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