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 long select_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 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) 310 memset(&rtv, 0, sizeof(rtv)); 311 rtv.tv_sec = rts.tv_sec; 312 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 313 314 if (!copy_to_user(p, &rtv, sizeof(rtv))) 315 return ret; 316 317 } else if (!copy_to_user(p, &rts, sizeof(rts))) 318 return ret; 319 320 /* 321 * If an application puts its timeval in read-only memory, we 322 * don't want the Linux-specific update to the timeval to 323 * cause a fault after the select has completed 324 * successfully. However, because we're not updating the 325 * timeval, we can't restart the system call. 326 */ 327 328 sticky: 329 if (ret == -ERESTARTNOHAND) 330 ret = -EINTR; 331 return ret; 332 } 333 334 #define FDS_IN(fds, n) (fds->in + n) 335 #define FDS_OUT(fds, n) (fds->out + n) 336 #define FDS_EX(fds, n) (fds->ex + n) 337 338 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 339 340 static int max_select_fd(unsigned long n, fd_set_bits *fds) 341 { 342 unsigned long *open_fds; 343 unsigned long set; 344 int max; 345 struct fdtable *fdt; 346 347 /* handle last in-complete long-word first */ 348 set = ~(~0UL << (n & (__NFDBITS-1))); 349 n /= __NFDBITS; 350 fdt = files_fdtable(current->files); 351 open_fds = fdt->open_fds->fds_bits+n; 352 max = 0; 353 if (set) { 354 set &= BITS(fds, n); 355 if (set) { 356 if (!(set & ~*open_fds)) 357 goto get_max; 358 return -EBADF; 359 } 360 } 361 while (n) { 362 open_fds--; 363 n--; 364 set = BITS(fds, n); 365 if (!set) 366 continue; 367 if (set & ~*open_fds) 368 return -EBADF; 369 if (max) 370 continue; 371 get_max: 372 do { 373 max++; 374 set >>= 1; 375 } while (set); 376 max += n * __NFDBITS; 377 } 378 379 return max; 380 } 381 382 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) 383 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) 384 #define POLLEX_SET (POLLPRI) 385 386 static inline void wait_key_set(poll_table *wait, unsigned long in, 387 unsigned long out, unsigned long bit) 388 { 389 if (wait) { 390 wait->key = POLLEX_SET; 391 if (in & bit) 392 wait->key |= POLLIN_SET; 393 if (out & bit) 394 wait->key |= POLLOUT_SET; 395 } 396 } 397 398 int do_select(int n, fd_set_bits *fds, struct timespec *end_time) 399 { 400 ktime_t expire, *to = NULL; 401 struct poll_wqueues table; 402 poll_table *wait; 403 int retval, i, timed_out = 0; 404 unsigned long slack = 0; 405 406 rcu_read_lock(); 407 retval = max_select_fd(n, fds); 408 rcu_read_unlock(); 409 410 if (retval < 0) 411 return retval; 412 n = retval; 413 414 poll_initwait(&table); 415 wait = &table.pt; 416 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 417 wait = NULL; 418 timed_out = 1; 419 } 420 421 if (end_time && !timed_out) 422 slack = select_estimate_accuracy(end_time); 423 424 retval = 0; 425 for (;;) { 426 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; 427 428 inp = fds->in; outp = fds->out; exp = fds->ex; 429 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; 430 431 for (i = 0; i < n; ++rinp, ++routp, ++rexp) { 432 unsigned long in, out, ex, all_bits, bit = 1, mask, j; 433 unsigned long res_in = 0, res_out = 0, res_ex = 0; 434 const struct file_operations *f_op = NULL; 435 struct file *file = NULL; 436 437 in = *inp++; out = *outp++; ex = *exp++; 438 all_bits = in | out | ex; 439 if (all_bits == 0) { 440 i += __NFDBITS; 441 continue; 442 } 443 444 for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) { 445 int fput_needed; 446 if (i >= n) 447 break; 448 if (!(bit & all_bits)) 449 continue; 450 file = fget_light(i, &fput_needed); 451 if (file) { 452 f_op = file->f_op; 453 mask = DEFAULT_POLLMASK; 454 if (f_op && f_op->poll) { 455 wait_key_set(wait, in, out, bit); 456 mask = (*f_op->poll)(file, wait); 457 } 458 fput_light(file, fput_needed); 459 if ((mask & POLLIN_SET) && (in & bit)) { 460 res_in |= bit; 461 retval++; 462 wait = NULL; 463 } 464 if ((mask & POLLOUT_SET) && (out & bit)) { 465 res_out |= bit; 466 retval++; 467 wait = NULL; 468 } 469 if ((mask & POLLEX_SET) && (ex & bit)) { 470 res_ex |= bit; 471 retval++; 472 wait = NULL; 473 } 474 } 475 } 476 if (res_in) 477 *rinp = res_in; 478 if (res_out) 479 *routp = res_out; 480 if (res_ex) 481 *rexp = res_ex; 482 cond_resched(); 483 } 484 wait = NULL; 485 if (retval || timed_out || signal_pending(current)) 486 break; 487 if (table.error) { 488 retval = table.error; 489 break; 490 } 491 492 /* 493 * If this is the first loop and we have a timeout 494 * given, then we convert to ktime_t and set the to 495 * pointer to the expiry value. 496 */ 497 if (end_time && !to) { 498 expire = timespec_to_ktime(*end_time); 499 to = &expire; 500 } 501 502 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 503 to, slack)) 504 timed_out = 1; 505 } 506 507 poll_freewait(&table); 508 509 return retval; 510 } 511 512 /* 513 * We can actually return ERESTARTSYS instead of EINTR, but I'd 514 * like to be certain this leads to no problems. So I return 515 * EINTR just for safety. 516 * 517 * Update: ERESTARTSYS breaks at least the xview clock binary, so 518 * I'm trying ERESTARTNOHAND which restart only when you want to. 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 #ifdef __ARCH_WANT_SYS_OLD_SELECT 694 struct sel_arg_struct { 695 unsigned long n; 696 fd_set __user *inp, *outp, *exp; 697 struct timeval __user *tvp; 698 }; 699 700 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) 701 { 702 struct sel_arg_struct a; 703 704 if (copy_from_user(&a, arg, sizeof(a))) 705 return -EFAULT; 706 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp); 707 } 708 #endif 709 710 struct poll_list { 711 struct poll_list *next; 712 int len; 713 struct pollfd entries[0]; 714 }; 715 716 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 717 718 /* 719 * Fish for pollable events on the pollfd->fd file descriptor. We're only 720 * interested in events matching the pollfd->events mask, and the result 721 * matching that mask is both recorded in pollfd->revents and returned. The 722 * pwait poll_table will be used by the fd-provided poll handler for waiting, 723 * if non-NULL. 724 */ 725 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) 726 { 727 unsigned int mask; 728 int fd; 729 730 mask = 0; 731 fd = pollfd->fd; 732 if (fd >= 0) { 733 int fput_needed; 734 struct file * file; 735 736 file = fget_light(fd, &fput_needed); 737 mask = POLLNVAL; 738 if (file != NULL) { 739 mask = DEFAULT_POLLMASK; 740 if (file->f_op && file->f_op->poll) { 741 if (pwait) 742 pwait->key = pollfd->events | 743 POLLERR | POLLHUP; 744 mask = file->f_op->poll(file, pwait); 745 } 746 /* Mask out unneeded events. */ 747 mask &= pollfd->events | POLLERR | POLLHUP; 748 fput_light(file, fput_needed); 749 } 750 } 751 pollfd->revents = mask; 752 753 return mask; 754 } 755 756 static int do_poll(unsigned int nfds, struct poll_list *list, 757 struct poll_wqueues *wait, struct timespec *end_time) 758 { 759 poll_table* pt = &wait->pt; 760 ktime_t expire, *to = NULL; 761 int timed_out = 0, count = 0; 762 unsigned long slack = 0; 763 764 /* Optimise the no-wait case */ 765 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 766 pt = NULL; 767 timed_out = 1; 768 } 769 770 if (end_time && !timed_out) 771 slack = select_estimate_accuracy(end_time); 772 773 for (;;) { 774 struct poll_list *walk; 775 776 for (walk = list; walk != NULL; walk = walk->next) { 777 struct pollfd * pfd, * pfd_end; 778 779 pfd = walk->entries; 780 pfd_end = pfd + walk->len; 781 for (; pfd != pfd_end; pfd++) { 782 /* 783 * Fish for events. If we found one, record it 784 * and kill the poll_table, so we don't 785 * needlessly register any other waiters after 786 * this. They'll get immediately deregistered 787 * when we break out and return. 788 */ 789 if (do_pollfd(pfd, pt)) { 790 count++; 791 pt = NULL; 792 } 793 } 794 } 795 /* 796 * All waiters have already been registered, so don't provide 797 * a poll_table to them on the next loop iteration. 798 */ 799 pt = NULL; 800 if (!count) { 801 count = wait->error; 802 if (signal_pending(current)) 803 count = -EINTR; 804 } 805 if (count || timed_out) 806 break; 807 808 /* 809 * If this is the first loop and we have a timeout 810 * given, then we convert to ktime_t and set the to 811 * pointer to the expiry value. 812 */ 813 if (end_time && !to) { 814 expire = timespec_to_ktime(*end_time); 815 to = &expire; 816 } 817 818 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 819 timed_out = 1; 820 } 821 return count; 822 } 823 824 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 825 sizeof(struct pollfd)) 826 827 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 828 struct timespec *end_time) 829 { 830 struct poll_wqueues table; 831 int err = -EFAULT, fdcount, len, size; 832 /* Allocate small arguments on the stack to save memory and be 833 faster - use long to make sure the buffer is aligned properly 834 on 64 bit archs to avoid unaligned access */ 835 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 836 struct poll_list *const head = (struct poll_list *)stack_pps; 837 struct poll_list *walk = head; 838 unsigned long todo = nfds; 839 840 if (nfds > rlimit(RLIMIT_NOFILE)) 841 return -EINVAL; 842 843 len = min_t(unsigned int, nfds, N_STACK_PPS); 844 for (;;) { 845 walk->next = NULL; 846 walk->len = len; 847 if (!len) 848 break; 849 850 if (copy_from_user(walk->entries, ufds + nfds-todo, 851 sizeof(struct pollfd) * walk->len)) 852 goto out_fds; 853 854 todo -= walk->len; 855 if (!todo) 856 break; 857 858 len = min(todo, POLLFD_PER_PAGE); 859 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 860 walk = walk->next = kmalloc(size, GFP_KERNEL); 861 if (!walk) { 862 err = -ENOMEM; 863 goto out_fds; 864 } 865 } 866 867 poll_initwait(&table); 868 fdcount = do_poll(nfds, head, &table, end_time); 869 poll_freewait(&table); 870 871 for (walk = head; walk; walk = walk->next) { 872 struct pollfd *fds = walk->entries; 873 int j; 874 875 for (j = 0; j < walk->len; j++, ufds++) 876 if (__put_user(fds[j].revents, &ufds->revents)) 877 goto out_fds; 878 } 879 880 err = fdcount; 881 out_fds: 882 walk = head->next; 883 while (walk) { 884 struct poll_list *pos = walk; 885 walk = walk->next; 886 kfree(pos); 887 } 888 889 return err; 890 } 891 892 static long do_restart_poll(struct restart_block *restart_block) 893 { 894 struct pollfd __user *ufds = restart_block->poll.ufds; 895 int nfds = restart_block->poll.nfds; 896 struct timespec *to = NULL, end_time; 897 int ret; 898 899 if (restart_block->poll.has_timeout) { 900 end_time.tv_sec = restart_block->poll.tv_sec; 901 end_time.tv_nsec = restart_block->poll.tv_nsec; 902 to = &end_time; 903 } 904 905 ret = do_sys_poll(ufds, nfds, to); 906 907 if (ret == -EINTR) { 908 restart_block->fn = do_restart_poll; 909 ret = -ERESTART_RESTARTBLOCK; 910 } 911 return ret; 912 } 913 914 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 915 long, timeout_msecs) 916 { 917 struct timespec end_time, *to = NULL; 918 int ret; 919 920 if (timeout_msecs >= 0) { 921 to = &end_time; 922 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 923 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 924 } 925 926 ret = do_sys_poll(ufds, nfds, to); 927 928 if (ret == -EINTR) { 929 struct restart_block *restart_block; 930 931 restart_block = ¤t_thread_info()->restart_block; 932 restart_block->fn = do_restart_poll; 933 restart_block->poll.ufds = ufds; 934 restart_block->poll.nfds = nfds; 935 936 if (timeout_msecs >= 0) { 937 restart_block->poll.tv_sec = end_time.tv_sec; 938 restart_block->poll.tv_nsec = end_time.tv_nsec; 939 restart_block->poll.has_timeout = 1; 940 } else 941 restart_block->poll.has_timeout = 0; 942 943 ret = -ERESTART_RESTARTBLOCK; 944 } 945 return ret; 946 } 947 948 #ifdef HAVE_SET_RESTORE_SIGMASK 949 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 950 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 951 size_t, sigsetsize) 952 { 953 sigset_t ksigmask, sigsaved; 954 struct timespec ts, end_time, *to = NULL; 955 int ret; 956 957 if (tsp) { 958 if (copy_from_user(&ts, tsp, sizeof(ts))) 959 return -EFAULT; 960 961 to = &end_time; 962 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 963 return -EINVAL; 964 } 965 966 if (sigmask) { 967 /* XXX: Don't preclude handling different sized sigset_t's. */ 968 if (sigsetsize != sizeof(sigset_t)) 969 return -EINVAL; 970 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 971 return -EFAULT; 972 973 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 974 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 975 } 976 977 ret = do_sys_poll(ufds, nfds, to); 978 979 /* We can restart this syscall, usually */ 980 if (ret == -EINTR) { 981 /* 982 * Don't restore the signal mask yet. Let do_signal() deliver 983 * the signal on the way back to userspace, before the signal 984 * mask is restored. 985 */ 986 if (sigmask) { 987 memcpy(¤t->saved_sigmask, &sigsaved, 988 sizeof(sigsaved)); 989 set_restore_sigmask(); 990 } 991 ret = -ERESTARTNOHAND; 992 } else if (sigmask) 993 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 994 995 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 996 997 return ret; 998 } 999 #endif /* HAVE_SET_RESTORE_SIGMASK */ 1000