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