hurd/hurdselect.c

   1 /* Guts of both `select' and `poll' for Hurd.
   2    Copyright (C) 1991-2021 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <sys/time.h>
  20 #include <sys/types.h>
  21 #include <sys/poll.h>
  22 #include <hurd.h>
  23 #include <hurd/fd.h>
  24 #include <hurd/io_request.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <assert.h>
  28 #include <stdint.h>
  29 #include <limits.h>
  30 #include <time.h>
  31 #include <sysdep-cancel.h>
  32
  33 /* All user select types.  */
  34 #define SELECT_ALL (SELECT_READ | SELECT_WRITE | SELECT_URG)
  35
  36 /* Used to record that a particular select rpc returned.  Must be distinct
  37    from SELECT_ALL (which better not have the high bit set).  */
  38 #define SELECT_RETURNED ((SELECT_ALL << 1) & ~SELECT_ALL)
  39 #define SELECT_ERROR (SELECT_RETURNED << 1)
  40
  41 /* Check the first NFDS descriptors either in POLLFDS (if nonnnull) or in
  42    each of READFDS, WRITEFDS, EXCEPTFDS that is nonnull.  If TIMEOUT is not
  43    NULL, time out after waiting the interval specified therein.  Returns
  44    the number of ready descriptors, or -1 for errors.  */
  45 int
  46 _hurd_select (int nfds,
  47               struct pollfd *pollfds,
  48               fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
  49               const struct timespec *timeout, const sigset_t *sigmask)
  50 {
  51   int i;
  52   mach_port_t portset, sigport;
  53   int got, ready;
  54   error_t err;
  55   fd_set rfds, wfds, xfds;
  56   int firstfd, lastfd;
  57   mach_msg_id_t reply_msgid;
  58   mach_msg_timeout_t to;
  59   struct timespec ts;
  60   struct
  61     {
  62       struct hurd_userlink ulink;
  63       struct hurd_fd *cell;
  64       mach_port_t io_port;
  65       int type;
  66       mach_port_t reply_port;
  67       int error;
  68     } d[nfds];
  69   sigset_t oset;
  70   struct hurd_sigstate *ss;
  71
  72   union typeword                /* Use this to avoid unkosher casts.  */
  73     {
  74       mach_msg_type_t type;
  75       uint32_t word;
  76     };
  77   assert (sizeof (union typeword) == sizeof (mach_msg_type_t));
  78   assert (sizeof (uint32_t) == sizeof (mach_msg_type_t));
  79
  80   if (nfds < 0 || (pollfds == NULL && nfds > FD_SETSIZE))
  81     {
  82       errno = EINVAL;
  83       return -1;
  84     }
  85
  86 #define IO_SELECT_REPLY_MSGID (21012 + 100) /* XXX */
  87 #define IO_SELECT_TIMEOUT_REPLY_MSGID (21031 + 100) /* XXX */
  88
  89   if (timeout == NULL)
  90     reply_msgid = IO_SELECT_REPLY_MSGID;
  91   else
  92     {
  93       struct timespec now;
  94
  95       if (timeout->tv_sec < 0 || ! valid_nanoseconds (timeout->tv_nsec))
  96         {
  97           errno = EINVAL;
  98           return -1;
  99         }
 100
 101       err = __clock_gettime (CLOCK_REALTIME, &now);
 102       if (err)
 103         return -1;
 104
 105       ts.tv_sec = now.tv_sec + timeout->tv_sec;
 106       ts.tv_nsec = now.tv_nsec + timeout->tv_nsec;
 107
 108       if (ts.tv_nsec >= 1000000000)
 109         {
 110           ts.tv_sec++;
 111           ts.tv_nsec -= 1000000000;
 112         }
 113
 114       if (ts.tv_sec < 0)
 115         ts.tv_sec = LONG_MAX; /* XXX */
 116
 117       reply_msgid = IO_SELECT_TIMEOUT_REPLY_MSGID;
 118     }
 119
 120   if (sigmask)
 121     {
 122       /* Add a port to the portset for the case when we get the signal even
 123          before calling __mach_msg.  */
 124
 125       sigport = __mach_reply_port ();
 126
 127       ss = _hurd_self_sigstate ();
 128       _hurd_sigstate_lock (ss);
 129       /* And tell the signal thread to message us when a signal arrives.  */
 130       ss->suspended = sigport;
 131       _hurd_sigstate_unlock (ss);
 132
 133       if (__sigprocmask (SIG_SETMASK, sigmask, &oset))
 134         {
 135           _hurd_sigstate_lock (ss);
 136           ss->suspended = MACH_PORT_NULL;
 137           _hurd_sigstate_unlock (ss);
 138           __mach_port_destroy (__mach_task_self (), sigport);
 139           return -1;
 140         }
 141     }
 142   else
 143     sigport = MACH_PORT_NULL;
 144
 145   if (pollfds)
 146     {
 147       int error = 0;
 148       /* Collect interesting descriptors from the user's `pollfd' array.
 149          We do a first pass that reads the user's array before taking
 150          any locks.  The second pass then only touches our own stack,
 151          and gets the port references.  */
 152
 153       for (i = 0; i < nfds; ++i)
 154         if (pollfds[i].fd >= 0)
 155           {
 156             int type = 0;
 157             if (pollfds[i].events & POLLIN)
 158               type |= SELECT_READ;
 159             if (pollfds[i].events & POLLOUT)
 160               type |= SELECT_WRITE;
 161             if (pollfds[i].events & POLLPRI)
 162               type |= SELECT_URG;
 163
 164             d[i].io_port = pollfds[i].fd;
 165             d[i].type = type;
 166           }
 167         else
 168           d[i].type = 0;
 169
 170       HURD_CRITICAL_BEGIN;
 171       __mutex_lock (&_hurd_dtable_lock);
 172
 173       for (i = 0; i < nfds; ++i)
 174         if (d[i].type != 0)
 175           {
 176             const int fd = (int) d[i].io_port;
 177
 178             if (fd < _hurd_dtablesize)
 179               {
 180                 d[i].cell = _hurd_dtable[fd];
 181                 if (d[i].cell != NULL)
 182                   {
 183                     d[i].io_port = _hurd_port_get (&d[i].cell->port,
 184                                                    &d[i].ulink);
 185                     if (d[i].io_port != MACH_PORT_NULL)
 186                       continue;
 187                   }
 188               }
 189
 190             /* Bogus descriptor, make it EBADF already.  */
 191             d[i].error = EBADF;
 192             d[i].type = SELECT_ERROR;
 193             error = 1;
 194           }
 195
 196       __mutex_unlock (&_hurd_dtable_lock);
 197       HURD_CRITICAL_END;
 198
 199       if (error)
 200         {
 201           /* Set timeout to 0.  */
 202           err = __clock_gettime (CLOCK_REALTIME, &ts);
 203           if (err)
 204             {
 205               /* Really bad luck.  */
 206               err = errno;
 207               HURD_CRITICAL_BEGIN;
 208               __mutex_lock (&_hurd_dtable_lock);
 209               while (i-- > 0)
 210                 if (d[i].type & ~SELECT_ERROR != 0)
 211                   _hurd_port_free (&d[i].cell->port, &d[i].ulink,
 212                                    d[i].io_port);
 213               __mutex_unlock (&_hurd_dtable_lock);
 214               HURD_CRITICAL_END;
 215               if (sigmask)
 216                 __sigprocmask (SIG_SETMASK, &oset, NULL);
 217               errno = err;
 218               return -1;
 219             }
 220           reply_msgid = IO_SELECT_TIMEOUT_REPLY_MSGID;
 221         }
 222
 223       lastfd = i - 1;
 224       firstfd = i == 0 ? lastfd : 0;
 225     }
 226   else
 227     {
 228       /* Collect interested descriptors from the user's fd_set arguments.
 229          Use local copies so we can't crash from user bogosity.  */
 230
 231       if (readfds == NULL)
 232         FD_ZERO (&rfds);
 233       else
 234         rfds = *readfds;
 235       if (writefds == NULL)
 236         FD_ZERO (&wfds);
 237       else
 238         wfds = *writefds;
 239       if (exceptfds == NULL)
 240         FD_ZERO (&xfds);
 241       else
 242         xfds = *exceptfds;
 243
 244       HURD_CRITICAL_BEGIN;
 245       __mutex_lock (&_hurd_dtable_lock);
 246
 247       /* Collect the ports for interesting FDs.  */
 248       firstfd = lastfd = -1;
 249       for (i = 0; i < nfds; ++i)
 250         {
 251           int type = 0;
 252           if (readfds != NULL && FD_ISSET (i, &rfds))
 253             type |= SELECT_READ;
 254           if (writefds != NULL && FD_ISSET (i, &wfds))
 255             type |= SELECT_WRITE;
 256           if (exceptfds != NULL && FD_ISSET (i, &xfds))
 257             type |= SELECT_URG;
 258           d[i].type = type;
 259           if (type)
 260             {
 261               if (i < _hurd_dtablesize)
 262                 {
 263                   d[i].cell = _hurd_dtable[i];
 264                   if (d[i].cell != NULL)
 265                     d[i].io_port = _hurd_port_get (&d[i].cell->port,
 266                                                    &d[i].ulink);
 267                 }
 268               if (i >= _hurd_dtablesize || d[i].cell == NULL ||
 269                   d[i].io_port == MACH_PORT_NULL)
 270                 {
 271                   /* If one descriptor is bogus, we fail completely.  */
 272                   while (i-- > 0)
 273                     if (d[i].type != 0)
 274                       _hurd_port_free (&d[i].cell->port, &d[i].ulink,
 275                                        d[i].io_port);
 276                   break;
 277                 }
 278               lastfd = i;
 279               if (firstfd == -1)
 280                 firstfd = i;
 281             }
 282         }
 283
 284       __mutex_unlock (&_hurd_dtable_lock);
 285       HURD_CRITICAL_END;
 286
 287       if (i < nfds)
 288         {
 289           if (sigmask)
 290             __sigprocmask (SIG_SETMASK, &oset, NULL);
 291           errno = EBADF;
 292           return -1;
 293         }
 294
 295       if (nfds > _hurd_dtablesize)
 296         nfds = _hurd_dtablesize;
 297     }
 298
 299
 300   err = 0;
 301   got = 0;
 302
 303   /* Send them all io_select request messages.  */
 304
 305   if (firstfd == -1)
 306     {
 307       if (sigport == MACH_PORT_NULL)
 308         /* But not if there were no ports to deal with at all.
 309            We are just a pure timeout.  */
 310         portset = __mach_reply_port ();
 311       else
 312         portset = sigport;
 313     }
 314   else
 315     {
 316       portset = MACH_PORT_NULL;
 317
 318       for (i = firstfd; i <= lastfd; ++i)
 319         if (!(d[i].type & ~SELECT_ERROR))
 320           d[i].reply_port = MACH_PORT_NULL;
 321         else
 322           {
 323             int type = d[i].type;
 324             d[i].reply_port = __mach_reply_port ();
 325             if (timeout == NULL)
 326               err = __io_select_request (d[i].io_port, d[i].reply_port, type);
 327             else
 328               err = __io_select_timeout_request (d[i].io_port, d[i].reply_port,
 329                                                  ts, type);
 330             if (!err)
 331               {
 332                 if (firstfd == lastfd && sigport == MACH_PORT_NULL)
 333                   /* When there's a single descriptor, we don't need a
 334                      portset, so just pretend we have one, but really
 335                      use the single reply port.  */
 336                   portset = d[i].reply_port;
 337                 else if (got == 0)
 338                   /* We've got multiple reply ports, so we need a port set to
 339                      multiplex them.  */
 340                   {
 341                     /* We will wait again for a reply later.  */
 342                     if (portset == MACH_PORT_NULL)
 343                       /* Create the portset to receive all the replies on.  */
 344                       err = __mach_port_allocate (__mach_task_self (),
 345                                                   MACH_PORT_RIGHT_PORT_SET,
 346                                                   &portset);
 347                     if (! err)
 348                       /* Put this reply port in the port set.  */
 349                       __mach_port_move_member (__mach_task_self (),
 350                                                d[i].reply_port, portset);
 351                   }
 352               }
 353             else
 354               {
 355                 /* No error should happen, but record it for later
 356                    processing.  */
 357                 d[i].error = err;
 358                 d[i].type |= SELECT_ERROR;
 359                 ++got;
 360               }
 361             _hurd_port_free (&d[i].cell->port, &d[i].ulink, d[i].io_port);
 362           }
 363
 364       if (got == 0 && sigport != MACH_PORT_NULL)
 365         {
 366           if (portset == MACH_PORT_NULL)
 367             /* Create the portset to receive the signal message on.  */
 368             __mach_port_allocate (__mach_task_self (), MACH_PORT_RIGHT_PORT_SET,
 369                                   &portset);
 370           /* Put the signal reply port in the port set.  */
 371           __mach_port_move_member (__mach_task_self (), sigport, portset);
 372         }
 373     }
 374
 375   /* GOT is the number of replies (or errors), while READY is the number of
 376      replies with at least one type bit set.  */
 377   ready = 0;
 378
 379   /* Now wait for reply messages.  */
 380   if (!err && got == 0)
 381     {
 382       /* Now wait for io_select_reply messages on PORT,
 383          timing out as appropriate.  */
 384
 385       union
 386         {
 387           mach_msg_header_t head;
 388 #ifdef MACH_MSG_TRAILER_MINIMUM_SIZE
 389           struct
 390             {
 391               mach_msg_header_t head;
 392               NDR_record_t ndr;
 393               error_t err;
 394             } error;
 395           struct
 396             {
 397               mach_msg_header_t head;
 398               NDR_record_t ndr;
 399               error_t err;
 400               int result;
 401               mach_msg_trailer_t trailer;
 402             } success;
 403 #else
 404           struct
 405             {
 406               mach_msg_header_t head;
 407               union typeword err_type;
 408               error_t err;
 409             } error;
 410           struct
 411             {
 412               mach_msg_header_t head;
 413               union typeword err_type;
 414               error_t err;
 415               union typeword result_type;
 416               int result;
 417             } success;
 418 #endif
 419         } msg;
 420       mach_msg_option_t options;
 421       error_t msgerr;
 422
 423       /* We rely on servers to implement the timeout, but when there are none,
 424          do it on the client side.  */
 425       if (timeout != NULL && firstfd == -1)
 426         {
 427           options = MACH_RCV_TIMEOUT;
 428           to = timeout->tv_sec * 1000 + (timeout->tv_nsec + 999999) / 1000000;
 429         }
 430       else
 431         {
 432           options = 0;
 433           to = MACH_MSG_TIMEOUT_NONE;
 434         }
 435
 436       int cancel_oldtype = LIBC_CANCEL_ASYNC();
 437       while ((msgerr = __mach_msg (&msg.head,
 438                                    MACH_RCV_MSG | MACH_RCV_INTERRUPT | options,
 439                                    0, sizeof msg, portset, to,
 440                                    MACH_PORT_NULL)) == MACH_MSG_SUCCESS)
 441         {
 442           LIBC_CANCEL_RESET (cancel_oldtype);
 443
 444           /* We got a message.  Decode it.  */
 445 #ifdef MACH_MSG_TYPE_BIT
 446           const union typeword inttype =
 447           { type:
 448             { MACH_MSG_TYPE_INTEGER_T, sizeof (integer_t) * 8, 1, 1, 0, 0 }
 449           };
 450 #endif
 451
 452           if (sigport != MACH_PORT_NULL && sigport == msg.head.msgh_local_port)
 453             {
 454               /* We actually got interrupted by a signal before
 455                  __mach_msg; poll for further responses and then
 456                  return quickly. */
 457               err = EINTR;
 458               goto poll;
 459             }
 460
 461           if (msg.head.msgh_id == reply_msgid
 462               && msg.head.msgh_size >= sizeof msg.error
 463               && !(msg.head.msgh_bits & MACH_MSGH_BITS_COMPLEX)
 464 #ifdef MACH_MSG_TYPE_BIT
 465               && msg.error.err_type.word == inttype.word
 466 #endif
 467               )
 468             {
 469               /* This is a properly formatted message so far.
 470                  See if it is a success or a failure.  */
 471               if (msg.error.err == EINTR
 472                   && msg.head.msgh_size == sizeof msg.error)
 473                 {
 474                   /* EINTR response; poll for further responses
 475                      and then return quickly.  */
 476                   err = EINTR;
 477                   goto poll;
 478                 }
 479               /* Keep in mind msg.success.result can be 0 if a timeout
 480                  occurred.  */
 481               if (msg.error.err
 482 #ifdef MACH_MSG_TYPE_BIT
 483                   || msg.success.result_type.word != inttype.word
 484 #endif
 485                   || msg.head.msgh_size != sizeof msg.success)
 486                 {
 487                   /* Error or bogus reply.  */
 488                   if (!msg.error.err)
 489                     msg.error.err = EIO;
 490                   __mach_msg_destroy (&msg.head);
 491                 }
 492
 493               /* Look up the respondent's reply port and record its
 494                  readiness.  */
 495               {
 496                 int had = got;
 497                 if (firstfd != -1)
 498                   for (i = firstfd; i <= lastfd; ++i)
 499                     if (d[i].type
 500                         && d[i].reply_port == msg.head.msgh_local_port)
 501                       {
 502                         if (msg.error.err)
 503                           {
 504                             d[i].error = msg.error.err;
 505                             d[i].type = SELECT_ERROR;
 506                             ++ready;
 507                           }
 508                         else
 509                           {
 510                             d[i].type &= msg.success.result;
 511                             if (d[i].type)
 512                               ++ready;
 513                           }
 514
 515                         d[i].type |= SELECT_RETURNED;
 516                         ++got;
 517                       }
 518                 assert (got > had);
 519               }
 520             }
 521
 522           if (msg.head.msgh_remote_port != MACH_PORT_NULL)
 523             __mach_port_deallocate (__mach_task_self (),
 524                                     msg.head.msgh_remote_port);
 525
 526           if (got)
 527           poll:
 528             {
 529               /* Poll for another message.  */
 530               to = 0;
 531               options |= MACH_RCV_TIMEOUT;
 532             }
 533         }
 534       LIBC_CANCEL_RESET (cancel_oldtype);
 535
 536       if (msgerr == MACH_RCV_INTERRUPTED)
 537         /* Interruption on our side (e.g. signal reception).  */
 538         err = EINTR;
 539
 540       if (ready)
 541         /* At least one descriptor is known to be ready now, so we will
 542            return success.  */
 543         err = 0;
 544     }
 545
 546   if (firstfd != -1)
 547     for (i = firstfd; i <= lastfd; ++i)
 548       if (d[i].reply_port != MACH_PORT_NULL)
 549         __mach_port_destroy (__mach_task_self (), d[i].reply_port);
 550
 551   if (sigport != MACH_PORT_NULL)
 552     {
 553       _hurd_sigstate_lock (ss);
 554       ss->suspended = MACH_PORT_NULL;
 555       _hurd_sigstate_unlock (ss);
 556       __mach_port_destroy (__mach_task_self (), sigport);
 557     }
 558
 559   if ((firstfd == -1 && sigport == MACH_PORT_NULL)
 560       || ((firstfd != lastfd || sigport != MACH_PORT_NULL) && portset != MACH_PORT_NULL))
 561     /* Destroy PORTSET, but only if it's not actually the reply port for a
 562        single descriptor (in which case it's destroyed in the previous loop;
 563        not doing it here is just a bit more efficient).  */
 564     __mach_port_destroy (__mach_task_self (), portset);
 565
 566   if (err)
 567     {
 568       if (sigmask)
 569         __sigprocmask (SIG_SETMASK, &oset, NULL);
 570       return __hurd_fail (err);
 571     }
 572
 573   if (pollfds)
 574     /* Fill in the `revents' members of the user's array.  */
 575     for (i = 0; i < nfds; ++i)
 576       {
 577         int type = d[i].type;
 578         int_fast16_t revents = 0;
 579
 580         if (type & SELECT_ERROR)
 581           switch (d[i].error)
 582             {
 583               case EPIPE:
 584                 revents = POLLHUP;
 585                 break;
 586               case EBADF:
 587                 revents = POLLNVAL;
 588                 break;
 589               default:
 590                 revents = POLLERR;
 591                 break;
 592             }
 593         else
 594           if (type & SELECT_RETURNED)
 595             {
 596               if (type & SELECT_READ)
 597                 revents |= POLLIN;
 598               if (type & SELECT_WRITE)
 599                 revents |= POLLOUT;
 600               if (type & SELECT_URG)
 601                 revents |= POLLPRI;
 602             }
 603
 604         pollfds[i].revents = revents;
 605       }
 606   else
 607     {
 608       /* Below we recalculate READY to include an increment for each operation
 609          allowed on each fd.  */
 610       ready = 0;
 611
 612       /* Set the user bitarrays.  We only ever have to clear bits, as all
 613          desired ones are initially set.  */
 614       if (firstfd != -1)
 615         for (i = firstfd; i <= lastfd; ++i)
 616           {
 617             int type = d[i].type;
 618
 619             if ((type & SELECT_RETURNED) == 0)
 620               type = 0;
 621
 622             /* Callers of select don't expect to see errors, so we simulate
 623                readiness of the erring object and the next call hopefully
 624                will get the error again.  */
 625             if (type & SELECT_ERROR)
 626               {
 627                 type = 0;
 628                 if (readfds != NULL && FD_ISSET (i, readfds))
 629                   type |= SELECT_READ;
 630                 if (writefds != NULL && FD_ISSET (i, writefds))
 631                   type |= SELECT_WRITE;
 632                 if (exceptfds != NULL && FD_ISSET (i, exceptfds))
 633                   type |= SELECT_URG;
 634               }
 635
 636             if (type & SELECT_READ)
 637               ready++;
 638             else if (readfds)
 639               FD_CLR (i, readfds);
 640             if (type & SELECT_WRITE)
 641               ready++;
 642             else if (writefds)
 643               FD_CLR (i, writefds);
 644             if (type & SELECT_URG)
 645               ready++;
 646             else if (exceptfds)
 647               FD_CLR (i, exceptfds);
 648           }
 649     }
 650
 651   if (sigmask && __sigprocmask (SIG_SETMASK, &oset, NULL))
 652     return -1;
 653
 654   return ready;
 655 }