elf/dl-deps.c

   1 /* Load the dependencies of a mapped object.
   2    Copyright (C) 1996 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <link.h>
  21 #include <errno.h>
  22 #include <dlfcn.h>
  23 #include <stdlib.h>
  24
  25 void
  26 _dl_map_object_deps (struct link_map *map,
  27                      struct link_map **preloads, unsigned int npreloads,
  28                      int trace_mode)
  29 {
  30   struct list
  31     {
  32       struct link_map *map;
  33       struct list *next;
  34     };
  35   struct list head[1 + npreloads], *tailp, *scanp;
  36   unsigned int nlist;
  37
  38   /* Start the search list with one element: MAP itself.  */
  39   head[0].map = map;
  40
  41   /* Add the preloaded items after MAP but before any of its dependencies.  */
  42   for (nlist = 0; nlist < npreloads; ++nlist)
  43     {
  44       head[nlist].next = &head[nlist + 1];
  45       head[nlist + 1].map = preloads[nlist];
  46     }
  47
  48   /* Terminate the list.  */
  49   head[nlist].next = NULL;
  50
  51   /* Start here for adding dependencies to the list.  */
  52   tailp = &head[nlist++];
  53
  54   /* We use `l_reserved' as a mark bit to detect objects we have already
  55      put in the search list and avoid adding duplicate elements later in
  56      the list.  */
  57   map->l_reserved = 1;
  58
  59   /* Process each element of the search list, loading each of its immediate
  60      dependencies and appending them to the list as we step through it.
  61      This produces a flat, ordered list that represents a breadth-first
  62      search of the dependency tree.  */
  63   for (scanp = head; scanp; scanp = scanp->next)
  64     {
  65       struct link_map *l = scanp->map;
  66
  67       if (l->l_info[DT_NEEDED])
  68         {
  69           const char *strtab
  70             = ((void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
  71           const ElfW(Dyn) *d;
  72           for (d = l->l_ld; d->d_tag != DT_NULL; ++d)
  73             if (d->d_tag == DT_NEEDED)
  74               {
  75                 /* Map in the needed object.  */
  76                 struct link_map *dep
  77                   = _dl_map_object (l, strtab + d->d_un.d_val,
  78                                     l->l_type == lt_executable ? lt_library :
  79                                     l->l_type, trace_mode);
  80
  81                 if (dep->l_reserved)
  82                   /* This object is already in the search list we are
  83                      building.  Don't add a duplicate pointer.  Release the
  84                      reference just added by _dl_map_object.  */
  85                   --dep->l_opencount;
  86                 else
  87                   {
  88                     /* Append DEP to the search list.  */
  89                     tailp->next = alloca (sizeof *tailp);
  90                     tailp = tailp->next;
  91                     tailp->map = dep;
  92                     tailp->next = NULL;
  93                     ++nlist;
  94                     /* Set the mark bit that says it's already in the list.  */
  95                     dep->l_reserved = 1;
  96                   }
  97               }
  98         }
  99     }
 100
 101   /* Store the search list we built in the object.  It will be used for
 102      searches in the scope of this object.  */
 103   map->l_searchlist = malloc (nlist * sizeof (struct link_map *));
 104   map->l_nsearchlist = nlist;
 105
 106   nlist = 0;
 107   for (scanp = head; scanp; scanp = scanp->next)
 108     {
 109       map->l_searchlist[nlist++] = scanp->map;
 110
 111       /* Now clear all the mark bits we set in the objects on the search list
 112          to avoid duplicates, so the next call starts fresh.  */
 113       scanp->map->l_reserved = 0;
 114     }
 115 }