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glibc  2.9
Functions
hurdexec.c File Reference
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <hurd.h>
#include <hurd/fd.h>
#include <hurd/signal.h>
#include <hurd/id.h>
#include <assert.h>
#include <argz.h>

Go to the source code of this file.

Functions

error_t _hurd_exec (task_t task, file_t file, char *const argv[], char *const envp[])

Function Documentation

error_t _hurd_exec ( task_t  task,
file_t  file,
char *const  argv[],
char *const  envp[] 
)

Definition at line 37 of file hurdexec.c.

{
  error_t err;
  char *args, *env;
  size_t argslen, envlen;
  int ints[INIT_INT_MAX];
  mach_port_t ports[_hurd_nports];
  struct hurd_userlink ulink_ports[_hurd_nports];
  inline void free_port (unsigned int i)
    {
      _hurd_port_free (&_hurd_ports[i], &ulink_ports[i], ports[i]);
    }
  file_t *dtable;
  unsigned int dtablesize, i;
  struct hurd_port **dtable_cells;
  struct hurd_userlink *ulink_dtable;
  struct hurd_sigstate *ss;
  mach_port_t *please_dealloc, *pdp;
  int reauth = 0;

  /* XXX needs to be hurdmalloc XXX */
  if (argv == NULL)
    args = NULL, argslen = 0;
  else if (err = __argz_create (argv, &args, &argslen))
    return err;
  if (envp == NULL)
    env = NULL, envlen = 0;
  else if (err = __argz_create (envp, &env, &envlen))
    goto outargs;

  /* Load up the ports to give to the new program.  */
  for (i = 0; i < _hurd_nports; ++i)
    if (i == INIT_PORT_PROC && task != __mach_task_self ())
      {
       /* This is another task, so we need to ask the proc server
          for the right proc server port for it.  */
       if (err = __USEPORT (PROC, __proc_task2proc (port, task, &ports[i])))
         {
           while (--i > 0)
             free_port (i);
           goto outenv;
         }
      }
    else
      ports[i] = _hurd_port_get (&_hurd_ports[i], &ulink_ports[i]);


  /* Load up the ints to give the new program.  */
  for (i = 0; i < INIT_INT_MAX; ++i)
    switch (i)
      {
      case INIT_UMASK:
       ints[i] = _hurd_umask;
       break;

      case INIT_SIGMASK:
      case INIT_SIGIGN:
      case INIT_SIGPENDING:
       /* We will set these all below.  */
       break;

      case INIT_TRACEMASK:
       ints[i] = _hurdsig_traced;
       break;

      default:
       ints[i] = 0;
      }

  ss = _hurd_self_sigstate ();

  assert (! __spin_lock_locked (&ss->critical_section_lock));
  __spin_lock (&ss->critical_section_lock);

  __spin_lock (&ss->lock);
  ints[INIT_SIGMASK] = ss->blocked;
  ints[INIT_SIGPENDING] = ss->pending;
  ints[INIT_SIGIGN] = 0;
  for (i = 1; i < NSIG; ++i)
    if (ss->actions[i].sa_handler == SIG_IGN)
      ints[INIT_SIGIGN] |= __sigmask (i);

  /* We hold the sigstate lock until the exec has failed so that no signal
     can arrive between when we pack the blocked and ignored signals, and
     when the exec actually happens.  A signal handler could change what
     signals are blocked and ignored.  Either the change will be reflected
     in the exec, or the signal will never be delivered.  Setting the
     critical section flag avoids anything we call trying to acquire the
     sigstate lock.  */

  __spin_unlock (&ss->lock);

  /* Pack up the descriptor table to give the new program.  */
  __mutex_lock (&_hurd_dtable_lock);

  dtablesize = _hurd_dtable ? _hurd_dtablesize : _hurd_init_dtablesize;

  if (task == __mach_task_self ())
    /* Request the exec server to deallocate some ports from us if the exec
       succeeds.  The init ports and descriptor ports will arrive in the
       new program's exec_startup message.  If we failed to deallocate
       them, the new program would have duplicate user references for them.
       But we cannot deallocate them ourselves, because we must still have
       them after a failed exec call.  */
    please_dealloc = __alloca ((_hurd_nports + 3 + (3 * dtablesize))
                            * sizeof (mach_port_t));
  else
    please_dealloc = NULL;
  pdp = please_dealloc;

  if (_hurd_dtable != NULL)
    {
      dtable = __alloca (dtablesize * sizeof (dtable[0]));
      ulink_dtable = __alloca (dtablesize * sizeof (ulink_dtable[0]));
      dtable_cells = __alloca (dtablesize * sizeof (dtable_cells[0]));
      for (i = 0; i < dtablesize; ++i)
       {
         struct hurd_fd *const d = _hurd_dtable[i];
         if (d == NULL)
           {
             dtable[i] = MACH_PORT_NULL;
             continue;
           }
         __spin_lock (&d->port.lock);
         if (d->flags & FD_CLOEXEC)
           {
             /* This descriptor is marked to be closed on exec.
               So don't pass it to the new program.  */
             dtable[i] = MACH_PORT_NULL;
             if (pdp && d->port.port != MACH_PORT_NULL)
              {
                /* We still need to deallocate the ports.  */
                *pdp++ = d->port.port;
                if (d->ctty.port != MACH_PORT_NULL)
                  *pdp++ = d->ctty.port;
              }
             __spin_unlock (&d->port.lock);
           }
         else
           {
             if (pdp && d->ctty.port != MACH_PORT_NULL)
              /* All the elements of DTABLE are added to PLEASE_DEALLOC
                 below, so we needn't add the port itself.
                 But we must deallocate the ctty port as well as
                 the normal port that got installed in DTABLE[I].  */
              *pdp++ = d->ctty.port;
             dtable[i] = _hurd_port_locked_get (&d->port, &ulink_dtable[i]);
             dtable_cells[i] = &d->port;
           }
       }
    }
  else
    {
      dtable = _hurd_init_dtable;
      ulink_dtable = NULL;
      dtable_cells = NULL;
    }

  /* Prune trailing null ports from the descriptor table.  */
  while (dtablesize > 0 && dtable[dtablesize - 1] == MACH_PORT_NULL)
    --dtablesize;

  /* See if we need to diddle the auth port of the new program.
     The purpose of this is to get the effect setting the saved-set UID and
     GID to the respective effective IDs after the exec, as POSIX.1 requires.
     Note that we don't reauthenticate with the proc server; that would be a
     no-op since it only keeps track of the effective UIDs, and if it did
     keep track of the available IDs we would have the problem that we'd be
     changing the IDs before the exec and have to change them back after a
     failure.  Arguably we could skip all the reauthentications because the
     available IDs have no bearing on any filesystem.  But the conservative
     approach is to reauthenticate all the io ports so that no state anywhere
     reflects that our whole ID set differs from what we've set it to.  */
  __mutex_lock (&_hurd_id.lock);
  err = _hurd_check_ids ();
  if (err == 0 && ((_hurd_id.aux.nuids >= 2 && _hurd_id.gen.nuids >= 1
                  && _hurd_id.aux.uids[1] != _hurd_id.gen.uids[0])
                 || (_hurd_id.aux.ngids >= 2 && _hurd_id.gen.ngids >= 1
                     && _hurd_id.aux.gids[1] != _hurd_id.gen.gids[0])))
    {
      /* We have euid != svuid or egid != svgid.  POSIX.1 says that exec
        sets svuid = euid and svgid = egid.  So we must get a new auth
        port and reauthenticate everything with it.  We'll pass the new
        ports in file_exec instead of our own ports.  */

      auth_t newauth;

      _hurd_id.aux.uids[1] = _hurd_id.gen.uids[0];
      _hurd_id.aux.gids[1] = _hurd_id.gen.gids[0];
      _hurd_id.valid = 0;
      if (_hurd_id.rid_auth != MACH_PORT_NULL)
       {
         __mach_port_deallocate (__mach_task_self (), _hurd_id.rid_auth);
         _hurd_id.rid_auth = MACH_PORT_NULL;
       }

      err = __auth_makeauth (ports[INIT_PORT_AUTH],
                          NULL, MACH_MSG_TYPE_COPY_SEND, 0,
                          _hurd_id.gen.uids, _hurd_id.gen.nuids,
                          _hurd_id.aux.uids, _hurd_id.aux.nuids,
                          _hurd_id.gen.gids, _hurd_id.gen.ngids,
                          _hurd_id.aux.gids, _hurd_id.aux.ngids,
                          &newauth);
      if (err == 0)
       {
         /* Now we have to reauthenticate the ports with this new ID.
          */

         inline error_t reauth_io (io_t port, io_t *newport)
           {
             mach_port_t ref = __mach_reply_port ();
             *newport = MACH_PORT_NULL;
             error_t err = __io_reauthenticate (port,
                                           ref, MACH_MSG_TYPE_MAKE_SEND);
             if (!err)
              err = __auth_user_authenticate (newauth,
                                          ref, MACH_MSG_TYPE_MAKE_SEND,
                                          newport);
             __mach_port_destroy (__mach_task_self (), ref);
             return err;
           }
         inline void reauth_port (unsigned int idx)
           {
             io_t newport;
             err = reauth_io (ports[idx], &newport) ?: err;
             if (pdp)
              *pdp++ = ports[idx]; /* XXX presumed still in _hurd_ports */
             free_port (idx);
             ports[idx] = newport;
           }

         if (pdp)
           *pdp++ = ports[INIT_PORT_AUTH];
         free_port (INIT_PORT_AUTH);
         ports[INIT_PORT_AUTH] = newauth;

         reauth_port (INIT_PORT_CRDIR);
         reauth_port (INIT_PORT_CWDIR);

         if (!err)
           {
             /* Now we'll reauthenticate each file descriptor.  */
             if (ulink_dtable == NULL)
              {
                assert (dtable == _hurd_init_dtable);
                dtable = __alloca (dtablesize * sizeof (dtable[0]));
                for (i = 0; i < dtablesize; ++i)
                  if (_hurd_init_dtable[i] != MACH_PORT_NULL)
                    {
                     if (pdp)
                       *pdp++ = _hurd_init_dtable[i];
                     err = reauth_io (_hurd_init_dtable[i], &dtable[i]);
                     if (err)
                       {
                         while (++i < dtablesize)
                           dtable[i] = MACH_PORT_NULL;
                         break;
                       }
                    }
                  else
                    dtable[i] = MACH_PORT_NULL;
              }
             else
              {
                if (pdp)
                  {
                    /* Ask to deallocate all the old fd ports,
                      since we will have new ones in DTABLE.  */
                    memcpy (pdp, dtable, dtablesize * sizeof pdp[0]);
                    pdp += dtablesize;
                  }
                for (i = 0; i < dtablesize; ++i)
                  if (dtable[i] != MACH_PORT_NULL)
                    {
                     io_t newport;
                     err = reauth_io (dtable[i], &newport);
                     _hurd_port_free (dtable_cells[i], &ulink_dtable[i],
                                    dtable[i]);
                     dtable[i] = newport;
                     if (err)
                       {
                         while (++i < dtablesize)
                           _hurd_port_free (dtable_cells[i],
                                          &ulink_dtable[i], dtable[i]);
                         break;
                       }
                    }
                ulink_dtable = NULL;
                dtable_cells = NULL;
              }
           }
       }

      reauth = 1;
    }
  __mutex_unlock (&_hurd_id.lock);

  /* The information is all set up now.  Try to exec the file.  */
  if (!err)
    {
      int flags;

      if (pdp)
       {
         /* Request the exec server to deallocate some ports from us if
            the exec succeeds.  The init ports and descriptor ports will
            arrive in the new program's exec_startup message.  If we
            failed to deallocate them, the new program would have
            duplicate user references for them.  But we cannot deallocate
            them ourselves, because we must still have them after a failed
            exec call.  */

         for (i = 0; i < _hurd_nports; ++i)
           *pdp++ = ports[i];
         for (i = 0; i < dtablesize; ++i)
           *pdp++ = dtable[i];
       }

      flags = 0;
#ifdef EXEC_SIGTRAP
      /* PTRACE_TRACEME sets all bits in _hurdsig_traced, which is
        propagated through exec by INIT_TRACEMASK, so this checks if
        PTRACE_TRACEME has been called in this process in any of its
        current or prior lives.  */
      if (__sigismember (&_hurdsig_traced, SIGKILL))
       flags |= EXEC_SIGTRAP;
#endif
      err = __file_exec (file, task, flags,
                      args, argslen, env, envlen,
                      dtable, MACH_MSG_TYPE_COPY_SEND, dtablesize,
                      ports, MACH_MSG_TYPE_COPY_SEND, _hurd_nports,
                      ints, INIT_INT_MAX,
                      please_dealloc, pdp - please_dealloc,
                      &_hurd_msgport, task == __mach_task_self () ? 1 : 0);
    }

  /* Release references to the standard ports.  */
  for (i = 0; i < _hurd_nports; ++i)
    if ((i == INIT_PORT_PROC && task != __mach_task_self ())
       || (reauth && (i == INIT_PORT_AUTH
                     || i == INIT_PORT_CRDIR || i == INIT_PORT_CWDIR)))
      __mach_port_deallocate (__mach_task_self (), ports[i]);
    else
      free_port (i);

  /* Release references to the file descriptor ports.  */
  if (ulink_dtable != NULL)
    {
      for (i = 0; i < dtablesize; ++i)
       if (dtable[i] != MACH_PORT_NULL)
         _hurd_port_free (dtable_cells[i], &ulink_dtable[i], dtable[i]);
    }
  else if (dtable && dtable != _hurd_init_dtable)
    for (i = 0; i < dtablesize; ++i)
      __mach_port_deallocate (__mach_task_self (), dtable[i]);

  /* Release lock on the file descriptor table. */
  __mutex_unlock (&_hurd_dtable_lock);

  /* Safe to let signals happen now.  */
  _hurd_critical_section_unlock (ss);

 outargs:
  free (args);
 outenv:
  free (env);
  return err;
}

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