fs/select.c

   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/syscalls.h>
  19 #include <linux/module.h>
  20 #include <linux/slab.h>
  21 #include <linux/poll.h>
  22 #include <linux/personality.h> /* for STICKY_TIMEOUTS */
  23 #include <linux/file.h>
  24 #include <linux/fdtable.h>
  25 #include <linux/fs.h>
  26 #include <linux/rcupdate.h>
  27 #include <linux/hrtimer.h>
  28
  29 #include <asm/uaccess.h>
  30
  31
  32 /*
  33  * Estimate expected accuracy in ns from a timeval.
  34  *
  35  * After quite a bit of churning around, we've settled on
  36  * a simple thing of taking 0.1% of the timeout as the
  37  * slack, with a cap of 100 msec.
  38  * "nice" tasks get a 0.5% slack instead.
  39  *
  40  * Consider this comment an open invitation to come up with even
  41  * better solutions..
  42  */
  43
  44 static long __estimate_accuracy(struct timespec *tv)
  45 {
  46         long slack;
  47         int divfactor = 1000;
  48
  49         if (task_nice(current) > 0)
  50                 divfactor = divfactor / 5;
  51
  52         slack = tv->tv_nsec / divfactor;
  53         slack += tv->tv_sec * (NSEC_PER_SEC/divfactor);
  54
  55         if (slack > 100 * NSEC_PER_MSEC)
  56                 slack =  100 * NSEC_PER_MSEC;
  57
  58         if (slack < 0)
  59                 slack = 0;
  60         return slack;
  61 }
  62
  63 static long estimate_accuracy(struct timespec *tv)
  64 {
  65         unsigned long ret;
  66         struct timespec now;
  67
  68         /*
  69          * Realtime tasks get a slack of 0 for obvious reasons.
  70          */
  71
  72         if (rt_task(current))
  73                 return 0;
  74
  75         ktime_get_ts(&now);
  76         now = timespec_sub(*tv, now);
  77         ret = __estimate_accuracy(&now);
  78         if (ret < current->timer_slack_ns)
  79                 return current->timer_slack_ns;
  80         return ret;
  81 }
  82
  83
  84
  85 struct poll_table_page {
  86         struct poll_table_page * next;
  87         struct poll_table_entry * entry;
  88         struct poll_table_entry entries[0];
  89 };
  90
  91 #define POLL_TABLE_FULL(table) \
  92         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
  93
  94 /*
  95  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
  96  * I have rewritten this, taking some shortcuts: This code may not be easy to
  97  * follow, but it should be free of race-conditions, and it's practical. If you
  98  * understand what I'm doing here, then you understand how the linux
  99  * sleep/wakeup mechanism works.
 100  *
 101  * Two very simple procedures, poll_wait() and poll_freewait() make all the
 102  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
 103  * as all select/poll functions have to call it to add an entry to the
 104  * poll table.
 105  */
 106 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 107                        poll_table *p);
 108
 109 void poll_initwait(struct poll_wqueues *pwq)
 110 {
 111         init_poll_funcptr(&pwq->pt, __pollwait);
 112         pwq->error = 0;
 113         pwq->table = NULL;
 114         pwq->inline_index = 0;
 115 }
 116
 117 EXPORT_SYMBOL(poll_initwait);
 118
 119 static void free_poll_entry(struct poll_table_entry *entry)
 120 {
 121         remove_wait_queue(entry->wait_address, &entry->wait);
 122         fput(entry->filp);
 123 }
 124
 125 void poll_freewait(struct poll_wqueues *pwq)
 126 {
 127         struct poll_table_page * p = pwq->table;
 128         int i;
 129         for (i = 0; i < pwq->inline_index; i++)
 130                 free_poll_entry(pwq->inline_entries + i);
 131         while (p) {
 132                 struct poll_table_entry * entry;
 133                 struct poll_table_page *old;
 134
 135                 entry = p->entry;
 136                 do {
 137                         entry--;
 138                         free_poll_entry(entry);
 139                 } while (entry > p->entries);
 140                 old = p;
 141                 p = p->next;
 142                 free_page((unsigned long) old);
 143         }
 144 }
 145
 146 EXPORT_SYMBOL(poll_freewait);
 147
 148 static struct poll_table_entry *poll_get_entry(poll_table *_p)
 149 {
 150         struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
 151         struct poll_table_page *table = p->table;
 152
 153         if (p->inline_index < N_INLINE_POLL_ENTRIES)
 154                 return p->inline_entries + p->inline_index++;
 155
 156         if (!table || POLL_TABLE_FULL(table)) {
 157                 struct poll_table_page *new_table;
 158
 159                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
 160                 if (!new_table) {
 161                         p->error = -ENOMEM;
 162                         __set_current_state(TASK_RUNNING);
 163                         return NULL;
 164                 }
 165                 new_table->entry = new_table->entries;
 166                 new_table->next = table;
 167                 p->table = new_table;
 168                 table = new_table;
 169         }
 170
 171         return table->entry++;
 172 }
 173
 174 /* Add a new entry */
 175 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 176                                 poll_table *p)
 177 {
 178         struct poll_table_entry *entry = poll_get_entry(p);
 179         if (!entry)
 180                 return;
 181         get_file(filp);
 182         entry->filp = filp;
 183         entry->wait_address = wait_address;
 184         init_waitqueue_entry(&entry->wait, current);
 185         add_wait_queue(wait_address, &entry->wait);
 186 }
 187
 188 /**
 189  * poll_select_set_timeout - helper function to setup the timeout value
 190  * @to:         pointer to timespec variable for the final timeout
 191  * @sec:        seconds (from user space)
 192  * @nsec:       nanoseconds (from user space)
 193  *
 194  * Note, we do not use a timespec for the user space value here, That
 195  * way we can use the function for timeval and compat interfaces as well.
 196  *
 197  * Returns -EINVAL if sec/nsec are not normalized. Otherwise 0.
 198  */
 199 int poll_select_set_timeout(struct timespec *to, long sec, long nsec)
 200 {
 201         struct timespec ts = {.tv_sec = sec, .tv_nsec = nsec};
 202
 203         if (!timespec_valid(&ts))
 204                 return -EINVAL;
 205
 206         /* Optimize for the zero timeout value here */
 207         if (!sec && !nsec) {
 208                 to->tv_sec = to->tv_nsec = 0;
 209         } else {
 210                 ktime_get_ts(to);
 211                 *to = timespec_add_safe(*to, ts);
 212         }
 213         return 0;
 214 }
 215
 216 static int poll_select_copy_remaining(struct timespec *end_time, void __user *p,
 217                                       int timeval, int ret)
 218 {
 219         struct timespec rts;
 220         struct timeval rtv;
 221
 222         if (!p)
 223                 return ret;
 224
 225         if (current->personality & STICKY_TIMEOUTS)
 226                 goto sticky;
 227
 228         /* No update for zero timeout */
 229         if (!end_time->tv_sec && !end_time->tv_nsec)
 230                 return ret;
 231
 232         ktime_get_ts(&rts);
 233         rts = timespec_sub(*end_time, rts);
 234         if (rts.tv_sec < 0)
 235                 rts.tv_sec = rts.tv_nsec = 0;
 236
 237         if (timeval) {
 238                 rtv.tv_sec = rts.tv_sec;
 239                 rtv.tv_usec = rts.tv_nsec / NSEC_PER_USEC;
 240
 241                 if (!copy_to_user(p, &rtv, sizeof(rtv)))
 242                         return ret;
 243
 244         } else if (!copy_to_user(p, &rts, sizeof(rts)))
 245                 return ret;
 246
 247         /*
 248          * If an application puts its timeval in read-only memory, we
 249          * don't want the Linux-specific update to the timeval to
 250          * cause a fault after the select has completed
 251          * successfully. However, because we're not updating the
 252          * timeval, we can't restart the system call.
 253          */
 254
 255 sticky:
 256         if (ret == -ERESTARTNOHAND)
 257                 ret = -EINTR;
 258         return ret;
 259 }
 260
 261 #define FDS_IN(fds, n)          (fds->in + n)
 262 #define FDS_OUT(fds, n)         (fds->out + n)
 263 #define FDS_EX(fds, n)          (fds->ex + n)
 264
 265 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 266
 267 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 268 {
 269         unsigned long *open_fds;
 270         unsigned long set;
 271         int max;
 272         struct fdtable *fdt;
 273
 274         /* handle last in-complete long-word first */
 275         set = ~(~0UL << (n & (__NFDBITS-1)));
 276         n /= __NFDBITS;
 277         fdt = files_fdtable(current->files);
 278         open_fds = fdt->open_fds->fds_bits+n;
 279         max = 0;
 280         if (set) {
 281                 set &= BITS(fds, n);
 282                 if (set) {
 283                         if (!(set & ~*open_fds))
 284                                 goto get_max;
 285                         return -EBADF;
 286                 }
 287         }
 288         while (n) {
 289                 open_fds--;
 290                 n--;
 291                 set = BITS(fds, n);
 292                 if (!set)
 293                         continue;
 294                 if (set & ~*open_fds)
 295                         return -EBADF;
 296                 if (max)
 297                         continue;
 298 get_max:
 299                 do {
 300                         max++;
 301                         set >>= 1;
 302                 } while (set);
 303                 max += n * __NFDBITS;
 304         }
 305
 306         return max;
 307 }
 308
 309 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 310 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 311 #define POLLEX_SET (POLLPRI)
 312
 313 int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
 314 {
 315         ktime_t expire, *to = NULL;
 316         struct poll_wqueues table;
 317         poll_table *wait;
 318         int retval, i, timed_out = 0;
 319         unsigned long slack = 0;
 320
 321         rcu_read_lock();
 322         retval = max_select_fd(n, fds);
 323         rcu_read_unlock();
 324
 325         if (retval < 0)
 326                 return retval;
 327         n = retval;
 328
 329         poll_initwait(&table);
 330         wait = &table.pt;
 331         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 332                 wait = NULL;
 333                 timed_out = 1;
 334         }
 335
 336         if (end_time && !timed_out)
 337                 slack = estimate_accuracy(end_time);
 338
 339         retval = 0;
 340         for (;;) {
 341                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 342
 343                 set_current_state(TASK_INTERRUPTIBLE);
 344
 345                 inp = fds->in; outp = fds->out; exp = fds->ex;
 346                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 347
 348                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 349                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 350                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 351                         const struct file_operations *f_op = NULL;
 352                         struct file *file = NULL;
 353
 354                         in = *inp++; out = *outp++; ex = *exp++;
 355                         all_bits = in | out | ex;
 356                         if (all_bits == 0) {
 357                                 i += __NFDBITS;
 358                                 continue;
 359                         }
 360
 361                         for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
 362                                 int fput_needed;
 363                                 if (i >= n)
 364                                         break;
 365                                 if (!(bit & all_bits))
 366                                         continue;
 367                                 file = fget_light(i, &fput_needed);
 368                                 if (file) {
 369                                         f_op = file->f_op;
 370                                         mask = DEFAULT_POLLMASK;
 371                                         if (f_op && f_op->poll)
 372                                                 mask = (*f_op->poll)(file, retval ? NULL : wait);
 373                                         fput_light(file, fput_needed);
 374                                         if ((mask & POLLIN_SET) && (in & bit)) {
 375                                                 res_in |= bit;
 376                                                 retval++;
 377                                         }
 378                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 379                                                 res_out |= bit;
 380                                                 retval++;
 381                                         }
 382                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 383                                                 res_ex |= bit;
 384                                                 retval++;
 385                                         }
 386                                 }
 387                         }
 388                         if (res_in)
 389                                 *rinp = res_in;
 390                         if (res_out)
 391                                 *routp = res_out;
 392                         if (res_ex)
 393                                 *rexp = res_ex;
 394                         cond_resched();
 395                 }
 396                 wait = NULL;
 397                 if (retval || timed_out || signal_pending(current))
 398                         break;
 399                 if (table.error) {
 400                         retval = table.error;
 401                         break;
 402                 }
 403
 404                 /*
 405                  * If this is the first loop and we have a timeout
 406                  * given, then we convert to ktime_t and set the to
 407                  * pointer to the expiry value.
 408                  */
 409                 if (end_time && !to) {
 410                         expire = timespec_to_ktime(*end_time);
 411                         to = &expire;
 412                 }
 413
 414                 if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
 415                         timed_out = 1;
 416         }
 417         __set_current_state(TASK_RUNNING);
 418
 419         poll_freewait(&table);
 420
 421         return retval;
 422 }
 423
 424 /*
 425  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 426  * like to be certain this leads to no problems. So I return
 427  * EINTR just for safety.
 428  *
 429  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 430  * I'm trying ERESTARTNOHAND which restart only when you want to.
 431  */
 432 #define MAX_SELECT_SECONDS \
 433         ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
 434
 435 int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 436                            fd_set __user *exp, struct timespec *end_time)
 437 {
 438         fd_set_bits fds;
 439         void *bits;
 440         int ret, max_fds;
 441         unsigned int size;
 442         struct fdtable *fdt;
 443         /* Allocate small arguments on the stack to save memory and be faster */
 444         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
 445
 446         ret = -EINVAL;
 447         if (n < 0)
 448                 goto out_nofds;
 449
 450         /* max_fds can increase, so grab it once to avoid race */
 451         rcu_read_lock();
 452         fdt = files_fdtable(current->files);
 453         max_fds = fdt->max_fds;
 454         rcu_read_unlock();
 455         if (n > max_fds)
 456                 n = max_fds;
 457
 458         /*
 459          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 460          * since we used fdset we need to allocate memory in units of
 461          * long-words.
 462          */
 463         size = FDS_BYTES(n);
 464         bits = stack_fds;
 465         if (size > sizeof(stack_fds) / 6) {
 466                 /* Not enough space in on-stack array; must use kmalloc */
 467                 ret = -ENOMEM;
 468                 bits = kmalloc(6 * size, GFP_KERNEL);
 469                 if (!bits)
 470                         goto out_nofds;
 471         }
 472         fds.in      = bits;
 473         fds.out     = bits +   size;
 474         fds.ex      = bits + 2*size;
 475         fds.res_in  = bits + 3*size;
 476         fds.res_out = bits + 4*size;
 477         fds.res_ex  = bits + 5*size;
 478
 479         if ((ret = get_fd_set(n, inp, fds.in)) ||
 480             (ret = get_fd_set(n, outp, fds.out)) ||
 481             (ret = get_fd_set(n, exp, fds.ex)))
 482                 goto out;
 483         zero_fd_set(n, fds.res_in);
 484         zero_fd_set(n, fds.res_out);
 485         zero_fd_set(n, fds.res_ex);
 486
 487         ret = do_select(n, &fds, end_time);
 488
 489         if (ret < 0)
 490                 goto out;
 491         if (!ret) {
 492                 ret = -ERESTARTNOHAND;
 493                 if (signal_pending(current))
 494                         goto out;
 495                 ret = 0;
 496         }
 497
 498         if (set_fd_set(n, inp, fds.res_in) ||
 499             set_fd_set(n, outp, fds.res_out) ||
 500             set_fd_set(n, exp, fds.res_ex))
 501                 ret = -EFAULT;
 502
 503 out:
 504         if (bits != stack_fds)
 505                 kfree(bits);
 506 out_nofds:
 507         return ret;
 508 }
 509
 510 asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 511                         fd_set __user *exp, struct timeval __user *tvp)
 512 {
 513         struct timespec end_time, *to = NULL;
 514         struct timeval tv;
 515         int ret;
 516
 517         if (tvp) {
 518                 if (copy_from_user(&tv, tvp, sizeof(tv)))
 519                         return -EFAULT;
 520
 521                 to = &end_time;
 522                 if (poll_select_set_timeout(to,
 523                                 tv.tv_sec + (tv.tv_usec / USEC_PER_SEC),
 524                                 (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
 525                         return -EINVAL;
 526         }
 527
 528         ret = core_sys_select(n, inp, outp, exp, to);
 529         ret = poll_select_copy_remaining(&end_time, tvp, 1, ret);
 530
 531         return ret;
 532 }
 533
 534 #ifdef HAVE_SET_RESTORE_SIGMASK
 535 asmlinkage long sys_pselect7(int n, fd_set __user *inp, fd_set __user *outp,
 536                 fd_set __user *exp, struct timespec __user *tsp,
 537                 const sigset_t __user *sigmask, size_t sigsetsize)
 538 {
 539         sigset_t ksigmask, sigsaved;
 540         struct timespec ts, end_time, *to = NULL;
 541         int ret;
 542
 543         if (tsp) {
 544                 if (copy_from_user(&ts, tsp, sizeof(ts)))
 545                         return -EFAULT;
 546
 547                 to = &end_time;
 548                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 549                         return -EINVAL;
 550         }
 551
 552         if (sigmask) {
 553                 /* XXX: Don't preclude handling different sized sigset_t's.  */
 554                 if (sigsetsize != sizeof(sigset_t))
 555                         return -EINVAL;
 556                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 557                         return -EFAULT;
 558
 559                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 560                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 561         }
 562
 563         ret = core_sys_select(n, inp, outp, exp, &end_time);
 564         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 565
 566         if (ret == -ERESTARTNOHAND) {
 567                 /*
 568                  * Don't restore the signal mask yet. Let do_signal() deliver
 569                  * the signal on the way back to userspace, before the signal
 570                  * mask is restored.
 571                  */
 572                 if (sigmask) {
 573                         memcpy(&current->saved_sigmask, &sigsaved,
 574                                         sizeof(sigsaved));
 575                         set_restore_sigmask();
 576                 }
 577         } else if (sigmask)
 578                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 579
 580         return ret;
 581 }
 582
 583 /*
 584  * Most architectures can't handle 7-argument syscalls. So we provide a
 585  * 6-argument version where the sixth argument is a pointer to a structure
 586  * which has a pointer to the sigset_t itself followed by a size_t containing
 587  * the sigset size.
 588  */
 589 asmlinkage long sys_pselect6(int n, fd_set __user *inp, fd_set __user *outp,
 590         fd_set __user *exp, struct timespec __user *tsp, void __user *sig)
 591 {
 592         size_t sigsetsize = 0;
 593         sigset_t __user *up = NULL;
 594
 595         if (sig) {
 596                 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 597                     || __get_user(up, (sigset_t __user * __user *)sig)
 598                     || __get_user(sigsetsize,
 599                                 (size_t __user *)(sig+sizeof(void *))))
 600                         return -EFAULT;
 601         }
 602
 603         return sys_pselect7(n, inp, outp, exp, tsp, up, sigsetsize);
 604 }
 605 #endif /* HAVE_SET_RESTORE_SIGMASK */
 606
 607 struct poll_list {
 608         struct poll_list *next;
 609         int len;
 610         struct pollfd entries[0];
 611 };
 612
 613 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 614
 615 /*
 616  * Fish for pollable events on the pollfd->fd file descriptor. We're only
 617  * interested in events matching the pollfd->events mask, and the result
 618  * matching that mask is both recorded in pollfd->revents and returned. The
 619  * pwait poll_table will be used by the fd-provided poll handler for waiting,
 620  * if non-NULL.
 621  */
 622 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
 623 {
 624         unsigned int mask;
 625         int fd;
 626
 627         mask = 0;
 628         fd = pollfd->fd;
 629         if (fd >= 0) {
 630                 int fput_needed;
 631                 struct file * file;
 632
 633                 file = fget_light(fd, &fput_needed);
 634                 mask = POLLNVAL;
 635                 if (file != NULL) {
 636                         mask = DEFAULT_POLLMASK;
 637                         if (file->f_op && file->f_op->poll)
 638                                 mask = file->f_op->poll(file, pwait);
 639                         /* Mask out unneeded events. */
 640                         mask &= pollfd->events | POLLERR | POLLHUP;
 641                         fput_light(file, fput_needed);
 642                 }
 643         }
 644         pollfd->revents = mask;
 645
 646         return mask;
 647 }
 648
 649 static int do_poll(unsigned int nfds,  struct poll_list *list,
 650                    struct poll_wqueues *wait, struct timespec *end_time)
 651 {
 652         poll_table* pt = &wait->pt;
 653         ktime_t expire, *to = NULL;
 654         int timed_out = 0, count = 0;
 655         unsigned long slack = 0;
 656
 657         /* Optimise the no-wait case */
 658         if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
 659                 pt = NULL;
 660                 timed_out = 1;
 661         }
 662
 663         if (end_time && !timed_out)
 664                 slack = estimate_accuracy(end_time);
 665
 666         for (;;) {
 667                 struct poll_list *walk;
 668
 669                 set_current_state(TASK_INTERRUPTIBLE);
 670                 for (walk = list; walk != NULL; walk = walk->next) {
 671                         struct pollfd * pfd, * pfd_end;
 672
 673                         pfd = walk->entries;
 674                         pfd_end = pfd + walk->len;
 675                         for (; pfd != pfd_end; pfd++) {
 676                                 /*
 677                                  * Fish for events. If we found one, record it
 678                                  * and kill the poll_table, so we don't
 679                                  * needlessly register any other waiters after
 680                                  * this. They'll get immediately deregistered
 681                                  * when we break out and return.
 682                                  */
 683                                 if (do_pollfd(pfd, pt)) {
 684                                         count++;
 685                                         pt = NULL;
 686                                 }
 687                         }
 688                 }
 689                 /*
 690                  * All waiters have already been registered, so don't provide
 691                  * a poll_table to them on the next loop iteration.
 692                  */
 693                 pt = NULL;
 694                 if (!count) {
 695                         count = wait->error;
 696                         if (signal_pending(current))
 697                                 count = -EINTR;
 698                 }
 699                 if (count || timed_out)
 700                         break;
 701
 702                 /*
 703                  * If this is the first loop and we have a timeout
 704                  * given, then we convert to ktime_t and set the to
 705                  * pointer to the expiry value.
 706                  */
 707                 if (end_time && !to) {
 708                         expire = timespec_to_ktime(*end_time);
 709                         to = &expire;
 710                 }
 711
 712                 if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
 713                         timed_out = 1;
 714         }
 715         __set_current_state(TASK_RUNNING);
 716         return count;
 717 }
 718
 719 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 720                         sizeof(struct pollfd))
 721
 722 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 723                 struct timespec *end_time)
 724 {
 725         struct poll_wqueues table;
 726         int err = -EFAULT, fdcount, len, size;
 727         /* Allocate small arguments on the stack to save memory and be
 728            faster - use long to make sure the buffer is aligned properly
 729            on 64 bit archs to avoid unaligned access */
 730         long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 731         struct poll_list *const head = (struct poll_list *)stack_pps;
 732         struct poll_list *walk = head;
 733         unsigned long todo = nfds;
 734
 735         if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 736                 return -EINVAL;
 737
 738         len = min_t(unsigned int, nfds, N_STACK_PPS);
 739         for (;;) {
 740                 walk->next = NULL;
 741                 walk->len = len;
 742                 if (!len)
 743                         break;
 744
 745                 if (copy_from_user(walk->entries, ufds + nfds-todo,
 746                                         sizeof(struct pollfd) * walk->len))
 747                         goto out_fds;
 748
 749                 todo -= walk->len;
 750                 if (!todo)
 751                         break;
 752
 753                 len = min(todo, POLLFD_PER_PAGE);
 754                 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 755                 walk = walk->next = kmalloc(size, GFP_KERNEL);
 756                 if (!walk) {
 757                         err = -ENOMEM;
 758                         goto out_fds;
 759                 }
 760         }
 761
 762         poll_initwait(&table);
 763         fdcount = do_poll(nfds, head, &table, end_time);
 764         poll_freewait(&table);
 765
 766         for (walk = head; walk; walk = walk->next) {
 767                 struct pollfd *fds = walk->entries;
 768                 int j;
 769
 770                 for (j = 0; j < walk->len; j++, ufds++)
 771                         if (__put_user(fds[j].revents, &ufds->revents))
 772                                 goto out_fds;
 773         }
 774
 775         err = fdcount;
 776 out_fds:
 777         walk = head->next;
 778         while (walk) {
 779                 struct poll_list *pos = walk;
 780                 walk = walk->next;
 781                 kfree(pos);
 782         }
 783
 784         return err;
 785 }
 786
 787 static long do_restart_poll(struct restart_block *restart_block)
 788 {
 789         struct pollfd __user *ufds = restart_block->poll.ufds;
 790         int nfds = restart_block->poll.nfds;
 791         struct timespec *to = NULL, end_time;
 792         int ret;
 793
 794         if (restart_block->poll.has_timeout) {
 795                 end_time.tv_sec = restart_block->poll.tv_sec;
 796                 end_time.tv_nsec = restart_block->poll.tv_nsec;
 797                 to = &end_time;
 798         }
 799
 800         ret = do_sys_poll(ufds, nfds, to);
 801
 802         if (ret == -EINTR) {
 803                 restart_block->fn = do_restart_poll;
 804                 ret = -ERESTART_RESTARTBLOCK;
 805         }
 806         return ret;
 807 }
 808
 809 asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 810                         long timeout_msecs)
 811 {
 812         struct timespec end_time, *to = NULL;
 813         int ret;
 814
 815         if (timeout_msecs >= 0) {
 816                 to = &end_time;
 817                 poll_select_set_timeout(to, timeout_msecs / MSEC_PER_SEC,
 818                         NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
 819         }
 820
 821         ret = do_sys_poll(ufds, nfds, to);
 822
 823         if (ret == -EINTR) {
 824                 struct restart_block *restart_block;
 825
 826                 restart_block = &current_thread_info()->restart_block;
 827                 restart_block->fn = do_restart_poll;
 828                 restart_block->poll.ufds = ufds;
 829                 restart_block->poll.nfds = nfds;
 830
 831                 if (timeout_msecs >= 0) {
 832                         restart_block->poll.tv_sec = end_time.tv_sec;
 833                         restart_block->poll.tv_nsec = end_time.tv_nsec;
 834                         restart_block->poll.has_timeout = 1;
 835                 } else
 836                         restart_block->poll.has_timeout = 0;
 837
 838                 ret = -ERESTART_RESTARTBLOCK;
 839         }
 840         return ret;
 841 }
 842
 843 #ifdef HAVE_SET_RESTORE_SIGMASK
 844 asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
 845         struct timespec __user *tsp, const sigset_t __user *sigmask,
 846         size_t sigsetsize)
 847 {
 848         sigset_t ksigmask, sigsaved;
 849         struct timespec ts, end_time, *to = NULL;
 850         int ret;
 851
 852         if (tsp) {
 853                 if (copy_from_user(&ts, tsp, sizeof(ts)))
 854                         return -EFAULT;
 855
 856                 to = &end_time;
 857                 if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec))
 858                         return -EINVAL;
 859         }
 860
 861         if (sigmask) {
 862                 /* XXX: Don't preclude handling different sized sigset_t's.  */
 863                 if (sigsetsize != sizeof(sigset_t))
 864                         return -EINVAL;
 865                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 866                         return -EFAULT;
 867
 868                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 869                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 870         }
 871
 872         ret = do_sys_poll(ufds, nfds, to);
 873
 874         /* We can restart this syscall, usually */
 875         if (ret == -EINTR) {
 876                 /*
 877                  * Don't restore the signal mask yet. Let do_signal() deliver
 878                  * the signal on the way back to userspace, before the signal
 879                  * mask is restored.
 880                  */
 881                 if (sigmask) {
 882                         memcpy(&current->saved_sigmask, &sigsaved,
 883                                         sizeof(sigsaved));
 884                         set_restore_sigmask();
 885                 }
 886                 ret = -ERESTARTNOHAND;
 887         } else if (sigmask)
 888                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 889
 890         ret = poll_select_copy_remaining(&end_time, tsp, 0, ret);
 891
 892         return ret;
 893 }
 894 #endif /* HAVE_SET_RESTORE_SIGMASK */