sysdeps/mach/hurd/fork.c

   1 /* Copyright (C) 1994-2019 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    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <unistd.h>
  20 #include <hurd.h>
  21 #include <hurd/signal.h>
  22 #include <hurd/threadvar.h>
  23 #include <setjmp.h>
  24 #include <thread_state.h>
  25 #include <sysdep.h>             /* For stack growth direction.  */
  26 #include "set-hooks.h"
  27 #include <assert.h>
  28 #include "hurdmalloc.h"         /* XXX */
  29 #include <tls.h>
  30 #include <malloc/malloc-internal.h>
  31
  32 #undef __fork
  33
  34
  35 /* Things that want to be locked while forking.  */
  36 symbol_set_declare (_hurd_fork_locks)
  37
  38
  39 /* Application callbacks registered through pthread_atfork.  */
  40 DEFINE_HOOK (_hurd_atfork_prepare_hook, (void));
  41 DEFINE_HOOK (_hurd_atfork_child_hook, (void));
  42 DEFINE_HOOK (_hurd_atfork_parent_hook, (void));
  43
  44 /* Things that want to be called before we fork, to prepare the parent for
  45    task_create, when the new child task will inherit our address space.  */
  46 DEFINE_HOOK (_hurd_fork_prepare_hook, (void));
  47
  48 /* Things that want to be called when we are forking, with the above all
  49    locked.  They are passed the task port of the child.  The child process
  50    is all set up except for doing proc_child, and has no threads yet.  */
  51 DEFINE_HOOK (_hurd_fork_setup_hook, (void));
  52
  53 /* Things to be run in the child fork.  */
  54 DEFINE_HOOK (_hurd_fork_child_hook, (void));
  55
  56 /* Things to be run in the parent fork.  */
  57 DEFINE_HOOK (_hurd_fork_parent_hook, (void));
  58
  59
  60 /* Clone the calling process, creating an exact copy.
  61    Return -1 for errors, 0 to the new process,
  62    and the process ID of the new process to the old process.  */
  63 pid_t
  64 __fork (void)
  65 {
  66   jmp_buf env;
  67   pid_t pid;
  68   size_t i;
  69   error_t err;
  70   struct hurd_sigstate *volatile ss;
  71
  72   RUN_HOOK (_hurd_atfork_prepare_hook, ());
  73
  74   ss = _hurd_self_sigstate ();
  75   __spin_lock (&ss->critical_section_lock);
  76
  77 #undef  LOSE
  78 #define LOSE do { assert_perror (err); goto lose; } while (0) /* XXX */
  79
  80   if (! setjmp (env))
  81     {
  82       process_t newproc;
  83       task_t newtask;
  84       thread_t thread, sigthread;
  85       mach_port_urefs_t thread_refs, sigthread_refs;
  86       struct machine_thread_state state;
  87       mach_msg_type_number_t statecount;
  88       mach_port_t *portnames = NULL;
  89       mach_msg_type_number_t nportnames = 0;
  90       mach_port_type_t *porttypes = NULL;
  91       mach_msg_type_number_t nporttypes = 0;
  92       thread_t *threads = NULL;
  93       mach_msg_type_number_t nthreads = 0;
  94       int ports_locked = 0, stopped = 0;
  95
  96       void resume_threads (void)
  97         {
  98           if (! stopped)
  99             return;
 100
 101           assert (threads);
 102
 103           for (i = 0; i < nthreads; ++i)
 104             if (threads[i] != ss->thread)
 105               __thread_resume (threads[i]);
 106           stopped = 0;
 107         }
 108
 109       /* Run things that prepare for forking before we create the task.  */
 110       RUN_HOOK (_hurd_fork_prepare_hook, ());
 111
 112       /* Lock things that want to be locked before we fork.  */
 113       {
 114         void *const *p;
 115         for (p = symbol_set_first_element (_hurd_fork_locks);
 116              ! symbol_set_end_p (_hurd_fork_locks, p);
 117              ++p)
 118           __mutex_lock (*p);
 119       }
 120       __mutex_lock (&_hurd_siglock);
 121
 122       /* Acquire malloc locks.  This needs to come last because fork
 123          handlers may use malloc, and the libio list lock has an
 124          indirect malloc dependency as well (via the getdelim
 125          function).  */
 126       call_function_static_weak (__malloc_fork_lock_parent);
 127       _hurd_malloc_fork_prepare ();
 128
 129       newtask = MACH_PORT_NULL;
 130       thread = sigthread = MACH_PORT_NULL;
 131       newproc = MACH_PORT_NULL;
 132
 133       /* Lock all the port cells for the standard ports while we copy the
 134          address space.  We want to insert all the send rights into the
 135          child with the same names.  */
 136       for (i = 0; i < _hurd_nports; ++i)
 137         __spin_lock (&_hurd_ports[i].lock);
 138       ports_locked = 1;
 139
 140
 141       /* Keep our SS locked while stopping other threads, so they don't get a
 142          chance to have it locked in the copied space.  */
 143       __spin_lock (&ss->lock);
 144       /* Stop all other threads while copying the address space,
 145          so nothing changes.  */
 146       err = __proc_dostop (_hurd_ports[INIT_PORT_PROC].port, ss->thread);
 147       __spin_unlock (&ss->lock);
 148       if (!err)
 149         {
 150           stopped = 1;
 151
 152 #define XXX_KERNEL_PAGE_FAULT_BUG /* XXX work around page fault bug in mk */
 153
 154 #ifdef XXX_KERNEL_PAGE_FAULT_BUG
 155           /* Gag me with a pitchfork.
 156              The bug scenario is this:
 157
 158              - The page containing __mach_task_self_ is paged out.
 159              - The signal thread was faulting on that page when we
 160                suspended it via proc_dostop.  It holds some lock, or set
 161                some busy bit, or somesuch.
 162              - Now this thread faults on that same page.
 163              - GRATUIOUS DEADLOCK
 164
 165              We can break the deadlock by aborting the thread that faulted
 166              first, which if the bug happened was the signal thread because
 167              it is the only other thread and we just suspended it.
 168              */
 169           __thread_abort (_hurd_msgport_thread);
 170 #endif
 171           /* Create the child task.  It will inherit a copy of our memory.  */
 172           err = __task_create (__mach_task_self (),
 173 #ifdef KERN_INVALID_LEDGER
 174                                NULL, 0, /* OSF Mach */
 175 #endif
 176                                1, &newtask);
 177         }
 178
 179       /* Unlock the global signal state lock, so we do not
 180          block the signal thread any longer than necessary.  */
 181       __mutex_unlock (&_hurd_siglock);
 182
 183       if (err)
 184         LOSE;
 185
 186       /* Fetch the names of all ports used in this task.  */
 187       if (err = __mach_port_names (__mach_task_self (),
 188                                    &portnames, &nportnames,
 189                                    &porttypes, &nporttypes))
 190         LOSE;
 191       if (nportnames != nporttypes)
 192         {
 193           err = EGRATUITOUS;
 194           LOSE;
 195         }
 196
 197       /* Get send rights for all the threads in this task.
 198          We want to avoid giving these rights to the child.  */
 199       if (err = __task_threads (__mach_task_self (), &threads, &nthreads))
 200         LOSE;
 201
 202       /* Get the child process's proc server port.  We will insert it into
 203          the child with the same name as we use for our own proc server
 204          port; and we will need it to set the child's message port.  */
 205       if (err = __proc_task2proc (_hurd_ports[INIT_PORT_PROC].port,
 206                                   newtask, &newproc))
 207         LOSE;
 208
 209       /* Insert all our port rights into the child task.  */
 210       thread_refs = sigthread_refs = 0;
 211       for (i = 0; i < nportnames; ++i)
 212         {
 213           if (porttypes[i] & MACH_PORT_TYPE_RECEIVE)
 214             {
 215               /* This is a receive right.  We want to give the child task
 216                  its own new receive right under the same name.  */
 217               if (err = __mach_port_allocate_name (newtask,
 218                                                    MACH_PORT_RIGHT_RECEIVE,
 219                                                    portnames[i]))
 220                 LOSE;
 221               if (porttypes[i] & MACH_PORT_TYPE_SEND)
 222                 {
 223                   /* Give the child as many send rights for its receive
 224                      right as we have for ours.  */
 225                   mach_port_urefs_t refs;
 226                   mach_port_t port;
 227                   mach_msg_type_name_t poly;
 228                   if (err = __mach_port_get_refs (__mach_task_self (),
 229                                                   portnames[i],
 230                                                   MACH_PORT_RIGHT_SEND,
 231                                                   &refs))
 232                     LOSE;
 233                   if (err = __mach_port_extract_right (newtask,
 234                                                        portnames[i],
 235                                                        MACH_MSG_TYPE_MAKE_SEND,
 236                                                        &port, &poly))
 237                     LOSE;
 238                   if (portnames[i] == _hurd_msgport)
 239                     {
 240                       /* We just created a receive right for the child's
 241                          message port and are about to insert send rights
 242                          for it.  Now, while we happen to have a send right
 243                          for it, give it to the proc server.  */
 244                       mach_port_t old;
 245                       if (err = __proc_setmsgport (newproc, port, &old))
 246                         LOSE;
 247                       if (old != MACH_PORT_NULL)
 248                         /* XXX what to do here? */
 249                         __mach_port_deallocate (__mach_task_self (), old);
 250                       /* The new task will receive its own exceptions
 251                          on its message port.  */
 252                       if (err =
 253 #ifdef TASK_EXCEPTION_PORT
 254                           __task_set_special_port (newtask,
 255                                                    TASK_EXCEPTION_PORT,
 256                                                    port)
 257 #elif defined (EXC_MASK_ALL)
 258                           __task_set_exception_ports
 259                           (newtask, EXC_MASK_ALL & ~(EXC_MASK_SYSCALL
 260                                                      | EXC_MASK_MACH_SYSCALL
 261                                                      | EXC_MASK_RPC_ALERT),
 262                            port, EXCEPTION_DEFAULT, MACHINE_THREAD_STATE)
 263 #else
 264 # error task_set_exception_port?
 265 #endif
 266                           )
 267                         LOSE;
 268                     }
 269                   if (err = __mach_port_insert_right (newtask,
 270                                                       portnames[i],
 271                                                       port,
 272                                                       MACH_MSG_TYPE_MOVE_SEND))
 273                     LOSE;
 274                   if (refs > 1 &&
 275                       (err = __mach_port_mod_refs (newtask,
 276                                                    portnames[i],
 277                                                    MACH_PORT_RIGHT_SEND,
 278                                                    refs - 1)))
 279                     LOSE;
 280                 }
 281               if (porttypes[i] & MACH_PORT_TYPE_SEND_ONCE)
 282                 {
 283                   /* Give the child a send-once right for its receive right,
 284                      since we have one for ours.  */
 285                   mach_port_t port;
 286                   mach_msg_type_name_t poly;
 287                   if (err = __mach_port_extract_right
 288                       (newtask,
 289                        portnames[i],
 290                        MACH_MSG_TYPE_MAKE_SEND_ONCE,
 291                        &port, &poly))
 292                     LOSE;
 293                   if (err = __mach_port_insert_right
 294                       (newtask,
 295                        portnames[i], port,
 296                        MACH_MSG_TYPE_MOVE_SEND_ONCE))
 297                     LOSE;
 298                 }
 299             }
 300           else if (porttypes[i] &
 301                    (MACH_PORT_TYPE_SEND|MACH_PORT_TYPE_DEAD_NAME))
 302             {
 303               /* This is a send right or a dead name.
 304                  Give the child as many references for it as we have.  */
 305               mach_port_urefs_t refs = 0, *record_refs = NULL;
 306               mach_port_t insert;
 307               mach_msg_type_name_t insert_type = MACH_MSG_TYPE_COPY_SEND;
 308               if (portnames[i] == newtask || portnames[i] == newproc)
 309                 /* Skip the name we use for the child's task or proc ports.  */
 310                 continue;
 311               if (portnames[i] == __mach_task_self ())
 312                 /* For the name we use for our own task port,
 313                    insert the child's task port instead.  */
 314                 insert = newtask;
 315               else if (portnames[i] == _hurd_ports[INIT_PORT_PROC].port)
 316                 {
 317                   /* Use the proc server port for the new task.  */
 318                   insert = newproc;
 319                   insert_type = MACH_MSG_TYPE_COPY_SEND;
 320                 }
 321               else if (portnames[i] == ss->thread)
 322                 {
 323                   /* For the name we use for our own thread port, we will
 324                      insert the thread port for the child main user thread
 325                      after we create it.  */
 326                   insert = MACH_PORT_NULL;
 327                   record_refs = &thread_refs;
 328                   /* Allocate a dead name right for this name as a
 329                      placeholder, so the kernel will not chose this name
 330                      for any other new port (it might use it for one of the
 331                      rights created when a thread is created).  */
 332                   if (err = __mach_port_allocate_name
 333                       (newtask, MACH_PORT_RIGHT_DEAD_NAME, portnames[i]))
 334                     LOSE;
 335                 }
 336               else if (portnames[i] == _hurd_msgport_thread)
 337                 /* For the name we use for our signal thread's thread port,
 338                    we will insert the thread port for the child's signal
 339                    thread after we create it.  */
 340                 {
 341                   insert = MACH_PORT_NULL;
 342                   record_refs = &sigthread_refs;
 343                   /* Allocate a dead name right as a placeholder.  */
 344                   if (err = __mach_port_allocate_name
 345                       (newtask, MACH_PORT_RIGHT_DEAD_NAME, portnames[i]))
 346                     LOSE;
 347                 }
 348               else
 349                 {
 350                   /* Skip the name we use for any of our own thread ports.  */
 351                   mach_msg_type_number_t j;
 352                   for (j = 0; j < nthreads; ++j)
 353                     if (portnames[i] == threads[j])
 354                       break;
 355                   if (j < nthreads)
 356                     continue;
 357
 358                   /* Copy our own send right.  */
 359                   insert = portnames[i];
 360                 }
 361               /* Find out how many user references we have for
 362                  the send right with this name.  */
 363               if (err = __mach_port_get_refs (__mach_task_self (),
 364                                               portnames[i],
 365                                               MACH_PORT_RIGHT_SEND,
 366                                               record_refs ?: &refs))
 367                 LOSE;
 368               if (insert == MACH_PORT_NULL)
 369                 continue;
 370               if (insert == portnames[i] &&
 371                   (porttypes[i] & MACH_PORT_TYPE_DEAD_NAME))
 372                 /* This is a dead name; allocate another dead name
 373                    with the same name in the child.  */
 374               allocate_dead_name:
 375                 err = __mach_port_allocate_name (newtask,
 376                                                  MACH_PORT_RIGHT_DEAD_NAME,
 377                                                  portnames[i]);
 378               else
 379                 /* Insert the chosen send right into the child.  */
 380                 err = __mach_port_insert_right (newtask,
 381                                                 portnames[i],
 382                                                 insert, insert_type);
 383               switch (err)
 384                 {
 385                 case KERN_NAME_EXISTS:
 386                   {
 387                     /* It already has a send right under this name (?!).
 388                        Well, it starts out with a send right for its task
 389                        port, and inherits the bootstrap and exception ports
 390                        from us.  */
 391                     mach_port_t childport;
 392                     mach_msg_type_name_t poly;
 393                     assert (__mach_port_extract_right (newtask, portnames[i],
 394                                                        MACH_MSG_TYPE_COPY_SEND,
 395                                                        &childport,
 396                                                        &poly) == 0 &&
 397                             childport == insert &&
 398                             __mach_port_deallocate (__mach_task_self (),
 399                                                     childport) == 0);
 400                     break;
 401                   }
 402
 403                 case KERN_INVALID_CAPABILITY:
 404                   /* The port just died.  It was a send right,
 405                      and now it's a dead name.  */
 406                   goto allocate_dead_name;
 407
 408                 default:
 409                   LOSE;
 410                   break;
 411
 412                 case KERN_SUCCESS:
 413                   /* Give the child as many user references as we have.  */
 414                   if (refs > 1 &&
 415                       (err = __mach_port_mod_refs (newtask,
 416                                                    portnames[i],
 417                                                    MACH_PORT_RIGHT_SEND,
 418                                                    refs - 1)))
 419                     LOSE;
 420                 }
 421             }
 422         }
 423
 424       /* Unlock the standard port cells.  The child must unlock its own
 425          copies too.  */
 426       for (i = 0; i < _hurd_nports; ++i)
 427         __spin_unlock (&_hurd_ports[i].lock);
 428       ports_locked = 0;
 429
 430       /* All state has now been copied from the parent.  It is safe to
 431          resume other parent threads.  */
 432       resume_threads ();
 433
 434       /* Create the child main user thread and signal thread.  */
 435       if ((err = __thread_create (newtask, &thread)) ||
 436           (err = __thread_create (newtask, &sigthread)))
 437         LOSE;
 438
 439       /* Insert send rights for those threads.  We previously allocated
 440          dead name rights with the names we want to give the thread ports
 441          in the child as placeholders.  Now deallocate them so we can use
 442          the names.  */
 443       if ((err = __mach_port_deallocate (newtask, ss->thread)) ||
 444           (err = __mach_port_insert_right (newtask, ss->thread,
 445                                            thread, MACH_MSG_TYPE_COPY_SEND)))
 446         LOSE;
 447       if (thread_refs > 1 &&
 448           (err = __mach_port_mod_refs (newtask, ss->thread,
 449                                        MACH_PORT_RIGHT_SEND,
 450                                        thread_refs - 1)))
 451         LOSE;
 452       if ((_hurd_msgport_thread != MACH_PORT_NULL) /* Let user have none.  */
 453           && ((err = __mach_port_deallocate (newtask, _hurd_msgport_thread)) ||
 454               (err = __mach_port_insert_right (newtask, _hurd_msgport_thread,
 455                                                sigthread,
 456                                                MACH_MSG_TYPE_COPY_SEND))))
 457         LOSE;
 458       if (sigthread_refs > 1 &&
 459           (err = __mach_port_mod_refs (newtask, _hurd_msgport_thread,
 460                                        MACH_PORT_RIGHT_SEND,
 461                                        sigthread_refs - 1)))
 462         LOSE;
 463
 464       /* This seems like a convenient juncture to copy the proc server's
 465          idea of what addresses our argv and envp are found at from the
 466          parent into the child.  Since we happen to know that the child
 467          shares our memory image, it is we who should do this copying.  */
 468       {
 469         vm_address_t argv, envp;
 470         err = (__USEPORT (PROC, __proc_get_arg_locations (port, &argv, &envp))
 471                ?: __proc_set_arg_locations (newproc, argv, envp));
 472         if (err)
 473           LOSE;
 474       }
 475
 476       /* Set the child signal thread up to run the msgport server function
 477          using the same signal thread stack copied from our address space.
 478          We fetch the state before longjmp'ing it so that miscellaneous
 479          registers not affected by longjmp (such as i386 segment registers)
 480          are in their normal default state.  */
 481       statecount = MACHINE_THREAD_STATE_COUNT;
 482       if (err = __thread_get_state (_hurd_msgport_thread,
 483                                     MACHINE_THREAD_STATE_FLAVOR,
 484                                     (natural_t *) &state, &statecount))
 485         LOSE;
 486 #ifdef STACK_GROWTH_UP
 487       if (__hurd_sigthread_stack_base == 0)
 488         {
 489           state.SP &= __hurd_threadvar_stack_mask;
 490           state.SP += __hurd_threadvar_stack_offset;
 491         }
 492       else
 493         state.SP = __hurd_sigthread_stack_base;
 494 #else
 495       if (__hurd_sigthread_stack_end == 0)
 496         {
 497           /* The signal thread has a stack assigned by cthreads.
 498              The threadvar_stack variables conveniently tell us how
 499              to get to the highest address in the stack, just below
 500              the per-thread variables.  */
 501           state.SP &= __hurd_threadvar_stack_mask;
 502           state.SP += __hurd_threadvar_stack_offset;
 503         }
 504       else
 505         state.SP = __hurd_sigthread_stack_end;
 506 #endif
 507       MACHINE_THREAD_STATE_SET_PC (&state,
 508                                    (unsigned long int) _hurd_msgport_receive);
 509
 510       /* Do special signal thread setup for TLS if needed.  */
 511       if (err = _hurd_tls_fork (sigthread, _hurd_msgport_thread, &state))
 512         LOSE;
 513
 514       if (err = __thread_set_state (sigthread, MACHINE_THREAD_STATE_FLAVOR,
 515                                     (natural_t *) &state, statecount))
 516         LOSE;
 517       /* We do not thread_resume SIGTHREAD here because the child
 518          fork needs to do more setup before it can take signals.  */
 519
 520       /* Set the child user thread up to return 1 from the setjmp above.  */
 521       _hurd_longjmp_thread_state (&state, env, 1);
 522
 523       /* Do special thread setup for TLS if needed.  */
 524       if (err = _hurd_tls_fork (thread, ss->thread, &state))
 525         LOSE;
 526
 527       if (err = __thread_set_state (thread, MACHINE_THREAD_STATE_FLAVOR,
 528                                     (natural_t *) &state, statecount))
 529         LOSE;
 530
 531       /* Get the PID of the child from the proc server.  We must do this
 532          before calling proc_child below, because at that point any
 533          authorized POSIX.1 process may kill the child task with SIGKILL.  */
 534       if (err = __USEPORT (PROC, __proc_task2pid (port, newtask, &pid)))
 535         LOSE;
 536
 537       /* Register the child with the proc server.  It is important that
 538          this be that last thing we do before starting the child thread
 539          running.  Once proc_child has been done for the task, it appears
 540          as a POSIX.1 process.  Any errors we get must be detected before
 541          this point, and the child must have a message port so it responds
 542          to POSIX.1 signals.  */
 543       if (err = __USEPORT (PROC, __proc_child (port, newtask)))
 544         LOSE;
 545
 546       /* This must be the absolutely last thing we do; we can't assume that
 547          the child will remain alive for even a moment once we do this.  We
 548          ignore errors because we have committed to the fork and are not
 549          allowed to return them after the process becomes visible to
 550          POSIX.1 (which happened right above when we called proc_child).  */
 551       (void) __thread_resume (thread);
 552
 553     lose:
 554       if (ports_locked)
 555         for (i = 0; i < _hurd_nports; ++i)
 556           __spin_unlock (&_hurd_ports[i].lock);
 557
 558       resume_threads ();
 559
 560       if (newtask != MACH_PORT_NULL)
 561         {
 562           if (err)
 563             __task_terminate (newtask);
 564           __mach_port_deallocate (__mach_task_self (), newtask);
 565         }
 566       if (thread != MACH_PORT_NULL)
 567         __mach_port_deallocate (__mach_task_self (), thread);
 568       if (sigthread != MACH_PORT_NULL)
 569         __mach_port_deallocate (__mach_task_self (), sigthread);
 570       if (newproc != MACH_PORT_NULL)
 571         __mach_port_deallocate (__mach_task_self (), newproc);
 572
 573       if (portnames)
 574         __vm_deallocate (__mach_task_self (),
 575                          (vm_address_t) portnames,
 576                          nportnames * sizeof (*portnames));
 577       if (porttypes)
 578         __vm_deallocate (__mach_task_self (),
 579                          (vm_address_t) porttypes,
 580                          nporttypes * sizeof (*porttypes));
 581       if (threads)
 582         {
 583           for (i = 0; i < nthreads; ++i)
 584             __mach_port_deallocate (__mach_task_self (), threads[i]);
 585           __vm_deallocate (__mach_task_self (),
 586                            (vm_address_t) threads,
 587                            nthreads * sizeof (*threads));
 588         }
 589
 590       /* Release malloc locks.  */
 591       _hurd_malloc_fork_parent ();
 592       call_function_static_weak (__malloc_fork_unlock_parent);
 593
 594       /* Run things that want to run in the parent to restore it to
 595          normality.  Usually prepare hooks and parent hooks are
 596          symmetrical: the prepare hook arrests state in some way for the
 597          fork, and the parent hook restores the state for the parent to
 598          continue executing normally.  */
 599       RUN_HOOK (_hurd_fork_parent_hook, ());
 600     }
 601   else
 602     {
 603       struct hurd_sigstate *oldstates;
 604
 605       /* We are the child task.  Unlock the standard port cells, which were
 606          locked in the parent when we copied its memory.  The parent has
 607          inserted send rights with the names that were in the cells then.  */
 608       for (i = 0; i < _hurd_nports; ++i)
 609         __spin_unlock (&_hurd_ports[i].lock);
 610
 611       /* We are one of the (exactly) two threads in this new task, we
 612          will take the task-global signals.  */
 613       _hurd_sigthread = ss->thread;
 614
 615       /* Claim our sigstate structure and unchain the rest: the
 616          threads existed in the parent task but don't exist in this
 617          task (the child process).  Delay freeing them until later
 618          because some of the further setup and unlocking might be
 619          required for free to work.  Before we finish cleaning up,
 620          we will reclaim the signal thread's sigstate structure (if
 621          it had one).  */
 622       oldstates = _hurd_sigstates;
 623       if (oldstates == ss)
 624         oldstates = ss->next;
 625       else
 626         {
 627           while (_hurd_sigstates->next != ss)
 628             _hurd_sigstates = _hurd_sigstates->next;
 629           _hurd_sigstates->next = ss->next;
 630         }
 631       ss->next = NULL;
 632       _hurd_sigstates = ss;
 633       __mutex_unlock (&_hurd_siglock);
 634
 635       /* Fetch our new process IDs from the proc server.  No need to
 636          refetch our pgrp; it is always inherited from the parent (so
 637          _hurd_pgrp is already correct), and the proc server will send us a
 638          proc_newids notification when it changes.  */
 639       err = __USEPORT (PROC, __proc_getpids (port, &_hurd_pid, &_hurd_ppid,
 640                                              &_hurd_orphaned));
 641
 642       /* Forking clears the trace flag.  */
 643       __sigemptyset (&_hurdsig_traced);
 644
 645       /* Release malloc locks.  */
 646       _hurd_malloc_fork_child ();
 647       call_function_static_weak (__malloc_fork_unlock_child);
 648
 649       /* Run things that want to run in the child task to set up.  */
 650       RUN_HOOK (_hurd_fork_child_hook, ());
 651
 652       /* Set up proc server-assisted fault recovery for the signal thread.  */
 653       _hurdsig_fault_init ();
 654
 655       /* Start the signal thread listening on the message port.  */
 656       if (!err)
 657         err = __thread_resume (_hurd_msgport_thread);
 658
 659       /* Reclaim the signal thread's sigstate structure and free the
 660          other old sigstate structures.  */
 661       while (oldstates != NULL)
 662         {
 663           struct hurd_sigstate *next = oldstates->next;
 664
 665           if (oldstates->thread == _hurd_msgport_thread)
 666             {
 667               /* If we have a second signal state structure then we
 668                  must have been through here before--not good.  */
 669               assert (_hurd_sigstates->next == 0);
 670               _hurd_sigstates->next = oldstates;
 671               oldstates->next = 0;
 672             }
 673           else
 674             free (oldstates);
 675
 676           oldstates = next;
 677         }
 678
 679       /* XXX what to do if we have any errors here? */
 680
 681       pid = 0;
 682     }
 683
 684   /* Unlock things we locked before creating the child task.
 685      They are locked in both the parent and child tasks.  */
 686   {
 687     void *const *p;
 688     for (p = symbol_set_first_element (_hurd_fork_locks);
 689          ! symbol_set_end_p (_hurd_fork_locks, p);
 690          ++p)
 691       __mutex_unlock (*p);
 692   }
 693
 694   _hurd_critical_section_unlock (ss);
 695
 696   if (!err)
 697     {
 698       if (pid != 0)
 699         RUN_HOOK (_hurd_atfork_parent_hook, ());
 700       else
 701         RUN_HOOK (_hurd_atfork_child_hook, ());
 702     }
 703
 704   return err ? __hurd_fail (err) : pid;
 705 }
 706 libc_hidden_def (__fork)
 707
 708 weak_alias (__fork, fork)