1 /* 2 * This file contains the procedures for the handling of select and poll 3 * 4 * Created for Linux based loosely upon Mathius Lattner's minix 5 * patches by Peter MacDonald. Heavily edited by Linus. 6 * 7 * 4 February 1994 8 * COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS 9 * flag set in its personality we do *not* modify the given timeout 10 * parameter to reflect time remaining. 11 * 12 * 24 January 2000 13 * Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation 14 * of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian). 15 */ 16 17 #include <linux/kernel.h> 18 #include <linux/sched.h> 19 #include <linux/syscalls.h> 20 #include <linux/module.h> 21 #include <linux/slab.h> 22 #include <linux/poll.h> 23 #include <linux/personality.h> /* for STICKY_TIMEOUTS */ 24 #include <linux/file.h> 25 #include <linux/fdtable.h> 26 #include <linux/fs.h> 27 #include <linux/rcupdate.h> 28 #include <linux/hrtimer.h> 29 30 #include <asm/uaccess.h> 31 32 33 /* 34 * Estimate expected accuracy in ns from a timeval. 35 * 36 * After quite a bit of churning around, we've settled on 37 * a simple thing of taking 0.1% of the timeout as the 38 * slack, with a cap of 100 msec. 39 * "nice" tasks get a 0.5% slack instead. 40 * 41 * Consider this comment an open invitation to come up with even 42 * better solutions.. 43 */ 44 45 #define MAX_SLACK (100 * NSEC_PER_MSEC) 46 47 static long __estimate_accuracy(struct timespec *tv) 48 { 49 long slack; 50 int divfactor = 1000; 51 52 if (tv->tv_sec < 0) 53 return 0; 54 55 if (task_nice(current) > 0) 56 divfactor = divfactor / 5; 57 58 if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor)) 59 return MAX_SLACK; 60 61 slack = tv->tv_nsec / divfactor; 62 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); 63 64 if (slack > MAX_SLACK) 65 return MAX_SLACK; 66 67 return slack; 68 } 69 70 static long estimate_accuracy(struct timespec *tv) 71 { 72 unsigned long ret; 73 struct timespec now; 74 75 /* 76 * Realtime tasks get a slack of 0 for obvious reasons. 77 */ 78 79 if (rt_task(current)) 80 return 0; 81 82 ktime_get_ts(&now); 83 now = timespec_sub(*tv, now); 84 ret = __estimate_accuracy(&now); 85 if (ret < current->timer_slack_ns) 86 return current->timer_slack_ns; 87 return ret; 88 } 89 90 91 92 struct poll_table_page { 93 struct poll_table_page * next; 94 struct poll_table_entry * entry; 95 struct poll_table_entry entries[0]; 96 }; 97 98 #define POLL_TABLE_FULL(table) \ 99 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table)) 100 101 /* 102 * Ok, Peter made a complicated, but straightforward multiple_wait() function. 103 * I have rewritten this, taking some shortcuts: This code may not be easy to 104 * follow, but it should be free of race-conditions, and it's practical. If you 105 * understand what I'm doing here, then you understand how the linux 106 * sleep/wakeup mechanism works. 107 * 108 * Two very simple procedures, poll_wait() and poll_freewait() make all the 109 * work. poll_wait() is an inline-function defined in <linux/poll.h>, 110 * as all select/poll functions have to call it to add an entry to the 111 * poll table. 112 */ 113 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 114 poll_table *p); 115 116 void poll_initwait(struct poll_wqueues *pwq) 117 { 118 init_poll_funcptr(&pwq->pt, __pollwait); 119 pwq->polling_task = current; 120 pwq->triggered = 0; 121 pwq->error = 0; 122 pwq->table = NULL; 123 pwq->inline_index = 0; 124 } 125 EXPORT_SYMBOL(poll_initwait); 126 127 static void free_poll_entry(struct poll_table_entry *entry) 128 { 129 remove_wait_queue(entry->wait_address, &entry->wait); 130 fput(entry->filp); 131 } 132 133 void poll_freewait(struct poll_wqueues *pwq) 134 { 135 struct poll_table_page * p = pwq->table; 136 int i; 137 for (i = 0; i < pwq->inline_index; i++) 138 free_poll_entry(pwq->inline_entries + i); 139 while (p) { 140 struct poll_table_entry * entry; 141 struct poll_table_page *old; 142 143 entry = p->entry; 144 do { 145 entry--; 146 free_poll_entry(entry); 147 } while (entry > p->entries); 148 old = p; 149 p = p->next; 150 free_page((unsigned long) old); 151 } 152 } 153 EXPORT_SYMBOL(poll_freewait); 154 155 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) 156 { 157 struct poll_table_page *table = p->table; 158 159 if (p->inline_index < N_INLINE_POLL_ENTRIES) 160 return p->inline_entries + p->inline_index++; 161 162 if (!table || POLL_TABLE_FULL(table)) { 163 struct poll_table_page *new_table; 164 165 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL); 166 if (!new_table) { 167 p->error = -ENOMEM; 168 return NULL; 169 } 170 new_table->entry = new_table->entries; 171 new_table->next = table; 172 p->table = new_table; 173 table = new_table; 174 } 175 176 return table->entry++; 177 } 178 179 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 180 { 181 struct poll_wqueues *pwq = wait->private; 182 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); 183 184 /* 185 * Although this function is called under waitqueue lock, LOCK 186 * doesn't imply write barrier and the users expect write 187 * barrier semantics on wakeup functions. The following 188 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up() 189 * and is paired with set_mb() in poll_schedule_timeout. 190 */ 191 smp_wmb(); 192 pwq->triggered = 1; 193 194 /* 195 * Perform the default wake up operation using a dummy 196 * waitqueue. 197 * 198 * TODO: This is hacky but there currently is no interface to 199 * pass in @sync. @sync is scheduled to be removed and once 200 * that happens, wake_up_process() can be used directly. 201 */ 202 return default_wake_function(&dummy_wait, mode, sync, key); 203 } 204 205 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 206 { 207 struct poll_table_entry *entry; 208 209 entry = container_of(wait, struct poll_table_entry, wait); 210 if (key && !((unsigned long)key & entry->key)) 211 return 0; 212 return __pollwake(wait, mode, sync, key); 213 } 214 215 /* Add a new entry */ 216 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 217 poll_table *p) 218 { 219 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); 220 struct poll_table_entry *entry = poll_get_entry(pwq); 221 if (!entry) 222 return; 223 get_file(filp); 224 entry->filp = filp; 225 entry->wait_address = wait_address; 226 entry->key = p->key; 227 init_waitqueue_func_entry(&entry->wait, pollwake); 228 entry->wait.private = pwq; 229 add_wait_queue(wait_address, &entry->wait); 230 } 231 232 int poll_schedule_timeout(struct poll_wqueues *pwq, int state, 233 ktime_t *expires, unsigned long slack) 234 { 235 int rc = -EINTR; 236 237 set_current_state(state); 238 if (!pwq->triggered) 239 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS); 240 __set_current_state(TASK_RUNNING); 241 242 /* 243 * Prepare for the next iteration. 244 * 245 * The following set_mb() serves two purposes. First, it's 246 * the counterpart rmb of the wmb in pollwake() such that data 247 * written before wake up is always visible after wake up. 248 * Second, the full barrier guarantees that triggered clearing 249 * doesn't pass event check of the next iteration. Note that 250 * this problem doesn't exist for the first iteration as 251 * add_wait_queue() has full barrier semantics. 252 */ 253 set_mb(pwq->triggered, 0); 254 255 return rc; 256 } 257 EXPORT_SYMBOL(poll_schedule_timeout); 258 259 /** 260 * poll_select_set_timeout - helper function to setup the timeout value 261 * @to: pointer to timespec variable for the final timeout 262 * @sec: seconds (from user space) 263 * @nsec: nanoseconds (from user space) 264 * 265 * Note, we do not use a timespec for the user space value here, That 266 * way we can use the function for timeval and compat interfaces as well. 267 * 268 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. 269 */ 270 int poll_select_set_timeout(struct timespec *to, long sec, long nsec) 271 { 272 struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec}; 273 274 if (!timespec_valid(&ts)) 275 return -EINVAL; 276 277 /* Optimize for the zero timeout value here */ 278 if (!sec && !nsec) { 279 to->tv_sec = to->tv_nsec = 0; 280 } else { 281 ktime_get_ts(to); 282 *to = timespec_add_safe(*to, ts); 283 } 284 return 0; 285 } 286 287 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p, 288 int timeval, int ret) 289 { 290 struct timespec rts; 291 struct timeval rtv; 292 293 if (!p) 294 return ret; 295 296 if (current->personality & STICKY_TIMEOUTS) 297 goto sticky; 298 299 /* No update for zero timeout */ 300 if (!end_time->tv_sec && !end_time->tv_nsec) 301 return ret; 302 303 ktime_get_ts(&rts); 304 rts = timespec_sub(*end_time, rts); 305 if (rts.tv_sec < 0) 306 rts.tv_sec = rts.tv_nsec = 0; 307 308 if (timeval) { 309 rtv.tv_sec = rts.tv_sec; 310 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 311 312 if (!copy_to_user(p, &rtv, sizeof(rtv))) 313 return ret; 314 315 } else if (!copy_to_user(p, &rts, sizeof(rts))) 316 return ret; 317 318 /* 319 * If an application puts its timeval in read-only memory, we 320 * don't want the Linux-specific update to the timeval to 321 * cause a fault after the select has completed 322 * successfully. However, because we're not updating the 323 * timeval, we can't restart the system call. 324 */ 325 326 sticky: 327 if (ret == -ERESTARTNOHAND) 328 ret = -EINTR; 329 return ret; 330 } 331 332 #define FDS_IN(fds, n) (fds->in + n) 333 #define FDS_OUT(fds, n) (fds->out + n) 334 #define FDS_EX(fds, n) (fds->ex + n) 335 336 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 337 338 static int max_select_fd(unsigned long n, fd_set_bits *fds) 339 { 340 unsigned long *open_fds; 341 unsigned long set; 342 int max; 343 struct fdtable *fdt; 344 345 /* handle last in-complete long-word first */ 346 set = ~(~0UL << (n & (__NFDBITS-1))); 347 n /= __NFDBITS; 348 fdt = files_fdtable(current->files); 349 open_fds = fdt->open_fds->fds_bits+n; 350 max = 0; 351 if (set) { 352 set &= BITS(fds, n); 353 if (set) { 354 if (!(set & ~*open_fds)) 355 goto get_max; 356 return -EBADF; 357 } 358 } 359 while (n) { 360 open_fds--; 361 n--; 362 set = BITS(fds, n); 363 if (!set) 364 continue; 365 if (set & ~*open_fds) 366 return -EBADF; 367 if (max) 368 continue; 369 get_max: 370 do { 371 max++; 372 set >>= 1; 373 } while (set); 374 max += n * __NFDBITS; 375 } 376 377 return max; 378 } 379 380 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) 381 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) 382 #define POLLEX_SET (POLLPRI) 383 384 static inline void wait_key_set(poll_table *wait, unsigned long in, 385 unsigned long out, unsigned long bit) 386 { 387 if (wait) { 388 wait->key = POLLEX_SET; 389 if (in & bit) 390 wait->key |= POLLIN_SET; 391 if (out & bit) 392 wait->key |= POLLOUT_SET; 393 } 394 } 395 396 int do_select(int n, fd_set_bits *fds, struct timespec *end_time) 397 { 398 ktime_t expire, *to = NULL; 399 struct poll_wqueues table; 400 poll_table *wait; 401 int retval, i, timed_out = 0; 402 unsigned long slack = 0; 403 404 rcu_read_lock(); 405 retval = max_select_fd(n, fds); 406 rcu_read_unlock(); 407 408 if (retval < 0) 409 return retval; 410 n = retval; 411 412 poll_initwait(&table); 413 wait = &table.pt; 414 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 415 wait = NULL; 416 timed_out = 1; 417 } 418 419 if (end_time && !timed_out) 420 slack = estimate_accuracy(end_time); 421 422 retval = 0; 423 for (;;) { 424 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; 425 426 inp = fds->in; outp = fds->out; exp = fds->ex; 427 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; 428 429 for (i = 0; i < n; ++rinp, ++routp, ++rexp) { 430 unsigned long in, out, ex, all_bits, bit = 1, mask, j; 431 unsigned long res_in = 0, res_out = 0, res_ex = 0; 432 const struct file_operations *f_op = NULL; 433 struct file *file = NULL; 434 435 in = *inp++; out = *outp++; ex = *exp++; 436 all_bits = in | out | ex; 437 if (all_bits == 0) { 438 i += __NFDBITS; 439 continue; 440 } 441 442 for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) { 443 int fput_needed; 444 if (i >= n) 445 break; 446 if (!(bit & all_bits)) 447 continue; 448 file = fget_light(i, &fput_needed); 449 if (file) { 450 f_op = file->f_op; 451 mask = DEFAULT_POLLMASK; 452 if (f_op && f_op->poll) { 453 wait_key_set(wait, in, out, bit); 454 mask = (*f_op->poll)(file, wait); 455 } 456 fput_light(file, fput_needed); 457 if ((mask & POLLIN_SET) && (in & bit)) { 458 res_in |= bit; 459 retval++; 460 wait = NULL; 461 } 462 if ((mask & POLLOUT_SET) && (out & bit)) { 463 res_out |= bit; 464 retval++; 465 wait = NULL; 466 } 467 if ((mask & POLLEX_SET) && (ex & bit)) { 468 res_ex |= bit; 469 retval++; 470 wait = NULL; 471 } 472 } 473 } 474 if (res_in) 475 *rinp = res_in; 476 if (res_out) 477 *routp = res_out; 478 if (res_ex) 479 *rexp = res_ex; 480 cond_resched(); 481 } 482 wait = NULL; 483 if (retval || timed_out || signal_pending(current)) 484 break; 485 if (table.error) { 486 retval = table.error; 487 break; 488 } 489 490 /* 491 * If this is the first loop and we have a timeout 492 * given, then we convert to ktime_t and set the to 493 * pointer to the expiry value. 494 */ 495 if (end_time && !to) { 496 expire = timespec_to_ktime(*end_time); 497 to = &expire; 498 } 499 500 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 501 to, slack)) 502 timed_out = 1; 503 } 504 505 poll_freewait(&table); 506 507 return retval; 508 } 509 510 /* 511 * We can actually return ERESTARTSYS instead of EINTR, but I'd 512 * like to be certain this leads to no problems. So I return 513 * EINTR just for safety. 514 * 515 * Update: ERESTARTSYS breaks at least the xview clock binary, so 516 * I'm trying ERESTARTNOHAND which restart only when you want to. 517 */ 518 #define MAX_SELECT_SECONDS \ 519 ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1) 520 521 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 522 fd_set __user *exp, struct timespec *end_time) 523 { 524 fd_set_bits fds; 525 void *bits; 526 int ret, max_fds; 527 unsigned int size; 528 struct fdtable *fdt; 529 /* Allocate small arguments on the stack to save memory and be faster */ 530 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 531 532 ret = -EINVAL; 533 if (n < 0) 534 goto out_nofds; 535 536 /* max_fds can increase, so grab it once to avoid race */ 537 rcu_read_lock(); 538 fdt = files_fdtable(current->files); 539 max_fds = fdt->max_fds; 540 rcu_read_unlock(); 541 if (n > max_fds) 542 n = max_fds; 543 544 /* 545 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 546 * since we used fdset we need to allocate memory in units of 547 * long-words. 548 */ 549 size = FDS_BYTES(n); 550 bits = stack_fds; 551 if (size > sizeof(stack_fds) / 6) { 552 /* Not enough space in on-stack array; must use kmalloc */ 553 ret = -ENOMEM; 554 bits = kmalloc(6 * size, GFP_KERNEL); 555 if (!bits) 556 goto out_nofds; 557 } 558 fds.in = bits; 559 fds.out = bits + size; 560 fds.ex = bits + 2*size; 561 fds.res_in = bits + 3*size; 562 fds.res_out = bits + 4*size; 563 fds.res_ex = bits + 5*size; 564 565 if ((ret = get_fd_set(n, inp, fds.in)) || 566 (ret = get_fd_set(n, outp, fds.out)) || 567 (ret = get_fd_set(n, exp, fds.ex))) 568 goto out; 569 zero_fd_set(n, fds.res_in); 570 zero_fd_set(n, fds.res_out); 571 zero_fd_set(n, fds.res_ex); 572 573 ret = do_select(n, &fds, end_time); 574 575 if (ret < 0) 576 goto out; 577 if (!ret) { 578 ret = -ERESTARTNOHAND; 579 if (signal_pending(current)) 580 goto out; 581 ret = 0; 582 } 583 584 if (set_fd_set(n, inp, fds.res_in) || 585 set_fd_set(n, outp, fds.res_out) || 586 set_fd_set(n, exp, fds.res_ex)) 587 ret = -EFAULT; 588 589 out: 590 if (bits != stack_fds) 591 kfree(bits); 592 out_nofds: 593 return ret; 594 } 595 596 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 597 fd_set __user *, exp, struct timeval __user *, tvp) 598 { 599 struct timespec end_time, *to = NULL; 600 struct timeval tv; 601 int ret; 602 603 if (tvp) { 604 if (copy_from_user(&tv, tvp, sizeof(tv))) 605 return -EFAULT; 606 607 to = &end_time; 608 if (poll_select_set_timeout(to, 609 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 610 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 611 return -EINVAL; 612 } 613 614 ret = core_sys_select(n, inp, outp, exp, to); 615 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret); 616 617 return ret; 618 } 619 620 #ifdef HAVE_SET_RESTORE_SIGMASK 621 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 622 fd_set __user *exp, struct timespec __user *tsp, 623 const sigset_t __user *sigmask, size_t sigsetsize) 624 { 625 sigset_t ksigmask, sigsaved; 626 struct timespec ts, end_time, *to = NULL; 627 int ret; 628 629 if (tsp) { 630 if (copy_from_user(&ts, tsp, sizeof(ts))) 631 return -EFAULT; 632 633 to = &end_time; 634 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 635 return -EINVAL; 636 } 637 638 if (sigmask) { 639 /* XXX: Don't preclude handling different sized sigset_t's. */ 640 if (sigsetsize != sizeof(sigset_t)) 641 return -EINVAL; 642 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 643 return -EFAULT; 644 645 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 646 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 647 } 648 649 ret = core_sys_select(n, inp, outp, exp, to); 650 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 651 652 if (ret == -ERESTARTNOHAND) { 653 /* 654 * Don't restore the signal mask yet. Let do_signal() deliver 655 * the signal on the way back to userspace, before the signal 656 * mask is restored. 657 */ 658 if (sigmask) { 659 memcpy(¤t->saved_sigmask, &sigsaved, 660 sizeof(sigsaved)); 661 set_restore_sigmask(); 662 } 663 } else if (sigmask) 664 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 665 666 return ret; 667 } 668 669 /* 670 * Most architectures can't handle 7-argument syscalls. So we provide a 671 * 6-argument version where the sixth argument is a pointer to a structure 672 * which has a pointer to the sigset_t itself followed by a size_t containing 673 * the sigset size. 674 */ 675 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 676 fd_set __user *, exp, struct timespec __user *, tsp, 677 void __user *, sig) 678 { 679 size_t sigsetsize = 0; 680 sigset_t __user *up = NULL; 681 682 if (sig) { 683 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) 684 || __get_user(up, (sigset_t __user * __user *)sig) 685 || __get_user(sigsetsize, 686 (size_t __user *)(sig+sizeof(void *)))) 687 return -EFAULT; 688 } 689 690 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize); 691 } 692 #endif /* HAVE_SET_RESTORE_SIGMASK */ 693 694 struct poll_list { 695 struct poll_list *next; 696 int len; 697 struct pollfd entries[0]; 698 }; 699 700 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 701 702 /* 703 * Fish for pollable events on the pollfd->fd file descriptor. We're only 704 * interested in events matching the pollfd->events mask, and the result 705 * matching that mask is both recorded in pollfd->revents and returned. The 706 * pwait poll_table will be used by the fd-provided poll handler for waiting, 707 * if non-NULL. 708 */ 709 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) 710 { 711 unsigned int mask; 712 int fd; 713 714 mask = 0; 715 fd = pollfd->fd; 716 if (fd >= 0) { 717 int fput_needed; 718 struct file * file; 719 720 file = fget_light(fd, &fput_needed); 721 mask = POLLNVAL; 722 if (file != NULL) { 723 mask = DEFAULT_POLLMASK; 724 if (file->f_op && file->f_op->poll) { 725 if (pwait) 726 pwait->key = pollfd->events | 727 POLLERR | POLLHUP; 728 mask = file->f_op->poll(file, pwait); 729 } 730 /* Mask out unneeded events. */ 731 mask &= pollfd->events | POLLERR | POLLHUP; 732 fput_light(file, fput_needed); 733 } 734 } 735 pollfd->revents = mask; 736 737 return mask; 738 } 739 740 static int do_poll(unsigned int nfds, struct poll_list *list, 741 struct poll_wqueues *wait, struct timespec *end_time) 742 { 743 poll_table* pt = &wait->pt; 744 ktime_t expire, *to = NULL; 745 int timed_out = 0, count = 0; 746 unsigned long slack = 0; 747 748 /* Optimise the no-wait case */ 749 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 750 pt = NULL; 751 timed_out = 1; 752 } 753 754 if (end_time && !timed_out) 755 slack = estimate_accuracy(end_time); 756 757 for (;;) { 758 struct poll_list *walk; 759 760 for (walk = list; walk != NULL; walk = walk->next) { 761 struct pollfd * pfd, * pfd_end; 762 763 pfd = walk->entries; 764 pfd_end = pfd + walk->len; 765 for (; pfd != pfd_end; pfd++) { 766 /* 767 * Fish for events. If we found one, record it 768 * and kill the poll_table, so we don't 769 * needlessly register any other waiters after 770 * this. They'll get immediately deregistered 771 * when we break out and return. 772 */ 773 if (do_pollfd(pfd, pt)) { 774 count++; 775 pt = NULL; 776 } 777 } 778 } 779 /* 780 * All waiters have already been registered, so don't provide 781 * a poll_table to them on the next loop iteration. 782 */ 783 pt = NULL; 784 if (!count) { 785 count = wait->error; 786 if (signal_pending(current)) 787 count = -EINTR; 788 } 789 if (count || timed_out) 790 break; 791 792 /* 793 * If this is the first loop and we have a timeout 794 * given, then we convert to ktime_t and set the to 795 * pointer to the expiry value. 796 */ 797 if (end_time && !to) { 798 expire = timespec_to_ktime(*end_time); 799 to = &expire; 800 } 801 802 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 803 timed_out = 1; 804 } 805 return count; 806 } 807 808 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 809 sizeof(struct pollfd)) 810 811 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 812 struct timespec *end_time) 813 { 814 struct poll_wqueues table; 815 int err = -EFAULT, fdcount, len, size; 816 /* Allocate small arguments on the stack to save memory and be 817 faster - use long to make sure the buffer is aligned properly 818 on 64 bit archs to avoid unaligned access */ 819 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 820 struct poll_list *const head = (struct poll_list *)stack_pps; 821 struct poll_list *walk = head; 822 unsigned long todo = nfds; 823 824 if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur) 825 return -EINVAL; 826 827 len = min_t(unsigned int, nfds, N_STACK_PPS); 828 for (;;) { 829 walk->next = NULL; 830 walk->len = len; 831 if (!len) 832 break; 833 834 if (copy_from_user(walk->entries, ufds + nfds-todo, 835 sizeof(struct pollfd) * walk->len)) 836 goto out_fds; 837 838 todo -= walk->len; 839 if (!todo) 840 break; 841 842 len = min(todo, POLLFD_PER_PAGE); 843 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 844 walk = walk->next = kmalloc(size, GFP_KERNEL); 845 if (!walk) { 846 err = -ENOMEM; 847 goto out_fds; 848 } 849 } 850 851 poll_initwait(&table); 852 fdcount = do_poll(nfds, head, &table, end_time); 853 poll_freewait(&table); 854 855 for (walk = head; walk; walk = walk->next) { 856 struct pollfd *fds = walk->entries; 857 int j; 858 859 for (j = 0; j < walk->len; j++, ufds++) 860 if (__put_user(fds[j].revents, &ufds->revents)) 861 goto out_fds; 862 } 863 864 err = fdcount; 865 out_fds: 866 walk = head->next; 867 while (walk) { 868 struct poll_list *pos = walk; 869 walk = walk->next; 870 kfree(pos); 871 } 872 873 return err; 874 } 875 876 static long do_restart_poll(struct restart_block *restart_block) 877 { 878 struct pollfd __user *ufds = restart_block->poll.ufds; 879 int nfds = restart_block->poll.nfds; 880 struct timespec *to = NULL, end_time; 881 int ret; 882 883 if (restart_block->poll.has_timeout) { 884 end_time.tv_sec = restart_block->poll.tv_sec; 885 end_time.tv_nsec = restart_block->poll.tv_nsec; 886 to = &end_time; 887 } 888 889 ret = do_sys_poll(ufds, nfds, to); 890 891 if (ret == -EINTR) { 892 restart_block->fn = do_restart_poll; 893 ret = -ERESTART_RESTARTBLOCK; 894 } 895 return ret; 896 } 897 898 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 899 long, timeout_msecs) 900 { 901 struct timespec end_time, *to = NULL; 902 int ret; 903 904 if (timeout_msecs >= 0) { 905 to = &end_time; 906 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 907 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 908 } 909 910 ret = do_sys_poll(ufds, nfds, to); 911 912 if (ret == -EINTR) { 913 struct restart_block *restart_block; 914 915 restart_block = ¤t_thread_info()->restart_block; 916 restart_block->fn = do_restart_poll; 917 restart_block->poll.ufds = ufds; 918 restart_block->poll.nfds = nfds; 919 920 if (timeout_msecs >= 0) { 921 restart_block->poll.tv_sec = end_time.tv_sec; 922 restart_block->poll.tv_nsec = end_time.tv_nsec; 923 restart_block->poll.has_timeout = 1; 924 } else 925 restart_block->poll.has_timeout = 0; 926 927 ret = -ERESTART_RESTARTBLOCK; 928 } 929 return ret; 930 } 931 932 #ifdef HAVE_SET_RESTORE_SIGMASK 933 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 934 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 935 size_t, sigsetsize) 936 { 937 sigset_t ksigmask, sigsaved; 938 struct timespec ts, end_time, *to = NULL; 939 int ret; 940 941 if (tsp) { 942 if (copy_from_user(&ts, tsp, sizeof(ts))) 943 return -EFAULT; 944 945 to = &end_time; 946 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 947 return -EINVAL; 948 } 949 950 if (sigmask) { 951 /* XXX: Don't preclude handling different sized sigset_t's. */ 952 if (sigsetsize != sizeof(sigset_t)) 953 return -EINVAL; 954 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 955 return -EFAULT; 956 957 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 958 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 959 } 960 961 ret = do_sys_poll(ufds, nfds, to); 962 963 /* We can restart this syscall, usually */ 964 if (ret == -EINTR) { 965 /* 966 * Don't restore the signal mask yet. Let do_signal() deliver 967 * the signal on the way back to userspace, before the signal 968 * mask is restored. 969 */ 970 if (sigmask) { 971 memcpy(¤t->saved_sigmask, &sigsaved, 972 sizeof(sigsaved)); 973 set_restore_sigmask(); 974 } 975 ret = -ERESTARTNOHAND; 976 } else if (sigmask) 977 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 978 979 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 980 981 return ret; 982 } 983 #endif /* HAVE_SET_RESTORE_SIGMASK */ 984