hurd/hurdselect.c

   1 /* Guts of both `select' and `poll' for Hurd.
   2    Copyright (C) 1991-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sys/types.h>
  20 #include <sys/poll.h>
  21 #include <hurd.h>
  22 #include <hurd/fd.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <assert.h>
  26 #include <stdint.h>
  27
  28 /* All user select types.  */
  29 #define SELECT_ALL (SELECT_READ | SELECT_WRITE | SELECT_URG)
  30
  31 /* Used to record that a particular select rpc returned.  Must be distinct
  32    from SELECT_ALL (which better not have the high bit set).  */
  33 #define SELECT_RETURNED ((SELECT_ALL << 1) & ~SELECT_ALL)
  34
  35 /* Check the first NFDS descriptors either in POLLFDS (if nonnnull) or in
  36    each of READFDS, WRITEFDS, EXCEPTFDS that is nonnull.  If TIMEOUT is not
  37    NULL, time out after waiting the interval specified therein.  Returns
  38    the number of ready descriptors, or -1 for errors.  */
  39 int
  40 _hurd_select (int nfds,
  41               struct pollfd *pollfds,
  42               fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
  43               const struct timespec *timeout, const sigset_t *sigmask)
  44 {
  45   int i;
  46   mach_port_t portset;
  47   int got;
  48   error_t err;
  49   fd_set rfds, wfds, xfds;
  50   int firstfd, lastfd;
  51   mach_msg_timeout_t to = 0;
  52   struct
  53     {
  54       struct hurd_userlink ulink;
  55       struct hurd_fd *cell;
  56       mach_port_t io_port;
  57       int type;
  58       mach_port_t reply_port;
  59     } d[nfds];
  60   sigset_t oset;
  61
  62   union typeword                /* Use this to avoid unkosher casts.  */
  63     {
  64       mach_msg_type_t type;
  65       uint32_t word;
  66     };
  67   assert (sizeof (union typeword) == sizeof (mach_msg_type_t));
  68   assert (sizeof (uint32_t) == sizeof (mach_msg_type_t));
  69
  70   if (nfds < 0 || (pollfds == NULL && nfds > FD_SETSIZE))
  71     {
  72       errno = EINVAL;
  73       return -1;
  74     }
  75
  76   if (timeout != NULL)
  77     {
  78       if (timeout->tv_sec < 0 || timeout->tv_nsec < 0)
  79         {
  80           errno = EINVAL;
  81           return -1;
  82         }
  83
  84       to = (timeout->tv_sec * 1000 +
  85             (timeout->tv_nsec + 999999) / 1000000);
  86     }
  87
  88   if (sigmask && __sigprocmask (SIG_SETMASK, sigmask, &oset))
  89     return -1;
  90
  91   if (pollfds)
  92     {
  93       /* Collect interesting descriptors from the user's `pollfd' array.
  94          We do a first pass that reads the user's array before taking
  95          any locks.  The second pass then only touches our own stack,
  96          and gets the port references.  */
  97
  98       for (i = 0; i < nfds; ++i)
  99         if (pollfds[i].fd >= 0)
 100           {
 101             int type = 0;
 102             if (pollfds[i].events & POLLIN)
 103               type |= SELECT_READ;
 104             if (pollfds[i].events & POLLOUT)
 105               type |= SELECT_WRITE;
 106             if (pollfds[i].events & POLLPRI)
 107               type |= SELECT_URG;
 108
 109             d[i].io_port = pollfds[i].fd;
 110             d[i].type = type;
 111           }
 112         else
 113           d[i].type = 0;
 114
 115       HURD_CRITICAL_BEGIN;
 116       __mutex_lock (&_hurd_dtable_lock);
 117
 118       for (i = 0; i < nfds; ++i)
 119         if (d[i].type != 0)
 120           {
 121             const int fd = (int) d[i].io_port;
 122
 123             if (fd < _hurd_dtablesize)
 124               {
 125                 d[i].cell = _hurd_dtable[fd];
 126                 d[i].io_port = _hurd_port_get (&d[i].cell->port, &d[i].ulink);
 127                 if (d[i].io_port != MACH_PORT_NULL)
 128                   continue;
 129               }
 130
 131             /* If one descriptor is bogus, we fail completely.  */
 132             while (i-- > 0)
 133               if (d[i].type != 0)
 134                 _hurd_port_free (&d[i].cell->port,
 135                                  &d[i].ulink, d[i].io_port);
 136             break;
 137           }
 138
 139       __mutex_unlock (&_hurd_dtable_lock);
 140       HURD_CRITICAL_END;
 141
 142       if (i < nfds)
 143         {
 144           if (sigmask)
 145             __sigprocmask (SIG_SETMASK, &oset, NULL);
 146           errno = EBADF;
 147           return -1;
 148         }
 149
 150       lastfd = i - 1;
 151       firstfd = i == 0 ? lastfd : 0;
 152     }
 153   else
 154     {
 155       /* Collect interested descriptors from the user's fd_set arguments.
 156          Use local copies so we can't crash from user bogosity.  */
 157
 158       if (readfds == NULL)
 159         FD_ZERO (&rfds);
 160       else
 161         rfds = *readfds;
 162       if (writefds == NULL)
 163         FD_ZERO (&wfds);
 164       else
 165         wfds = *writefds;
 166       if (exceptfds == NULL)
 167         FD_ZERO (&xfds);
 168       else
 169         xfds = *exceptfds;
 170
 171       HURD_CRITICAL_BEGIN;
 172       __mutex_lock (&_hurd_dtable_lock);
 173
 174       if (nfds > _hurd_dtablesize)
 175         nfds = _hurd_dtablesize;
 176
 177       /* Collect the ports for interesting FDs.  */
 178       firstfd = lastfd = -1;
 179       for (i = 0; i < nfds; ++i)
 180         {
 181           int type = 0;
 182           if (readfds != NULL && FD_ISSET (i, &rfds))
 183             type |= SELECT_READ;
 184           if (writefds != NULL && FD_ISSET (i, &wfds))
 185             type |= SELECT_WRITE;
 186           if (exceptfds != NULL && FD_ISSET (i, &xfds))
 187             type |= SELECT_URG;
 188           d[i].type = type;
 189           if (type)
 190             {
 191               d[i].cell = _hurd_dtable[i];
 192               d[i].io_port = _hurd_port_get (&d[i].cell->port, &d[i].ulink);
 193               if (d[i].io_port == MACH_PORT_NULL)
 194                 {
 195                   /* If one descriptor is bogus, we fail completely.  */
 196                   while (i-- > 0)
 197                     if (d[i].type != 0)
 198                       _hurd_port_free (&d[i].cell->port, &d[i].ulink,
 199                                        d[i].io_port);
 200                   break;
 201                 }
 202               lastfd = i;
 203               if (firstfd == -1)
 204                 firstfd = i;
 205             }
 206         }
 207
 208       __mutex_unlock (&_hurd_dtable_lock);
 209       HURD_CRITICAL_END;
 210
 211       if (i < nfds)
 212         {
 213           if (sigmask)
 214             __sigprocmask (SIG_SETMASK, &oset, NULL);
 215           errno = EBADF;
 216           return -1;
 217         }
 218     }
 219
 220
 221   err = 0;
 222   got = 0;
 223
 224   /* Send them all io_select request messages.  */
 225
 226   if (firstfd == -1)
 227     /* But not if there were no ports to deal with at all.
 228        We are just a pure timeout.  */
 229     portset = __mach_reply_port ();
 230   else
 231     {
 232       portset = MACH_PORT_NULL;
 233
 234       for (i = firstfd; i <= lastfd; ++i)
 235         if (d[i].type)
 236           {
 237             int type = d[i].type;
 238             d[i].reply_port = __mach_reply_port ();
 239             err = __io_select (d[i].io_port, d[i].reply_port,
 240                                /* Poll only if there's a single descriptor.  */
 241                                (firstfd == lastfd) ? to : 0,
 242                                &type);
 243             switch (err)
 244               {
 245               case MACH_RCV_TIMED_OUT:
 246                 /* No immediate response.  This is normal.  */
 247                 err = 0;
 248                 if (firstfd == lastfd)
 249                   /* When there's a single descriptor, we don't need a
 250                      portset, so just pretend we have one, but really
 251                      use the single reply port.  */
 252                   portset = d[i].reply_port;
 253                 else if (got == 0)
 254                   /* We've got multiple reply ports, so we need a port set to
 255                      multiplex them.  */
 256                   {
 257                     /* We will wait again for a reply later.  */
 258                     if (portset == MACH_PORT_NULL)
 259                       /* Create the portset to receive all the replies on.  */
 260                       err = __mach_port_allocate (__mach_task_self (),
 261                                                   MACH_PORT_RIGHT_PORT_SET,
 262                                                   &portset);
 263                     if (! err)
 264                       /* Put this reply port in the port set.  */
 265                       __mach_port_move_member (__mach_task_self (),
 266                                                d[i].reply_port, portset);
 267                   }
 268                 break;
 269
 270               default:
 271                 /* No other error should happen.  Callers of select
 272                    don't expect to see errors, so we simulate
 273                    readiness of the erring object and the next call
 274                    hopefully will get the error again.  */
 275                 type = SELECT_ALL;
 276                 /* FALLTHROUGH */
 277
 278               case 0:
 279                 /* We got an answer.  */
 280                 if ((type & SELECT_ALL) == 0)
 281                   /* Bogus answer; treat like an error, as a fake positive.  */
 282                   type = SELECT_ALL;
 283
 284                 /* This port is already ready already.  */
 285                 d[i].type &= type;
 286                 d[i].type |= SELECT_RETURNED;
 287                 ++got;
 288                 break;
 289               }
 290             _hurd_port_free (&d[i].cell->port, &d[i].ulink, d[i].io_port);
 291           }
 292     }
 293
 294   /* Now wait for reply messages.  */
 295   if (!err && got == 0)
 296     {
 297       /* Now wait for io_select_reply messages on PORT,
 298          timing out as appropriate.  */
 299
 300       union
 301         {
 302           mach_msg_header_t head;
 303 #ifdef MACH_MSG_TRAILER_MINIMUM_SIZE
 304           struct
 305             {
 306               mach_msg_header_t head;
 307               NDR_record_t ndr;
 308               error_t err;
 309             } error;
 310           struct
 311             {
 312               mach_msg_header_t head;
 313               NDR_record_t ndr;
 314               error_t err;
 315               int result;
 316               mach_msg_trailer_t trailer;
 317             } success;
 318 #else
 319           struct
 320             {
 321               mach_msg_header_t head;
 322               union typeword err_type;
 323               error_t err;
 324             } error;
 325           struct
 326             {
 327               mach_msg_header_t head;
 328               union typeword err_type;
 329               error_t err;
 330               union typeword result_type;
 331               int result;
 332             } success;
 333 #endif
 334         } msg;
 335       mach_msg_option_t options = (timeout == NULL ? 0 : MACH_RCV_TIMEOUT);
 336       error_t msgerr;
 337       while ((msgerr = __mach_msg (&msg.head,
 338                                    MACH_RCV_MSG | MACH_RCV_INTERRUPT | options,
 339                                    0, sizeof msg, portset, to,
 340                                    MACH_PORT_NULL)) == MACH_MSG_SUCCESS)
 341         {
 342           /* We got a message.  Decode it.  */
 343 #define IO_SELECT_REPLY_MSGID (21012 + 100) /* XXX */
 344 #ifdef MACH_MSG_TYPE_BIT
 345           const union typeword inttype =
 346           { type:
 347             { MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8, 1, 1, 0, 0 }
 348           };
 349 #endif
 350           if (msg.head.msgh_id == IO_SELECT_REPLY_MSGID &&
 351               msg.head.msgh_size >= sizeof msg.error &&
 352               !(msg.head.msgh_bits & MACH_MSGH_BITS_COMPLEX) &&
 353 #ifdef MACH_MSG_TYPE_BIT
 354               msg.error.err_type.word == inttype.word
 355 #endif
 356               )
 357             {
 358               /* This is a properly formatted message so far.
 359                  See if it is a success or a failure.  */
 360               if (msg.error.err == EINTR &&
 361                   msg.head.msgh_size == sizeof msg.error)
 362                 {
 363                   /* EINTR response; poll for further responses
 364                      and then return quickly.  */
 365                   err = EINTR;
 366                   goto poll;
 367                 }
 368               if (msg.error.err ||
 369                   msg.head.msgh_size != sizeof msg.success ||
 370 #ifdef MACH_MSG_TYPE_BIT
 371                   msg.success.result_type.word != inttype.word ||
 372 #endif
 373                   (msg.success.result & SELECT_ALL) == 0)
 374                 {
 375                   /* Error or bogus reply.  Simulate readiness.  */
 376                   __mach_msg_destroy (&msg.head);
 377                   msg.success.result = SELECT_ALL;
 378                 }
 379
 380               /* Look up the respondent's reply port and record its
 381                  readiness.  */
 382               {
 383                 int had = got;
 384                 if (firstfd != -1)
 385                   for (i = firstfd; i <= lastfd; ++i)
 386                     if (d[i].type
 387                         && d[i].reply_port == msg.head.msgh_local_port)
 388                       {
 389                         d[i].type &= msg.success.result;
 390                         d[i].type |= SELECT_RETURNED;
 391                         ++got;
 392                       }
 393                 assert (got > had);
 394               }
 395             }
 396
 397           if (msg.head.msgh_remote_port != MACH_PORT_NULL)
 398             __mach_port_deallocate (__mach_task_self (),
 399                                     msg.head.msgh_remote_port);
 400
 401           if (got)
 402           poll:
 403             {
 404               /* Poll for another message.  */
 405               to = 0;
 406               options |= MACH_RCV_TIMEOUT;
 407             }
 408         }
 409
 410       if (msgerr == MACH_RCV_INTERRUPTED)
 411         /* Interruption on our side (e.g. signal reception).  */
 412         err = EINTR;
 413
 414       if (got)
 415         /* At least one descriptor is known to be ready now, so we will
 416            return success.  */
 417         err = 0;
 418     }
 419
 420   if (firstfd != -1)
 421     for (i = firstfd; i <= lastfd; ++i)
 422       if (d[i].type)
 423         __mach_port_destroy (__mach_task_self (), d[i].reply_port);
 424   if (firstfd == -1 || (firstfd != lastfd && portset != MACH_PORT_NULL))
 425     /* Destroy PORTSET, but only if it's not actually the reply port for a
 426        single descriptor (in which case it's destroyed in the previous loop;
 427        not doing it here is just a bit more efficient).  */
 428     __mach_port_destroy (__mach_task_self (), portset);
 429
 430   if (err)
 431     {
 432       if (sigmask)
 433         __sigprocmask (SIG_SETMASK, &oset, NULL);
 434       return __hurd_fail (err);
 435     }
 436
 437   if (pollfds)
 438     /* Fill in the `revents' members of the user's array.  */
 439     for (i = 0; i < nfds; ++i)
 440       {
 441         int type = d[i].type;
 442         int_fast16_t revents = 0;
 443
 444         if (type & SELECT_RETURNED)
 445           {
 446             if (type & SELECT_READ)
 447               revents |= POLLIN;
 448             if (type & SELECT_WRITE)
 449               revents |= POLLOUT;
 450             if (type & SELECT_URG)
 451               revents |= POLLPRI;
 452           }
 453
 454         pollfds[i].revents = revents;
 455       }
 456   else
 457     {
 458       /* Below we recalculate GOT to include an increment for each operation
 459          allowed on each fd.  */
 460       got = 0;
 461
 462       /* Set the user bitarrays.  We only ever have to clear bits, as all
 463          desired ones are initially set.  */
 464       if (firstfd != -1)
 465         for (i = firstfd; i <= lastfd; ++i)
 466           {
 467             int type = d[i].type;
 468
 469             if ((type & SELECT_RETURNED) == 0)
 470               type = 0;
 471
 472             if (type & SELECT_READ)
 473               got++;
 474             else if (readfds)
 475               FD_CLR (i, readfds);
 476             if (type & SELECT_WRITE)
 477               got++;
 478             else if (writefds)
 479               FD_CLR (i, writefds);
 480             if (type & SELECT_URG)
 481               got++;
 482             else if (exceptfds)
 483               FD_CLR (i, exceptfds);
 484           }
 485     }
 486
 487   if (sigmask && __sigprocmask (SIG_SETMASK, &oset, NULL))
 488     return -1;
 489
 490   return got;
 491 }