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 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 198 { 199 struct poll_table_entry *entry; 200 201 entry = container_of(wait, struct poll_table_entry, wait); 202 if (key && !((unsigned long)key & entry->key)) 203 return 0; 204 return __pollwake(wait, mode, sync, key); 205 } 206 207 /* Add a new entry */ 208 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 209 poll_table *p) 210 { 211 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); 212 struct poll_table_entry *entry = poll_get_entry(pwq); 213 if (!entry) 214 return; 215 get_file(filp); 216 entry->filp = filp; 217 entry->wait_address = wait_address; 218 entry->key = p->key; 219 init_waitqueue_func_entry(&entry->wait, pollwake); 220 entry->wait.private = pwq; 221 add_wait_queue(wait_address, &entry->wait); 222 } 223 224 int poll_schedule_timeout(struct poll_wqueues *pwq, int state, 225 ktime_t *expires, unsigned long slack) 226 { 227 int rc = -EINTR; 228 229 set_current_state(state); 230 if (!pwq->triggered) 231 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS); 232 __set_current_state(TASK_RUNNING); 233 234 /* 235 * Prepare for the next iteration. 236 * 237 * The following set_mb() serves two purposes. First, it's 238 * the counterpart rmb of the wmb in pollwake() such that data 239 * written before wake up is always visible after wake up. 240 * Second, the full barrier guarantees that triggered clearing 241 * doesn't pass event check of the next iteration. Note that 242 * this problem doesn't exist for the first iteration as 243 * add_wait_queue() has full barrier semantics. 244 */ 245 set_mb(pwq->triggered, 0); 246 247 return rc; 248 } 249 EXPORT_SYMBOL(poll_schedule_timeout); 250 251 /** 252 * poll_select_set_timeout - helper function to setup the timeout value 253 * @to: pointer to timespec variable for the final timeout 254 * @sec: seconds (from user space) 255 * @nsec: nanoseconds (from user space) 256 * 257 * Note, we do not use a timespec for the user space value here, That 258 * way we can use the function for timeval and compat interfaces as well. 259 * 260 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. 261 */ 262 int poll_select_set_timeout(struct timespec *to, long sec, long nsec) 263 { 264 struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec}; 265 266 if (!timespec_valid(&ts)) 267 return -EINVAL; 268 269 /* Optimize for the zero timeout value here */ 270 if (!sec && !nsec) { 271 to->tv_sec = to->tv_nsec = 0; 272 } else { 273 ktime_get_ts(to); 274 *to = timespec_add_safe(*to, ts); 275 } 276 return 0; 277 } 278 279 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p, 280 int timeval, int ret) 281 { 282 struct timespec rts; 283 struct timeval rtv; 284 285 if (!p) 286 return ret; 287 288 if (current->personality & STICKY_TIMEOUTS) 289 goto sticky; 290 291 /* No update for zero timeout */ 292 if (!end_time->tv_sec && !end_time->tv_nsec) 293 return ret; 294 295 ktime_get_ts(&rts); 296 rts = timespec_sub(*end_time, rts); 297 if (rts.tv_sec < 0) 298 rts.tv_sec = rts.tv_nsec = 0; 299 300 if (timeval) { 301 rtv.tv_sec = rts.tv_sec; 302 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 303 304 if (!copy_to_user(p, &rtv, sizeof(rtv))) 305 return ret; 306 307 } else if (!copy_to_user(p, &rts, sizeof(rts))) 308 return ret; 309 310 /* 311 * If an application puts its timeval in read-only memory, we 312 * don't want the Linux-specific update to the timeval to 313 * cause a fault after the select has completed 314 * successfully. However, because we're not updating the 315 * timeval, we can't restart the system call. 316 */ 317 318 sticky: 319 if (ret == -ERESTARTNOHAND) 320 ret = -EINTR; 321 return ret; 322 } 323 324 #define FDS_IN(fds, n) (fds->in + n) 325 #define FDS_OUT(fds, n) (fds->out + n) 326 #define FDS_EX(fds, n) (fds->ex + n) 327 328 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 329 330 static int max_select_fd(unsigned long n, fd_set_bits *fds) 331 { 332 unsigned long *open_fds; 333 unsigned long set; 334 int max; 335 struct fdtable *fdt; 336 337 /* handle last in-complete long-word first */ 338 set = ~(~0UL << (n & (__NFDBITS-1))); 339 n /= __NFDBITS; 340 fdt = files_fdtable(current->files); 341 open_fds = fdt->open_fds->fds_bits+n; 342 max = 0; 343 if (set) { 344 set &= BITS(fds, n); 345 if (set) { 346 if (!(set & ~*open_fds)) 347 goto get_max; 348 return -EBADF; 349 } 350 } 351 while (n) { 352 open_fds--; 353 n--; 354 set = BITS(fds, n); 355 if (!set) 356 continue; 357 if (set & ~*open_fds) 358 return -EBADF; 359 if (max) 360 continue; 361 get_max: 362 do { 363 max++; 364 set >>= 1; 365 } while (set); 366 max += n * __NFDBITS; 367 } 368 369 return max; 370 } 371 372 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) 373 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) 374 #define POLLEX_SET (POLLPRI) 375 376 static inline void wait_key_set(poll_table *wait, unsigned long in, 377 unsigned long out, unsigned long bit) 378 { 379 if (wait) { 380 wait->key = POLLEX_SET; 381 if (in & bit) 382 wait->key |= POLLIN_SET; 383 if (out & bit) 384 wait->key |= POLLOUT_SET; 385 } 386 } 387 388 int do_select(int n, fd_set_bits *fds, struct timespec *end_time) 389 { 390 ktime_t expire, *to = NULL; 391 struct poll_wqueues table; 392 poll_table *wait; 393 int retval, i, timed_out = 0; 394 unsigned long slack = 0; 395 396 rcu_read_lock(); 397 retval = max_select_fd(n, fds); 398 rcu_read_unlock(); 399 400 if (retval < 0) 401 return retval; 402 n = retval; 403 404 poll_initwait(&table); 405 wait = &table.pt; 406 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 407 wait = NULL; 408 timed_out = 1; 409 } 410 411 if (end_time && !timed_out) 412 slack = estimate_accuracy(end_time); 413 414 retval = 0; 415 for (;;) { 416 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; 417 418 inp = fds->in; outp = fds->out; exp = fds->ex; 419 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; 420 421 for (i = 0; i < n; ++rinp, ++routp, ++rexp) { 422 unsigned long in, out, ex, all_bits, bit = 1, mask, j; 423 unsigned long res_in = 0, res_out = 0, res_ex = 0; 424 const struct file_operations *f_op = NULL; 425 struct file *file = NULL; 426 427 in = *inp++; out = *outp++; ex = *exp++; 428 all_bits = in | out | ex; 429 if (all_bits == 0) { 430 i += __NFDBITS; 431 continue; 432 } 433 434 for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) { 435 int fput_needed; 436 if (i >= n) 437 break; 438 if (!(bit & all_bits)) 439 continue; 440 file = fget_light(i, &fput_needed); 441 if (file) { 442 f_op = file->f_op; 443 mask = DEFAULT_POLLMASK; 444 if (f_op && f_op->poll) { 445 wait_key_set(wait, in, out, bit); 446 mask = (*f_op->poll)(file, wait); 447 } 448 fput_light(file, fput_needed); 449 if ((mask & POLLIN_SET) && (in & bit)) { 450 res_in |= bit; 451 retval++; 452 wait = NULL; 453 } 454 if ((mask & POLLOUT_SET) && (out & bit)) { 455 res_out |= bit; 456 retval++; 457 wait = NULL; 458 } 459 if ((mask & POLLEX_SET) && (ex & bit)) { 460 res_ex |= bit; 461 retval++; 462 wait = NULL; 463 } 464 } 465 } 466 if (res_in) 467 *rinp = res_in; 468 if (res_out) 469 *routp = res_out; 470 if (res_ex) 471 *rexp = res_ex; 472 cond_resched(); 473 } 474 wait = NULL; 475 if (retval || timed_out || signal_pending(current)) 476 break; 477 if (table.error) { 478 retval = table.error; 479 break; 480 } 481 482 /* 483 * If this is the first loop and we have a timeout 484 * given, then we convert to ktime_t and set the to 485 * pointer to the expiry value. 486 */ 487 if (end_time && !to) { 488 expire = timespec_to_ktime(*end_time); 489 to = &expire; 490 } 491 492 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 493 to, slack)) 494 timed_out = 1; 495 } 496 497 poll_freewait(&table); 498 499 return retval; 500 } 501 502 /* 503 * We can actually return ERESTARTSYS instead of EINTR, but I'd 504 * like to be certain this leads to no problems. So I return 505 * EINTR just for safety. 506 * 507 * Update: ERESTARTSYS breaks at least the xview clock binary, so 508 * I'm trying ERESTARTNOHAND which restart only when you want to. 509 */ 510 #define MAX_SELECT_SECONDS \ 511 ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1) 512 513 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 514 fd_set __user *exp, struct timespec *end_time) 515 { 516 fd_set_bits fds; 517 void *bits; 518 int ret, max_fds; 519 unsigned int size; 520 struct fdtable *fdt; 521 /* Allocate small arguments on the stack to save memory and be faster */ 522 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 523 524 ret = -EINVAL; 525 if (n < 0) 526 goto out_nofds; 527 528 /* max_fds can increase, so grab it once to avoid race */ 529 rcu_read_lock(); 530 fdt = files_fdtable(current->files); 531 max_fds = fdt->max_fds; 532 rcu_read_unlock(); 533 if (n > max_fds) 534 n = max_fds; 535 536 /* 537 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 538 * since we used fdset we need to allocate memory in units of 539 * long-words. 540 */ 541 size = FDS_BYTES(n); 542 bits = stack_fds; 543 if (size > sizeof(stack_fds) / 6) { 544 /* Not enough space in on-stack array; must use kmalloc */ 545 ret = -ENOMEM; 546 bits = kmalloc(6 * size, GFP_KERNEL); 547 if (!bits) 548 goto out_nofds; 549 } 550 fds.in = bits; 551 fds.out = bits + size; 552 fds.ex = bits + 2*size; 553 fds.res_in = bits + 3*size; 554 fds.res_out = bits + 4*size; 555 fds.res_ex = bits + 5*size; 556 557 if ((ret = get_fd_set(n, inp, fds.in)) || 558 (ret = get_fd_set(n, outp, fds.out)) || 559 (ret = get_fd_set(n, exp, fds.ex))) 560 goto out; 561 zero_fd_set(n, fds.res_in); 562 zero_fd_set(n, fds.res_out); 563 zero_fd_set(n, fds.res_ex); 564 565 ret = do_select(n, &fds, end_time); 566 567 if (ret < 0) 568 goto out; 569 if (!ret) { 570 ret = -ERESTARTNOHAND; 571 if (signal_pending(current)) 572 goto out; 573 ret = 0; 574 } 575 576 if (set_fd_set(n, inp, fds.res_in) || 577 set_fd_set(n, outp, fds.res_out) || 578 set_fd_set(n, exp, fds.res_ex)) 579 ret = -EFAULT; 580 581 out: 582 if (bits != stack_fds) 583 kfree(bits); 584 out_nofds: 585 return ret; 586 } 587 588 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 589 fd_set __user *, exp, struct timeval __user *, tvp) 590 { 591 struct timespec end_time, *to = NULL; 592 struct timeval tv; 593 int ret; 594 595 if (tvp) { 596 if (copy_from_user(&tv, tvp, sizeof(tv))) 597 return -EFAULT; 598 599 to = &end_time; 600 if (poll_select_set_timeout(to, 601 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 602 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 603 return -EINVAL; 604 } 605 606 ret = core_sys_select(n, inp, outp, exp, to); 607 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret); 608 609 return ret; 610 } 611 612 #ifdef HAVE_SET_RESTORE_SIGMASK 613 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 614 fd_set __user *exp, struct timespec __user *tsp, 615 const sigset_t __user *sigmask, size_t sigsetsize) 616 { 617 sigset_t ksigmask, sigsaved; 618 struct timespec ts, end_time, *to = NULL; 619 int ret; 620 621 if (tsp) { 622 if (copy_from_user(&ts, tsp, sizeof(ts))) 623 return -EFAULT; 624 625 to = &end_time; 626 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 627 return -EINVAL; 628 } 629 630 if (sigmask) { 631 /* XXX: Don't preclude handling different sized sigset_t's. */ 632 if (sigsetsize != sizeof(sigset_t)) 633 return -EINVAL; 634 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 635 return -EFAULT; 636 637 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 638 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 639 } 640 641 ret = core_sys_select(n, inp, outp, exp, to); 642 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 643 644 if (ret == -ERESTARTNOHAND) { 645 /* 646 * Don't restore the signal mask yet. Let do_signal() deliver 647 * the signal on the way back to userspace, before the signal 648 * mask is restored. 649 */ 650 if (sigmask) { 651 memcpy(¤t->saved_sigmask, &sigsaved, 652 sizeof(sigsaved)); 653 set_restore_sigmask(); 654 } 655 } else if (sigmask) 656 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 657 658 return ret; 659 } 660 661 /* 662 * Most architectures can't handle 7-argument syscalls. So we provide a 663 * 6-argument version where the sixth argument is a pointer to a structure 664 * which has a pointer to the sigset_t itself followed by a size_t containing 665 * the sigset size. 666 */ 667 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 668 fd_set __user *, exp, struct timespec __user *, tsp, 669 void __user *, sig) 670 { 671 size_t sigsetsize = 0; 672 sigset_t __user *up = NULL; 673 674 if (sig) { 675 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) 676 || __get_user(up, (sigset_t __user * __user *)sig) 677 || __get_user(sigsetsize, 678 (size_t __user *)(sig+sizeof(void *)))) 679 return -EFAULT; 680 } 681 682 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize); 683 } 684 #endif /* HAVE_SET_RESTORE_SIGMASK */ 685 686 struct poll_list { 687 struct poll_list *next; 688 int len; 689 struct pollfd entries[0]; 690 }; 691 692 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 693 694 /* 695 * Fish for pollable events on the pollfd->fd file descriptor. We're only 696 * interested in events matching the pollfd->events mask, and the result 697 * matching that mask is both recorded in pollfd->revents and returned. The 698 * pwait poll_table will be used by the fd-provided poll handler for waiting, 699 * if non-NULL. 700 */ 701 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) 702 { 703 unsigned int mask; 704 int fd; 705 706 mask = 0; 707 fd = pollfd->fd; 708 if (fd >= 0) { 709 int fput_needed; 710 struct file * file; 711 712 file = fget_light(fd, &fput_needed); 713 mask = POLLNVAL; 714 if (file != NULL) { 715 mask = DEFAULT_POLLMASK; 716 if (file->f_op && file->f_op->poll) { 717 if (pwait) 718 pwait->key = pollfd->events | 719 POLLERR | POLLHUP; 720 mask = file->f_op->poll(file, pwait); 721 } 722 /* Mask out unneeded events. */ 723 mask &= pollfd->events | POLLERR | POLLHUP; 724 fput_light(file, fput_needed); 725 } 726 } 727 pollfd->revents = mask; 728 729 return mask; 730 } 731 732 static int do_poll(unsigned int nfds, struct poll_list *list, 733 struct poll_wqueues *wait, struct timespec *end_time) 734 { 735 poll_table* pt = &wait->pt; 736 ktime_t expire, *to = NULL; 737 int timed_out = 0, count = 0; 738 unsigned long slack = 0; 739 740 /* Optimise the no-wait case */ 741 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 742 pt = NULL; 743 timed_out = 1; 744 } 745 746 if (end_time && !timed_out) 747 slack = estimate_accuracy(end_time); 748 749 for (;;) { 750 struct poll_list *walk; 751 752 for (walk = list; walk != NULL; walk = walk->next) { 753 struct pollfd * pfd, * pfd_end; 754 755 pfd = walk->entries; 756 pfd_end = pfd + walk->len; 757 for (; pfd != pfd_end; pfd++) { 758 /* 759 * Fish for events. If we found one, record it 760 * and kill the poll_table, so we don't 761 * needlessly register any other waiters after 762 * this. They'll get immediately deregistered 763 * when we break out and return. 764 */ 765 if (do_pollfd(pfd, pt)) { 766 count++; 767 pt = NULL; 768 } 769 } 770 } 771 /* 772 * All waiters have already been registered, so don't provide 773 * a poll_table to them on the next loop iteration. 774 */ 775 pt = NULL; 776 if (!count) { 777 count = wait->error; 778 if (signal_pending(current)) 779 count = -EINTR; 780 } 781 if (count || timed_out) 782 break; 783 784 /* 785 * If this is the first loop and we have a timeout 786 * given, then we convert to ktime_t and set the to 787 * pointer to the expiry value. 788 */ 789 if (end_time && !to) { 790 expire = timespec_to_ktime(*end_time); 791 to = &expire; 792 } 793 794 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 795 timed_out = 1; 796 } 797 return count; 798 } 799 800 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 801 sizeof(struct pollfd)) 802 803 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 804 struct timespec *end_time) 805 { 806 struct poll_wqueues table; 807 int err = -EFAULT, fdcount, len, size; 808 /* Allocate small arguments on the stack to save memory and be 809 faster - use long to make sure the buffer is aligned properly 810 on 64 bit archs to avoid unaligned access */ 811 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 812 struct poll_list *const head = (struct poll_list *)stack_pps; 813 struct poll_list *walk = head; 814 unsigned long todo = nfds; 815 816 if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur) 817 return -EINVAL; 818 819 len = min_t(unsigned int, nfds, N_STACK_PPS); 820 for (;;) { 821 walk->next = NULL; 822 walk->len = len; 823 if (!len) 824 break; 825 826 if (copy_from_user(walk->entries, ufds + nfds-todo, 827 sizeof(struct pollfd) * walk->len)) 828 goto out_fds; 829 830 todo -= walk->len; 831 if (!todo) 832 break; 833 834 len = min(todo, POLLFD_PER_PAGE); 835 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 836 walk = walk->next = kmalloc(size, GFP_KERNEL); 837 if (!walk) { 838 err = -ENOMEM; 839 goto out_fds; 840 } 841 } 842 843 poll_initwait(&table); 844 fdcount = do_poll(nfds, head, &table, end_time); 845 poll_freewait(&table); 846 847 for (walk = head; walk; walk = walk->next) { 848 struct pollfd *fds = walk->entries; 849 int j; 850 851 for (j = 0; j < walk->len; j++, ufds++) 852 if (__put_user(fds[j].revents, &ufds->revents)) 853 goto out_fds; 854 } 855 856 err = fdcount; 857 out_fds: 858 walk = head->next; 859 while (walk) { 860 struct poll_list *pos = walk; 861 walk = walk->next; 862 kfree(pos); 863 } 864 865 return err; 866 } 867 868 static long do_restart_poll(struct restart_block *restart_block) 869 { 870 struct pollfd __user *ufds = restart_block->poll.ufds; 871 int nfds = restart_block->poll.nfds; 872 struct timespec *to = NULL, end_time; 873 int ret; 874 875 if (restart_block->poll.has_timeout) { 876 end_time.tv_sec = restart_block->poll.tv_sec; 877 end_time.tv_nsec = restart_block->poll.tv_nsec; 878 to = &end_time; 879 } 880 881 ret = do_sys_poll(ufds, nfds, to); 882 883 if (ret == -EINTR) { 884 restart_block->fn = do_restart_poll; 885 ret = -ERESTART_RESTARTBLOCK; 886 } 887 return ret; 888 } 889 890 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 891 long, timeout_msecs) 892 { 893 struct timespec end_time, *to = NULL; 894 int ret; 895 896 if (timeout_msecs >= 0) { 897 to = &end_time; 898 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 899 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 900 } 901 902 ret = do_sys_poll(ufds, nfds, to); 903 904 if (ret == -EINTR) { 905 struct restart_block *restart_block; 906 907 restart_block = ¤t_thread_info()->restart_block; 908 restart_block->fn = do_restart_poll; 909 restart_block->poll.ufds = ufds; 910 restart_block->poll.nfds = nfds; 911 912 if (timeout_msecs >= 0) { 913 restart_block->poll.tv_sec = end_time.tv_sec; 914 restart_block->poll.tv_nsec = end_time.tv_nsec; 915 restart_block->poll.has_timeout = 1; 916 } else 917 restart_block->poll.has_timeout = 0; 918 919 ret = -ERESTART_RESTARTBLOCK; 920 } 921 return ret; 922 } 923 924 #ifdef HAVE_SET_RESTORE_SIGMASK 925 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 926 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 927 size_t, sigsetsize) 928 { 929 sigset_t ksigmask, sigsaved; 930 struct timespec ts, end_time, *to = NULL; 931 int ret; 932 933 if (tsp) { 934 if (copy_from_user(&ts, tsp, sizeof(ts))) 935 return -EFAULT; 936 937 to = &end_time; 938 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 939 return -EINVAL; 940 } 941 942 if (sigmask) { 943 /* XXX: Don't preclude handling different sized sigset_t's. */ 944 if (sigsetsize != sizeof(sigset_t)) 945 return -EINVAL; 946 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 947 return -EFAULT; 948 949 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 950 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 951 } 952 953 ret = do_sys_poll(ufds, nfds, to); 954 955 /* We can restart this syscall, usually */ 956 if (ret == -EINTR) { 957 /* 958 * Don't restore the signal mask yet. Let do_signal() deliver 959 * the signal on the way back to userspace, before the signal 960 * mask is restored. 961 */ 962 if (sigmask) { 963 memcpy(¤t->saved_sigmask, &sigsaved, 964 sizeof(sigsaved)); 965 set_restore_sigmask(); 966 } 967 ret = -ERESTARTNOHAND; 968 } else if (sigmask) 969 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 970 971 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 972 973 return ret; 974 } 975 #endif /* HAVE_SET_RESTORE_SIGMASK */ 976