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