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 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 + 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 wait->_key = POLLEX_SET; 390 if (in & bit) 391 wait->_key |= POLLIN_SET; 392 if (out & bit) 393 wait->_key |= POLLOUT_SET; 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->_qproc = NULL; 416 timed_out = 1; 417 } 418 419 if (end_time && !timed_out) 420 slack = select_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->_qproc = NULL; 461 } 462 if ((mask & POLLOUT_SET) && (out & bit)) { 463 res_out |= bit; 464 retval++; 465 wait->_qproc = NULL; 466 } 467 if ((mask & POLLEX_SET) && (ex & bit)) { 468 res_ex |= bit; 469 retval++; 470 wait->_qproc = 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->_qproc = 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 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 519 fd_set __user *exp, struct timespec *end_time) 520 { 521 fd_set_bits fds; 522 void *bits; 523 int ret, max_fds; 524 unsigned int size; 525 struct fdtable *fdt; 526 /* Allocate small arguments on the stack to save memory and be faster */ 527 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 528 529 ret = -EINVAL; 530 if (n < 0) 531 goto out_nofds; 532 533 /* max_fds can increase, so grab it once to avoid race */ 534 rcu_read_lock(); 535 fdt = files_fdtable(current->files); 536 max_fds = fdt->max_fds; 537 rcu_read_unlock(); 538 if (n > max_fds) 539 n = max_fds; 540 541 /* 542 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 543 * since we used fdset we need to allocate memory in units of 544 * long-words. 545 */ 546 size = FDS_BYTES(n); 547 bits = stack_fds; 548 if (size > sizeof(stack_fds) / 6) { 549 /* Not enough space in on-stack array; must use kmalloc */ 550 ret = -ENOMEM; 551 bits = kmalloc(6 * size, GFP_KERNEL); 552 if (!bits) 553 goto out_nofds; 554 } 555 fds.in = bits; 556 fds.out = bits + size; 557 fds.ex = bits + 2*size; 558 fds.res_in = bits + 3*size; 559 fds.res_out = bits + 4*size; 560 fds.res_ex = bits + 5*size; 561 562 if ((ret = get_fd_set(n, inp, fds.in)) || 563 (ret = get_fd_set(n, outp, fds.out)) || 564 (ret = get_fd_set(n, exp, fds.ex))) 565 goto out; 566 zero_fd_set(n, fds.res_in); 567 zero_fd_set(n, fds.res_out); 568 zero_fd_set(n, fds.res_ex); 569 570 ret = do_select(n, &fds, end_time); 571 572 if (ret < 0) 573 goto out; 574 if (!ret) { 575 ret = -ERESTARTNOHAND; 576 if (signal_pending(current)) 577 goto out; 578 ret = 0; 579 } 580 581 if (set_fd_set(n, inp, fds.res_in) || 582 set_fd_set(n, outp, fds.res_out) || 583 set_fd_set(n, exp, fds.res_ex)) 584 ret = -EFAULT; 585 586 out: 587 if (bits != stack_fds) 588 kfree(bits); 589 out_nofds: 590 return ret; 591 } 592 593 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 594 fd_set __user *, exp, struct timeval __user *, tvp) 595 { 596 struct timespec end_time, *to = NULL; 597 struct timeval tv; 598 int ret; 599 600 if (tvp) { 601 if (copy_from_user(&tv, tvp, sizeof(tv))) 602 return -EFAULT; 603 604 to = &end_time; 605 if (poll_select_set_timeout(to, 606 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 607 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 608 return -EINVAL; 609 } 610 611 ret = core_sys_select(n, inp, outp, exp, to); 612 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret); 613 614 return ret; 615 } 616 617 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 618 fd_set __user *exp, struct timespec __user *tsp, 619 const sigset_t __user *sigmask, size_t sigsetsize) 620 { 621 sigset_t ksigmask, sigsaved; 622 struct timespec ts, end_time, *to = NULL; 623 int ret; 624 625 if (tsp) { 626 if (copy_from_user(&ts, tsp, sizeof(ts))) 627 return -EFAULT; 628 629 to = &end_time; 630 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 631 return -EINVAL; 632 } 633 634 if (sigmask) { 635 /* XXX: Don't preclude handling different sized sigset_t's. */ 636 if (sigsetsize != sizeof(sigset_t)) 637 return -EINVAL; 638 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 639 return -EFAULT; 640 641 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 642 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 643 } 644 645 ret = core_sys_select(n, inp, outp, exp, to); 646 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 647 648 if (ret == -ERESTARTNOHAND) { 649 /* 650 * Don't restore the signal mask yet. Let do_signal() deliver 651 * the signal on the way back to userspace, before the signal 652 * mask is restored. 653 */ 654 if (sigmask) { 655 memcpy(¤t->saved_sigmask, &sigsaved, 656 sizeof(sigsaved)); 657 set_restore_sigmask(); 658 } 659 } else if (sigmask) 660 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 661 662 return ret; 663 } 664 665 /* 666 * Most architectures can't handle 7-argument syscalls. So we provide a 667 * 6-argument version where the sixth argument is a pointer to a structure 668 * which has a pointer to the sigset_t itself followed by a size_t containing 669 * the sigset size. 670 */ 671 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 672 fd_set __user *, exp, struct timespec __user *, tsp, 673 void __user *, sig) 674 { 675 size_t sigsetsize = 0; 676 sigset_t __user *up = NULL; 677 678 if (sig) { 679 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) 680 || __get_user(up, (sigset_t __user * __user *)sig) 681 || __get_user(sigsetsize, 682 (size_t __user *)(sig+sizeof(void *)))) 683 return -EFAULT; 684 } 685 686 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize); 687 } 688 689 #ifdef __ARCH_WANT_SYS_OLD_SELECT 690 struct sel_arg_struct { 691 unsigned long n; 692 fd_set __user *inp, *outp, *exp; 693 struct timeval __user *tvp; 694 }; 695 696 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) 697 { 698 struct sel_arg_struct a; 699 700 if (copy_from_user(&a, arg, sizeof(a))) 701 return -EFAULT; 702 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp); 703 } 704 #endif 705 706 struct poll_list { 707 struct poll_list *next; 708 int len; 709 struct pollfd entries[0]; 710 }; 711 712 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 713 714 /* 715 * Fish for pollable events on the pollfd->fd file descriptor. We're only 716 * interested in events matching the pollfd->events mask, and the result 717 * matching that mask is both recorded in pollfd->revents and returned. The 718 * pwait poll_table will be used by the fd-provided poll handler for waiting, 719 * if pwait->_qproc is non-NULL. 720 */ 721 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) 722 { 723 unsigned int mask; 724 int fd; 725 726 mask = 0; 727 fd = pollfd->fd; 728 if (fd >= 0) { 729 int fput_needed; 730 struct file * file; 731 732 file = fget_light(fd, &fput_needed); 733 mask = POLLNVAL; 734 if (file != NULL) { 735 mask = DEFAULT_POLLMASK; 736 if (file->f_op && file->f_op->poll) { 737 pwait->_key = pollfd->events|POLLERR|POLLHUP; 738 mask = file->f_op->poll(file, pwait); 739 } 740 /* Mask out unneeded events. */ 741 mask &= pollfd->events | POLLERR | POLLHUP; 742 fput_light(file, fput_needed); 743 } 744 } 745 pollfd->revents = mask; 746 747 return mask; 748 } 749 750 static int do_poll(unsigned int nfds, struct poll_list *list, 751 struct poll_wqueues *wait, struct timespec *end_time) 752 { 753 poll_table* pt = &wait->pt; 754 ktime_t expire, *to = NULL; 755 int timed_out = 0, count = 0; 756 unsigned long slack = 0; 757 758 /* Optimise the no-wait case */ 759 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 760 pt->_qproc = NULL; 761 timed_out = 1; 762 } 763 764 if (end_time && !timed_out) 765 slack = select_estimate_accuracy(end_time); 766 767 for (;;) { 768 struct poll_list *walk; 769 770 for (walk = list; walk != NULL; walk = walk->next) { 771 struct pollfd * pfd, * pfd_end; 772 773 pfd = walk->entries; 774 pfd_end = pfd + walk->len; 775 for (; pfd != pfd_end; pfd++) { 776 /* 777 * Fish for events. If we found one, record it 778 * and kill poll_table->_qproc, so we don't 779 * needlessly register any other waiters after 780 * this. They'll get immediately deregistered 781 * when we break out and return. 782 */ 783 if (do_pollfd(pfd, pt)) { 784 count++; 785 pt->_qproc = NULL; 786 } 787 } 788 } 789 /* 790 * All waiters have already been registered, so don't provide 791 * a poll_table->_qproc to them on the next loop iteration. 792 */ 793 pt->_qproc = NULL; 794 if (!count) { 795 count = wait->error; 796 if (signal_pending(current)) 797 count = -EINTR; 798 } 799 if (count || timed_out) 800 break; 801 802 /* 803 * If this is the first loop and we have a timeout 804 * given, then we convert to ktime_t and set the to 805 * pointer to the expiry value. 806 */ 807 if (end_time && !to) { 808 expire = timespec_to_ktime(*end_time); 809 to = &expire; 810 } 811 812 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 813 timed_out = 1; 814 } 815 return count; 816 } 817 818 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 819 sizeof(struct pollfd)) 820 821 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 822 struct timespec *end_time) 823 { 824 struct poll_wqueues table; 825 int err = -EFAULT, fdcount, len, size; 826 /* Allocate small arguments on the stack to save memory and be 827 faster - use long to make sure the buffer is aligned properly 828 on 64 bit archs to avoid unaligned access */ 829 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 830 struct poll_list *const head = (struct poll_list *)stack_pps; 831 struct poll_list *walk = head; 832 unsigned long todo = nfds; 833 834 if (nfds > rlimit(RLIMIT_NOFILE)) 835 return -EINVAL; 836 837 len = min_t(unsigned int, nfds, N_STACK_PPS); 838 for (;;) { 839 walk->next = NULL; 840 walk->len = len; 841 if (!len) 842 break; 843 844 if (copy_from_user(walk->entries, ufds + nfds-todo, 845 sizeof(struct pollfd) * walk->len)) 846 goto out_fds; 847 848 todo -= walk->len; 849 if (!todo) 850 break; 851 852 len = min(todo, POLLFD_PER_PAGE); 853 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 854 walk = walk->next = kmalloc(size, GFP_KERNEL); 855 if (!walk) { 856 err = -ENOMEM; 857 goto out_fds; 858 } 859 } 860 861 poll_initwait(&table); 862 fdcount = do_poll(nfds, head, &table, end_time); 863 poll_freewait(&table); 864 865 for (walk = head; walk; walk = walk->next) { 866 struct pollfd *fds = walk->entries; 867 int j; 868 869 for (j = 0; j < walk->len; j++, ufds++) 870 if (__put_user(fds[j].revents, &ufds->revents)) 871 goto out_fds; 872 } 873 874 err = fdcount; 875 out_fds: 876 walk = head->next; 877 while (walk) { 878 struct poll_list *pos = walk; 879 walk = walk->next; 880 kfree(pos); 881 } 882 883 return err; 884 } 885 886 static long do_restart_poll(struct restart_block *restart_block) 887 { 888 struct pollfd __user *ufds = restart_block->poll.ufds; 889 int nfds = restart_block->poll.nfds; 890 struct timespec *to = NULL, end_time; 891 int ret; 892 893 if (restart_block->poll.has_timeout) { 894 end_time.tv_sec = restart_block->poll.tv_sec; 895 end_time.tv_nsec = restart_block->poll.tv_nsec; 896 to = &end_time; 897 } 898 899 ret = do_sys_poll(ufds, nfds, to); 900 901 if (ret == -EINTR) { 902 restart_block->fn = do_restart_poll; 903 ret = -ERESTART_RESTARTBLOCK; 904 } 905 return ret; 906 } 907 908 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 909 int, timeout_msecs) 910 { 911 struct timespec end_time, *to = NULL; 912 int ret; 913 914 if (timeout_msecs >= 0) { 915 to = &end_time; 916 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 917 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 918 } 919 920 ret = do_sys_poll(ufds, nfds, to); 921 922 if (ret == -EINTR) { 923 struct restart_block *restart_block; 924 925 restart_block = ¤t_thread_info()->restart_block; 926 restart_block->fn = do_restart_poll; 927 restart_block->poll.ufds = ufds; 928 restart_block->poll.nfds = nfds; 929 930 if (timeout_msecs >= 0) { 931 restart_block->poll.tv_sec = end_time.tv_sec; 932 restart_block->poll.tv_nsec = end_time.tv_nsec; 933 restart_block->poll.has_timeout = 1; 934 } else 935 restart_block->poll.has_timeout = 0; 936 937 ret = -ERESTART_RESTARTBLOCK; 938 } 939 return ret; 940 } 941 942 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 943 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 944 size_t, sigsetsize) 945 { 946 sigset_t ksigmask, sigsaved; 947 struct timespec ts, end_time, *to = NULL; 948 int ret; 949 950 if (tsp) { 951 if (copy_from_user(&ts, tsp, sizeof(ts))) 952 return -EFAULT; 953 954 to = &end_time; 955 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 956 return -EINVAL; 957 } 958 959 if (sigmask) { 960 /* XXX: Don't preclude handling different sized sigset_t's. */ 961 if (sigsetsize != sizeof(sigset_t)) 962 return -EINVAL; 963 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 964 return -EFAULT; 965 966 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 967 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 968 } 969 970 ret = do_sys_poll(ufds, nfds, to); 971 972 /* We can restart this syscall, usually */ 973 if (ret == -EINTR) { 974 /* 975 * Don't restore the signal mask yet. Let do_signal() deliver 976 * the signal on the way back to userspace, before the signal 977 * mask is restored. 978 */ 979 if (sigmask) { 980 memcpy(¤t->saved_sigmask, &sigsaved, 981 sizeof(sigsaved)); 982 set_restore_sigmask(); 983 } 984 ret = -ERESTARTNOHAND; 985 } else if (sigmask) 986 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 987 988 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 989 990 return ret; 991 } 992