hurd/dtable.c

   1 /* Copyright (C) 1991-2022 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           /* Allocate a new file descriptor structure.  */
  64           struct hurd_fd *new = malloc (sizeof (struct hurd_fd));
  65           if (new == NULL)
  66             __libc_fatal ("hurd: Can't allocate initial file descriptors\n");
  67
  68           /* Initialize the port cells.  */
  69           _hurd_port_init (&new->port, MACH_PORT_NULL);
  70           _hurd_port_init (&new->ctty, MACH_PORT_NULL);
  71
  72           /* Install the port in the descriptor.
  73              This sets up all the ctty magic.  */
  74           _hurd_port2fd (new, _hurd_init_dtable[i], 0);
  75
  76           _hurd_dtable[i] = new;
  77         }
  78     }
  79
  80   /* Clear out the initial descriptor table.
  81      Everything must use _hurd_dtable now.  */
  82   __vm_deallocate (__mach_task_self (),
  83                    (vm_address_t) _hurd_init_dtable,
  84                    _hurd_init_dtablesize * sizeof (_hurd_init_dtable[0]));
  85   _hurd_init_dtable = NULL;
  86   _hurd_init_dtablesize = 0;
  87
  88   /* Initialize the remaining empty slots in the table.  */
  89   for (; i < _hurd_dtablesize; ++i)
  90     _hurd_dtable[i] = NULL;
  91
  92   /* Run things that want to run after the file descriptor table
  93      is initialized.  */
  94   RUN_RELHOOK (_hurd_fd_subinit, ());
  95 }
  96
  97 SET_RELHOOK (_hurd_subinit, init_dtable);
  98
  99 /* XXX when the linker supports it, the following functions should all be
 100    elsewhere and just have text_set_elements here.  */
 101 \f
 102 /* Called by `getdport' to do its work.  */
 103
 104 static file_t
 105 get_dtable_port (int fd)
 106 {
 107   struct hurd_fd *d = _hurd_fd_get (fd);
 108   file_t dport;
 109
 110   if (!d)
 111     return __hurd_fail (EBADF), MACH_PORT_NULL;
 112
 113   HURD_CRITICAL_BEGIN;
 114
 115   dport = HURD_PORT_USE (&d->port,
 116                          ({
 117                            error_t err;
 118                            mach_port_t outport;
 119                            err = __mach_port_mod_refs (__mach_task_self (),
 120                                                        port,
 121                                                        MACH_PORT_RIGHT_SEND,
 122                                                        1);
 123                            if (err)
 124                              {
 125                                errno = err;
 126                                outport = MACH_PORT_NULL;
 127                              }
 128                            else
 129                              outport = port;
 130                            outport;
 131                          }));
 132
 133   HURD_CRITICAL_END;
 134
 135   return dport;
 136 }
 137
 138 file_t (*_hurd_getdport_fn) (int fd) = get_dtable_port;
 139 \f
 140 #include <hurd/signal.h>
 141
 142 /* We are in the child fork; the dtable lock is still held.
 143    The parent has inserted send rights for all the normal io ports,
 144    but we must recover ctty-special ports for ourselves.  */
 145 static error_t
 146 fork_child_dtable (void)
 147 {
 148   error_t err;
 149   int i;
 150
 151   err = 0;
 152
 153   for (i = 0; !err && i < _hurd_dtablesize; ++i)
 154     {
 155       struct hurd_fd *d = _hurd_dtable[i];
 156       if (d == NULL)
 157         continue;
 158
 159       /* No other thread is using the send rights in the child task.  */
 160       d->port.users = d->ctty.users = NULL;
 161
 162       if (d->ctty.port != MACH_PORT_NULL)
 163         {
 164           /* There was a ctty-special port in the parent.
 165              We need to get one for ourselves too.  */
 166           __mach_port_deallocate (__mach_task_self (), d->ctty.port);
 167           err = __term_open_ctty (d->port.port, _hurd_pid, _hurd_pgrp,
 168                                   &d->ctty.port);
 169           if (err)
 170             d->ctty.port = MACH_PORT_NULL;
 171         }
 172
 173       /* XXX for each fd with a cntlmap, reauth and re-map_cntl.  */
 174     }
 175   return err;
 176
 177   (void) &fork_child_dtable;    /* Avoid "defined but not used" warning.  */
 178 }
 179
 180 data_set_element (_hurd_fork_locks, _hurd_dtable_lock); /* XXX ld bug: bss */
 181 text_set_element (_hurd_fork_child_hook, fork_child_dtable);
 182 \f
 183 /* Called when our process group has changed.  */
 184
 185 static void
 186 ctty_new_pgrp (void)
 187 {
 188   int i;
 189
 190 retry:
 191   HURD_CRITICAL_BEGIN;
 192   __mutex_lock (&_hurd_dtable_lock);
 193
 194   if (__USEPORT (CTTYID, port == MACH_PORT_NULL))
 195     {
 196       /* We have no controlling terminal.  If we haven't had one recently,
 197          but our pgrp is being pointlessly diddled anyway, then we will
 198          have nothing to do in the loop below because no fd will have a
 199          ctty port at all.
 200
 201          More likely, a setsid call is responsible both for the change
 202          in pgrp and for clearing the cttyid port.  In that case, setsid
 203          held the dtable lock while updating the dtable to clear all the
 204          ctty ports, and ergo must have finished doing so before we run here.
 205          So we can be sure, again, that the loop below has no work to do.  */
 206     }
 207   else
 208     for (i = 0; i < _hurd_dtablesize; ++i)
 209       {
 210         struct hurd_fd *const d = _hurd_dtable[i];
 211         struct hurd_userlink ulink, ctty_ulink;
 212         io_t port, ctty;
 213
 214         if (d == NULL)
 215           /* Nothing to do for an unused descriptor cell.  */
 216           continue;
 217
 218         port = _hurd_port_get (&d->port, &ulink);
 219         ctty = _hurd_port_get (&d->ctty, &ctty_ulink);
 220
 221         if (ctty != MACH_PORT_NULL)
 222           {
 223             /* This fd has a ctty-special port.  We need a new one, to tell
 224                the io server of our different process group.  */
 225             io_t new;
 226             error_t err;
 227             if ((err = __term_open_ctty (port, _hurd_pid, _hurd_pgrp, &new)))
 228               {
 229                 if (err == EINTR)
 230                   {
 231                     /* Got a signal while inside an RPC of the critical section, retry again */
 232                     __mutex_unlock (&_hurd_dtable_lock);
 233                     HURD_CRITICAL_UNLOCK;
 234                     goto retry;
 235                   }
 236                 new = MACH_PORT_NULL;
 237               }
 238             _hurd_port_set (&d->ctty, new);
 239           }
 240
 241         _hurd_port_free (&d->port, &ulink, port);
 242         _hurd_port_free (&d->ctty, &ctty_ulink, ctty);
 243       }
 244
 245   __mutex_unlock (&_hurd_dtable_lock);
 246   HURD_CRITICAL_END;
 247
 248   (void) &ctty_new_pgrp;        /* Avoid "defined but not used" warning.  */
 249 }
 250
 251 text_set_element (_hurd_pgrp_changed_hook, ctty_new_pgrp);
 252 \f
 253 /* Called to reauthenticate the dtable when the auth port changes.  */
 254
 255 static void
 256 reauth_dtable (void)
 257 {
 258   int i;
 259
 260   HURD_CRITICAL_BEGIN;
 261   __mutex_lock (&_hurd_dtable_lock);
 262
 263   for (i = 0; i < _hurd_dtablesize; ++i)
 264     {
 265       struct hurd_fd *const d = _hurd_dtable[i];
 266       mach_port_t new, newctty, ref;
 267
 268       if (d == NULL)
 269         /* Nothing to do for an unused descriptor cell.  */
 270         continue;
 271
 272       ref = __mach_reply_port ();
 273
 274       /* Take the descriptor cell's lock.  */
 275       __spin_lock (&d->port.lock);
 276
 277       /* Reauthenticate the descriptor's port.  */
 278       if (d->port.port != MACH_PORT_NULL
 279           && ! __io_reauthenticate (d->port.port,
 280                                     ref, MACH_MSG_TYPE_MAKE_SEND)
 281           && ! __USEPORT (AUTH, __auth_user_authenticate
 282                           (port,
 283                            ref, MACH_MSG_TYPE_MAKE_SEND,
 284                            &new)))
 285         {
 286           /* Replace the port in the descriptor cell
 287              with the newly reauthenticated port.  */
 288
 289           if (d->ctty.port != MACH_PORT_NULL
 290               && ! __io_reauthenticate (d->ctty.port,
 291                                         ref, MACH_MSG_TYPE_MAKE_SEND)
 292               && ! __USEPORT (AUTH, __auth_user_authenticate
 293                               (port,
 294                                ref, MACH_MSG_TYPE_MAKE_SEND,
 295                                &newctty)))
 296             _hurd_port_set (&d->ctty, newctty);
 297
 298           _hurd_port_locked_set (&d->port, new);
 299         }
 300       else
 301         /* Lost.  Leave this descriptor cell alone.  */
 302         __spin_unlock (&d->port.lock);
 303
 304       __mach_port_destroy (__mach_task_self (), ref);
 305     }
 306
 307   __mutex_unlock (&_hurd_dtable_lock);
 308   HURD_CRITICAL_END;
 309
 310   (void) &reauth_dtable;        /* Avoid "defined but not used" warning.  */
 311 }
 312
 313 text_set_element (_hurd_reauth_hook, reauth_dtable);