hurd/dtable.c

   1 /* Copyright (C) 1991-2024 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 Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the 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    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <hurd.h>
  19 #include <hurd/term.h>
  20 #include <hurd/fd.h>
  21 #include <stdlib.h>
  22 #include <stdio.h>
  23 #include <fcntl.h>
  24 #include <limits.h>
  25 #include <lock-intern.h>        /* For `struct mutex'.  */
  26 #include "set-hooks.h"
  27 #include "hurdmalloc.h"         /* XXX */
  28
  29
  30 struct mutex _hurd_dtable_lock = MUTEX_INITIALIZER; /* XXX ld bug; must init */
  31 struct hurd_fd **_hurd_dtable;
  32 int _hurd_dtablesize;
  33
  34
  35 DEFINE_HOOK (_hurd_fd_subinit, (void));
  36
  37 /* Initialize the file descriptor table at startup.  */
  38
  39 static void attribute_used_retain
  40 init_dtable (void)
  41 {
  42   int i;
  43
  44   __mutex_init (&_hurd_dtable_lock);
  45
  46   /* The initial size of the descriptor table is that of the passed-in
  47      table.  It will be expanded as necessary up to _hurd_dtable_rlimit.  */
  48   _hurd_dtablesize = _hurd_init_dtablesize;
  49
  50   /* Allocate the vector of pointers.  */
  51   _hurd_dtable = malloc (_hurd_dtablesize * sizeof (*_hurd_dtable));
  52   if (_hurd_dtablesize != 0 && _hurd_dtable == NULL)
  53     __libc_fatal ("hurd: Can't allocate file descriptor table\n");
  54
  55   /* Initialize the descriptor table.  */
  56   for (i = 0; (unsigned int) i < _hurd_init_dtablesize; ++i)
  57     {
  58       if (_hurd_init_dtable[i] == MACH_PORT_NULL)
  59         /* An unused descriptor is marked by a null pointer.  */
  60         _hurd_dtable[i] = NULL;
  61       else
  62         {
  63           int copy;
  64           /* Allocate a new file descriptor structure.  */
  65           struct hurd_fd *new = malloc (sizeof (struct hurd_fd));
  66           if (new == NULL)
  67             __libc_fatal ("hurd: Can't allocate initial file descriptors\n");
  68
  69           /* See if this file descriptor is the same as a previous one we have
  70              already installed.  In this case, we can just copy over the same
  71              ctty port without making any more RPCs.  We only check the the
  72              immediately preceding fd and fd 0 -- this should be enough to
  73              handle the common cases while not requiring quadratic
  74              complexity.  */
  75           if (i > 0 && _hurd_init_dtable[i] == _hurd_init_dtable[i - 1])
  76             copy = i - 1;
  77           else if (i > 0 && _hurd_init_dtable[i] == _hurd_init_dtable[0])
  78             copy = 0;
  79           else
  80             copy = -1;
  81
  82           if (copy < 0)
  83             {
  84               /* Initialize the port cells.  */
  85               _hurd_port_init (&new->port, MACH_PORT_NULL);
  86               _hurd_port_init (&new->ctty, MACH_PORT_NULL);
  87
  88               /* Install the port in the descriptor.
  89                  This sets up all the ctty magic.  */
  90               _hurd_port2fd (new, _hurd_init_dtable[i], 0);
  91             }
  92           else
  93             {
  94               /* Copy over ctty from the already set up file descriptor that
  95                  contains the same port.  We can access the contents of the
  96                  cell without any locking since no one could have seen it
  97                  yet.  */
  98               mach_port_t ctty = _hurd_dtable[copy]->ctty.port;
  99
 100               if (MACH_PORT_VALID (ctty))
 101                 __mach_port_mod_refs (__mach_task_self (), ctty,
 102                                       MACH_PORT_RIGHT_SEND, +1);
 103
 104               _hurd_port_init (&new->port, _hurd_init_dtable[i]);
 105               _hurd_port_init (&new->ctty, ctty);
 106             }
 107
 108           _hurd_dtable[i] = new;
 109         }
 110     }
 111
 112   /* Clear out the initial descriptor table.
 113      Everything must use _hurd_dtable now.  */
 114   __vm_deallocate (__mach_task_self (),
 115                    (vm_address_t) _hurd_init_dtable,
 116                    _hurd_init_dtablesize * sizeof (_hurd_init_dtable[0]));
 117   _hurd_init_dtable = NULL;
 118   _hurd_init_dtablesize = 0;
 119
 120   /* Initialize the remaining empty slots in the table.  */
 121   for (; i < _hurd_dtablesize; ++i)
 122     _hurd_dtable[i] = NULL;
 123
 124   /* Run things that want to run after the file descriptor table
 125      is initialized.  */
 126   RUN_RELHOOK (_hurd_fd_subinit, ());
 127 }
 128
 129 SET_RELHOOK (_hurd_subinit, init_dtable);
 130
 131 /* XXX when the linker supports it, the following functions should all be
 132    elsewhere and just have text_set_elements here.  */
 133 \f
 134 /* Called by `getdport' to do its work.  */
 135
 136 static file_t
 137 get_dtable_port (int fd)
 138 {
 139   struct hurd_fd *d = _hurd_fd_get (fd);
 140   file_t dport;
 141
 142   if (!d)
 143     return __hurd_fail (EBADF), MACH_PORT_NULL;
 144
 145   HURD_CRITICAL_BEGIN;
 146
 147   dport = HURD_PORT_USE (&d->port,
 148                          ({
 149                            error_t err;
 150                            mach_port_t outport;
 151                            err = __mach_port_mod_refs (__mach_task_self (),
 152                                                        port,
 153                                                        MACH_PORT_RIGHT_SEND,
 154                                                        1);
 155                            if (err)
 156                              {
 157                                errno = err;
 158                                outport = MACH_PORT_NULL;
 159                              }
 160                            else
 161                              outport = port;
 162                            outport;
 163                          }));
 164
 165   HURD_CRITICAL_END;
 166
 167   return dport;
 168 }
 169
 170 file_t (*_hurd_getdport_fn) (int fd) = get_dtable_port;
 171 \f
 172 #include <hurd/signal.h>
 173
 174 /* We are in the child fork; the dtable lock is still held.
 175    The parent has inserted send rights for all the normal io ports,
 176    but we must recover ctty-special ports for ourselves.  */
 177 static error_t
 178 fork_child_dtable (void)
 179 {
 180   error_t err;
 181   int i;
 182
 183   err = 0;
 184
 185   for (i = 0; !err && i < _hurd_dtablesize; ++i)
 186     {
 187       struct hurd_fd *d = _hurd_dtable[i];
 188       if (d == NULL)
 189         continue;
 190
 191       /* No other thread is using the send rights in the child task.  */
 192       d->port.users = d->ctty.users = NULL;
 193
 194       if (d->ctty.port != MACH_PORT_NULL)
 195         {
 196           /* There was a ctty-special port in the parent.
 197              We need to get one for ourselves too.  */
 198           __mach_port_deallocate (__mach_task_self (), d->ctty.port);
 199           err = __term_open_ctty (d->port.port, _hurd_pid, _hurd_pgrp,
 200                                   &d->ctty.port);
 201           if (err)
 202             d->ctty.port = MACH_PORT_NULL;
 203         }
 204
 205       /* XXX for each fd with a cntlmap, reauth and re-map_cntl.  */
 206     }
 207   return err;
 208
 209   (void) &fork_child_dtable;    /* Avoid "defined but not used" warning.  */
 210 }
 211
 212 data_set_element (_hurd_fork_locks, _hurd_dtable_lock); /* XXX ld bug: bss */
 213 text_set_element (_hurd_fork_child_hook, fork_child_dtable);
 214 \f
 215 /* Called when our process group has changed.  */
 216
 217 static void
 218 ctty_new_pgrp (void)
 219 {
 220   int i;
 221
 222 retry:
 223   HURD_CRITICAL_BEGIN;
 224   __mutex_lock (&_hurd_dtable_lock);
 225
 226   if (__USEPORT (CTTYID, port == MACH_PORT_NULL))
 227     {
 228       /* We have no controlling terminal.  If we haven't had one recently,
 229          but our pgrp is being pointlessly diddled anyway, then we will
 230          have nothing to do in the loop below because no fd will have a
 231          ctty port at all.
 232
 233          More likely, a setsid call is responsible both for the change
 234          in pgrp and for clearing the cttyid port.  In that case, setsid
 235          held the dtable lock while updating the dtable to clear all the
 236          ctty ports, and ergo must have finished doing so before we run here.
 237          So we can be sure, again, that the loop below has no work to do.  */
 238     }
 239   else
 240     for (i = 0; i < _hurd_dtablesize; ++i)
 241       {
 242         struct hurd_fd *const d = _hurd_dtable[i];
 243         struct hurd_userlink ulink, ctty_ulink;
 244         io_t port, ctty;
 245
 246         if (d == NULL)
 247           /* Nothing to do for an unused descriptor cell.  */
 248           continue;
 249
 250         port = _hurd_port_get (&d->port, &ulink);
 251         ctty = _hurd_port_get (&d->ctty, &ctty_ulink);
 252
 253         if (ctty != MACH_PORT_NULL)
 254           {
 255             /* This fd has a ctty-special port.  We need a new one, to tell
 256                the io server of our different process group.  */
 257             io_t new;
 258             error_t err;
 259             if ((err = __term_open_ctty (port, _hurd_pid, _hurd_pgrp, &new)))
 260               {
 261                 if (err == EINTR)
 262                   {
 263                     /* Got a signal while inside an RPC of the critical section, retry again */
 264                     __mutex_unlock (&_hurd_dtable_lock);
 265                     HURD_CRITICAL_UNLOCK;
 266                     goto retry;
 267                   }
 268                 new = MACH_PORT_NULL;
 269               }
 270             _hurd_port_set (&d->ctty, new);
 271           }
 272
 273         _hurd_port_free (&d->port, &ulink, port);
 274         _hurd_port_free (&d->ctty, &ctty_ulink, ctty);
 275       }
 276
 277   __mutex_unlock (&_hurd_dtable_lock);
 278   HURD_CRITICAL_END;
 279
 280   (void) &ctty_new_pgrp;        /* Avoid "defined but not used" warning.  */
 281 }
 282
 283 text_set_element (_hurd_pgrp_changed_hook, ctty_new_pgrp);
 284 \f
 285 /* Called to reauthenticate the dtable when the auth port changes.  */
 286
 287 static void
 288 reauth_dtable (void)
 289 {
 290   int i;
 291
 292 retry:
 293   HURD_CRITICAL_BEGIN;
 294   __mutex_lock (&_hurd_dtable_lock);
 295
 296   for (i = 0; i < _hurd_dtablesize; ++i)
 297     {
 298       struct hurd_fd *const d = _hurd_dtable[i];
 299       mach_port_t new, newctty, ref;
 300       error_t err = 0;
 301
 302       if (d == NULL)
 303         /* Nothing to do for an unused descriptor cell.  */
 304         continue;
 305
 306       ref = __mach_reply_port ();
 307
 308       /* Take the descriptor cell's lock.  */
 309       __spin_lock (&d->port.lock);
 310
 311       /* Reauthenticate the descriptor's port.  */
 312       if (d->port.port != MACH_PORT_NULL
 313           && ! (err = __io_reauthenticate (d->port.port,
 314                                            ref, MACH_MSG_TYPE_MAKE_SEND))
 315           && ! (err = __USEPORT (AUTH, __auth_user_authenticate
 316                                  (port,
 317                                   ref, MACH_MSG_TYPE_MAKE_SEND,
 318                                   &new))))
 319         {
 320           /* Replace the port in the descriptor cell
 321              with the newly reauthenticated port.  */
 322
 323           if (d->ctty.port != MACH_PORT_NULL
 324               && ! (err = __io_reauthenticate (d->ctty.port,
 325                                                ref, MACH_MSG_TYPE_MAKE_SEND))
 326               && ! (err = __USEPORT (AUTH, __auth_user_authenticate
 327                                      (port,
 328                                       ref, MACH_MSG_TYPE_MAKE_SEND,
 329                                       &newctty))))
 330             _hurd_port_set (&d->ctty, newctty);
 331
 332           _hurd_port_locked_set (&d->port, new);
 333         }
 334       else
 335         /* Lost.  Leave this descriptor cell alone.  */
 336         __spin_unlock (&d->port.lock);
 337
 338       __mach_port_destroy (__mach_task_self (), ref);
 339
 340       if (err == EINTR)
 341         {
 342           /* Got a signal while inside an RPC of the critical section,
 343              retry again */
 344           __mutex_unlock (&_hurd_dtable_lock);
 345           HURD_CRITICAL_UNLOCK;
 346           goto retry;
 347         }
 348     }
 349
 350   __mutex_unlock (&_hurd_dtable_lock);
 351   HURD_CRITICAL_END;
 352
 353   (void) &reauth_dtable;        /* Avoid "defined but not used" warning.  */
 354 }
 355
 356 text_set_element (_hurd_reauth_hook, reauth_dtable);