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 #include <linux/vmalloc.h> 33 34 #include <asm/uaccess.h> 35 36 37 /* 38 * Estimate expected accuracy in ns from a timeval. 39 * 40 * After quite a bit of churning around, we've settled on 41 * a simple thing of taking 0.1% of the timeout as the 42 * slack, with a cap of 100 msec. 43 * "nice" tasks get a 0.5% slack instead. 44 * 45 * Consider this comment an open invitation to come up with even 46 * better solutions.. 47 */ 48 49 #define MAX_SLACK (100 * NSEC_PER_MSEC) 50 51 static long __estimate_accuracy(struct timespec64 *tv) 52 { 53 long slack; 54 int divfactor = 1000; 55 56 if (tv->tv_sec < 0) 57 return 0; 58 59 if (task_nice(current) > 0) 60 divfactor = divfactor / 5; 61 62 if (tv->tv_sec > MAX_SLACK / (NSEC_PER_SEC/divfactor)) 63 return MAX_SLACK; 64 65 slack = tv->tv_nsec / divfactor; 66 slack += tv->tv_sec * (NSEC_PER_SEC/divfactor); 67 68 if (slack > MAX_SLACK) 69 return MAX_SLACK; 70 71 return slack; 72 } 73 74 u64 select_estimate_accuracy(struct timespec64 *tv) 75 { 76 u64 ret; 77 struct timespec64 now; 78 79 /* 80 * Realtime tasks get a slack of 0 for obvious reasons. 81 */ 82 83 if (rt_task(current)) 84 return 0; 85 86 ktime_get_ts64(&now); 87 now = timespec64_sub(*tv, now); 88 ret = __estimate_accuracy(&now); 89 if (ret < current->timer_slack_ns) 90 return current->timer_slack_ns; 91 return ret; 92 } 93 94 95 96 struct poll_table_page { 97 struct poll_table_page * next; 98 struct poll_table_entry * entry; 99 struct poll_table_entry entries[0]; 100 }; 101 102 #define POLL_TABLE_FULL(table) \ 103 ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table)) 104 105 /* 106 * Ok, Peter made a complicated, but straightforward multiple_wait() function. 107 * I have rewritten this, taking some shortcuts: This code may not be easy to 108 * follow, but it should be free of race-conditions, and it's practical. If you 109 * understand what I'm doing here, then you understand how the linux 110 * sleep/wakeup mechanism works. 111 * 112 * Two very simple procedures, poll_wait() and poll_freewait() make all the 113 * work. poll_wait() is an inline-function defined in <linux/poll.h>, 114 * as all select/poll functions have to call it to add an entry to the 115 * poll table. 116 */ 117 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 118 poll_table *p); 119 120 void poll_initwait(struct poll_wqueues *pwq) 121 { 122 init_poll_funcptr(&pwq->pt, __pollwait); 123 pwq->polling_task = current; 124 pwq->triggered = 0; 125 pwq->error = 0; 126 pwq->table = NULL; 127 pwq->inline_index = 0; 128 } 129 EXPORT_SYMBOL(poll_initwait); 130 131 static void free_poll_entry(struct poll_table_entry *entry) 132 { 133 remove_wait_queue(entry->wait_address, &entry->wait); 134 fput(entry->filp); 135 } 136 137 void poll_freewait(struct poll_wqueues *pwq) 138 { 139 struct poll_table_page * p = pwq->table; 140 int i; 141 for (i = 0; i < pwq->inline_index; i++) 142 free_poll_entry(pwq->inline_entries + i); 143 while (p) { 144 struct poll_table_entry * entry; 145 struct poll_table_page *old; 146 147 entry = p->entry; 148 do { 149 entry--; 150 free_poll_entry(entry); 151 } while (entry > p->entries); 152 old = p; 153 p = p->next; 154 free_page((unsigned long) old); 155 } 156 } 157 EXPORT_SYMBOL(poll_freewait); 158 159 static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) 160 { 161 struct poll_table_page *table = p->table; 162 163 if (p->inline_index < N_INLINE_POLL_ENTRIES) 164 return p->inline_entries + p->inline_index++; 165 166 if (!table || POLL_TABLE_FULL(table)) { 167 struct poll_table_page *new_table; 168 169 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL); 170 if (!new_table) { 171 p->error = -ENOMEM; 172 return NULL; 173 } 174 new_table->entry = new_table->entries; 175 new_table->next = table; 176 p->table = new_table; 177 table = new_table; 178 } 179 180 return table->entry++; 181 } 182 183 static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 184 { 185 struct poll_wqueues *pwq = wait->private; 186 DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); 187 188 /* 189 * Although this function is called under waitqueue lock, LOCK 190 * doesn't imply write barrier and the users expect write 191 * barrier semantics on wakeup functions. The following 192 * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up() 193 * and is paired with smp_store_mb() in poll_schedule_timeout. 194 */ 195 smp_wmb(); 196 pwq->triggered = 1; 197 198 /* 199 * Perform the default wake up operation using a dummy 200 * waitqueue. 201 * 202 * TODO: This is hacky but there currently is no interface to 203 * pass in @sync. @sync is scheduled to be removed and once 204 * that happens, wake_up_process() can be used directly. 205 */ 206 return default_wake_function(&dummy_wait, mode, sync, key); 207 } 208 209 static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) 210 { 211 struct poll_table_entry *entry; 212 213 entry = container_of(wait, struct poll_table_entry, wait); 214 if (key && !((unsigned long)key & entry->key)) 215 return 0; 216 return __pollwake(wait, mode, sync, key); 217 } 218 219 /* Add a new entry */ 220 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, 221 poll_table *p) 222 { 223 struct poll_wqueues *pwq = container_of(p, struct poll_wqueues, pt); 224 struct poll_table_entry *entry = poll_get_entry(pwq); 225 if (!entry) 226 return; 227 entry->filp = get_file(filp); 228 entry->wait_address = wait_address; 229 entry->key = p->_key; 230 init_waitqueue_func_entry(&entry->wait, pollwake); 231 entry->wait.private = pwq; 232 add_wait_queue(wait_address, &entry->wait); 233 } 234 235 int poll_schedule_timeout(struct poll_wqueues *pwq, int state, 236 ktime_t *expires, unsigned long slack) 237 { 238 int rc = -EINTR; 239 240 set_current_state(state); 241 if (!pwq->triggered) 242 rc = schedule_hrtimeout_range(expires, slack, HRTIMER_MODE_ABS); 243 __set_current_state(TASK_RUNNING); 244 245 /* 246 * Prepare for the next iteration. 247 * 248 * The following smp_store_mb() serves two purposes. First, it's 249 * the counterpart rmb of the wmb in pollwake() such that data 250 * written before wake up is always visible after wake up. 251 * Second, the full barrier guarantees that triggered clearing 252 * doesn't pass event check of the next iteration. Note that 253 * this problem doesn't exist for the first iteration as 254 * add_wait_queue() has full barrier semantics. 255 */ 256 smp_store_mb(pwq->triggered, 0); 257 258 return rc; 259 } 260 EXPORT_SYMBOL(poll_schedule_timeout); 261 262 /** 263 * poll_select_set_timeout - helper function to setup the timeout value 264 * @to: pointer to timespec64 variable for the final timeout 265 * @sec: seconds (from user space) 266 * @nsec: nanoseconds (from user space) 267 * 268 * Note, we do not use a timespec for the user space value here, That 269 * way we can use the function for timeval and compat interfaces as well. 270 * 271 * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0. 272 */ 273 int poll_select_set_timeout(struct timespec64 *to, time64_t sec, long nsec) 274 { 275 struct timespec64 ts = {.tv_sec = sec, .tv_nsec = nsec}; 276 277 if (!timespec64_valid(&ts)) 278 return -EINVAL; 279 280 /* Optimize for the zero timeout value here */ 281 if (!sec && !nsec) { 282 to->tv_sec = to->tv_nsec = 0; 283 } else { 284 ktime_get_ts64(to); 285 *to = timespec64_add_safe(*to, ts); 286 } 287 return 0; 288 } 289 290 static int poll_select_copy_remaining(struct timespec64 *end_time, 291 void __user *p, 292 int timeval, int ret) 293 { 294 struct timespec64 rts64; 295 struct timespec rts; 296 struct timeval rtv; 297 298 if (!p) 299 return ret; 300 301 if (current->personality & STICKY_TIMEOUTS) 302 goto sticky; 303 304 /* No update for zero timeout */ 305 if (!end_time->tv_sec && !end_time->tv_nsec) 306 return ret; 307 308 ktime_get_ts64(&rts64); 309 rts64 = timespec64_sub(*end_time, rts64); 310 if (rts64.tv_sec < 0) 311 rts64.tv_sec = rts64.tv_nsec = 0; 312 313 rts = timespec64_to_timespec(rts64); 314 315 if (timeval) { 316 if (sizeof(rtv) > sizeof(rtv.tv_sec) + sizeof(rtv.tv_usec)) 317 memset(&rtv, 0, sizeof(rtv)); 318 rtv.tv_sec = rts64.tv_sec; 319 rtv.tv_usec = rts64.tv_nsec / NSEC_PER_USEC; 320 321 if (!copy_to_user(p, &rtv, sizeof(rtv))) 322 return ret; 323 324 } else if (!copy_to_user(p, &rts, sizeof(rts))) 325 return ret; 326 327 /* 328 * If an application puts its timeval in read-only memory, we 329 * don't want the Linux-specific update to the timeval to 330 * cause a fault after the select has completed 331 * successfully. However, because we're not updating the 332 * timeval, we can't restart the system call. 333 */ 334 335 sticky: 336 if (ret == -ERESTARTNOHAND) 337 ret = -EINTR; 338 return ret; 339 } 340 341 #define FDS_IN(fds, n) (fds->in + n) 342 #define FDS_OUT(fds, n) (fds->out + n) 343 #define FDS_EX(fds, n) (fds->ex + n) 344 345 #define BITS(fds, n) (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n)) 346 347 static int max_select_fd(unsigned long n, fd_set_bits *fds) 348 { 349 unsigned long *open_fds; 350 unsigned long set; 351 int max; 352 struct fdtable *fdt; 353 354 /* handle last in-complete long-word first */ 355 set = ~(~0UL << (n & (BITS_PER_LONG-1))); 356 n /= BITS_PER_LONG; 357 fdt = files_fdtable(current->files); 358 open_fds = fdt->open_fds + n; 359 max = 0; 360 if (set) { 361 set &= BITS(fds, n); 362 if (set) { 363 if (!(set & ~*open_fds)) 364 goto get_max; 365 return -EBADF; 366 } 367 } 368 while (n) { 369 open_fds--; 370 n--; 371 set = BITS(fds, n); 372 if (!set) 373 continue; 374 if (set & ~*open_fds) 375 return -EBADF; 376 if (max) 377 continue; 378 get_max: 379 do { 380 max++; 381 set >>= 1; 382 } while (set); 383 max += n * BITS_PER_LONG; 384 } 385 386 return max; 387 } 388 389 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR) 390 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) 391 #define POLLEX_SET (POLLPRI) 392 393 static inline void wait_key_set(poll_table *wait, unsigned long in, 394 unsigned long out, unsigned long bit, 395 unsigned int ll_flag) 396 { 397 wait->_key = POLLEX_SET | ll_flag; 398 if (in & bit) 399 wait->_key |= POLLIN_SET; 400 if (out & bit) 401 wait->_key |= POLLOUT_SET; 402 } 403 404 int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time) 405 { 406 ktime_t expire, *to = NULL; 407 struct poll_wqueues table; 408 poll_table *wait; 409 int retval, i, timed_out = 0; 410 u64 slack = 0; 411 unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; 412 unsigned long busy_end = 0; 413 414 rcu_read_lock(); 415 retval = max_select_fd(n, fds); 416 rcu_read_unlock(); 417 418 if (retval < 0) 419 return retval; 420 n = retval; 421 422 poll_initwait(&table); 423 wait = &table.pt; 424 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 425 wait->_qproc = NULL; 426 timed_out = 1; 427 } 428 429 if (end_time && !timed_out) 430 slack = select_estimate_accuracy(end_time); 431 432 retval = 0; 433 for (;;) { 434 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp; 435 bool can_busy_loop = false; 436 437 inp = fds->in; outp = fds->out; exp = fds->ex; 438 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex; 439 440 for (i = 0; i < n; ++rinp, ++routp, ++rexp) { 441 unsigned long in, out, ex, all_bits, bit = 1, mask, j; 442 unsigned long res_in = 0, res_out = 0, res_ex = 0; 443 444 in = *inp++; out = *outp++; ex = *exp++; 445 all_bits = in | out | ex; 446 if (all_bits == 0) { 447 i += BITS_PER_LONG; 448 continue; 449 } 450 451 for (j = 0; j < BITS_PER_LONG; ++j, ++i, bit <<= 1) { 452 struct fd f; 453 if (i >= n) 454 break; 455 if (!(bit & all_bits)) 456 continue; 457 f = fdget(i); 458 if (f.file) { 459 const struct file_operations *f_op; 460 f_op = f.file->f_op; 461 mask = DEFAULT_POLLMASK; 462 if (f_op->poll) { 463 wait_key_set(wait, in, out, 464 bit, busy_flag); 465 mask = (*f_op->poll)(f.file, wait); 466 } 467 fdput(f); 468 if ((mask & POLLIN_SET) && (in & bit)) { 469 res_in |= bit; 470 retval++; 471 wait->_qproc = NULL; 472 } 473 if ((mask & POLLOUT_SET) && (out & bit)) { 474 res_out |= bit; 475 retval++; 476 wait->_qproc = NULL; 477 } 478 if ((mask & POLLEX_SET) && (ex & bit)) { 479 res_ex |= bit; 480 retval++; 481 wait->_qproc = NULL; 482 } 483 /* got something, stop busy polling */ 484 if (retval) { 485 can_busy_loop = false; 486 busy_flag = 0; 487 488 /* 489 * only remember a returned 490 * POLL_BUSY_LOOP if we asked for it 491 */ 492 } else if (busy_flag & mask) 493 can_busy_loop = true; 494 495 } 496 } 497 if (res_in) 498 *rinp = res_in; 499 if (res_out) 500 *routp = res_out; 501 if (res_ex) 502 *rexp = res_ex; 503 cond_resched(); 504 } 505 wait->_qproc = NULL; 506 if (retval || timed_out || signal_pending(current)) 507 break; 508 if (table.error) { 509 retval = table.error; 510 break; 511 } 512 513 /* only if found POLL_BUSY_LOOP sockets && not out of time */ 514 if (can_busy_loop && !need_resched()) { 515 if (!busy_end) { 516 busy_end = busy_loop_end_time(); 517 continue; 518 } 519 if (!busy_loop_timeout(busy_end)) 520 continue; 521 } 522 busy_flag = 0; 523 524 /* 525 * If this is the first loop and we have a timeout 526 * given, then we convert to ktime_t and set the to 527 * pointer to the expiry value. 528 */ 529 if (end_time && !to) { 530 expire = timespec64_to_ktime(*end_time); 531 to = &expire; 532 } 533 534 if (!poll_schedule_timeout(&table, TASK_INTERRUPTIBLE, 535 to, slack)) 536 timed_out = 1; 537 } 538 539 poll_freewait(&table); 540 541 return retval; 542 } 543 544 /* 545 * We can actually return ERESTARTSYS instead of EINTR, but I'd 546 * like to be certain this leads to no problems. So I return 547 * EINTR just for safety. 548 * 549 * Update: ERESTARTSYS breaks at least the xview clock binary, so 550 * I'm trying ERESTARTNOHAND which restart only when you want to. 551 */ 552 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp, 553 fd_set __user *exp, struct timespec64 *end_time) 554 { 555 fd_set_bits fds; 556 void *bits; 557 int ret, max_fds; 558 size_t size, alloc_size; 559 struct fdtable *fdt; 560 /* Allocate small arguments on the stack to save memory and be faster */ 561 long stack_fds[SELECT_STACK_ALLOC/sizeof(long)]; 562 563 ret = -EINVAL; 564 if (n < 0) 565 goto out_nofds; 566 567 /* max_fds can increase, so grab it once to avoid race */ 568 rcu_read_lock(); 569 fdt = files_fdtable(current->files); 570 max_fds = fdt->max_fds; 571 rcu_read_unlock(); 572 if (n > max_fds) 573 n = max_fds; 574 575 /* 576 * We need 6 bitmaps (in/out/ex for both incoming and outgoing), 577 * since we used fdset we need to allocate memory in units of 578 * long-words. 579 */ 580 size = FDS_BYTES(n); 581 bits = stack_fds; 582 if (size > sizeof(stack_fds) / 6) { 583 /* Not enough space in on-stack array; must use kmalloc */ 584 ret = -ENOMEM; 585 if (size > (SIZE_MAX / 6)) 586 goto out_nofds; 587 588 alloc_size = 6 * size; 589 bits = kmalloc(alloc_size, GFP_KERNEL|__GFP_NOWARN); 590 if (!bits && alloc_size > PAGE_SIZE) 591 bits = vmalloc(alloc_size); 592 593 if (!bits) 594 goto out_nofds; 595 } 596 fds.in = bits; 597 fds.out = bits + size; 598 fds.ex = bits + 2*size; 599 fds.res_in = bits + 3*size; 600 fds.res_out = bits + 4*size; 601 fds.res_ex = bits + 5*size; 602 603 if ((ret = get_fd_set(n, inp, fds.in)) || 604 (ret = get_fd_set(n, outp, fds.out)) || 605 (ret = get_fd_set(n, exp, fds.ex))) 606 goto out; 607 zero_fd_set(n, fds.res_in); 608 zero_fd_set(n, fds.res_out); 609 zero_fd_set(n, fds.res_ex); 610 611 ret = do_select(n, &fds, end_time); 612 613 if (ret < 0) 614 goto out; 615 if (!ret) { 616 ret = -ERESTARTNOHAND; 617 if (signal_pending(current)) 618 goto out; 619 ret = 0; 620 } 621 622 if (set_fd_set(n, inp, fds.res_in) || 623 set_fd_set(n, outp, fds.res_out) || 624 set_fd_set(n, exp, fds.res_ex)) 625 ret = -EFAULT; 626 627 out: 628 if (bits != stack_fds) 629 kvfree(bits); 630 out_nofds: 631 return ret; 632 } 633 634 SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp, 635 fd_set __user *, exp, struct timeval __user *, tvp) 636 { 637 struct timespec64 end_time, *to = NULL; 638 struct timeval tv; 639 int ret; 640 641 if (tvp) { 642 if (copy_from_user(&tv, tvp, sizeof(tv))) 643 return -EFAULT; 644 645 to = &end_time; 646 if (poll_select_set_timeout(to, 647 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC), 648 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC)) 649 return -EINVAL; 650 } 651 652 ret = core_sys_select(n, inp, outp, exp, to); 653 ret = poll_select_copy_remaining(&end_time, tvp, 1, ret); 654 655 return ret; 656 } 657 658 static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp, 659 fd_set __user *exp, struct timespec __user *tsp, 660 const sigset_t __user *sigmask, size_t sigsetsize) 661 { 662 sigset_t ksigmask, sigsaved; 663 struct timespec ts; 664 struct timespec64 ts64, end_time, *to = NULL; 665 int ret; 666 667 if (tsp) { 668 if (copy_from_user(&ts, tsp, sizeof(ts))) 669 return -EFAULT; 670 ts64 = timespec_to_timespec64(ts); 671 672 to = &end_time; 673 if (poll_select_set_timeout(to, ts64.tv_sec, ts64.tv_nsec)) 674 return -EINVAL; 675 } 676 677 if (sigmask) { 678 /* XXX: Don't preclude handling different sized sigset_t's. */ 679 if (sigsetsize != sizeof(sigset_t)) 680 return -EINVAL; 681 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 682 return -EFAULT; 683 684 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 685 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 686 } 687 688 ret = core_sys_select(n, inp, outp, exp, to); 689 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 690 691 if (ret == -ERESTARTNOHAND) { 692 /* 693 * Don't restore the signal mask yet. Let do_signal() deliver 694 * the signal on the way back to userspace, before the signal 695 * mask is restored. 696 */ 697 if (sigmask) { 698 memcpy(¤t->saved_sigmask, &sigsaved, 699 sizeof(sigsaved)); 700 set_restore_sigmask(); 701 } 702 } else if (sigmask) 703 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 704 705 return ret; 706 } 707 708 /* 709 * Most architectures can't handle 7-argument syscalls. So we provide a 710 * 6-argument version where the sixth argument is a pointer to a structure 711 * which has a pointer to the sigset_t itself followed by a size_t containing 712 * the sigset size. 713 */ 714 SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp, 715 fd_set __user *, exp, struct timespec __user *, tsp, 716 void __user *, sig) 717 { 718 size_t sigsetsize = 0; 719 sigset_t __user *up = NULL; 720 721 if (sig) { 722 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t)) 723 || __get_user(up, (sigset_t __user * __user *)sig) 724 || __get_user(sigsetsize, 725 (size_t __user *)(sig+sizeof(void *)))) 726 return -EFAULT; 727 } 728 729 return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize); 730 } 731 732 #ifdef __ARCH_WANT_SYS_OLD_SELECT 733 struct sel_arg_struct { 734 unsigned long n; 735 fd_set __user *inp, *outp, *exp; 736 struct timeval __user *tvp; 737 }; 738 739 SYSCALL_DEFINE1(old_select, struct sel_arg_struct __user *, arg) 740 { 741 struct sel_arg_struct a; 742 743 if (copy_from_user(&a, arg, sizeof(a))) 744 return -EFAULT; 745 return sys_select(a.n, a.inp, a.outp, a.exp, a.tvp); 746 } 747 #endif 748 749 struct poll_list { 750 struct poll_list *next; 751 int len; 752 struct pollfd entries[0]; 753 }; 754 755 #define POLLFD_PER_PAGE ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd)) 756 757 /* 758 * Fish for pollable events on the pollfd->fd file descriptor. We're only 759 * interested in events matching the pollfd->events mask, and the result 760 * matching that mask is both recorded in pollfd->revents and returned. The 761 * pwait poll_table will be used by the fd-provided poll handler for waiting, 762 * if pwait->_qproc is non-NULL. 763 */ 764 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait, 765 bool *can_busy_poll, 766 unsigned int busy_flag) 767 { 768 unsigned int mask; 769 int fd; 770 771 mask = 0; 772 fd = pollfd->fd; 773 if (fd >= 0) { 774 struct fd f = fdget(fd); 775 mask = POLLNVAL; 776 if (f.file) { 777 mask = DEFAULT_POLLMASK; 778 if (f.file->f_op->poll) { 779 pwait->_key = pollfd->events|POLLERR|POLLHUP; 780 pwait->_key |= busy_flag; 781 mask = f.file->f_op->poll(f.file, pwait); 782 if (mask & busy_flag) 783 *can_busy_poll = true; 784 } 785 /* Mask out unneeded events. */ 786 mask &= pollfd->events | POLLERR | POLLHUP; 787 fdput(f); 788 } 789 } 790 pollfd->revents = mask; 791 792 return mask; 793 } 794 795 static int do_poll(struct poll_list *list, struct poll_wqueues *wait, 796 struct timespec64 *end_time) 797 { 798 poll_table* pt = &wait->pt; 799 ktime_t expire, *to = NULL; 800 int timed_out = 0, count = 0; 801 u64 slack = 0; 802 unsigned int busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0; 803 unsigned long busy_end = 0; 804 805 /* Optimise the no-wait case */ 806 if (end_time && !end_time->tv_sec && !end_time->tv_nsec) { 807 pt->_qproc = NULL; 808 timed_out = 1; 809 } 810 811 if (end_time && !timed_out) 812 slack = select_estimate_accuracy(end_time); 813 814 for (;;) { 815 struct poll_list *walk; 816 bool can_busy_loop = false; 817 818 for (walk = list; walk != NULL; walk = walk->next) { 819 struct pollfd * pfd, * pfd_end; 820 821 pfd = walk->entries; 822 pfd_end = pfd + walk->len; 823 for (; pfd != pfd_end; pfd++) { 824 /* 825 * Fish for events. If we found one, record it 826 * and kill poll_table->_qproc, so we don't 827 * needlessly register any other waiters after 828 * this. They'll get immediately deregistered 829 * when we break out and return. 830 */ 831 if (do_pollfd(pfd, pt, &can_busy_loop, 832 busy_flag)) { 833 count++; 834 pt->_qproc = NULL; 835 /* found something, stop busy polling */ 836 busy_flag = 0; 837 can_busy_loop = false; 838 } 839 } 840 } 841 /* 842 * All waiters have already been registered, so don't provide 843 * a poll_table->_qproc to them on the next loop iteration. 844 */ 845 pt->_qproc = NULL; 846 if (!count) { 847 count = wait->error; 848 if (signal_pending(current)) 849 count = -EINTR; 850 } 851 if (count || timed_out) 852 break; 853 854 /* only if found POLL_BUSY_LOOP sockets && not out of time */ 855 if (can_busy_loop && !need_resched()) { 856 if (!busy_end) { 857 busy_end = busy_loop_end_time(); 858 continue; 859 } 860 if (!busy_loop_timeout(busy_end)) 861 continue; 862 } 863 busy_flag = 0; 864 865 /* 866 * If this is the first loop and we have a timeout 867 * given, then we convert to ktime_t and set the to 868 * pointer to the expiry value. 869 */ 870 if (end_time && !to) { 871 expire = timespec64_to_ktime(*end_time); 872 to = &expire; 873 } 874 875 if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, to, slack)) 876 timed_out = 1; 877 } 878 return count; 879 } 880 881 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list)) / \ 882 sizeof(struct pollfd)) 883 884 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, 885 struct timespec64 *end_time) 886 { 887 struct poll_wqueues table; 888 int err = -EFAULT, fdcount, len, size; 889 /* Allocate small arguments on the stack to save memory and be 890 faster - use long to make sure the buffer is aligned properly 891 on 64 bit archs to avoid unaligned access */ 892 long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; 893 struct poll_list *const head = (struct poll_list *)stack_pps; 894 struct poll_list *walk = head; 895 unsigned long todo = nfds; 896 897 if (nfds > rlimit(RLIMIT_NOFILE)) 898 return -EINVAL; 899 900 len = min_t(unsigned int, nfds, N_STACK_PPS); 901 for (;;) { 902 walk->next = NULL; 903 walk->len = len; 904 if (!len) 905 break; 906 907 if (copy_from_user(walk->entries, ufds + nfds-todo, 908 sizeof(struct pollfd) * walk->len)) 909 goto out_fds; 910 911 todo -= walk->len; 912 if (!todo) 913 break; 914 915 len = min(todo, POLLFD_PER_PAGE); 916 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; 917 walk = walk->next = kmalloc(size, GFP_KERNEL); 918 if (!walk) { 919 err = -ENOMEM; 920 goto out_fds; 921 } 922 } 923 924 poll_initwait(&table); 925 fdcount = do_poll(head, &table, end_time); 926 poll_freewait(&table); 927 928 for (walk = head; walk; walk = walk->next) { 929 struct pollfd *fds = walk->entries; 930 int j; 931 932 for (j = 0; j < walk->len; j++, ufds++) 933 if (__put_user(fds[j].revents, &ufds->revents)) 934 goto out_fds; 935 } 936 937 err = fdcount; 938 out_fds: 939 walk = head->next; 940 while (walk) { 941 struct poll_list *pos = walk; 942 walk = walk->next; 943 kfree(pos); 944 } 945 946 return err; 947 } 948 949 static long do_restart_poll(struct restart_block *restart_block) 950 { 951 struct pollfd __user *ufds = restart_block->poll.ufds; 952 int nfds = restart_block->poll.nfds; 953 struct timespec64 *to = NULL, end_time; 954 int ret; 955 956 if (restart_block->poll.has_timeout) { 957 end_time.tv_sec = restart_block->poll.tv_sec; 958 end_time.tv_nsec = restart_block->poll.tv_nsec; 959 to = &end_time; 960 } 961 962 ret = do_sys_poll(ufds, nfds, to); 963 964 if (ret == -EINTR) { 965 restart_block->fn = do_restart_poll; 966 ret = -ERESTART_RESTARTBLOCK; 967 } 968 return ret; 969 } 970 971 SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds, 972 int, timeout_msecs) 973 { 974 struct timespec64 end_time, *to = NULL; 975 int ret; 976 977 if (timeout_msecs >= 0) { 978 to = &end_time; 979 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC, 980 NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC)); 981 } 982 983 ret = do_sys_poll(ufds, nfds, to); 984 985 if (ret == -EINTR) { 986 struct restart_block *restart_block; 987 988 restart_block = ¤t->restart_block; 989 restart_block->fn = do_restart_poll; 990 restart_block->poll.ufds = ufds; 991 restart_block->poll.nfds = nfds; 992 993 if (timeout_msecs >= 0) { 994 restart_block->poll.tv_sec = end_time.tv_sec; 995 restart_block->poll.tv_nsec = end_time.tv_nsec; 996 restart_block->poll.has_timeout = 1; 997 } else 998 restart_block->poll.has_timeout = 0; 999 1000 ret = -ERESTART_RESTARTBLOCK; 1001 } 1002 return ret; 1003 } 1004 1005 SYSCALL_DEFINE5(ppoll, struct pollfd __user *, ufds, unsigned int, nfds, 1006 struct timespec __user *, tsp, const sigset_t __user *, sigmask, 1007 size_t, sigsetsize) 1008 { 1009 sigset_t ksigmask, sigsaved; 1010 struct timespec ts; 1011 struct timespec64 end_time, *to = NULL; 1012 int ret; 1013 1014 if (tsp) { 1015 if (copy_from_user(&ts, tsp, sizeof(ts))) 1016 return -EFAULT; 1017 1018 to = &end_time; 1019 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) 1020 return -EINVAL; 1021 } 1022 1023 if (sigmask) { 1024 /* XXX: Don't preclude handling different sized sigset_t's. */ 1025 if (sigsetsize != sizeof(sigset_t)) 1026 return -EINVAL; 1027 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask))) 1028 return -EFAULT; 1029 1030 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP)); 1031 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved); 1032 } 1033 1034 ret = do_sys_poll(ufds, nfds, to); 1035 1036 /* We can restart this syscall, usually */ 1037 if (ret == -EINTR) { 1038 /* 1039 * Don't restore the signal mask yet. Let do_signal() deliver 1040 * the signal on the way back to userspace, before the signal 1041 * mask is restored. 1042 */ 1043 if (sigmask) { 1044 memcpy(¤t->saved_sigmask, &sigsaved, 1045 sizeof(sigsaved)); 1046 set_restore_sigmask(); 1047 } 1048 ret = -ERESTARTNOHAND; 1049 } else if (sigmask) 1050 sigprocmask(SIG_SETMASK, &sigsaved, NULL); 1051 1052 ret = poll_select_copy_remaining(&end_time, tsp, 0, ret); 1053 1054 return ret; 1055 } 1056