sysdeps/mach/hurd/select.c

   1 /* Copyright (C) 1991, 92, 93, 94, 95, 96 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <sys/types.h>
  21 #include <hurd.h>
  22 #include <hurd/fd.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <assert.h>
  26
  27 /* All user select types.  */
  28 #define SELECT_ALL (SELECT_READ | SELECT_WRITE | SELECT_URG)
  29
  30 /* Used to record that a particular select rpc returned. Must be distinct
  31    from SELECT_ALL (which better not have the high bit set).  */
  32 #define SELECT_RETURNED ((SELECT_ALL << 1) & ~SELECT_ALL)
  33
  34 /* Check the first NFDS descriptors each in READFDS (if not NULL) for read
  35    readiness, in WRITEFDS (if not NULL) for write readiness, and in EXCEPTFDS
  36    (if not NULL) for exceptional conditions.  If TIMEOUT is not NULL, time out
  37    after waiting the interval specified therein.  Returns the number of ready
  38    descriptors, or -1 for errors.  */
  39 int
  40 DEFUN(__select, (nfds, readfds, writefds, exceptfds, timeout),
  41       int nfds AND fd_set *readfds AND fd_set *writefds AND
  42       fd_set *exceptfds AND struct timeval *timeout)
  43 {
  44   int i;
  45   mach_port_t portset;
  46   int got;
  47   error_t err;
  48   fd_set rfds, wfds, xfds;
  49   int firstfd, lastfd;
  50   mach_msg_timeout_t to = (timeout != NULL ?
  51                            (timeout->tv_sec * 1000 +
  52                             timeout->tv_usec / 1000) :
  53                            0);
  54   struct
  55     {
  56       struct hurd_userlink ulink;
  57       struct hurd_fd *cell;
  58       mach_port_t io_port;
  59       int type;
  60       mach_port_t reply_port;
  61     } d[nfds];
  62
  63   /* Use local copies so we can't crash from user bogosity.  */
  64   if (readfds == NULL)
  65     FD_ZERO (&rfds);
  66   else
  67     rfds = *readfds;
  68   if (writefds == NULL)
  69     FD_ZERO (&wfds);
  70   else
  71     wfds = *writefds;
  72   if (exceptfds == NULL)
  73     FD_ZERO (&xfds);
  74   else
  75     xfds = *exceptfds;
  76
  77   HURD_CRITICAL_BEGIN;
  78   __mutex_lock (&_hurd_dtable_lock);
  79
  80   if (nfds > _hurd_dtablesize)
  81     nfds = _hurd_dtablesize;
  82
  83   /* Collect the ports for interesting FDs.  */
  84   firstfd = lastfd = -1;
  85   for (i = 0; i < nfds; ++i)
  86     {
  87       int type = 0;
  88       if (readfds != NULL && FD_ISSET (i, &rfds))
  89         type |= SELECT_READ;
  90       if (writefds != NULL && FD_ISSET (i, &wfds))
  91         type |= SELECT_WRITE;
  92       if (exceptfds != NULL && FD_ISSET (i, &xfds))
  93         type |= SELECT_URG;
  94       d[i].type = type;
  95       if (type)
  96         {
  97           d[i].cell = _hurd_dtable[i];
  98           d[i].io_port = _hurd_port_get (&d[i].cell->port, &d[i].ulink);
  99           if (d[i].io_port == MACH_PORT_NULL)
 100             {
 101               /* If one descriptor is bogus, we fail completely.  */
 102               while (i-- > 0)
 103                 _hurd_port_free (&d[i].cell->port, &d[i].ulink, d[i].io_port);
 104               errno = EBADF;
 105               break;
 106             }
 107           lastfd = i;
 108           if (firstfd == -1)
 109             firstfd = i;
 110         }
 111     }
 112
 113   __mutex_unlock (&_hurd_dtable_lock);
 114   HURD_CRITICAL_END;
 115
 116   if (i < nfds)
 117     return -1;
 118
 119   /* Send them all io_select request messages.  */
 120   err = 0;
 121   got = 0;
 122   portset = MACH_PORT_NULL;
 123   for (i = firstfd; i <= lastfd; ++i)
 124     if (d[i].type)
 125       {
 126         int type = d[i].type;
 127         d[i].reply_port = __mach_reply_port ();
 128         err = __io_select (d[i].io_port, d[i].reply_port,
 129                            /* Poll only when there's a single descriptor.  */
 130                            (firstfd == lastfd) ? to : 0,
 131                            &type);
 132         switch (err)
 133           {
 134           case MACH_RCV_TIMED_OUT:
 135             /* No immediate response.  This is normal.  */
 136             err = 0;
 137             if (firstfd == lastfd)
 138               /* When there's a single descriptor, we don't need a portset,
 139                  so just pretend we have one, but really use the single reply
 140                  port.  */
 141               portset = d[i].reply_port;
 142             else if (got == 0)
 143               /* We've got multiple reply ports, so we need a port set to
 144                  multiplex them.  */
 145               {
 146                 /* We will wait again for a reply later.  */
 147                 if (portset == MACH_PORT_NULL)
 148                   /* Create the portset to receive all the replies on.  */
 149                   err = __mach_port_allocate (__mach_task_self (),
 150                                               MACH_PORT_RIGHT_PORT_SET,
 151                                               &portset);
 152                 if (! err)
 153                   /* Put this reply port in the port set.  */
 154                   __mach_port_move_member (__mach_task_self (),
 155                                            d[i].reply_port, portset);
 156               }
 157             break;
 158
 159           default:
 160             /* No other error should happen.  Callers of select don't
 161                expect to see errors, so we simulate readiness of the erring
 162                object and the next call hopefully will get the error again.  */
 163             type = SELECT_ALL;
 164             /* FALLTHROUGH */
 165
 166           case 0:
 167             /* We got an answer.  */
 168             if ((type & SELECT_ALL) == 0)
 169               /* Bogus answer; treat like an error, as a fake positive.  */
 170               type = SELECT_ALL;
 171
 172             /* This port is already ready already.  */
 173             d[i].type &= type;
 174             d[i].type |= SELECT_RETURNED;
 175             ++got;
 176             break;
 177           }
 178         _hurd_port_free (&d[i].cell->port, &d[i].ulink, d[i].io_port);
 179       }
 180
 181   /* Now wait for reply messages.  */
 182   if (!err && got == 0)
 183     {
 184       /* Now wait for io_select_reply messages on PORT,
 185          timing out as appropriate.  */
 186
 187       union
 188         {
 189           mach_msg_header_t head;
 190           struct
 191             {
 192               mach_msg_header_t head;
 193               mach_msg_type_t err_type;
 194               error_t err;
 195             } error;
 196           struct
 197             {
 198               mach_msg_header_t head;
 199               mach_msg_type_t err_type;
 200               error_t err;
 201               mach_msg_type_t result_type;
 202               int result;
 203             } success;
 204         } msg;
 205       mach_msg_option_t options = (timeout == NULL ? 0 : MACH_RCV_TIMEOUT);
 206       error_t msgerr;
 207       while ((msgerr = __mach_msg (&msg.head,
 208                                    MACH_RCV_MSG | options,
 209                                    0, sizeof msg, portset, to,
 210                                    MACH_PORT_NULL)) == MACH_MSG_SUCCESS)
 211         {
 212           /* We got a message.  Decode it.  */
 213 #define IO_SELECT_REPLY_MSGID (21012 + 100) /* XXX */
 214           const mach_msg_type_t inttype =
 215             { MACH_MSG_TYPE_INTEGER_32, 32, 1, 1, 0, 0 };
 216           if (msg.head.msgh_id == IO_SELECT_REPLY_MSGID &&
 217               msg.head.msgh_size >= sizeof msg.error &&
 218               !(msg.head.msgh_bits & MACH_MSGH_BITS_COMPLEX) &&
 219               *(int *) &msg.error.err_type == *(int *) &inttype)
 220             {
 221               /* This is a properly formatted message so far.
 222                  See if it is a success or a failure.  */
 223               if (msg.error.err == EINTR &&
 224                   msg.head.msgh_size == sizeof msg.error)
 225                 {
 226                   /* EINTR response; poll for further responses
 227                      and then return quickly.  */
 228                   err = EINTR;
 229                   goto poll;
 230                 }
 231               if (msg.error.err ||
 232                   msg.head.msgh_size != sizeof msg.success ||
 233                   *(int *) &msg.success.result_type != *(int *) &inttype ||
 234                   (msg.success.result & SELECT_ALL) == 0)
 235                 {
 236                   /* Error or bogus reply.  Simulate readiness.  */
 237                   __mach_msg_destroy (&msg);
 238                   msg.success.result = SELECT_ALL;
 239                 }
 240
 241               /* Look up the respondant's reply port and record its
 242                  readiness.  */
 243               {
 244                 int had = got;
 245                 for (i = firstfd; i <= lastfd; ++i)
 246                   if (d[i].type && d[i].reply_port == msg.head.msgh_local_port)
 247                     {
 248                       d[i].type &= msg.success.result;
 249                       d[i].type |= SELECT_RETURNED;
 250                       ++got;
 251                     }
 252                 assert (got > had);
 253               }
 254             }
 255
 256           if (msg.head.msgh_remote_port != MACH_PORT_NULL)
 257             __mach_port_deallocate (__mach_task_self (),
 258                                     msg.head.msgh_remote_port);
 259
 260           if (got)
 261           poll:
 262             {
 263               /* Poll for another message.  */
 264               to = 0;
 265               options |= MACH_RCV_TIMEOUT;
 266             }
 267         }
 268
 269       if (err == MACH_RCV_TIMED_OUT)
 270         /* This is the normal value for ERR.  We might have timed out and
 271            read no messages.  Otherwise, after receiving the first message,
 272            we poll for more messages.  We receive with a timeout of 0 to
 273            effect a poll, so ERR is MACH_RCV_TIMED_OUT when the poll finds no
 274            message waiting.  */
 275         err = 0;
 276
 277       if (got)
 278         /* At least one descriptor is known to be ready now, so we will
 279            return success.  */
 280         err = 0;
 281     }
 282
 283   for (i = firstfd; i <= lastfd; ++i)
 284     if (d[i].type)
 285       __mach_port_destroy (__mach_task_self (), d[i].reply_port);
 286   if (firstfd != lastfd && portset != MACH_PORT_NULL)
 287     /* Destroy PORTSET, but only if it's not actually the reply port for a
 288        single descriptor (in which case it's destroyed in the previous loop;
 289        not doing it here is just a bit more efficient).  */
 290     __mach_port_destroy (__mach_task_self (), portset);
 291
 292   if (err)
 293     return __hurd_fail (err);
 294
 295   /* Below we recalculate GOT to include an increment for each operation
 296      allowed on each fd.  */
 297   got = 0;
 298
 299   /* Set the user bitarrays.  We only ever have to clear bits, as all desired
 300      ones are initially set.  */
 301   for (i = firstfd; i <= lastfd; ++i)
 302     {
 303       int type = d[i].type;
 304
 305       if ((type & SELECT_RETURNED) == 0)
 306         type = 0;
 307
 308       if (type & SELECT_READ)
 309         got++;
 310       else if (readfds)
 311         FD_CLR (i, readfds);
 312       if (type & SELECT_WRITE)
 313         got++;
 314       else if (writefds)
 315         FD_CLR (i, writefds);
 316       if (type & SELECT_URG)
 317         got++;
 318       else if (exceptfds)
 319         FD_CLR (i, exceptfds);
 320     }
 321
 322   return got;
 323 }
 324
 325 weak_alias (__select, select)