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Linux/fs/select.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * This file contains the procedures for the handling of select and poll
  4  *
  5  * Created for Linux based loosely upon Mathius Lattner's minix
  6  * patches by Peter MacDonald. Heavily edited by Linus.
  7  *
  8  *  4 February 1994
  9  *     COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
 10  *     flag set in its personality we do *not* modify the given timeout
 11  *     parameter to reflect time remaining.
 12  *
 13  *  24 January 2000
 14  *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation 
 15  *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
 16  */
 17 
 18 #include <linux/kernel.h>
 19 #include <linux/sched/signal.h>
 20 #include <linux/sched/rt.h>
 21 #include <linux/syscalls.h>
 22 #include <linux/export.h>
 23 #include <linux/slab.h>
 24 #include <linux/poll.h>
 25 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
 26 #include <linux/file.h>
 27 #include <linux/fdtable.h>
 28 #include <linux/fs.h>
 29 #include <linux/rcupdate.h>
 30 #include <linux/hrtimer.h>
 31 #include <linux/freezer.h>
 32 #include <net/busy_poll.h>
 33 #include <linux/vmalloc.h>
 34 
 35 #include <linux/uaccess.h>
 36 
 37 
 38 /*
 39  * Estimate expected accuracy in ns from a timeval.
 40  *
 41  * After quite a bit of churning around, we've settled on
 42  * a simple thing of taking 0.1% of the timeout as the
 43  * slack, with a cap of 100 msec.
 44  * "nice" tasks get a 0.5% slack instead.
 45  *
 46  * Consider this comment an open invitation to come up with even
 47  * better solutions..
 48  */
 49 
 50 #define MAX_SLACK       (100 * NSEC_PER_MSEC)
 51 
 52 static long __estimate_accuracy(struct timespec64 *tv)
 53 {
 54         long slack;
 55         int divfactor = 1000;
 56 
 57         if (tv->tv_sec < 0)
 58                 return 0;
 59 
 60         if (task_nice(current) > 0)
 61                 divfactor = divfactor / 5;
 62 
 63         if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor))
 64                 return MAX_SLACK;
 65 
 66         slack = tv->tv_nsec / divfactor;
 67         slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
 68 
 69         if (slack > MAX_SLACK)
 70                 return MAX_SLACK;
 71 
 72         return slack;
 73 }
 74 
 75 u64 select_estimate_accuracy(struct timespec64 *tv)
 76 {
 77         u64 ret;
 78         struct timespec64 now;
 79 
 80         /*
 81          * Realtime tasks get a slack of 0 for obvious reasons.
 82          */
 83 
 84         if (rt_task(current))
 85                 return 0;
 86 
 87         ktime_get_ts64(&now);
 88         now = timespec64_sub(*tv, now);
 89         ret = __estimate_accuracy(&now);
 90         if (ret < current->timer_slack_ns)
 91                 return current->timer_slack_ns;
 92         return ret;
 93 }
 94 
 95 
 96 
 97 struct poll_table_page {
 98         struct poll_table_page * next;
 99         struct poll_table_entry * entry;
100         struct poll_table_entry entries[0];
101 };
102 
103 #define POLL_TABLE_FULL(table) \
104         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
105 
106 /*
107  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
108  * I have rewritten this, taking some shortcuts: This code may not be easy to
109  * follow, but it should be free of race-conditions, and it's practical. If you
110  * understand what I'm doing here, then you understand how the linux
111  * sleep/wakeup mechanism works.
112  *
113  * Two very simple procedures, poll_wait() and poll_freewait() make all the
114  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
115  * as all select/poll functions have to call it to add an entry to the
116  * poll table.
117  */
118 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
119                        poll_table *p);
120 
121 void poll_initwait(struct poll_wqueues *pwq)
122 {
123         init_poll_funcptr(&pwq->pt, __pollwait);
124         pwq->polling_task = current;
125         pwq->triggered = 0;
126         pwq->error = 0;
127         pwq->table = NULL;
128         pwq->inline_index = 0;
129 }
130 EXPORT_SYMBOL(poll_initwait);
131 
132 static void free_poll_entry(struct poll_table_entry *entry)
133 {
134         remove_wait_queue(entry->wait_address, &entry->wait);
135         fput(entry->filp);
136 }
137 
138 void poll_freewait(struct poll_wqueues *pwq)
139 {
140         struct poll_table_page * p = pwq->table;
141         int i;
142         for (i = 0; i < pwq->inline_index; i++)
143                 free_poll_entry(pwq->inline_entries + i);
144         while (p) {
145                 struct poll_table_entry * entry;
146                 struct poll_table_page *old;
147 
148                 entry = p->entry;
149                 do {
150                         entry--;
151                         free_poll_entry(entry);
152                 } while (entry > p->entries);
153                 old = p;
154                 p = p->next;
155                 free_page((unsigned long) old);
156         }
157 }
158 EXPORT_SYMBOL(poll_freewait);
159 
160 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p)
161 {
162         struct poll_table_page *table = p->table;
163 
164         if (p->inline_index < N_INLINE_POLL_ENTRIES)
165                 return p->inline_entries + p->inline_index++;
166 
167         if (!table || POLL_TABLE_FULL(table)) {
168                 struct poll_table_page *new_table;
169 
170                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
171                 if (!new_table) {
172                         p->error = -ENOMEM;
173                         return NULL;
174                 }
175                 new_table->entry = new_table->entries;
176                 new_table->next = table;
177                 p->table = new_table;
178                 table = new_table;
179         }
180 
181         return table->entry++;
182 }
183 
184 static int __pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
185 {
186         struct poll_wqueues *pwq = wait->private;
187         DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task);
188 
189         /*
190          * Although this function is called under waitqueue lock, LOCK
191          * doesn't imply write barrier and the users expect write
192          * barrier semantics on wakeup functions.  The following
193          * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up()
194          * and is paired with smp_store_mb() in poll_schedule_timeout.
195          */
196         smp_wmb();
197         pwq->triggered = 1;
198 
199         /*
200          * Perform the default wake up operation using a dummy
201          * waitqueue.
202          *
203          * TODO: This is hacky but there currently is no interface to
204          * pass in @sync.  @sync is scheduled to be removed and once
205          * that happens, wake_up_process() can be used directly.
206          */
207         return default_wake_function(&dummy_wait, mode, sync, key);
208 }
209 
210 static int pollwake(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
211 {
212         struct poll_table_entry *entry;
213 
214         entry = container_of(wait, struct poll_table_entry, wait);
215         if (key && !(key_to_poll(key) & entry->key))
216                 return 0;
217         return __pollwake(wait, mode, sync, key);
218 }
219 
220 /* Add a new entry */
221 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
222                                 poll_table *p)
223 {
224         struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt);
225         struct poll_table_entry *entry = poll_get_entry(pwq);
226         if (!entry)
227                 return;
228         entry->filp = get_file(filp);
229         entry->wait_address = wait_address;
230         entry->key = p->_key;
231         init_waitqueue_func_entry(&entry->wait, pollwake);
232         entry->wait.private = pwq;
233         add_wait_queue(wait_address, &entry->wait);
234 }
235 
236 static int poll_schedule_timeout(struct poll_wqueues *pwq, int state,
237                           ktime_t *expires, unsigned long slack)
238 {
239         int rc = -EINTR;
240 
241         set_current_state(state);
242         if (!pwq->triggered)
243                 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS);
244         __set_current_state(TASK_RUNNING);
245 
246         /*
247          * Prepare for the next iteration.
248          *
249          * The following smp_store_mb() serves two purposes.  First, it's
250          * the counterpart rmb of the wmb in pollwake() such that data
251          * written before wake up is always visible after wake up.
252          * Second, the full barrier guarantees that triggered clearing
253          * doesn't pass event check of the next iteration.  Note that
254          * this problem doesn't exist for the first iteration as
255          * add_wait_queue() has full barrier semantics.
256          */
257         smp_store_mb(pwq->triggered, 0);
258 
259         return rc;
260 }
261 
262 /**
263  * poll_select_set_timeout - helper function to setup the timeout value
264  * @to:         pointer to timespec64 variable for the final timeout
265  * @sec:        seconds (from user space)
266  * @nsec:       nanoseconds (from user space)
267  *
268  * Note, we do not use a timespec for the user space value here, That
269  * way we can use the function for timeval and compat interfaces as well.
270  *
271  * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
272  */
273 int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec)
274 {
275         struct timespec64 ts = {.tv_sec = sec, .tv_nsec = nsec};
276 
277         if (!timespec64_valid(&ts))
278                 return -EINVAL;
279 
280         /* Optimize for the zero timeout value here */
281         if (!sec && !nsec) {
282                 to->tv_sec = to->tv_nsec = 0;
283         } else {
284                 ktime_get_ts64(to);
285                 *to = timespec64_add_safe(*to, ts);
286         }
287         return 0;
288 }
289 
290 static int poll_select_copy_remaining(struct timespec64 *end_time,
291                                       void __user *p,
292                                       int timeval, int ret)
293 {
294         struct timespec64 rts;
295         struct timeval rtv;
296 
297         if (!p)
298                 return ret;
299 
300         if (current->personality & STICKY_TIMEOUTS)
301                 goto sticky;
302 
303         /* No update for zero timeout */
304         if (!end_time->tv_sec && !end_time->tv_nsec)
305                 return ret;
306 
307         ktime_get_ts64(&rts);
308         rts = timespec64_sub(*end_time, rts);
309         if (rts.tv_sec < 0)
310                 rts.tv_sec = rts.tv_nsec = 0;
311 
312 
313         if (timeval) {
314                 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec))
315                         memset(&rtv, 0, sizeof(rtv));
316                 rtv.tv_sec = rts.tv_sec;
317                 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
318 
319                 if (!copy_to_user(p, &rtv, sizeof(rtv)))
320                         return ret;
321 
322         } else if (!put_timespec64(&rts, p))
323                 return ret;
324 
325         /*
326          * If an application puts its timeval in read-only memory, we
327          * don't want the Linux-specific update to the timeval to
328          * cause a fault after the select has completed
329          * successfully. However, because we're not updating the
330          * timeval, we can't restart the system call.
331          */
332 
333 sticky:
334         if (ret == -ERESTARTNOHAND)
335                 ret = -EINTR;
336         return ret;
337 }
338 
339 /*
340  * Scalable version of the fd_set.
341  */
342 
343 typedef struct {
344         unsigned long *in, *out, *ex;
345         unsigned long *res_in, *res_out, *res_ex;
346 } fd_set_bits;
347 
348 /*
349  * How many longwords for "nr" bits?
350  */
351 #define FDS_BITPERLONG  (8*sizeof(long))
352 #define FDS_LONGS(nr)   (((nr)+FDS_BITPERLONG-1)/FDS_BITPERLONG)
353 #define FDS_BYTES(nr)   (FDS_LONGS(nr)*sizeof(long))
354 
355 /*
356  * We do a VERIFY_WRITE here even though we are only reading this time:
357  * we'll write to it eventually..
358  *
359  * Use "unsigned long" accesses to let user-mode fd_set's be long-aligned.
360  */
361 static inline
362 int get_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
363 {
364         nr = FDS_BYTES(nr);
365         if (ufdset)
366                 return copy_from_user(fdset, ufdset, nr) ? -EFAULT : 0;
367 
368         memset(fdset, 0, nr);
369         return 0;
370 }
371 
372 static inline unsigned long __must_check
373 set_fd_set(unsigned long nr, void __user *ufdset, unsigned long *fdset)
374 {
375         if (ufdset)
376                 return __copy_to_user(ufdset, fdset, FDS_BYTES(nr));
377         return 0;
378 }
379 
380 static inline
381 void zero_fd_set(unsigned long nr, unsigned long *fdset)
382 {
383         memset(fdset, 0, FDS_BYTES(nr));
384 }
385 
386 #define FDS_IN(fds, n)          (fds->in + n)
387 #define FDS_OUT(fds, n)         (fds->out + n)
388 #define FDS_EX(fds, n)          (fds->ex + n)
389 
390 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
391 
392 static int max_select_fd(unsigned long n, fd_set_bits *fds)
393 {
394         unsigned long *open_fds;
395         unsigned long set;
396         int max;
397         struct fdtable *fdt;
398 
399         /* handle last in-complete long-word first */
400         set = ~(~0UL << (n & (BITS_PER_LONG-1)));
401         n /= BITS_PER_LONG;
402         fdt = files_fdtable(current->files);
403         open_fds = fdt->open_fds + n;
404         max = 0;
405         if (set) {
406                 set &= BITS(fds, n);
407                 if (set) {
408                         if (!(set & ~*open_fds))
409                                 goto get_max;
410                         return -EBADF;
411                 }
412         }
413         while (n) {
414                 open_fds--;
415                 n--;
416                 set = BITS(fds, n);
417                 if (!set)
418                         continue;
419                 if (set & ~*open_fds)
420                         return -EBADF;
421                 if (max)
422                         continue;
423 get_max:
424                 do {
425                         max++;
426                         set >>= 1;
427                 } while (set);
428                 max += n * BITS_PER_LONG;
429         }
430 
431         return max;
432 }
433 
434 #define POLLIN_SET (EPOLLRDNORM | EPOLLRDBAND | EPOLLIN | EPOLLHUP | EPOLLERR)
435 #define POLLOUT_SET (EPOLLWRBAND | EPOLLWRNORM | EPOLLOUT | EPOLLERR)
436 #define POLLEX_SET (EPOLLPRI)
437 
438 static inline void wait_key_set(poll_table *wait, unsigned long in,
439                                 unsigned long out, unsigned long bit,
440                                 __poll_t ll_flag)
441 {
442         wait->_key = POLLEX_SET | ll_flag;
443         if (in & bit)
444                 wait->_key |= POLLIN_SET;
445         if (out & bit)
446                 wait->_key |= POLLOUT_SET;
447 }
448 
449 static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
450 {
451         ktime_t expire, *to = NULL;
452         struct poll_wqueues table;
453         poll_table *wait;
454         int retval, i, timed_out = 0;
455         u64 slack = 0;
456         __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
457         unsigned long busy_start = 0;
458 
459         rcu_read_lock();
460         retval = max_select_fd(n, fds);
461         rcu_read_unlock();
462 
463         if (retval < 0)
464                 return retval;
465         n = retval;
466 
467         poll_initwait(&table);
468         wait = &table.pt;
469         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
470                 wait->_qproc = NULL;
471                 timed_out = 1;
472         }
473 
474         if (end_time && !timed_out)
475                 slack = select_estimate_accuracy(end_time);
476 
477         retval = 0;
478         for (;;) {
479                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
480                 bool can_busy_loop = false;
481 
482                 inp = fds->in; outp = fds->out; exp = fds->ex;
483                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
484 
485                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
486                         unsigned long in, out, ex, all_bits, bit = 1, j;
487                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
488                         __poll_t mask;
489 
490                         in = *inp++; out = *outp++; ex = *exp++;
491                         all_bits = in | out | ex;
492                         if (all_bits == 0) {
493                                 i += BITS_PER_LONG;
494                                 continue;
495                         }
496 
497                         for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) {
498                                 struct fd f;
499                                 if (i >= n)
500                                         break;
501                                 if (!(bit & all_bits))
502                                         continue;
503                                 f = fdget(i);
504                                 if (f.file) {
505                                         wait_key_set(wait, in, out, bit,
506                                                      busy_flag);
507                                         mask = vfs_poll(f.file, wait);
508 
509                                         fdput(f);
510                                         if ((mask & POLLIN_SET) && (in & bit)) {
511                                                 res_in |= bit;
512                                                 retval++;
513                                                 wait->_qproc = NULL;
514                                         }
515                                         if ((mask & POLLOUT_SET) && (out & bit)) {
516                                                 res_out |= bit;
517                                                 retval++;
518                                                 wait->_qproc = NULL;
519                                         }
520                                         if ((mask & POLLEX_SET) && (ex & bit)) {
521                                                 res_ex |= bit;
522                                                 retval++;
523                                                 wait->_qproc = NULL;
524                                         }
525                                         /* got something, stop busy polling */
526                                         if (retval) {
527                                                 can_busy_loop = false;
528                                                 busy_flag = 0;
529 
530                                         /*
531                                          * only remember a returned
532                                          * POLL_BUSY_LOOP if we asked for it
533                                          */
534                                         } else if (busy_flag & mask)
535                                                 can_busy_loop = true;
536 
537                                 }
538                         }
539                         if (res_in)
540                                 *rinp = res_in;
541                         if (res_out)
542                                 *routp = res_out;
543                         if (res_ex)
544                                 *rexp = res_ex;
545                         cond_resched();
546                 }
547                 wait->_qproc = NULL;
548                 if (retval || timed_out || signal_pending(current))
549                         break;
550                 if (table.error) {
551                         retval = table.error;
552                         break;
553                 }
554 
555                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
556                 if (can_busy_loop && !need_resched()) {
557                         if (!busy_start) {
558                                 busy_start = busy_loop_current_time();
559                                 continue;
560                         }
561                         if (!busy_loop_timeout(busy_start))
562                                 continue;
563                 }
564                 busy_flag = 0;
565 
566                 /*
567                  * If this is the first loop and we have a timeout
568                  * given, then we convert to ktime_t and set the to
569                  * pointer to the expiry value.
570                  */
571                 if (end_time && !to) {
572                         expire = timespec64_to_ktime(*end_time);
573                         to = &expire;
574                 }
575 
576                 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE,
577                                            to, slack))
578                         timed_out = 1;
579         }
580 
581         poll_freewait(&table);
582 
583         return retval;
584 }
585 
586 /*
587  * We can actually return ERESTARTSYS instead of EINTR, but I'd
588  * like to be certain this leads to no problems. So I return
589  * EINTR just for safety.
590  *
591  * Update: ERESTARTSYS breaks at least the xview clock binary, so
592  * I'm trying ERESTARTNOHAND which restart only when you want to.
593  */
594 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
595                            fd_set __user *exp, struct timespec64 *end_time)
596 {
597         fd_set_bits fds;
598         void *bits;
599         int ret, max_fds;
600         size_t size, alloc_size;
601         struct fdtable *fdt;
602         /* Allocate small arguments on the stack to save memory and be faster */
603         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
604 
605         ret = -EINVAL;
606         if (n < 0)
607                 goto out_nofds;
608 
609         /* max_fds can increase, so grab it once to avoid race */
610         rcu_read_lock();
611         fdt = files_fdtable(current->files);
612         max_fds = fdt->max_fds;
613         rcu_read_unlock();
614         if (n > max_fds)
615                 n = max_fds;
616 
617         /*
618          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
619          * since we used fdset we need to allocate memory in units of
620          * long-words. 
621          */
622         size = FDS_BYTES(n);
623         bits = stack_fds;
624         if (size > sizeof(stack_fds) / 6) {
625                 /* Not enough space in on-stack array; must use kmalloc */
626                 ret = -ENOMEM;
627                 if (size > (SIZE_MAX / 6))
628                         goto out_nofds;
629 
630                 alloc_size = 6 * size;
631                 bits = kvmalloc(alloc_size, GFP_KERNEL);
632                 if (!bits)
633                         goto out_nofds;
634         }
635         fds.in      = bits;
636         fds.out     = bits +   size;
637         fds.ex      = bits + 2*size;
638         fds.res_in  = bits + 3*size;
639         fds.res_out = bits + 4*size;
640         fds.res_ex  = bits + 5*size;
641 
642         if ((ret = get_fd_set(n, inp, fds.in)) ||
643             (ret = get_fd_set(n, outp, fds.out)) ||
644             (ret = get_fd_set(n, exp, fds.ex)))
645                 goto out;
646         zero_fd_set(n, fds.res_in);
647         zero_fd_set(n, fds.res_out);
648         zero_fd_set(n, fds.res_ex);
649 
650         ret = do_select(n, &fds, end_time);
651 
652         if (ret < 0)
653                 goto out;
654         if (!ret) {
655                 ret = -ERESTARTNOHAND;
656                 if (signal_pending(current))
657                         goto out;
658                 ret = 0;
659         }
660 
661         if (set_fd_set(n, inp, fds.res_in) ||
662             set_fd_set(n, outp, fds.res_out) ||
663             set_fd_set(n, exp, fds.res_ex))
664                 ret = -EFAULT;
665 
666 out:
667         if (bits != stack_fds)
668                 kvfree(bits);
669 out_nofds:
670         return ret;
671 }
672 
673 static int kern_select(int n, fd_set __user *inp, fd_set __user *outp,
674                        fd_set __user *exp, struct timeval __user *tvp)
675 {
676         struct timespec64 end_time, *to = NULL;
677         struct timeval tv;
678         int ret;
679 
680         if (tvp) {
681                 if (copy_from_user(&tv, tvp, sizeof(tv)))
682                         return -EFAULT;
683 
684                 to = &end_time;
685                 if (poll_select_set_timeout(to,
686                                 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
687                                 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
688                         return -EINVAL;
689         }
690 
691         ret = core_sys_select(n, inp, outp, exp, to);
692         ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
693 
694         return ret;
695 }
696 
697 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
698                 fd_set __user *, exp, struct timeval __user *, tvp)
699 {
700         return kern_select(n, inp, outp, exp, tvp);
701 }
702 
703 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
704                        fd_set __user *exp, struct timespec __user *tsp,
705                        const sigset_t __user *sigmask, size_t sigsetsize)
706 {
707         sigset_t ksigmask, sigsaved;
708         struct timespec64 ts, end_time, *to = NULL;
709         int ret;
710 
711         if (tsp) {
712                 if (get_timespec64(&ts, tsp))
713                         return -EFAULT;
714 
715                 to = &end_time;
716                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
717                         return -EINVAL;
718         }
719 
720         if (sigmask) {
721                 /* XXX: Don't preclude handling different sized sigset_t's.  */
722                 if (sigsetsize != sizeof(sigset_t))
723                         return -EINVAL;
724                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
725                         return -EFAULT;
726 
727                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
728                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
729         }
730 
731         ret = core_sys_select(n, inp, outp, exp, to);
732         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
733 
734         if (ret == -ERESTARTNOHAND) {
735                 /*
736                  * Don't restore the signal mask yet. Let do_signal() deliver
737                  * the signal on the way back to userspace, before the signal
738                  * mask is restored.
739                  */
740                 if (sigmask) {
741                         memcpy(&current->saved_sigmask, &sigsaved,
742                                         sizeof(sigsaved));
743                         set_restore_sigmask();
744                 }
745         } else if (sigmask)
746                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
747 
748         return ret;
749 }
750 
751 /*
752  * Most architectures can't handle 7-argument syscalls. So we provide a
753  * 6-argument version where the sixth argument is a pointer to a structure
754  * which has a pointer to the sigset_t itself followed by a size_t containing
755  * the sigset size.
756  */
757 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
758                 fd_set __user *, exp, struct timespec __user *, tsp,
759                 void __user *, sig)
760 {
761         size_t sigsetsize = 0;
762         sigset_t __user *up = NULL;
763 
764         if (sig) {
765                 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
766                     || __get_user(up, (sigset_t __user * __user *)sig)
767                     || __get_user(sigsetsize,
768                                 (size_t __user *)(sig+sizeof(void *))))
769                         return -EFAULT;
770         }
771 
772         return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize);
773 }
774 
775 #ifdef __ARCH_WANT_SYS_OLD_SELECT
776 struct sel_arg_struct {
777         unsigned long n;
778         fd_set __user *inp, *outp, *exp;
779         struct timeval __user *tvp;
780 };
781 
782 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg)
783 {
784         struct sel_arg_struct a;
785 
786         if (copy_from_user(&a, arg, sizeof(a)))
787                 return -EFAULT;
788         return kern_select(a.n, a.inp, a.outp, a.exp, a.tvp);
789 }
790 #endif
791 
792 struct poll_list {
793         struct poll_list *next;
794         int len;
795         struct pollfd entries[0];
796 };
797 
798 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
799 
800 /*
801  * Fish for pollable events on the pollfd->fd file descriptor. We're only
802  * interested in events matching the pollfd->events mask, and the result
803  * matching that mask is both recorded in pollfd->revents and returned. The
804  * pwait poll_table will be used by the fd-provided poll handler for waiting,
805  * if pwait->_qproc is non-NULL.
806  */
807 static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
808                                      bool *can_busy_poll,
809                                      __poll_t busy_flag)
810 {
811         int fd = pollfd->fd;
812         __poll_t mask = 0, filter;
813         struct fd f;
814 
815         if (fd < 0)
816                 goto out;
817         mask = EPOLLNVAL;
818         f = fdget(fd);
819         if (!f.file)
820                 goto out;
821 
822         /* userland u16 ->events contains POLL... bitmap */
823         filter = demangle_poll(pollfd->events) | EPOLLERR | EPOLLHUP;
824         pwait->_key = filter | busy_flag;
825         mask = vfs_poll(f.file, pwait);
826         if (mask & busy_flag)
827                 *can_busy_poll = true;
828         mask &= filter;         /* Mask out unneeded events. */
829         fdput(f);
830 
831 out:
832         /* ... and so does ->revents */
833         pollfd->revents = mangle_poll(mask);
834         return mask;
835 }
836 
837 static int do_poll(struct poll_list *list, struct poll_wqueues *wait,
838                    struct timespec64 *end_time)
839 {
840         poll_table* pt = &wait->pt;
841         ktime_t expire, *to = NULL;
842         int timed_out = 0, count = 0;
843         u64 slack = 0;
844         __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;
845         unsigned long busy_start = 0;
846 
847         /* Optimise the no-wait case */
848         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
849                 pt->_qproc = NULL;
850                 timed_out = 1;
851         }
852 
853         if (end_time && !timed_out)
854                 slack = select_estimate_accuracy(end_time);
855 
856         for (;;) {
857                 struct poll_list *walk;
858                 bool can_busy_loop = false;
859 
860                 for (walk = list; walk != NULL; walk = walk->next) {
861                         struct pollfd * pfd, * pfd_end;
862 
863                         pfd = walk->entries;
864                         pfd_end = pfd + walk->len;
865                         for (; pfd != pfd_end; pfd++) {
866                                 /*
867                                  * Fish for events. If we found one, record it
868                                  * and kill poll_table->_qproc, so we don't
869                                  * needlessly register any other waiters after
870                                  * this. They'll get immediately deregistered
871                                  * when we break out and return.
872                                  */
873                                 if (do_pollfd(pfd, pt, &can_busy_loop,
874                                               busy_flag)) {
875                                         count++;
876                                         pt->_qproc = NULL;
877                                         /* found something, stop busy polling */
878                                         busy_flag = 0;
879                                         can_busy_loop = false;
880                                 }
881                         }
882                 }
883                 /*
884                  * All waiters have already been registered, so don't provide
885                  * a poll_table->_qproc to them on the next loop iteration.
886                  */
887                 pt->_qproc = NULL;
888                 if (!count) {
889                         count = wait->error;
890                         if (signal_pending(current))
891                                 count = -EINTR;
892                 }
893                 if (count || timed_out)
894                         break;
895 
896                 /* only if found POLL_BUSY_LOOP sockets && not out of time */
897                 if (can_busy_loop && !need_resched()) {
898                         if (!busy_start) {
899                                 busy_start = busy_loop_current_time();
900                                 continue;
901                         }
902                         if (!busy_loop_timeout(busy_start))
903                                 continue;
904                 }
905                 busy_flag = 0;
906 
907                 /*
908                  * If this is the first loop and we have a timeout
909                  * given, then we convert to ktime_t and set the to
910                  * pointer to the expiry value.
911                  */
912                 if (end_time && !to) {
913                         expire = timespec64_to_ktime(*end_time);
914                         to = &expire;
915                 }
916 
917                 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack))
918                         timed_out = 1;
919         }
920         return count;
921 }
922 
923 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
924                         sizeof(struct pollfd))
925 
926 static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
927                 struct timespec64 *end_time)
928 {
929         struct poll_wqueues table;
930         int err = -EFAULT, fdcount, len, size;
931         /* Allocate small arguments on the stack to save memory and be
932            faster - use long to make sure the buffer is aligned properly
933            on 64 bit archs to avoid unaligned access */
934         long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
935         struct poll_list *const head = (struct poll_list *)stack_pps;
936         struct poll_list *walk = head;
937         unsigned long todo = nfds;
938 
939         if (nfds > rlimit(RLIMIT_NOFILE))
940                 return -EINVAL;
941 
942         len = min_t(unsigned int, nfds, N_STACK_PPS);
943         for (;;) {
944                 walk->next = NULL;
945                 walk->len = len;
946                 if (!len)
947                         break;
948 
949                 if (copy_from_user(walk->entries, ufds + nfds-todo,
950                                         sizeof(struct pollfd) * walk->len))
951                         goto out_fds;
952 
953                 todo -= walk->len;
954                 if (!todo)
955                         break;
956 
957                 len = min(todo, POLLFD_PER_PAGE);
958                 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
959                 walk = walk->next = kmalloc(size, GFP_KERNEL);
960                 if (!walk) {
961                         err = -ENOMEM;
962                         goto out_fds;
963                 }
964         }
965 
966         poll_initwait(&table);
967         fdcount = do_poll(head, &table, end_time);
968         poll_freewait(&table);
969 
970         for (walk = head; walk; walk = walk->next) {
971                 struct pollfd *fds = walk->entries;
972                 int j;
973 
974                 for (j = 0; j < walk->len; j++, ufds++)
975                         if (__put_user(fds[j].revents, &ufds->revents))
976                                 goto out_fds;
977         }
978 
979         err = fdcount;
980 out_fds:
981         walk = head->next;
982         while (walk) {
983                 struct poll_list *pos = walk;
984                 walk = walk->next;
985                 kfree(pos);
986         }
987 
988         return err;
989 }
990 
991 static long do_restart_poll(struct restart_block *restart_block)
992 {
993         struct pollfd __user *ufds = restart_block->poll.ufds;
994         int nfds = restart_block->poll.nfds;
995         struct timespec64 *to = NULL, end_time;
996         int ret;
997 
998         if (restart_block->poll.has_timeout) {
999                 end_time.tv_sec = restart_block->poll.tv_sec;
1000                 end_time.tv_nsec = restart_block->poll.tv_nsec;
1001                 to = &end_time;
1002         }
1003 
1004         ret = do_sys_poll(ufds, nfds, to);
1005 
1006         if (ret == -EINTR) {
1007                 restart_block->fn = do_restart_poll;
1008                 ret = -ERESTART_RESTARTBLOCK;
1009         }
1010         return ret;
1011 }
1012 
1013 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
1014                 int, timeout_msecs)
1015 {
1016         struct timespec64 end_time, *to = NULL;
1017         int ret;
1018 
1019         if (timeout_msecs >= 0) {
1020                 to = &end_time;
1021                 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
1022                         NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
1023         }
1024 
1025         ret = do_sys_poll(ufds, nfds, to);
1026 
1027         if (ret == -EINTR) {
1028                 struct restart_block *restart_block;
1029 
1030                 restart_block = &current->restart_block;
1031                 restart_block->fn = do_restart_poll;
1032                 restart_block->poll.ufds = ufds;
1033                 restart_block->poll.nfds = nfds;
1034 
1035                 if (timeout_msecs >= 0) {
1036                         restart_block->poll.tv_sec = end_time.tv_sec;
1037                         restart_block->poll.tv_nsec = end_time.tv_nsec;
1038                         restart_block->poll.has_timeout = 1;
1039                 } else
1040                         restart_block->poll.has_timeout = 0;
1041 
1042                 ret = -ERESTART_RESTARTBLOCK;
1043         }
1044         return ret;
1045 }
1046 
1047 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds,
1048                 struct timespec __user *, tsp, const sigset_t __user *, sigmask,
1049                 size_t, sigsetsize)
1050 {
1051         sigset_t ksigmask, sigsaved;
1052         struct timespec64 ts, end_time, *to = NULL;
1053         int ret;
1054 
1055         if (tsp) {
1056                 if (get_timespec64(&ts, tsp))
1057                         return -EFAULT;
1058 
1059                 to = &end_time;
1060                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1061                         return -EINVAL;
1062         }
1063 
1064         if (sigmask) {
1065                 /* XXX: Don't preclude handling different sized sigset_t's.  */
1066                 if (sigsetsize != sizeof(sigset_t))
1067                         return -EINVAL;
1068                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
1069                         return -EFAULT;
1070 
1071                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1072                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1073         }
1074 
1075         ret = do_sys_poll(ufds, nfds, to);
1076 
1077         /* We can restart this syscall, usually */
1078         if (ret == -EINTR) {
1079                 /*
1080                  * Don't restore the signal mask yet. Let do_signal() deliver
1081                  * the signal on the way back to userspace, before the signal
1082                  * mask is restored.
1083                  */
1084                 if (sigmask) {
1085                         memcpy(&current->saved_sigmask, &sigsaved,
1086                                         sizeof(sigsaved));
1087                         set_restore_sigmask();
1088                 }
1089                 ret = -ERESTARTNOHAND;
1090         } else if (sigmask)
1091                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1092 
1093         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
1094 
1095         return ret;
1096 }
1097 
1098 #ifdef CONFIG_COMPAT
1099 #define __COMPAT_NFDBITS       (8 * sizeof(compat_ulong_t))
1100 
1101 static
1102 int compat_poll_select_copy_remaining(struct timespec64 *end_time, void __user *p,
1103                                       int timeval, int ret)
1104 {
1105         struct timespec64 ts;
1106 
1107         if (!p)
1108                 return ret;
1109 
1110         if (current->personality & STICKY_TIMEOUTS)
1111                 goto sticky;
1112 
1113         /* No update for zero timeout */
1114         if (!end_time->tv_sec && !end_time->tv_nsec)
1115                 return ret;
1116 
1117         ktime_get_ts64(&ts);
1118         ts = timespec64_sub(*end_time, ts);
1119         if (ts.tv_sec < 0)
1120                 ts.tv_sec = ts.tv_nsec = 0;
1121 
1122         if (timeval) {
1123                 struct old_timeval32 rtv;
1124 
1125                 rtv.tv_sec = ts.tv_sec;
1126                 rtv.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
1127 
1128                 if (!copy_to_user(p, &rtv, sizeof(rtv)))
1129                         return ret;
1130         } else {
1131                 if (!put_old_timespec32(&ts, p))
1132                         return ret;
1133         }
1134         /*
1135          * If an application puts its timeval in read-only memory, we
1136          * don't want the Linux-specific update to the timeval to
1137          * cause a fault after the select has completed
1138          * successfully. However, because we're not updating the
1139          * timeval, we can't restart the system call.
1140          */
1141 
1142 sticky:
1143         if (ret == -ERESTARTNOHAND)
1144                 ret = -EINTR;
1145         return ret;
1146 }
1147 
1148 /*
1149  * Ooo, nasty.  We need here to frob 32-bit unsigned longs to
1150  * 64-bit unsigned longs.
1151  */
1152 static
1153 int compat_get_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
1154                         unsigned long *fdset)
1155 {
1156         if (ufdset) {
1157                 return compat_get_bitmap(fdset, ufdset, nr);
1158         } else {
1159                 zero_fd_set(nr, fdset);
1160                 return 0;
1161         }
1162 }
1163 
1164 static
1165 int compat_set_fd_set(unsigned long nr, compat_ulong_t __user *ufdset,
1166                       unsigned long *fdset)
1167 {
1168         if (!ufdset)
1169                 return 0;
1170         return compat_put_bitmap(ufdset, fdset, nr);
1171 }
1172 
1173 
1174 /*
1175  * This is a virtual copy of sys_select from fs/select.c and probably
1176  * should be compared to it from time to time
1177  */
1178 
1179 /*
1180  * We can actually return ERESTARTSYS instead of EINTR, but I'd
1181  * like to be certain this leads to no problems. So I return
1182  * EINTR just for safety.
1183  *
1184  * Update: ERESTARTSYS breaks at least the xview clock binary, so
1185  * I'm trying ERESTARTNOHAND which restart only when you want to.
1186  */
1187 static int compat_core_sys_select(int n, compat_ulong_t __user *inp,
1188         compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1189         struct timespec64 *end_time)
1190 {
1191         fd_set_bits fds;
1192         void *bits;
1193         int size, max_fds, ret = -EINVAL;
1194         struct fdtable *fdt;
1195         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
1196 
1197         if (n < 0)
1198                 goto out_nofds;
1199 
1200         /* max_fds can increase, so grab it once to avoid race */
1201         rcu_read_lock();
1202         fdt = files_fdtable(current->files);
1203         max_fds = fdt->max_fds;
1204         rcu_read_unlock();
1205         if (n > max_fds)
1206                 n = max_fds;
1207 
1208         /*
1209          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
1210          * since we used fdset we need to allocate memory in units of
1211          * long-words.
1212          */
1213         size = FDS_BYTES(n);
1214         bits = stack_fds;
1215         if (size > sizeof(stack_fds) / 6) {
1216                 bits = kmalloc_array(6, size, GFP_KERNEL);
1217                 ret = -ENOMEM;
1218                 if (!bits)
1219                         goto out_nofds;
1220         }
1221         fds.in      = (unsigned long *)  bits;
1222         fds.out     = (unsigned long *) (bits +   size);
1223         fds.ex      = (unsigned long *) (bits + 2*size);
1224         fds.res_in  = (unsigned long *) (bits + 3*size);
1225         fds.res_out = (unsigned long *) (bits + 4*size);
1226         fds.res_ex  = (unsigned long *) (bits + 5*size);
1227 
1228         if ((ret = compat_get_fd_set(n, inp, fds.in)) ||
1229             (ret = compat_get_fd_set(n, outp, fds.out)) ||
1230             (ret = compat_get_fd_set(n, exp, fds.ex)))
1231                 goto out;
1232         zero_fd_set(n, fds.res_in);
1233         zero_fd_set(n, fds.res_out);
1234         zero_fd_set(n, fds.res_ex);
1235 
1236         ret = do_select(n, &fds, end_time);
1237 
1238         if (ret < 0)
1239                 goto out;
1240         if (!ret) {
1241                 ret = -ERESTARTNOHAND;
1242                 if (signal_pending(current))
1243                         goto out;
1244                 ret = 0;
1245         }
1246 
1247         if (compat_set_fd_set(n, inp, fds.res_in) ||
1248             compat_set_fd_set(n, outp, fds.res_out) ||
1249             compat_set_fd_set(n, exp, fds.res_ex))
1250                 ret = -EFAULT;
1251 out:
1252         if (bits != stack_fds)
1253                 kfree(bits);
1254 out_nofds:
1255         return ret;
1256 }
1257 
1258 static int do_compat_select(int n, compat_ulong_t __user *inp,
1259         compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1260         struct old_timeval32 __user *tvp)
1261 {
1262         struct timespec64 end_time, *to = NULL;
1263         struct old_timeval32 tv;
1264         int ret;
1265 
1266         if (tvp) {
1267                 if (copy_from_user(&tv, tvp, sizeof(tv)))
1268                         return -EFAULT;
1269 
1270                 to = &end_time;
1271                 if (poll_select_set_timeout(to,
1272                                 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
1273                                 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
1274                         return -EINVAL;
1275         }
1276 
1277         ret = compat_core_sys_select(n, inp, outp, exp, to);
1278         ret = compat_poll_select_copy_remaining(&end_time, tvp, 1, ret);
1279 
1280         return ret;
1281 }
1282 
1283 COMPAT_SYSCALL_DEFINE5(select, int, n, compat_ulong_t __user *, inp,
1284         compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
1285         struct old_timeval32 __user *, tvp)
1286 {
1287         return do_compat_select(n, inp, outp, exp, tvp);
1288 }
1289 
1290 struct compat_sel_arg_struct {
1291         compat_ulong_t n;
1292         compat_uptr_t inp;
1293         compat_uptr_t outp;
1294         compat_uptr_t exp;
1295         compat_uptr_t tvp;
1296 };
1297 
1298 COMPAT_SYSCALL_DEFINE1(old_select, struct compat_sel_arg_struct __user *, arg)
1299 {
1300         struct compat_sel_arg_struct a;
1301 
1302         if (copy_from_user(&a, arg, sizeof(a)))
1303                 return -EFAULT;
1304         return do_compat_select(a.n, compat_ptr(a.inp), compat_ptr(a.outp),
1305                                 compat_ptr(a.exp), compat_ptr(a.tvp));
1306 }
1307 
1308 static long do_compat_pselect(int n, compat_ulong_t __user *inp,
1309         compat_ulong_t __user *outp, compat_ulong_t __user *exp,
1310         struct old_timespec32 __user *tsp, compat_sigset_t __user *sigmask,
1311         compat_size_t sigsetsize)
1312 {
1313         sigset_t ksigmask, sigsaved;
1314         struct timespec64 ts, end_time, *to = NULL;
1315         int ret;
1316 
1317         if (tsp) {
1318                 if (get_old_timespec32(&ts, tsp))
1319                         return -EFAULT;
1320 
1321                 to = &end_time;
1322                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1323                         return -EINVAL;
1324         }
1325 
1326         if (sigmask) {
1327                 if (sigsetsize != sizeof(compat_sigset_t))
1328                         return -EINVAL;
1329                 if (get_compat_sigset(&ksigmask, sigmask))
1330                         return -EFAULT;
1331 
1332                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1333                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1334         }
1335 
1336         ret = compat_core_sys_select(n, inp, outp, exp, to);
1337         ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
1338 
1339         if (ret == -ERESTARTNOHAND) {
1340                 /*
1341                  * Don't restore the signal mask yet. Let do_signal() deliver
1342                  * the signal on the way back to userspace, before the signal
1343                  * mask is restored.
1344                  */
1345                 if (sigmask) {
1346                         memcpy(&current->saved_sigmask, &sigsaved,
1347                                         sizeof(sigsaved));
1348                         set_restore_sigmask();
1349                 }
1350         } else if (sigmask)
1351                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1352 
1353         return ret;
1354 }
1355 
1356 COMPAT_SYSCALL_DEFINE6(pselect6, int, n, compat_ulong_t __user *, inp,
1357         compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
1358         struct old_timespec32 __user *, tsp, void __user *, sig)
1359 {
1360         compat_size_t sigsetsize = 0;
1361         compat_uptr_t up = 0;
1362 
1363         if (sig) {
1364                 if (!access_ok(VERIFY_READ, sig,
1365                                 sizeof(compat_uptr_t)+sizeof(compat_size_t)) ||
1366                         __get_user(up, (compat_uptr_t __user *)sig) ||
1367                         __get_user(sigsetsize,
1368                                 (compat_size_t __user *)(sig+sizeof(up))))
1369                         return -EFAULT;
1370         }
1371         return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(up),
1372                                  sigsetsize);
1373 }
1374 
1375 COMPAT_SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds,
1376         unsigned int,  nfds, struct old_timespec32 __user *, tsp,
1377         const compat_sigset_t __user *, sigmask, compat_size_t, sigsetsize)
1378 {
1379         sigset_t ksigmask, sigsaved;
1380         struct timespec64 ts, end_time, *to = NULL;
1381         int ret;
1382 
1383         if (tsp) {
1384                 if (get_old_timespec32(&ts, tsp))
1385                         return -EFAULT;
1386 
1387                 to = &end_time;
1388                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
1389                         return -EINVAL;
1390         }
1391 
1392         if (sigmask) {
1393                 if (sigsetsize != sizeof(compat_sigset_t))
1394                         return -EINVAL;
1395                 if (get_compat_sigset(&ksigmask, sigmask))
1396                         return -EFAULT;
1397 
1398                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
1399                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
1400         }
1401 
1402         ret = do_sys_poll(ufds, nfds, to);
1403 
1404         /* We can restart this syscall, usually */
1405         if (ret == -EINTR) {
1406                 /*
1407                  * Don't restore the signal mask yet. Let do_signal() deliver
1408                  * the signal on the way back to userspace, before the signal
1409                  * mask is restored.
1410                  */
1411                 if (sigmask) {
1412                         memcpy(&current->saved_sigmask, &sigsaved,
1413                                 sizeof(sigsaved));
1414                         set_restore_sigmask();
1415                 }
1416                 ret = -ERESTARTNOHAND;
1417         } else if (sigmask)
1418                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
1419 
1420         ret = compat_poll_select_copy_remaining(&end_time, tsp, 0, ret);
1421 
1422         return ret;
1423 }
1424 #endif
1425 

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