git.oblomov.eu Git - linux-2.6/blob - 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/fs.h>
  25 #include <linux/rcupdate.h>
  26
  27 #include <asm/uaccess.h>
  28
  29 struct poll_table_page {
  30         struct poll_table_page * next;
  31         struct poll_table_entry * entry;
  32         struct poll_table_entry entries[0];
  33 };
  34
  35 #define POLL_TABLE_FULL(table) \
  36         ((unsigned long)((table)->entry+1) > PAGE_SIZE + (unsigned long)(table))
  37
  38 /*
  39  * Ok, Peter made a complicated, but straightforward multiple_wait() function.
  40  * I have rewritten this, taking some shortcuts: This code may not be easy to
  41  * follow, but it should be free of race-conditions, and it's practical. If you
  42  * understand what I'm doing here, then you understand how the linux
  43  * sleep/wakeup mechanism works.
  44  *
  45  * Two very simple procedures, poll_wait() and poll_freewait() make all the
  46  * work.  poll_wait() is an inline-function defined in <linux/poll.h>,
  47  * as all select/poll functions have to call it to add an entry to the
  48  * poll table.
  49  */
  50 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
  51                        poll_table *p);
  52
  53 void poll_initwait(struct poll_wqueues *pwq)
  54 {
  55         init_poll_funcptr(&pwq->pt, __pollwait);
  56         pwq->error = 0;
  57         pwq->table = NULL;
  58         pwq->inline_index = 0;
  59 }
  60
  61 EXPORT_SYMBOL(poll_initwait);
  62
  63 static void free_poll_entry(struct poll_table_entry *entry)
  64 {
  65         remove_wait_queue(entry->wait_address, &entry->wait);
  66         fput(entry->filp);
  67 }
  68
  69 void poll_freewait(struct poll_wqueues *pwq)
  70 {
  71         struct poll_table_page * p = pwq->table;
  72         int i;
  73         for (i = 0; i < pwq->inline_index; i++)
  74                 free_poll_entry(pwq->inline_entries + i);
  75         while (p) {
  76                 struct poll_table_entry * entry;
  77                 struct poll_table_page *old;
  78
  79                 entry = p->entry;
  80                 do {
  81                         entry--;
  82                         free_poll_entry(entry);
  83                 } while (entry > p->entries);
  84                 old = p;
  85                 p = p->next;
  86                 free_page((unsigned long) old);
  87         }
  88 }
  89
  90 EXPORT_SYMBOL(poll_freewait);
  91
  92 static struct poll_table_entry *poll_get_entry(poll_table *_p)
  93 {
  94         struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
  95         struct poll_table_page *table = p->table;
  96
  97         if (p->inline_index < N_INLINE_POLL_ENTRIES)
  98                 return p->inline_entries + p->inline_index++;
  99
 100         if (!table || POLL_TABLE_FULL(table)) {
 101                 struct poll_table_page *new_table;
 102
 103                 new_table = (struct poll_table_page *) __get_free_page(GFP_KERNEL);
 104                 if (!new_table) {
 105                         p->error = -ENOMEM;
 106                         __set_current_state(TASK_RUNNING);
 107                         return NULL;
 108                 }
 109                 new_table->entry = new_table->entries;
 110                 new_table->next = table;
 111                 p->table = new_table;
 112                 table = new_table;
 113         }
 114
 115         return table->entry++;
 116 }
 117
 118 /* Add a new entry */
 119 static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
 120                                 poll_table *p)
 121 {
 122         struct poll_table_entry *entry = poll_get_entry(p);
 123         if (!entry)
 124                 return;
 125         get_file(filp);
 126         entry->filp = filp;
 127         entry->wait_address = wait_address;
 128         init_waitqueue_entry(&entry->wait, current);
 129         add_wait_queue(wait_address, &entry->wait);
 130 }
 131
 132 #define FDS_IN(fds, n)          (fds->in + n)
 133 #define FDS_OUT(fds, n)         (fds->out + n)
 134 #define FDS_EX(fds, n)          (fds->ex + n)
 135
 136 #define BITS(fds, n)    (*FDS_IN(fds, n)|*FDS_OUT(fds, n)|*FDS_EX(fds, n))
 137
 138 static int max_select_fd(unsigned long n, fd_set_bits *fds)
 139 {
 140         unsigned long *open_fds;
 141         unsigned long set;
 142         int max;
 143         struct fdtable *fdt;
 144
 145         /* handle last in-complete long-word first */
 146         set = ~(~0UL << (n & (__NFDBITS-1)));
 147         n /= __NFDBITS;
 148         fdt = files_fdtable(current->files);
 149         open_fds = fdt->open_fds->fds_bits+n;
 150         max = 0;
 151         if (set) {
 152                 set &= BITS(fds, n);
 153                 if (set) {
 154                         if (!(set & ~*open_fds))
 155                                 goto get_max;
 156                         return -EBADF;
 157                 }
 158         }
 159         while (n) {
 160                 open_fds--;
 161                 n--;
 162                 set = BITS(fds, n);
 163                 if (!set)
 164                         continue;
 165                 if (set & ~*open_fds)
 166                         return -EBADF;
 167                 if (max)
 168                         continue;
 169 get_max:
 170                 do {
 171                         max++;
 172                         set >>= 1;
 173                 } while (set);
 174                 max += n * __NFDBITS;
 175         }
 176
 177         return max;
 178 }
 179
 180 #define POLLIN_SET (POLLRDNORM | POLLRDBAND | POLLIN | POLLHUP | POLLERR)
 181 #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
 182 #define POLLEX_SET (POLLPRI)
 183
 184 int do_select(int n, fd_set_bits *fds, s64 *timeout)
 185 {
 186         struct poll_wqueues table;
 187         poll_table *wait;
 188         int retval, i;
 189
 190         rcu_read_lock();
 191         retval = max_select_fd(n, fds);
 192         rcu_read_unlock();
 193
 194         if (retval < 0)
 195                 return retval;
 196         n = retval;
 197
 198         poll_initwait(&table);
 199         wait = &table.pt;
 200         if (!*timeout)
 201                 wait = NULL;
 202         retval = 0;
 203         for (;;) {
 204                 unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;
 205                 long __timeout;
 206
 207                 set_current_state(TASK_INTERRUPTIBLE);
 208
 209                 inp = fds->in; outp = fds->out; exp = fds->ex;
 210                 rinp = fds->res_in; routp = fds->res_out; rexp = fds->res_ex;
 211
 212                 for (i = 0; i < n; ++rinp, ++routp, ++rexp) {
 213                         unsigned long in, out, ex, all_bits, bit = 1, mask, j;
 214                         unsigned long res_in = 0, res_out = 0, res_ex = 0;
 215                         const struct file_operations *f_op = NULL;
 216                         struct file *file = NULL;
 217
 218                         in = *inp++; out = *outp++; ex = *exp++;
 219                         all_bits = in | out | ex;
 220                         if (all_bits == 0) {
 221                                 i += __NFDBITS;
 222                                 continue;
 223                         }
 224
 225                         for (j = 0; j < __NFDBITS; ++j, ++i, bit <<= 1) {
 226                                 int fput_needed;
 227                                 if (i >= n)
 228                                         break;
 229                                 if (!(bit & all_bits))
 230                                         continue;
 231                                 file = fget_light(i, &fput_needed);
 232                                 if (file) {
 233                                         f_op = file->f_op;
 234                                         mask = DEFAULT_POLLMASK;
 235                                         if (f_op && f_op->poll)
 236                                                 mask = (*f_op->poll)(file, retval ? NULL : wait);
 237                                         fput_light(file, fput_needed);
 238                                         if ((mask & POLLIN_SET) && (in & bit)) {
 239                                                 res_in |= bit;
 240                                                 retval++;
 241                                         }
 242                                         if ((mask & POLLOUT_SET) && (out & bit)) {
 243                                                 res_out |= bit;
 244                                                 retval++;
 245                                         }
 246                                         if ((mask & POLLEX_SET) && (ex & bit)) {
 247                                                 res_ex |= bit;
 248                                                 retval++;
 249                                         }
 250                                 }
 251                                 cond_resched();
 252                         }
 253                         if (res_in)
 254                                 *rinp = res_in;
 255                         if (res_out)
 256                                 *routp = res_out;
 257                         if (res_ex)
 258                                 *rexp = res_ex;
 259                 }
 260                 wait = NULL;
 261                 if (retval || !*timeout || signal_pending(current))
 262                         break;
 263                 if (table.error) {
 264                         retval = table.error;
 265                         break;
 266                 }
 267
 268                 if (*timeout < 0) {
 269                         /* Wait indefinitely */
 270                         __timeout = MAX_SCHEDULE_TIMEOUT;
 271                 } else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT - 1)) {
 272                         /* Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in a loop */
 273                         __timeout = MAX_SCHEDULE_TIMEOUT - 1;
 274                         *timeout -= __timeout;
 275                 } else {
 276                         __timeout = *timeout;
 277                         *timeout = 0;
 278                 }
 279                 __timeout = schedule_timeout(__timeout);
 280                 if (*timeout >= 0)
 281                         *timeout += __timeout;
 282         }
 283         __set_current_state(TASK_RUNNING);
 284
 285         poll_freewait(&table);
 286
 287         return retval;
 288 }
 289
 290 /*
 291  * We can actually return ERESTARTSYS instead of EINTR, but I'd
 292  * like to be certain this leads to no problems. So I return
 293  * EINTR just for safety.
 294  *
 295  * Update: ERESTARTSYS breaks at least the xview clock binary, so
 296  * I'm trying ERESTARTNOHAND which restart only when you want to.
 297  */
 298 #define MAX_SELECT_SECONDS \
 299         ((unsigned long) (MAX_SCHEDULE_TIMEOUT / HZ)-1)
 300
 301 static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 302                            fd_set __user *exp, s64 *timeout)
 303 {
 304         fd_set_bits fds;
 305         void *bits;
 306         int ret, max_fds;
 307         unsigned int size;
 308         struct fdtable *fdt;
 309         /* Allocate small arguments on the stack to save memory and be faster */
 310         long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
 311
 312         ret = -EINVAL;
 313         if (n < 0)
 314                 goto out_nofds;
 315
 316         /* max_fds can increase, so grab it once to avoid race */
 317         rcu_read_lock();
 318         fdt = files_fdtable(current->files);
 319         max_fds = fdt->max_fds;
 320         rcu_read_unlock();
 321         if (n > max_fds)
 322                 n = max_fds;
 323
 324         /*
 325          * We need 6 bitmaps (in/out/ex for both incoming and outgoing),
 326          * since we used fdset we need to allocate memory in units of
 327          * long-words.
 328          */
 329         size = FDS_BYTES(n);
 330         bits = stack_fds;
 331         if (size > sizeof(stack_fds) / 6) {
 332                 /* Not enough space in on-stack array; must use kmalloc */
 333                 ret = -ENOMEM;
 334                 bits = kmalloc(6 * size, GFP_KERNEL);
 335                 if (!bits)
 336                         goto out_nofds;
 337         }
 338         fds.in      = bits;
 339         fds.out     = bits +   size;
 340         fds.ex      = bits + 2*size;
 341         fds.res_in  = bits + 3*size;
 342         fds.res_out = bits + 4*size;
 343         fds.res_ex  = bits + 5*size;
 344
 345         if ((ret = get_fd_set(n, inp, fds.in)) ||
 346             (ret = get_fd_set(n, outp, fds.out)) ||
 347             (ret = get_fd_set(n, exp, fds.ex)))
 348                 goto out;
 349         zero_fd_set(n, fds.res_in);
 350         zero_fd_set(n, fds.res_out);
 351         zero_fd_set(n, fds.res_ex);
 352
 353         ret = do_select(n, &fds, timeout);
 354
 355         if (ret < 0)
 356                 goto out;
 357         if (!ret) {
 358                 ret = -ERESTARTNOHAND;
 359                 if (signal_pending(current))
 360                         goto out;
 361                 ret = 0;
 362         }
 363
 364         if (set_fd_set(n, inp, fds.res_in) ||
 365             set_fd_set(n, outp, fds.res_out) ||
 366             set_fd_set(n, exp, fds.res_ex))
 367                 ret = -EFAULT;
 368
 369 out:
 370         if (bits != stack_fds)
 371                 kfree(bits);
 372 out_nofds:
 373         return ret;
 374 }
 375
 376 asmlinkage long sys_select(int n, fd_set __user *inp, fd_set __user *outp,
 377                         fd_set __user *exp, struct timeval __user *tvp)
 378 {
 379         s64 timeout = -1;
 380         struct timeval tv;
 381         int ret;
 382
 383         if (tvp) {
 384                 if (copy_from_user(&tv, tvp, sizeof(tv)))
 385                         return -EFAULT;
 386
 387                 if (tv.tv_sec < 0 || tv.tv_usec < 0)
 388                         return -EINVAL;
 389
 390                 /* Cast to u64 to make GCC stop complaining */
 391                 if ((u64)tv.tv_sec >= (u64)MAX_INT64_SECONDS)
 392                         timeout = -1;   /* infinite */
 393                 else {
 394                         timeout = DIV_ROUND_UP(tv.tv_usec, USEC_PER_SEC/HZ);
 395                         timeout += tv.tv_sec * HZ;
 396                 }
 397         }
 398
 399         ret = core_sys_select(n, inp, outp, exp, &timeout);
 400
 401         if (tvp) {
 402                 struct timeval rtv;
 403
 404                 if (current->personality & STICKY_TIMEOUTS)
 405                         goto sticky;
 406                 rtv.tv_usec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ));
 407                 rtv.tv_sec = timeout;
 408                 if (timeval_compare(&rtv, &tv) >= 0)
 409                         rtv = tv;
 410                 if (copy_to_user(tvp, &rtv, sizeof(rtv))) {
 411 sticky:
 412                         /*
 413                          * If an application puts its timeval in read-only
 414                          * memory, we don't want the Linux-specific update to
 415                          * the timeval to cause a fault after the select has
 416                          * completed successfully. However, because we're not
 417                          * updating the timeval, we can't restart the system
 418                          * call.
 419                          */
 420                         if (ret == -ERESTARTNOHAND)
 421                                 ret = -EINTR;
 422                 }
 423         }
 424
 425         return ret;
 426 }
 427
 428 #ifdef TIF_RESTORE_SIGMASK
 429 asmlinkage long sys_pselect7(int n, fd_set __user *inp, fd_set __user *outp,
 430                 fd_set __user *exp, struct timespec __user *tsp,
 431                 const sigset_t __user *sigmask, size_t sigsetsize)
 432 {
 433         s64 timeout = MAX_SCHEDULE_TIMEOUT;
 434         sigset_t ksigmask, sigsaved;
 435         struct timespec ts;
 436         int ret;
 437
 438         if (tsp) {
 439                 if (copy_from_user(&ts, tsp, sizeof(ts)))
 440                         return -EFAULT;
 441
 442                 if (ts.tv_sec < 0 || ts.tv_nsec < 0)
 443                         return -EINVAL;
 444
 445                 /* Cast to u64 to make GCC stop complaining */
 446                 if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
 447                         timeout = -1;   /* infinite */
 448                 else {
 449                         timeout = DIV_ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ);
 450                         timeout += ts.tv_sec * HZ;
 451                 }
 452         }
 453
 454         if (sigmask) {
 455                 /* XXX: Don't preclude handling different sized sigset_t's.  */
 456                 if (sigsetsize != sizeof(sigset_t))
 457                         return -EINVAL;
 458                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 459                         return -EFAULT;
 460
 461                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 462                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 463         }
 464
 465         ret = core_sys_select(n, inp, outp, exp, &timeout);
 466
 467         if (tsp) {
 468                 struct timespec rts;
 469
 470                 if (current->personality & STICKY_TIMEOUTS)
 471                         goto sticky;
 472                 rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *
 473                                                 1000;
 474                 rts.tv_sec = timeout;
 475                 if (timespec_compare(&rts, &ts) >= 0)
 476                         rts = ts;
 477                 if (copy_to_user(tsp, &rts, sizeof(rts))) {
 478 sticky:
 479                         /*
 480                          * If an application puts its timeval in read-only
 481                          * memory, we don't want the Linux-specific update to
 482                          * the timeval to cause a fault after the select has
 483                          * completed successfully. However, because we're not
 484                          * updating the timeval, we can't restart the system
 485                          * call.
 486                          */
 487                         if (ret == -ERESTARTNOHAND)
 488                                 ret = -EINTR;
 489                 }
 490         }
 491
 492         if (ret == -ERESTARTNOHAND) {
 493                 /*
 494                  * Don't restore the signal mask yet. Let do_signal() deliver
 495                  * the signal on the way back to userspace, before the signal
 496                  * mask is restored.
 497                  */
 498                 if (sigmask) {
 499                         memcpy(&current->saved_sigmask, &sigsaved,
 500                                         sizeof(sigsaved));
 501                         set_thread_flag(TIF_RESTORE_SIGMASK);
 502                 }
 503         } else if (sigmask)
 504                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 505
 506         return ret;
 507 }
 508
 509 /*
 510  * Most architectures can't handle 7-argument syscalls. So we provide a
 511  * 6-argument version where the sixth argument is a pointer to a structure
 512  * which has a pointer to the sigset_t itself followed by a size_t containing
 513  * the sigset size.
 514  */
 515 asmlinkage long sys_pselect6(int n, fd_set __user *inp, fd_set __user *outp,
 516         fd_set __user *exp, struct timespec __user *tsp, void __user *sig)
 517 {
 518         size_t sigsetsize = 0;
 519         sigset_t __user *up = NULL;
 520
 521         if (sig) {
 522                 if (!access_ok(VERIFY_READ, sig, sizeof(void *)+sizeof(size_t))
 523                     || __get_user(up, (sigset_t __user * __user *)sig)
 524                     || __get_user(sigsetsize,
 525                                 (size_t __user *)(sig+sizeof(void *))))
 526                         return -EFAULT;
 527         }
 528
 529         return sys_pselect7(n, inp, outp, exp, tsp, up, sigsetsize);
 530 }
 531 #endif /* TIF_RESTORE_SIGMASK */
 532
 533 struct poll_list {
 534         struct poll_list *next;
 535         int len;
 536         struct pollfd entries[0];
 537 };
 538
 539 #define POLLFD_PER_PAGE  ((PAGE_SIZE-sizeof(struct poll_list)) / sizeof(struct pollfd))
 540
 541 /*
 542  * Fish for pollable events on the pollfd->fd file descriptor. We're only
 543  * interested in events matching the pollfd->events mask, and the result
 544  * matching that mask is both recorded in pollfd->revents and returned. The
 545  * pwait poll_table will be used by the fd-provided poll handler for waiting,
 546  * if non-NULL.
 547  */
 548 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
 549 {
 550         unsigned int mask;
 551         int fd;
 552
 553         mask = 0;
 554         fd = pollfd->fd;
 555         if (fd >= 0) {
 556                 int fput_needed;
 557                 struct file * file;
 558
 559                 file = fget_light(fd, &fput_needed);
 560                 mask = POLLNVAL;
 561                 if (file != NULL) {
 562                         mask = DEFAULT_POLLMASK;
 563                         if (file->f_op && file->f_op->poll)
 564                                 mask = file->f_op->poll(file, pwait);
 565                         /* Mask out unneeded events. */
 566                         mask &= pollfd->events | POLLERR | POLLHUP;
 567                         fput_light(file, fput_needed);
 568                 }
 569         }
 570         pollfd->revents = mask;
 571
 572         return mask;
 573 }
 574
 575 static int do_poll(unsigned int nfds,  struct poll_list *list,
 576                    struct poll_wqueues *wait, s64 *timeout)
 577 {
 578         int count = 0;
 579         poll_table* pt = &wait->pt;
 580
 581         /* Optimise the no-wait case */
 582         if (!(*timeout))
 583                 pt = NULL;
 584
 585         for (;;) {
 586                 struct poll_list *walk;
 587                 long __timeout;
 588
 589                 set_current_state(TASK_INTERRUPTIBLE);
 590                 for (walk = list; walk != NULL; walk = walk->next) {
 591                         struct pollfd * pfd, * pfd_end;
 592
 593                         pfd = walk->entries;
 594                         pfd_end = pfd + walk->len;
 595                         for (; pfd != pfd_end; pfd++) {
 596                                 /*
 597                                  * Fish for events. If we found one, record it
 598                                  * and kill the poll_table, so we don't
 599                                  * needlessly register any other waiters after
 600                                  * this. They'll get immediately deregistered
 601                                  * when we break out and return.
 602                                  */
 603                                 if (do_pollfd(pfd, pt)) {
 604                                         count++;
 605                                         pt = NULL;
 606                                 }
 607                         }
 608                 }
 609                 /*
 610                  * All waiters have already been registered, so don't provide
 611                  * a poll_table to them on the next loop iteration.
 612                  */
 613                 pt = NULL;
 614                 if (!count) {
 615                         count = wait->error;
 616                         if (signal_pending(current))
 617                                 count = -EINTR;
 618                 }
 619                 if (count || !*timeout)
 620                         break;
 621
 622                 if (*timeout < 0) {
 623                         /* Wait indefinitely */
 624                         __timeout = MAX_SCHEDULE_TIMEOUT;
 625                 } else if (unlikely(*timeout >= (s64)MAX_SCHEDULE_TIMEOUT-1)) {
 626                         /*
 627                          * Wait for longer than MAX_SCHEDULE_TIMEOUT. Do it in
 628                          * a loop
 629                          */
 630                         __timeout = MAX_SCHEDULE_TIMEOUT - 1;
 631                         *timeout -= __timeout;
 632                 } else {
 633                         __timeout = *timeout;
 634                         *timeout = 0;
 635                 }
 636
 637                 __timeout = schedule_timeout(__timeout);
 638                 if (*timeout >= 0)
 639                         *timeout += __timeout;
 640         }
 641         __set_current_state(TASK_RUNNING);
 642         return count;
 643 }
 644
 645 #define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
 646                         sizeof(struct pollfd))
 647
 648 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
 649 {
 650         struct poll_wqueues table;
 651         int err = -EFAULT, fdcount, len, size;
 652         /* Allocate small arguments on the stack to save memory and be
 653            faster - use long to make sure the buffer is aligned properly
 654            on 64 bit archs to avoid unaligned access */
 655         long stack_pps[POLL_STACK_ALLOC/sizeof(long)];
 656         struct poll_list *const head = (struct poll_list *)stack_pps;
 657         struct poll_list *walk = head;
 658         unsigned long todo = nfds;
 659
 660         if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
 661                 return -EINVAL;
 662
 663         len = min_t(unsigned int, nfds, N_STACK_PPS);
 664         for (;;) {
 665                 walk->next = NULL;
 666                 walk->len = len;
 667                 if (!len)
 668                         break;
 669
 670                 if (copy_from_user(walk->entries, ufds + nfds-todo,
 671                                         sizeof(struct pollfd) * walk->len))
 672                         goto out_fds;
 673
 674                 todo -= walk->len;
 675                 if (!todo)
 676                         break;
 677
 678                 len = min(todo, POLLFD_PER_PAGE);
 679                 size = sizeof(struct poll_list) + sizeof(struct pollfd) * len;
 680                 walk = walk->next = kmalloc(size, GFP_KERNEL);
 681                 if (!walk) {
 682                         err = -ENOMEM;
 683                         goto out_fds;
 684                 }
 685         }
 686
 687         poll_initwait(&table);
 688         fdcount = do_poll(nfds, head, &table, timeout);
 689         poll_freewait(&table);
 690
 691         for (walk = head; walk; walk = walk->next) {
 692                 struct pollfd *fds = walk->entries;
 693                 int j;
 694
 695                 for (j = 0; j < walk->len; j++, ufds++)
 696                         if (__put_user(fds[j].revents, &ufds->revents))
 697                                 goto out_fds;
 698         }
 699
 700         err = fdcount;
 701 out_fds:
 702         walk = head->next;
 703         while (walk) {
 704                 struct poll_list *pos = walk;
 705                 walk = walk->next;
 706                 kfree(pos);
 707         }
 708
 709         return err;
 710 }
 711
 712 static long do_restart_poll(struct restart_block *restart_block)
 713 {
 714         struct pollfd __user *ufds = (struct pollfd __user*)restart_block->arg0;
 715         int nfds = restart_block->arg1;
 716         s64 timeout = ((s64)restart_block->arg3<<32) | (s64)restart_block->arg2;
 717         int ret;
 718
 719         ret = do_sys_poll(ufds, nfds, &timeout);
 720         if (ret == -EINTR) {
 721                 restart_block->fn = do_restart_poll;
 722                 restart_block->arg2 = timeout & 0xFFFFFFFF;
 723                 restart_block->arg3 = (u64)timeout >> 32;
 724                 ret = -ERESTART_RESTARTBLOCK;
 725         }
 726         return ret;
 727 }
 728
 729 asmlinkage long sys_poll(struct pollfd __user *ufds, unsigned int nfds,
 730                         long timeout_msecs)
 731 {
 732         s64 timeout_jiffies;
 733         int ret;
 734
 735         if (timeout_msecs > 0) {
 736 #if HZ > 1000
 737                 /* We can only overflow if HZ > 1000 */
 738                 if (timeout_msecs / 1000 > (s64)0x7fffffffffffffffULL / (s64)HZ)
 739                         timeout_jiffies = -1;
 740                 else
 741 #endif
 742                         timeout_jiffies = msecs_to_jiffies(timeout_msecs) + 1;
 743         } else {
 744                 /* Infinite (< 0) or no (0) timeout */
 745                 timeout_jiffies = timeout_msecs;
 746         }
 747
 748         ret = do_sys_poll(ufds, nfds, &timeout_jiffies);
 749         if (ret == -EINTR) {
 750                 struct restart_block *restart_block;
 751                 restart_block = &current_thread_info()->restart_block;
 752                 restart_block->fn = do_restart_poll;
 753                 restart_block->arg0 = (unsigned long)ufds;
 754                 restart_block->arg1 = nfds;
 755                 restart_block->arg2 = timeout_jiffies & 0xFFFFFFFF;
 756                 restart_block->arg3 = (u64)timeout_jiffies >> 32;
 757                 ret = -ERESTART_RESTARTBLOCK;
 758         }
 759         return ret;
 760 }
 761
 762 #ifdef TIF_RESTORE_SIGMASK
 763 asmlinkage long sys_ppoll(struct pollfd __user *ufds, unsigned int nfds,
 764         struct timespec __user *tsp, const sigset_t __user *sigmask,
 765         size_t sigsetsize)
 766 {
 767         sigset_t ksigmask, sigsaved;
 768         struct timespec ts;
 769         s64 timeout = -1;
 770         int ret;
 771
 772         if (tsp) {
 773                 if (copy_from_user(&ts, tsp, sizeof(ts)))
 774                         return -EFAULT;
 775
 776                 /* Cast to u64 to make GCC stop complaining */
 777                 if ((u64)ts.tv_sec >= (u64)MAX_INT64_SECONDS)
 778                         timeout = -1;   /* infinite */
 779                 else {
 780                         timeout = DIV_ROUND_UP(ts.tv_nsec, NSEC_PER_SEC/HZ);
 781                         timeout += ts.tv_sec * HZ;
 782                 }
 783         }
 784
 785         if (sigmask) {
 786                 /* XXX: Don't preclude handling different sized sigset_t's.  */
 787                 if (sigsetsize != sizeof(sigset_t))
 788                         return -EINVAL;
 789                 if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
 790                         return -EFAULT;
 791
 792                 sigdelsetmask(&ksigmask, sigmask(SIGKILL)|sigmask(SIGSTOP));
 793                 sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
 794         }
 795
 796         ret = do_sys_poll(ufds, nfds, &timeout);
 797
 798         /* We can restart this syscall, usually */
 799         if (ret == -EINTR) {
 800                 /*
 801                  * Don't restore the signal mask yet. Let do_signal() deliver
 802                  * the signal on the way back to userspace, before the signal
 803                  * mask is restored.
 804                  */
 805                 if (sigmask) {
 806                         memcpy(&current->saved_sigmask, &sigsaved,
 807                                         sizeof(sigsaved));
 808                         set_thread_flag(TIF_RESTORE_SIGMASK);
 809                 }
 810                 ret = -ERESTARTNOHAND;
 811         } else if (sigmask)
 812                 sigprocmask(SIG_SETMASK, &sigsaved, NULL);
 813
 814         if (tsp && timeout >= 0) {
 815                 struct timespec rts;
 816
 817                 if (current->personality & STICKY_TIMEOUTS)
 818                         goto sticky;
 819                 /* Yes, we know it's actually an s64, but it's also positive. */
 820                 rts.tv_nsec = jiffies_to_usecs(do_div((*(u64*)&timeout), HZ)) *
 821                                                 1000;
 822                 rts.tv_sec = timeout;
 823                 if (timespec_compare(&rts, &ts) >= 0)
 824                         rts = ts;
 825                 if (copy_to_user(tsp, &rts, sizeof(rts))) {
 826                 sticky:
 827                         /*
 828                          * If an application puts its timeval in read-only
 829                          * memory, we don't want the Linux-specific update to
 830                          * the timeval to cause a fault after the select has
 831                          * completed successfully. However, because we're not
 832                          * updating the timeval, we can't restart the system
 833                          * call.
 834                          */
 835                         if (ret == -ERESTARTNOHAND && timeout >= 0)
 836                                 ret = -EINTR;
 837                 }
 838         }
 839
 840         return ret;
 841 }
 842 #endif /* TIF_RESTORE_SIGMASK */