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 #include <linux/sched/rt.h> 30 #include <linux/freezer.h> 31 #include <net/busy_poll.h> 32 33 #include <asm/uaccess.h> 34 35 36 /* 37 * Estimate expected accuracy in ns from a timeval. 38 * 39 * After quite a bit of churning around, we've settled on 40 * a simple thing of taking 0.1% of the timeout as the 41 * slack, with a cap of 100 msec. 42 * "nice" tasks get a 0.5% slack instead. 43 * 44 * Consider this comment an open invitation to come up with even 45 * better solutions.. 46 */ 47 48 #define MAX_SLACK (100 * NSEC_PER_MSEC) 49 50 static long __estimate_accuracy(struct timespec *tv) 51 { 52 long slack; 53 int divfactor = 1000; 54 55 if (tv->tv_sec < 0) 56 return 0; 57 58 if (task_nice(current) > 0) 59 divfactor = divfactor / 5; 60 61 if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor)) 62 return MAX_SLACK; 63 64 slack = tv->tv_nsec / divfactor; 65 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); 66 67 if (slack > MAX_SLACK) 68 return MAX_SLACK; 69 70 return slack; 71 } 72 73 long select_estimate_accuracy(struct timespec *tv) 74 { 75 unsigned long ret; 76 struct timespec now; 77 78 /* 79 * Realtime tasks get a slack of 0 for obvious reasons. 80 */ 81 82 if (rt_task(current)) 83 return 0; 84 85 ktime_get_ts(&now); 86 now = timespec_sub(*tv, now); 87 ret = __estimate_accuracy(&now); 88 if (ret < current->timer_slack_ns) 89 return current->timer_slack_ns; 90 return ret; 91 } 92 93 94 95 struct poll_table_page { 96 struct poll_table_page * next; 97 struct poll_table_entry * entry; 98 struct poll_table_entry entries[0]; 99 }; 100 101 #define POLL_TABLE_FULL(table) \ 102 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table)) 103 104 /* 105 * Ok, Peter made a complicated, but straightforward multiple_wait() function. 106 * I have rewritten this, taking some shortcuts: This code may not be easy to 107 * follow, but it should be free of race-conditions, and it's practical. If you 108 * understand what I'm doing here, then you understand how the linux 109 * sleep/wakeup mechanism works. 110 * 111 * Two very simple procedures, poll_wait() and poll_freewait() make all the 112 * work. poll_wait() is an inline-function defined in <linux/poll.h>, 113 * as all select/poll functions have to call it to add an entry to the 114 * poll table. 115 */ 116 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 117 poll_table *p); 118 119 void poll_initwait(struct poll_wqueues *pwq) 120 { 121 init_poll_funcptr(&pwq->pt, __pollwait); 122 pwq->polling_task = current; 123 pwq->triggered = 0; 124 pwq->error = 0; 125 pwq->table = NULL; 126 pwq->inline_index = 0; 127 } 128 EXPORT_SYMBOL(poll_initwait); 129 130 static void free_poll_entry(struct poll_table_entry *entry) 131 { 132 remove_wait_queue(entry->wait_address, &entry->wait); 133 fput(entry->filp); 134 } 135 136 void poll_freewait(struct poll_wqueues *pwq) 137 { 138 struct poll_table_page * p = pwq->table; 139 int i; 140 for (i = 0; i < pwq->inline_index; i++) 141 free_poll_entry(pwq->inline_entries + i); 142 while (p) { 143 struct poll_table_entry * entry; 144 struct poll_table_page *old; 145 146 entry = p->entry; 147 do { 148 entry--; 149 free_poll_entry(entry); 150 } while (entry > p->entries); 151 old = p; 152 p = p->next; 153 free_page((unsigned long) old); 154 } 155 } 156 EXPORT_SYMBOL(poll_freewait); 157 158 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) 159 { 160 struct poll_table_page *table = p->table; 161 162 if (p->inline_index < N_INLINE_POLL_ENTRIES) 163 return p->inline_entries + p->inline_index++; 164 165 if (!table || POLL_TABLE_FULL(table)) { 166 struct poll_table_page *new_table; 167 168 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL); 169 if (!new_table) { 170 p->error = -ENOMEM; 171 return NULL; 172 } 173 new_table->entry = new_table->entries; 174 new_table->next = table; 175 p->table = new_table; 176 table = new_table; 177 } 178 179 return table->entry++; 180 } 181 182 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 183 { 184 struct poll_wqueues *pwq = wait->private; 185 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); 186 187 /* 188 * Although this function is called under waitqueue lock, LOCK 189 * doesn't imply write barrier and the users expect write 190 * barrier semantics on wakeup functions. The following 191 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up() 192 * and is paired with smp_store_mb() in poll_schedule_timeout. 193 */ 194 smp_wmb(); 195 pwq->triggered = 1; 196 197 /* 198 * Perform the default wake up operation using a dummy 199 * waitqueue. 200 * 201 * TODO: This is hacky but there currently is no interface to 202 * pass in @sync. @sync is scheduled to be removed and once 203 * that happens, wake_up_process() can be used directly. 204 */ 205 return default_wake_function(&dummy_wait, mode, sync, key); 206 } 207 208 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 209 { 210 struct poll_table_entry *entry; 211 212 entry = container_of(wait, struct poll_table_entry, wait); 213 if (key && !((unsigned long)key & entry->key)) 214 return 0; 215 return __pollwake(wait, mode, sync, key); 216 } 217 218 /* Add a new entry */ 219 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 220 poll_table *p) 221 { 222 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); 223 struct poll_table_entry *entry = poll_get_entry(pwq); 224 if (!entry) 225 return; 226 entry->filp = get_file(filp); 227 entry->wait_address = wait_address; 228 entry->key = p->_key; 229 init_waitqueue_func_entry(&entry->wait, pollwake); 230 entry->wait.private = pwq; 231 add_wait_queue(wait_address, &entry->wait); 232 } 233 234 int poll_schedule_timeout(struct poll_wqueues *pwq, int state, 235 ktime_t *expires, unsigned long slack) 236 { 237 int rc = -EINTR; 238 239 set_current_state(state); 240 if (!pwq->triggered) 241 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS); 242 __set_current_state(TASK_RUNNING); 243 244 /* 245 * Prepare for the next iteration. 246 * 247 * The following smp_store_mb() serves two purposes. First, it's 248 * the counterpart rmb of the wmb in pollwake() such that data 249 * written before wake up is always visible after wake up. 250 * Second, the full barrier guarantees that triggered clearing 251 * doesn't pass event check of the next iteration. Note that 252 * this problem doesn't exist for the first iteration as 253 * add_wait_queue() has full barrier semantics. 254 */ 255 smp_store_mb(pwq->triggered, 0); 256 257 return rc; 258 } 259 EXPORT_SYMBOL(poll_schedule_timeout); 260 261 /** 262 * poll_select_set_timeout - helper function to setup the timeout value 263 * @to: pointer to timespec variable for the final timeout 264 * @sec: seconds (from user space) 265 * @nsec: nanoseconds (from user space) 266 * 267 * Note, we do not use a timespec for the user space value here, That 268 * way we can use the function for timeval and compat interfaces as well. 269 * 270 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. 271 */ 272 int poll_select_set_timeout(struct timespec *to, long sec, long nsec) 273 { 274 struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec}; 275 276 if (!timespec_valid(&ts)) 277 return -EINVAL; 278 279 /* Optimize for the zero timeout value here */ 280 if (!sec && !nsec) { 281 to->tv_sec = to->tv_nsec = 0; 282 } else { 283 ktime_get_ts(to); 284 *to = timespec_add_safe(*to, ts); 285 } 286 return 0; 287 } 288 289 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p, 290 int timeval, int ret) 291 { 292 struct timespec rts; 293 struct timeval rtv; 294 295 if (!p) 296 return ret; 297 298 if (current->personality & STICKY_TIMEOUTS) 299 goto sticky; 300 301 /* No update for zero timeout */ 302 if (!end_time->tv_sec && !end_time->tv_nsec) 303 return ret; 304 305 ktime_get_ts(&rts); 306 rts = timespec_sub(*end_time, rts); 307 if (rts.tv_sec < 0) 308 rts.tv_sec = rts.tv_nsec = 0; 309 310 if (timeval) { 311 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) 312 memset(&rtv, 0, sizeof(rtv)); 313 rtv.tv_sec = rts.tv_sec; 314 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC; 315 316 if (!copy_to_user(p, &rtv, sizeof(rtv))) 317 return ret; 318 319 } else if (!copy_to_user(p, &rts, sizeof(rts))) 320 return ret; 321 322 /* 323 * If an application puts its timeval in read-only memory, we 324 * don't want the Linux-specific update to the timeval to 325 * cause a fault after the select has completed 326 * successfully. However, because we're not updating the 327 * timeval, we can't restart the system call. 328 */ 329 330 sticky: 331 if (ret == -ERESTARTNOHAND) 332 ret = -EINTR; 333 return ret; 334 } 335 336 #define FDS_IN(fds, n) (fds->in + n) 337 #define FDS_OUT(fds, n) (fds->out + n) 338 #define FDS_EX(fds, n) (fds->ex + n) 339 340 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 341 342 static int max_select_fd(unsigned long n, fd_set_bits *fds) 343 { 344 unsigned long *open_fds; 345 unsigned long set; 346 int max; 347 struct fdtable *fdt; 348 349 /* handle last in-complete long-word first */ 350 set = ~(~0UL << (n & (BITS_PER_LONG-1))); 351 n /= BITS_PER_LONG; 352 fdt = files_fdtable(current->files); 353 open_fds = fdt->open_fds + n; 354 max = 0; 355 if (set) { 356 set &= BITS(fds, n); 357 if (set) { 358 if (!(set & ~*open_fds)) 359 goto get_max; 360 return -EBADF; 361 } 362 } 363 while (n) { 364 open_fds--; 365 n--; 366 set = BITS(fds, n); 367 if (!set) 368 continue; 369 if (set & ~*open_fds) 370 return -EBADF; 371 if (max) 372 continue; 373 get_max: 374 do { 375 max++; 376 set >>= 1; 377 } while (set); 378 max += n * BITS_PER_LONG; 379 } 380 381 return max; 382 } 383 384 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) 385 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) 386 #define POLLEX_SET (POLLPRI) 387 388 static inline void wait_key_set(poll_table *wait, unsigned long in, 389 unsigned long out, unsigned long bit, 390 unsigned int ll_flag) 391 { 392 wait->_key = POLLEX_SET | ll_flag; 393 if (in & bit) 394 wait->_key |= POLLIN_SET; 395 if (out & bit) 396 wait->_key |= POLLOUT_SET; 397 } 398 399 int do_select(int n, fd_set_bits *fds, struct timespec *end_time) 400 { 401 ktime_t expire, *to = NULL; 402 struct poll_wqueues table; 403 poll_table *wait; 404 int retval, i, timed_out = 0; 405 unsigned long slack = 0; 406 unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; 407 unsigned long busy_end = 0; 408 409 rcu_read_lock(); 410 retval = max_select_fd(n, fds); 411 rcu_read_unlock(); 412 413 if (retval < 0) 414 return retval; 415 n = retval; 416 417 poll_initwait(&table); 418 wait = &table.pt; 419 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 420 wait->_qproc = NULL; 421 timed_out = 1; 422 } 423 424 if (end_time && !timed_out) 425 slack = select_estimate_accuracy(end_time); 426 427 retval = 0; 428 for (;;) { 429 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; 430 bool can_busy_loop = false; 431 432 inp = fds->in; outp = fds->out; exp = fds->ex; 433 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; 434 435 for (i = 0; i < n; ++rinp, ++routp, ++rexp) { 436 unsigned long in, out, ex, all_bits, bit = 1, mask, j; 437 unsigned long res_in = 0, res_out = 0, res_ex = 0; 438 439 in = *inp++; out = *outp++; ex = *exp++; 440 all_bits = in | out | ex; 441 if (all_bits == 0) { 442 i += BITS_PER_LONG; 443 continue; 444 } 445 446 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) { 447 struct fd f; 448 if (i >= n) 449 break; 450 if (!(bit & all_bits)) 451 continue; 452 f = fdget(i); 453 if (f.file) { 454 const struct file_operations *f_op; 455 f_op = f.file->f_op; 456 mask = DEFAULT_POLLMASK; 457 if (f_op->poll) { 458 wait_key_set(wait, in, out, 459 bit, busy_flag); 460 mask = (*f_op->poll)(f.file, wait); 461 } 462 fdput(f); 463 if ((mask & POLLIN_SET) && (in & bit)) { 464 res_in |= bit; 465 retval++; 466 wait->_qproc = NULL; 467 } 468 if ((mask & POLLOUT_SET) && (out & bit)) { 469 res_out |= bit; 470 retval++; 471 wait->_qproc = NULL; 472 } 473 if ((mask & POLLEX_SET) && (ex & bit)) { 474 res_ex |= bit; 475 retval++; 476 wait->_qproc = NULL; 477 } 478 /* got something, stop busy polling */ 479 if (retval) { 480 can_busy_loop = false; 481 busy_flag = 0; 482 483 /* 484 * only remember a returned 485 * POLL_BUSY_LOOP if we asked for it 486 */ 487 } else if (busy_flag & mask) 488 can_busy_loop = true; 489 490 } 491 } 492 if (res_in) 493 *rinp = res_in; 494 if (res_out) 495 *routp = res_out; 496 if (res_ex) 497 *rexp = res_ex; 498 cond_resched(); 499 } 500 wait->_qproc = NULL; 501 if (retval || timed_out || signal_pending(current)) 502 break; 503 if (table.error) { 504 retval = table.error; 505 break; 506 } 507 508 /* only if found POLL_BUSY_LOOP sockets && not out of time */ 509 if (can_busy_loop && !need_resched()) { 510 if (!busy_end) { 511 busy_end = busy_loop_end_time(); 512 continue; 513 } 514 if (!busy_loop_timeout(busy_end)) 515 continue; 516 } 517 busy_flag = 0; 518 519 /* 520 * If this is the first loop and we have a timeout 521 * given, then we convert to ktime_t and set the to 522 * pointer to the expiry value. 523 */ 524 if (end_time && !to) { 525 expire = timespec_to_ktime(*end_time); 526 to = &expire; 527 } 528 529 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 530 to, slack)) 531 timed_out = 1; 532 } 533 534 poll_freewait(&table); 535 536 return retval; 537 } 538 539 /* 540 * We can actually return ERESTARTSYS instead of EINTR, but I'd 541 * like to be certain this leads to no problems. So I return 542 * EINTR just for safety. 543 * 544 * Update: ERESTARTSYS breaks at least the xview clock binary, so 545 * I'm trying ERESTARTNOHAND which restart only when you want to. 546 */ 547 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 548 fd_set __user *exp, struct timespec *end_time) 549 { 550 fd_set_bits fds; 551 void *bits; 552 int ret, max_fds; 553 unsigned int size; 554 struct fdtable *fdt; 555 /* Allocate small arguments on the stack to save memory and be faster */ 556 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 557 558 ret = -EINVAL; 559 if (n < 0) 560 goto out_nofds; 561 562 /* max_fds can increase, so grab it once to avoid race */ 563 rcu_read_lock(); 564 fdt = files_fdtable(current->files); 565 max_fds = fdt->max_fds; 566 rcu_read_unlock(); 567 if (n > max_fds) 568 n = max_fds; 569 570 /* 571 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 572 * since we used fdset we need to allocate memory in units of 573 * long-words. 574 */ 575 size = FDS_BYTES(n); 576 bits = stack_fds; 577 if (size > sizeof(stack_fds) / 6) { 578 /* Not enough space in on-stack array; must use kmalloc */ 579 ret = -ENOMEM; 580 bits = kmalloc(6 * size, GFP_KERNEL); 581 if (!bits) 582 goto out_nofds; 583 } 584 fds.in = bits; 585 fds.out = bits + size; 586 fds.ex = bits + 2*size; 587 fds.res_in = bits + 3*size; 588 fds.res_out = bits + 4*size; 589 fds.res_ex = bits + 5*size; 590 591 if ((ret = get_fd_set(n, inp, fds.in)) || 592 (ret = get_fd_set(n, outp, fds.out)) || 593 (ret = get_fd_set(n, exp, fds.ex))) 594 goto out; 595 zero_fd_set(n, fds.res_in); 596 zero_fd_set(n, fds.res_out); 597 zero_fd_set(n, fds.res_ex); 598 599 ret = do_select(n, &fds, end_time); 600 601 if (ret < 0) 602 goto out; 603 if (!ret) { 604 ret = -ERESTARTNOHAND; 605 if (signal_pending(current)) 606 goto out; 607 ret = 0; 608 } 609 610 if (set_fd_set(n, inp, fds.res_in) || 611 set_fd_set(n, outp, fds.res_out) || 612 set_fd_set(n, exp, fds.res_ex)) 613 ret = -EFAULT; 614 615 out: 616 if (bits != stack_fds) 617 kfree(bits); 618 out_nofds: 619 return ret; 620 } 621 622 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 623 fd_set __user *, exp, struct timeval __user *, tvp) 624 { 625 struct timespec end_time, *to = NULL; 626 struct timeval tv; 627 int ret; 628 629 if (tvp) { 630 if (copy_from_user(&tv, tvp, sizeof(tv))) 631 return -EFAULT; 632 633 to = &end_time; 634 if (poll_select_set_timeout(to, 635 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 636 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 637 return -EINVAL; 638 } 639 640 ret = core_sys_select(n, inp, outp, exp, to); 641 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret); 642 643 return ret; 644 } 645 646 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 647 fd_set __user *exp, struct timespec __user *tsp, 648 const sigset_t __user *sigmask, size_t sigsetsize) 649 { 650 sigset_t ksigmask, sigsaved; 651 struct timespec ts, end_time, *to = NULL; 652 int ret; 653 654 if (tsp) { 655 if (copy_from_user(&ts, tsp, sizeof(ts))) 656 return -EFAULT; 657 658 to = &end_time; 659 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 660 return -EINVAL; 661 } 662 663 if (sigmask) { 664 /* XXX: Don't preclude handling different sized sigset_t's. */ 665 if (sigsetsize != sizeof(sigset_t)) 666 return -EINVAL; 667 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 668 return -EFAULT; 669 670 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 671 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 672 } 673 674 ret = core_sys_select(n, inp, outp, exp, to); 675 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 676 677 if (ret == -ERESTARTNOHAND) { 678 /* 679 * Don't restore the signal mask yet. Let do_signal() deliver 680 * the signal on the way back to userspace, before the signal 681 * mask is restored. 682 */ 683 if (sigmask) { 684 memcpy(¤t->saved_sigmask, &sigsaved, 685 sizeof(sigsaved)); 686 set_restore_sigmask(); 687 } 688 } else if (sigmask) 689 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 690 691 return ret; 692 } 693 694 /* 695 * Most architectures can't handle 7-argument syscalls. So we provide a 696 * 6-argument version where the sixth argument is a pointer to a structure 697 * which has a pointer to the sigset_t itself followed by a size_t containing 698 * the sigset size. 699 */ 700 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 701 fd_set __user *, exp, struct timespec __user *, tsp, 702 void __user *, sig) 703 { 704 size_t sigsetsize = 0; 705 sigset_t __user *up = NULL; 706 707 if (sig) { 708 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) 709 || __get_user(up, (sigset_t __user * __user *)sig) 710 || __get_user(sigsetsize, 711 (size_t __user *)(sig+sizeof(void *)))) 712 return -EFAULT; 713 } 714 715 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize); 716 } 717 718 #ifdef __ARCH_WANT_SYS_OLD_SELECT 719 struct sel_arg_struct { 720 unsigned long n; 721 fd_set __user *inp, *outp, *exp; 722 struct timeval __user *tvp; 723 }; 724 725 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) 726 { 727 struct sel_arg_struct a; 728 729 if (copy_from_user(&a, arg, sizeof(a))) 730 return -EFAULT; 731 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp); 732 } 733 #endif 734 735 struct poll_list { 736 struct poll_list *next; 737 int len; 738 struct pollfd entries[0]; 739 }; 740 741 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 742 743 /* 744 * Fish for pollable events on the pollfd->fd file descriptor. We're only 745 * interested in events matching the pollfd->events mask, and the result 746 * matching that mask is both recorded in pollfd->revents and returned. The 747 * pwait poll_table will be used by the fd-provided poll handler for waiting, 748 * if pwait->_qproc is non-NULL. 749 */ 750 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait, 751 bool *can_busy_poll, 752 unsigned int busy_flag) 753 { 754 unsigned int mask; 755 int fd; 756 757 mask = 0; 758 fd = pollfd->fd; 759 if (fd >= 0) { 760 struct fd f = fdget(fd); 761 mask = POLLNVAL; 762 if (f.file) { 763 mask = DEFAULT_POLLMASK; 764 if (f.file->f_op->poll) { 765 pwait->_key = pollfd->events|POLLERR|POLLHUP; 766 pwait->_key |= busy_flag; 767 mask = f.file->f_op->poll(f.file, pwait); 768 if (mask & busy_flag) 769 *can_busy_poll = true; 770 } 771 /* Mask out unneeded events. */ 772 mask &= pollfd->events | POLLERR | POLLHUP; 773 fdput(f); 774 } 775 } 776 pollfd->revents = mask; 777 778 return mask; 779 } 780 781 static int do_poll(unsigned int nfds, struct poll_list *list, 782 struct poll_wqueues *wait, struct timespec *end_time) 783 { 784 poll_table* pt = &wait->pt; 785 ktime_t expire, *to = NULL; 786 int timed_out = 0, count = 0; 787 unsigned long slack = 0; 788 unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; 789 unsigned long busy_end = 0; 790 791 /* Optimise the no-wait case */ 792 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 793 pt->_qproc = NULL; 794 timed_out = 1; 795 } 796 797 if (end_time && !timed_out) 798 slack = select_estimate_accuracy(end_time); 799 800 for (;;) { 801 struct poll_list *walk; 802 bool can_busy_loop = false; 803 804 for (walk = list; walk != NULL; walk = walk->next) { 805 struct pollfd * pfd, * pfd_end; 806 807 pfd = walk->entries; 808 pfd_end = pfd + walk->len; 809 for (; pfd != pfd_end; pfd++) { 810 /* 811 * Fish for events. If we found one, record it 812 * and kill poll_table->_qproc, so we don't 813 * needlessly register any other waiters after 814 * this. They'll get immediately deregistered 815 * when we break out and return. 816 */ 817 if (do_pollfd(pfd, pt, &can_busy_loop, 818 busy_flag)) { 819 count++; 820 pt->_qproc = NULL; 821 /* found something, stop busy polling */ 822 busy_flag = 0; 823 can_busy_loop = false; 824 } 825 } 826 } 827 /* 828 * All waiters have already been registered, so don't provide 829 * a poll_table->_qproc to them on the next loop iteration. 830 */ 831 pt->_qproc = NULL; 832 if (!count) { 833 count = wait->error; 834 if (signal_pending(current)) 835 count = -EINTR; 836 } 837 if (count || timed_out) 838 break; 839 840 /* only if found POLL_BUSY_LOOP sockets && not out of time */ 841 if (can_busy_loop && !need_resched()) { 842 if (!busy_end) { 843 busy_end = busy_loop_end_time(); 844 continue; 845 } 846 if (!busy_loop_timeout(busy_end)) 847 continue; 848 } 849 busy_flag = 0; 850 851 /* 852 * If this is the first loop and we have a timeout 853 * given, then we convert to ktime_t and set the to 854 * pointer to the expiry value. 855 */ 856 if (end_time && !to) { 857 expire = timespec_to_ktime(*end_time); 858 to = &expire; 859 } 860 861 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 862 timed_out = 1; 863 } 864 return count; 865 } 866 867 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 868 sizeof(struct pollfd)) 869 870 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 871 struct timespec *end_time) 872 { 873 struct poll_wqueues table; 874 int err = -EFAULT, fdcount, len, size; 875 /* Allocate small arguments on the stack to save memory and be 876 faster - use long to make sure the buffer is aligned properly 877 on 64 bit archs to avoid unaligned access */ 878 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 879 struct poll_list *const head = (struct poll_list *)stack_pps; 880 struct poll_list *walk = head; 881 unsigned long todo = nfds; 882 883 if (nfds > rlimit(RLIMIT_NOFILE)) 884 return -EINVAL; 885 886 len = min_t(unsigned int, nfds, N_STACK_PPS); 887 for (;;) { 888 walk->next = NULL; 889 walk->len = len; 890 if (!len) 891 break; 892 893 if (copy_from_user(walk->entries, ufds + nfds-todo, 894 sizeof(struct pollfd) * walk->len)) 895 goto out_fds; 896 897 todo -= walk->len; 898 if (!todo) 899 break; 900 901 len = min(todo, POLLFD_PER_PAGE); 902 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 903 walk = walk->next = kmalloc(size, GFP_KERNEL); 904 if (!walk) { 905 err = -ENOMEM; 906 goto out_fds; 907 } 908 } 909 910 poll_initwait(&table); 911 fdcount = do_poll(nfds, head, &table, end_time); 912 poll_freewait(&table); 913 914 for (walk = head; walk; walk = walk->next) { 915 struct pollfd *fds = walk->entries; 916 int j; 917 918 for (j = 0; j < walk->len; j++, ufds++) 919 if (__put_user(fds[j].revents, &ufds->revents)) 920 goto out_fds; 921 } 922 923 err = fdcount; 924 out_fds: 925 walk = head->next; 926 while (walk) { 927 struct poll_list *pos = walk; 928 walk = walk->next; 929 kfree(pos); 930 } 931 932 return err; 933 } 934 935 static long do_restart_poll(struct restart_block *restart_block) 936 { 937 struct pollfd __user *ufds = restart_block->poll.ufds; 938 int nfds = restart_block->poll.nfds; 939 struct timespec *to = NULL, end_time; 940 int ret; 941 942 if (restart_block->poll.has_timeout) { 943 end_time.tv_sec = restart_block->poll.tv_sec; 944 end_time.tv_nsec = restart_block->poll.tv_nsec; 945 to = &end_time; 946 } 947 948 ret = do_sys_poll(ufds, nfds, to); 949 950 if (ret == -EINTR) { 951 restart_block->fn = do_restart_poll; 952 ret = -ERESTART_RESTARTBLOCK; 953 } 954 return ret; 955 } 956 957 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 958 int, timeout_msecs) 959 { 960 struct timespec end_time, *to = NULL; 961 int ret; 962 963 if (timeout_msecs >= 0) { 964 to = &end_time; 965 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 966 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 967 } 968 969 ret = do_sys_poll(ufds, nfds, to); 970 971 if (ret == -EINTR) { 972 struct restart_block *restart_block; 973 974 restart_block = ¤t->restart_block; 975 restart_block->fn = do_restart_poll; 976 restart_block->poll.ufds = ufds; 977 restart_block->poll.nfds = nfds; 978 979 if (timeout_msecs >= 0) { 980 restart_block->poll.tv_sec = end_time.tv_sec; 981 restart_block->poll.tv_nsec = end_time.tv_nsec; 982 restart_block->poll.has_timeout = 1; 983 } else 984 restart_block->poll.has_timeout = 0; 985 986 ret = -ERESTART_RESTARTBLOCK; 987 } 988 return ret; 989 } 990 991 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 992 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 993 size_t, sigsetsize) 994 { 995 sigset_t ksigmask, sigsaved; 996 struct timespec ts, end_time, *to = NULL; 997 int ret; 998 999 if (tsp) { 1000 if (copy_from_user(&ts, tsp, sizeof(ts))) 1001 return -EFAULT; 1002 1003 to = &end_time; 1004 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 1005 return -EINVAL; 1006 } 1007 1008 if (sigmask) { 1009 /* XXX: Don't preclude handling different sized sigset_t's. */ 1010 if (sigsetsize != sizeof(sigset_t)) 1011 return -EINVAL; 1012 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 1013 return -EFAULT; 1014 1015 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 1016 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 1017 } 1018 1019 ret = do_sys_poll(ufds, nfds, to); 1020 1021 /* We can restart this syscall, usually */ 1022 if (ret == -EINTR) { 1023 /* 1024 * Don't restore the signal mask yet. Let do_signal() deliver 1025 * the signal on the way back to userspace, before the signal 1026 * mask is restored. 1027 */ 1028 if (sigmask) { 1029 memcpy(¤t->saved_sigmask, &sigsaved, 1030 sizeof(sigsaved)); 1031 set_restore_sigmask(); 1032 } 1033 ret = -ERESTARTNOHAND; 1034 } else if (sigmask) 1035 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 1036 1037 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 1038 1039 return ret; 1040 } 1041