dl-deps.c

用于嵌入式Linux系统的标准C的库函数

		    /* We must be prepared that the addressed shared
		       object is not available.  */
		    err = _dl_catch_error (&objname, &errstring, openaux,
					   &args);
		    if (__builtin_expect (errstring != NULL, 0))
		      {
			/* We are not interested in the error message.  */
			assert (errstring != NULL);
			if (errstring != _dl_out_of_memory)
			  free ((char *) errstring);

			/* Simply ignore this error and continue the work.  */
			continue;
		      }
		  }
		else
		  {
		    int err;

		    /* Say that we are about to load an auxiliary library.  */
		    if (__builtin_expect (_dl_debug_mask & DL_DEBUG_LIBS, 0))
		      _dl_debug_printf ("load filtered object=%s"
					" requested by file=%s\n", name,
					l->l_name[0]
					? l->l_name : _dl_argv[0]);

		    /* For filter objects the dependency must be available.  */
		    err = _dl_catch_error (&objname, &errstring, openaux,
					   &args);
		    if (__builtin_expect (errstring != NULL, 0))
		      {
			if (err)
			  errno_reason = err;
			else
			  errno_reason = -1;
			goto out;
		      }
		  }

		/* The auxiliary object is actually available.
		   Incorporate the map in all the lists.  */

		/* Allocate new entry.  This always has to be done.  */
		newp = alloca (sizeof (struct list));

		/* We want to insert the new map before the current one,
		   but we have no back links.  So we copy the contents of
		   the current entry over.  Note that ORIG and NEWP now
		   have switched their meanings.  */
		memcpy (newp, orig, sizeof (*newp));

		/* Initialize new entry.  */
		orig->done = 0;
		orig->map = args.aux;

		/* Remember this dependency.  */
		if (needed != NULL)
		  needed[nneeded++] = args.aux;

		/* We must handle two situations here: the map is new,
		   so we must add it in all three lists.  If the map
		   is already known, we have two further possibilities:
		   - if the object is before the current map in the
		   search list, we do nothing.  It is already found
		   early
		   - if the object is after the current one, we must
		   move it just before the current map to make sure
		   the symbols are found early enough
		*/
		if (args.aux->l_reserved)
		  {
		    /* The object is already somewhere in the list.
		       Locate it first.  */
		    struct list *late;

		    /* This object is already in the search list we
		       are building.  Don't add a duplicate pointer.
		       Just added by _dl_map_object.  */
		    for (late = newp; late->next != NULL; late = late->next)
		      if (late->next->map == args.aux)
			break;

		    if (late->next != NULL)
		      {
			/* The object is somewhere behind the current
			   position in the search path.  We have to
			   move it to this earlier position.  */
			orig->next = newp;

			/* Now remove the later entry from the list
			   and adjust the tail pointer.  */
			if (tail == late->next)
			  tail = late;
			late->next = late->next->next;

			/* We must move the object earlier in the chain.  */
			if (args.aux->l_prev != NULL)
			  args.aux->l_prev->l_next = args.aux->l_next;
			if (args.aux->l_next != NULL)
			  args.aux->l_next->l_prev = args.aux->l_prev;

			args.aux->l_prev = newp->map->l_prev;
			newp->map->l_prev = args.aux;
			if (args.aux->l_prev != NULL)
			  args.aux->l_prev->l_next = args.aux;
			args.aux->l_next = newp->map;
		      }
		    else
		      {
			/* The object must be somewhere earlier in the
			   list.  Undo to the current list element what
			   we did above.  */
			memcpy (orig, newp, sizeof (*newp));
			continue;
		      }
		  }
		else
		  {
		    /* This is easy.  We just add the symbol right here.  */
		    orig->next = newp;
		    ++nlist;
		    /* Set the mark bit that says it's already in the list.  */
		    args.aux->l_reserved = 1;

		    /* The only problem is that in the double linked
		       list of all objects we don't have this new
		       object at the correct place.  Correct this here.  */
		    if (args.aux->l_prev)
		      args.aux->l_prev->l_next = args.aux->l_next;
		    if (args.aux->l_next)
		      args.aux->l_next->l_prev = args.aux->l_prev;

		    args.aux->l_prev = newp->map->l_prev;
		    newp->map->l_prev = args.aux;
		    if (args.aux->l_prev != NULL)
		      args.aux->l_prev->l_next = args.aux;
		    args.aux->l_next = newp->map;
		  }

		/* Move the tail pointer if necessary.  */
		if (orig == tail)
		  tail = newp;

		/* Move on the insert point.  */
		orig = newp;
	      }
	}

      /* Terminate the list of dependencies and store the array address.  */
      if (needed != NULL)
	{
	  needed[nneeded++] = NULL;

	  l->l_initfini = (struct link_map **)
	    malloc ((nneeded + 1) * sizeof needed[0]);
	  if (l->l_initfini == NULL)
	    _dl_signal_error (ENOMEM, map->l_name, NULL,
			      N_("cannot allocate dependency list"));
	  l->l_initfini[0] = l;
	  memcpy (&l->l_initfini[1], needed, nneeded * sizeof needed[0]);
	}

      /* If we have no auxiliary objects just go on to the next map.  */
      if (runp->done)
	do
	  runp = runp->next;
	while (runp != NULL && runp->done);
    }

 out:
  if (errno == 0 && errno_saved != 0)
    __set_errno (errno_saved);

  if (map->l_initfini != NULL && map->l_type == lt_loaded)
    {
      /* This object was previously loaded as a dependency and we have
	 a separate l_initfini list.  We don't need it anymore.  */
      assert (map->l_searchlist.r_list == NULL);
      free (map->l_initfini);
    }

  /* Store the search list we built in the object.  It will be used for
     searches in the scope of this object.  */
  map->l_initfini =
    (struct link_map **) malloc ((2 * nlist + 1)
				 * sizeof (struct link_map *));
  if (map->l_initfini == NULL)
    _dl_signal_error (ENOMEM, map->l_name, NULL,
		      N_("cannot allocate symbol search list"));


  map->l_searchlist.r_list = &map->l_initfini[nlist + 1];
  map->l_searchlist.r_nlist = nlist;

  for (nlist = 0, runp = known; runp; runp = runp->next)
    {
      if (__builtin_expect (trace_mode, 0) && runp->map->l_faked)
	/* This can happen when we trace the loading.  */
	--map->l_searchlist.r_nlist;
      else
	map->l_searchlist.r_list[nlist++] = runp->map;

      /* Now clear all the mark bits we set in the objects on the search list
	 to avoid duplicates, so the next call starts fresh.  */
      runp->map->l_reserved = 0;
    }

  /* Maybe we can remove some relocation dependencies now.  */
  assert (map->l_searchlist.r_list[0] == map);
  for (i = 0; i < map->l_reldepsact; ++i)
    {
      unsigned int j;

      for (j = 1; j < nlist; ++j)
	if (map->l_searchlist.r_list[j] == map->l_reldeps[i])
	  {
	    /* A direct or transitive dependency is also on the list
	       of relocation dependencies.  Remove the latter.  */
	    --map->l_reldeps[i]->l_opencount;

	    for (j = i + 1; j < map->l_reldepsact; ++j)
	      map->l_reldeps[j - 1] = map->l_reldeps[j];

	    --map->l_reldepsact;

	    /* Account for the '++i' performed by the 'for'.  */
	    --i;
	    break;
	  }
    }

  /* Now determine the order in which the initialization has to happen.  */
  memcpy (map->l_initfini, map->l_searchlist.r_list,
	  nlist * sizeof (struct link_map *));
  /* We can skip looking for the binary itself which is at the front
     of the search list.  Look through the list backward so that circular
     dependencies are not changing the order.  */
  for (i = 1; i < nlist; ++i)
    {
      struct link_map *l = map->l_searchlist.r_list[i];
      unsigned int j;
      unsigned int k;

      /* Find the place in the initfini list where the map is currently
	 located.  */
      for (j = 1; map->l_initfini[j] != l; ++j)
	;

      /* Find all object for which the current one is a dependency and
	 move the found object (if necessary) in front.  */
      for (k = j + 1; k < nlist; ++k)
	{
	  struct link_map **runp;

	  runp = map->l_initfini[k]->l_initfini;
	  if (runp != NULL)
	    {
	      while (*runp != NULL)
		if (__builtin_expect (*runp++ == l, 0))
		  {
		    struct link_map *here = map->l_initfini[k];

		    /* Move it now.  */
		    memmove (&map->l_initfini[j] + 1,
			     &map->l_initfini[j],
			     (k - j) * sizeof (struct link_map *));
		    map->l_initfini[j] = here;

		    break;
		  }
	    }
	}
    }
  /* Terminate the list of dependencies.  */
  map->l_initfini[nlist] = NULL;

  if (errno_reason)
    _dl_signal_error (errno_reason == -1 ? 0 : errno_reason,
		      objname, NULL, errstring);
}