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/export.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 entry->filp = get_file(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 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) 309 memset(&rtv, 0, sizeof(rtv)); 310 rtv.tv_sec = rts.tv_sec; 311 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 312 313 if (!copy_to_user(p, &rtv, sizeof(rtv))) 314 return ret; 315 316 } else if (!copy_to_user(p, &rts, sizeof(rts))) 317 return ret; 318 319 /* 320 * If an application puts its timeval in read-only memory, we 321 * don't want the Linux-specific update to the timeval to 322 * cause a fault after the select has completed 323 * successfully. However, because we're not updating the 324 * timeval, we can't restart the system call. 325 */ 326 327 sticky: 328 if (ret == -ERESTARTNOHAND) 329 ret = -EINTR; 330 return ret; 331 } 332 333 #define FDS_IN(fds, n) (fds->in + n) 334 #define FDS_OUT(fds, n) (fds->out + n) 335 #define FDS_EX(fds, n) (fds->ex + n) 336 337 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 338 339 static int max_select_fd(unsigned long n, fd_set_bits *fds) 340 { 341 unsigned long *open_fds; 342 unsigned long set; 343 int max; 344 struct fdtable *fdt; 345 346 /* handle last in-complete long-word first */ 347 set = ~(~0UL << (n & (BITS_PER_LONG-1))); 348 n /= BITS_PER_LONG; 349 fdt = files_fdtable(current->files); 350 open_fds = fdt->open_fds + n; 351 max = 0; 352 if (set) { 353 set &= BITS(fds, n); 354 if (set) { 355 if (!(set & ~*open_fds)) 356 goto get_max; 357 return -EBADF; 358 } 359 } 360 while (n) { 361 open_fds--; 362 n--; 363 set = BITS(fds, n); 364 if (!set) 365 continue; 366 if (set & ~*open_fds) 367 return -EBADF; 368 if (max) 369 continue; 370 get_max: 371 do { 372 max++; 373 set >>= 1; 374 } while (set); 375 max += n * BITS_PER_LONG; 376 } 377 378 return max; 379 } 380 381 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) 382 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) 383 #define POLLEX_SET (POLLPRI) 384 385 static inline void wait_key_set(poll_table *wait, unsigned long in, 386 unsigned long out, unsigned long bit) 387 { 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 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->_qproc = NULL; 415 timed_out = 1; 416 } 417 418 if (end_time && !timed_out) 419 slack = select_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; 431 432 in = *inp++; out = *outp++; ex = *exp++; 433 all_bits = in | out | ex; 434 if (all_bits == 0) { 435 i += BITS_PER_LONG; 436 continue; 437 } 438 439 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) { 440 struct fd f; 441 if (i >= n) 442 break; 443 if (!(bit & all_bits)) 444 continue; 445 f = fdget(i); 446 if (f.file) { 447 const struct file_operations *f_op; 448 f_op = f.file->f_op; 449 mask = DEFAULT_POLLMASK; 450 if (f_op && f_op->poll) { 451 wait_key_set(wait, in, out, bit); 452 mask = (*f_op->poll)(f.file, wait); 453 } 454 fdput(f); 455 if ((mask & POLLIN_SET) && (in & bit)) { 456 res_in |= bit; 457 retval++; 458 wait->_qproc = NULL; 459 } 460 if ((mask & POLLOUT_SET) && (out & bit)) { 461 res_out |= bit; 462 retval++; 463 wait->_qproc = NULL; 464 } 465 if ((mask & POLLEX_SET) && (ex & bit)) { 466 res_ex |= bit; 467 retval++; 468 wait->_qproc = NULL; 469 } 470 } 471 } 472 if (res_in) 473 *rinp = res_in; 474 if (res_out) 475 *routp = res_out; 476 if (res_ex) 477 *rexp = res_ex; 478 cond_resched(); 479 } 480 wait->_qproc = NULL; 481 if (retval || timed_out || signal_pending(current)) 482 break; 483 if (table.error) { 484 retval = table.error; 485 break; 486 } 487 488 /* 489 * If this is the first loop and we have a timeout 490 * given, then we convert to ktime_t and set the to 491 * pointer to the expiry value. 492 */ 493 if (end_time && !to) { 494 expire = timespec_to_ktime(*end_time); 495 to = &expire; 496 } 497 498 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 499 to, slack)) 500 timed_out = 1; 501 } 502 503 poll_freewait(&table); 504 505 return retval; 506 } 507 508 /* 509 * We can actually return ERESTARTSYS instead of EINTR, but I'd 510 * like to be certain this leads to no problems. So I return 511 * EINTR just for safety. 512 * 513 * Update: ERESTARTSYS breaks at least the xview clock binary, so 514 * I'm trying ERESTARTNOHAND which restart only when you want to. 515 */ 516 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 517 fd_set __user *exp, struct timespec *end_time) 518 { 519 fd_set_bits fds; 520 void *bits; 521 int ret, max_fds; 522 unsigned int size; 523 struct fdtable *fdt; 524 /* Allocate small arguments on the stack to save memory and be faster */ 525 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 526 527 ret = -EINVAL; 528 if (n < 0) 529 goto out_nofds; 530 531 /* max_fds can increase, so grab it once to avoid race */ 532 rcu_read_lock(); 533 fdt = files_fdtable(current->files); 534 max_fds = fdt->max_fds; 535 rcu_read_unlock(); 536 if (n > max_fds) 537 n = max_fds; 538 539 /* 540 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 541 * since we used fdset we need to allocate memory in units of 542 * long-words. 543 */ 544 size = FDS_BYTES(n); 545 bits = stack_fds; 546 if (size > sizeof(stack_fds) / 6) { 547 /* Not enough space in on-stack array; must use kmalloc */ 548 ret = -ENOMEM; 549 bits = kmalloc(6 * size, GFP_KERNEL); 550 if (!bits) 551 goto out_nofds; 552 } 553 fds.in = bits; 554 fds.out = bits + size; 555 fds.ex = bits + 2*size; 556 fds.res_in = bits + 3*size; 557 fds.res_out = bits + 4*size; 558 fds.res_ex = bits + 5*size; 559 560 if ((ret = get_fd_set(n, inp, fds.in)) || 561 (ret = get_fd_set(n, outp, fds.out)) || 562 (ret = get_fd_set(n, exp, fds.ex))) 563 goto out; 564 zero_fd_set(n, fds.res_in); 565 zero_fd_set(n, fds.res_out); 566 zero_fd_set(n, fds.res_ex); 567 568 ret = do_select(n, &fds, end_time); 569 570 if (ret < 0) 571 goto out; 572 if (!ret) { 573 ret = -ERESTARTNOHAND; 574 if (signal_pending(current)) 575 goto out; 576 ret = 0; 577 } 578 579 if (set_fd_set(n, inp, fds.res_in) || 580 set_fd_set(n, outp, fds.res_out) || 581 set_fd_set(n, exp, fds.res_ex)) 582 ret = -EFAULT; 583 584 out: 585 if (bits != stack_fds) 586 kfree(bits); 587 out_nofds: 588 return ret; 589 } 590 591 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 592 fd_set __user *, exp, struct timeval __user *, tvp) 593 { 594 struct timespec end_time, *to = NULL; 595 struct timeval tv; 596 int ret; 597 598 if (tvp) { 599 if (copy_from_user(&tv, tvp, sizeof(tv))) 600 return -EFAULT; 601 602 to = &end_time; 603 if (poll_select_set_timeout(to, 604 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 605 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 606 return -EINVAL; 607 } 608 609 ret = core_sys_select(n, inp, outp, exp, to); 610 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret); 611 612 return ret; 613 } 614 615 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 616 fd_set __user *exp, struct timespec __user *tsp, 617 const sigset_t __user *sigmask, size_t sigsetsize) 618 { 619 sigset_t ksigmask, sigsaved; 620 struct timespec ts, end_time, *to = NULL; 621 int ret; 622 623 if (tsp) { 624 if (copy_from_user(&ts, tsp, sizeof(ts))) 625 return -EFAULT; 626 627 to = &end_time; 628 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 629 return -EINVAL; 630 } 631 632 if (sigmask) { 633 /* XXX: Don't preclude handling different sized sigset_t's. */ 634 if (sigsetsize != sizeof(sigset_t)) 635 return -EINVAL; 636 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 637 return -EFAULT; 638 639 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 640 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 641 } 642 643 ret = core_sys_select(n, inp, outp, exp, to); 644 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 645 646 if (ret == -ERESTARTNOHAND) { 647 /* 648 * Don't restore the signal mask yet. Let do_signal() deliver 649 * the signal on the way back to userspace, before the signal 650 * mask is restored. 651 */ 652 if (sigmask) { 653 memcpy(¤t->saved_sigmask, &sigsaved, 654 sizeof(sigsaved)); 655 set_restore_sigmask(); 656 } 657 } else if (sigmask) 658 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 659 660 return ret; 661 } 662 663 /* 664 * Most architectures can't handle 7-argument syscalls. So we provide a 665 * 6-argument version where the sixth argument is a pointer to a structure 666 * which has a pointer to the sigset_t itself followed by a size_t containing 667 * the sigset size. 668 */ 669 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 670 fd_set __user *, exp, struct timespec __user *, tsp, 671 void __user *, sig) 672 { 673 size_t sigsetsize = 0; 674 sigset_t __user *up = NULL; 675 676 if (sig) { 677 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) 678 || __get_user(up, (sigset_t __user * __user *)sig) 679 || __get_user(sigsetsize, 680 (size_t __user *)(sig+sizeof(void *)))) 681 return -EFAULT; 682 } 683 684 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize); 685 } 686 687 #ifdef __ARCH_WANT_SYS_OLD_SELECT 688 struct sel_arg_struct { 689 unsigned long n; 690 fd_set __user *inp, *outp, *exp; 691 struct timeval __user *tvp; 692 }; 693 694 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) 695 { 696 struct sel_arg_struct a; 697 698 if (copy_from_user(&a, arg, sizeof(a))) 699 return -EFAULT; 700 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp); 701 } 702 #endif 703 704 struct poll_list { 705 struct poll_list *next; 706 int len; 707 struct pollfd entries[0]; 708 }; 709 710 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 711 712 /* 713 * Fish for pollable events on the pollfd->fd file descriptor. We're only 714 * interested in events matching the pollfd->events mask, and the result 715 * matching that mask is both recorded in pollfd->revents and returned. The 716 * pwait poll_table will be used by the fd-provided poll handler for waiting, 717 * if pwait->_qproc is non-NULL. 718 */ 719 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) 720 { 721 unsigned int mask; 722 int fd; 723 724 mask = 0; 725 fd = pollfd->fd; 726 if (fd >= 0) { 727 struct fd f = fdget(fd); 728 mask = POLLNVAL; 729 if (f.file) { 730 mask = DEFAULT_POLLMASK; 731 if (f.file->f_op && f.file->f_op->poll) { 732 pwait->_key = pollfd->events|POLLERR|POLLHUP; 733 mask = f.file->f_op->poll(f.file, pwait); 734 } 735 /* Mask out unneeded events. */ 736 mask &= pollfd->events | POLLERR | POLLHUP; 737 fdput(f); 738 } 739 } 740 pollfd->revents = mask; 741 742 return mask; 743 } 744 745 static int do_poll(unsigned int nfds, struct poll_list *list, 746 struct poll_wqueues *wait, struct timespec *end_time) 747 { 748 poll_table* pt = &wait->pt; 749 ktime_t expire, *to = NULL; 750 int timed_out = 0, count = 0; 751 unsigned long slack = 0; 752 753 /* Optimise the no-wait case */ 754 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 755 pt->_qproc = NULL; 756 timed_out = 1; 757 } 758 759 if (end_time && !timed_out) 760 slack = select_estimate_accuracy(end_time); 761 762 for (;;) { 763 struct poll_list *walk; 764 765 for (walk = list; walk != NULL; walk = walk->next) { 766 struct pollfd * pfd, * pfd_end; 767 768 pfd = walk->entries; 769 pfd_end = pfd + walk->len; 770 for (; pfd != pfd_end; pfd++) { 771 /* 772 * Fish for events. If we found one, record it 773 * and kill poll_table->_qproc, so we don't 774 * needlessly register any other waiters after 775 * this. They'll get immediately deregistered 776 * when we break out and return. 777 */ 778 if (do_pollfd(pfd, pt)) { 779 count++; 780 pt->_qproc = NULL; 781 } 782 } 783 } 784 /* 785 * All waiters have already been registered, so don't provide 786 * a poll_table->_qproc to them on the next loop iteration. 787 */ 788 pt->_qproc = NULL; 789 if (!count) { 790 count = wait->error; 791 if (signal_pending(current)) 792 count = -EINTR; 793 } 794 if (count || timed_out) 795 break; 796 797 /* 798 * If this is the first loop and we have a timeout 799 * given, then we convert to ktime_t and set the to 800 * pointer to the expiry value. 801 */ 802 if (end_time && !to) { 803 expire = timespec_to_ktime(*end_time); 804 to = &expire; 805 } 806 807 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 808 timed_out = 1; 809 } 810 return count; 811 } 812 813 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 814 sizeof(struct pollfd)) 815 816 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 817 struct timespec *end_time) 818 { 819 struct poll_wqueues table; 820 int err = -EFAULT, fdcount, len, size; 821 /* Allocate small arguments on the stack to save memory and be 822 faster - use long to make sure the buffer is aligned properly 823 on 64 bit archs to avoid unaligned access */ 824 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 825 struct poll_list *const head = (struct poll_list *)stack_pps; 826 struct poll_list *walk = head; 827 unsigned long todo = nfds; 828 829 if (nfds > rlimit(RLIMIT_NOFILE)) 830 return -EINVAL; 831 832 len = min_t(unsigned int, nfds, N_STACK_PPS); 833 for (;;) { 834 walk->next = NULL; 835 walk->len = len; 836 if (!len) 837 break; 838 839 if (copy_from_user(walk->entries, ufds + nfds-todo, 840 sizeof(struct pollfd) * walk->len)) 841 goto out_fds; 842 843 todo -= walk->len; 844 if (!todo) 845 break; 846 847 len = min(todo, POLLFD_PER_PAGE); 848 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 849 walk = walk->next = kmalloc(size, GFP_KERNEL); 850 if (!walk) { 851 err = -ENOMEM; 852 goto out_fds; 853 } 854 } 855 856 poll_initwait(&table); 857 fdcount = do_poll(nfds, head, &table, end_time); 858 poll_freewait(&table); 859 860 for (walk = head; walk; walk = walk->next) { 861 struct pollfd *fds = walk->entries; 862 int j; 863 864 for (j = 0; j < walk->len; j++, ufds++) 865 if (__put_user(fds[j].revents, &ufds->revents)) 866 goto out_fds; 867 } 868 869 err = fdcount; 870 out_fds: 871 walk = head->next; 872 while (walk) { 873 struct poll_list *pos = walk; 874 walk = walk->next; 875 kfree(pos); 876 } 877 878 return err; 879 } 880 881 static long do_restart_poll(struct restart_block *restart_block) 882 { 883 struct pollfd __user *ufds = restart_block->poll.ufds; 884 int nfds = restart_block->poll.nfds; 885 struct timespec *to = NULL, end_time; 886 int ret; 887 888 if (restart_block->poll.has_timeout) { 889 end_time.tv_sec = restart_block->poll.tv_sec; 890 end_time.tv_nsec = restart_block->poll.tv_nsec; 891 to = &end_time; 892 } 893 894 ret = do_sys_poll(ufds, nfds, to); 895 896 if (ret == -EINTR) { 897 restart_block->fn = do_restart_poll; 898 ret = -ERESTART_RESTARTBLOCK; 899 } 900 return ret; 901 } 902 903 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 904 int, timeout_msecs) 905 { 906 struct timespec end_time, *to = NULL; 907 int ret; 908 909 if (timeout_msecs >= 0) { 910 to = &end_time; 911 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 912 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 913 } 914 915 ret = do_sys_poll(ufds, nfds, to); 916 917 if (ret == -EINTR) { 918 struct restart_block *restart_block; 919 920 restart_block = ¤t_thread_info()->restart_block; 921 restart_block->fn = do_restart_poll; 922 restart_block->poll.ufds = ufds; 923 restart_block->poll.nfds = nfds; 924 925 if (timeout_msecs >= 0) { 926 restart_block->poll.tv_sec = end_time.tv_sec; 927 restart_block->poll.tv_nsec = end_time.tv_nsec; 928 restart_block->poll.has_timeout = 1; 929 } else 930 restart_block->poll.has_timeout = 0; 931 932 ret = -ERESTART_RESTARTBLOCK; 933 } 934 return ret; 935 } 936 937 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 938 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 939 size_t, sigsetsize) 940 { 941 sigset_t ksigmask, sigsaved; 942 struct timespec ts, end_time, *to = NULL; 943 int ret; 944 945 if (tsp) { 946 if (copy_from_user(&ts, tsp, sizeof(ts))) 947 return -EFAULT; 948 949 to = &end_time; 950 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 951 return -EINVAL; 952 } 953 954 if (sigmask) { 955 /* XXX: Don't preclude handling different sized sigset_t's. */ 956 if (sigsetsize != sizeof(sigset_t)) 957 return -EINVAL; 958 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 959 return -EFAULT; 960 961 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 962 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 963 } 964 965 ret = do_sys_poll(ufds, nfds, to); 966 967 /* We can restart this syscall, usually */ 968 if (ret == -EINTR) { 969 /* 970 * Don't restore the signal mask yet. Let do_signal() deliver 971 * the signal on the way back to userspace, before the signal 972 * mask is restored. 973 */ 974 if (sigmask) { 975 memcpy(¤t->saved_sigmask, &sigsaved, 976 sizeof(sigsaved)); 977 set_restore_sigmask(); 978 } 979 ret = -ERESTARTNOHAND; 980 } else if (sigmask) 981 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 982 983 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 984 985 return ret; 986 } 987