something, stop busy polling */
822                                         busy_flag = 0;
823                                         can_busy_loop = false;
824                                 }
825                         }
826                 }
827                 /*
828                  * All waiters have already been registered, so don't provide
829                  * a poll_table->_qproc to them on the next loop iteration.
830                  */
831                 pt->_qproc = NULL;
832                 if (!count) {
833                         count = wait->error;
834                         if (signal_pending(current))
835                                 count = -EINTR;
836                 }
837                 if (count || timed_out)
838                         break;
839 
840                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
841                 if (can_busy_loop && !need_resched()) {
842                         if (!busy_end) {
843                                 busy_end = busy_loop_end_time();
844                                 continue;
845                         }
846                         if (!busy_loop_timeout(busy_end))
847                                 continue;
848                 }
849                 busy_flag = 0;
850 
851                 /*
852                  * If this is the first loop and we have a timeout
853                  * given, then we convert to ktime_t and set the to
854                  * pointer to the expiry value.
855                  */
856                 if (end_time && !to) {
857                         expire = timespec_to_ktime(*end_time);
858                         to = &expire;
859                 }
860 
861                 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
862                         timed_out = 1;
863         }
864         return count;
865 }
866 
867 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
868                         sizeof(struct pollfd))
869 
870 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
871                 struct timespec *end_time)
872 {
873         struct poll_wqueues table;
874         int err = -EFAULT, fdcount, len, size;
875         /* Allocate small arguments on the stack to save memory and be
876            faster - use long to make sure the buffer is aligned properly
877            on 64 bit archs to avoid unaligned access */
878         long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
879         struct poll_list *const head = (struct poll_list *)stack_pps;
880         struct poll_list *walk = head;
881         unsigned long todo = nfds;
882 
883         if (nfds > rlimit(RLIMIT_NOFILE))
884                 return -EINVAL;
885 
886         len = min_t(unsigned int, nfds, N_STACK_PPS);
887         for (;;) {
888                 walk->next = NULL;
889                 walk->len = len;
890                 if (!len)
891                         break;
892 
893                 if (copy_from_user(walk->entries, ufds + nfds-todo,
894                                         sizeof(struct pollfd) * walk->len))
895                         goto out_fds;
896 
897                 todo -= walk->len;
898                 if (!todo)
899                         break;
900 
901                 len = min(todo, POLLFD_PER_PAGE);
902                 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
903                 walk = walk->next = kmalloc(size, GFP_KERNEL);
904                 if (!walk) {
905                         err = -ENOMEM;
906                         goto out_fds;
907                 }
908         }
909 
910         poll_initwait(&table);
911         fdcount = do_poll(nfds, head, &table, end_time);
912         poll_freewait(&table);
913 
914         for (walk = head; walk; walk = walk->next) {
915                 struct pollfd *fds = walk->entries;
916                 int j;
917 
918                 for (j = 0; j < walk->len; j++, ufds++)
919                         if (__put_user(fds[j].revents, &ufds->revents))
920                                 goto out_fds;
921         }
922 
923         err = fdcount;
924 out_fds:
925         walk = head->next;
926         while (walk) {
927                 struct poll_list *pos = walk;
928                 walk = walk->next;
929                 kfree(pos);
930         }
931 
932         return err;
933 }
934 
935 static long do_restart_poll(struct restart_block *restart_block)
936 {
937         struct pollfd __user *ufds = restart_block->poll.ufds;
938         int nfds = restart_block->poll.nfds;
939         struct timespec *to = NULL, end_time;
940         int ret;
941 
942         if (restart_block->poll.has_timeout) {
943                 end_time.tv_sec = restart_block->poll.tv_sec;
944                 end_time.tv_nsec = restart_block->poll.tv_nsec;
945                 to = &end_time;
946         }
947 
948         ret = do_sys_poll(ufds, nfds, to);
949 
950         if (ret == -EINTR) {
951                 restart_block->fn = do_restart_poll;
952                 ret = -ERESTART_RESTARTBLOCK;
953         }
954         return ret;
955 }
956 
957 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
958                 int, timeout_msecs)
959 {
960         struct timespec end_time, *to = NULL;
961         int ret;
962 
963         if (timeout_msecs >= 0) {
964                 to = &end_time;
965                 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
966                         NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
967         }
968 
969         ret = do_sys_poll(ufds, nfds, to);
970 
971         if (ret == -EINTR) {
972                 struct restart_block *restart_block;
973 
974                 restart_block = &current_thread_info()->restart_block;
975                 restart_block->fn = do_restart_poll;
976                 restart_block->poll.ufds = ufds;
977                 restart_block->poll.nfds = nfds;
978 
979                 if (timeout_msecs >= 0) {
980                         restart_block->poll.tv_sec = end_time.tv_sec;
981                         restart_block->poll.tv_nsec = end_time.tv_nsec;
982                         restart_block->poll.has_timeout = 1;
983                 } else
984                         restart_block->poll.has_timeout = 0;
985 
986                 ret = -ERESTART_RESTARTBLOCK;
987         }
988         return ret;
989 }
990 
991 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
992                 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
993                 size_t, sigsetsize)
994 {
995         sigset_t ksigmask, sigsaved;
996         struct timespec ts, end_time, *to = NULL;
997         int ret;
998 
999         if (tsp) {
1000                 if (copy_from_user(&ts, tsp, sizeof(ts)))
1001                         return -EFAULT;
1002 
1003                 to = &end_time;
1004                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1005                         return -EINVAL;
1006         }
1007 
1008         if (sigmask) {
1009                 /* XXX: Don't preclude handling different sized sigset_t's.  */
1010                 if (sigsetsize != sizeof(sigset_t))
1011                         return -EINVAL;
1012                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1013                         return -EFAULT;
1014 
1015                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1016                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1017         }
1018 
1019         ret = do_sys_poll(ufds, nfds, to);
1020 
1021         /* We can restart this syscall, usually */
1022         if (ret == -EINTR) {
1023                 /*
1024                  * Don't restore the signal mask yet. Let do_signal() deliver
1025                  * the signal on the way back to userspace, before the signal
1026                  * mask is restored.
1027                  */
1028                 if (sigmask) {
1029                         memcpy(&current->saved_sigmask, &sigsaved,
1030                                         sizeof(sigsaved));
1031                         set_restore_sigmask();
1032                 }
1033                 ret = -ERESTARTNOHAND;
1034         } else if (sigmask)
1035                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1036 
1037         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1038 
1039         return ret;
1040 }
1041 

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