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
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, 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 {
  29   struct list
  30     {
  31       struct link_map *map;
  32       struct list *next;
  33     };
  34   struct list head[1 + npreloads], *tailp, *scanp;
  35   unsigned int nlist;
  36
  37   /* Start the search list with one element: MAP itself.  */
  38   head[0].map = map;
  39
  40   /* Add the preloaded items after MAP but before any of its dependencies.  */
  41   for (nlist = 0; nlist < npreloads; ++nlist)
  42     {
  43       head[nlist].next = &head[nlist + 1];
  44       head[nlist + 1].map = preloads[nlist];
  45     }
  46
  47   /* Terminate the list.  */
  48   head[nlist++].next = NULL;
  49
  50   /* We use `l_reserved' as a mark bit to detect objects we have already
  51      put in the search list and avoid adding duplicate elements later in
  52      the list.  */
  53   map->l_reserved = 1;
  54
  55   /* Process each element of the search list, loading each of its immediate
  56      dependencies and appending them to the list as we step through it.
  57      This produces a flat, ordered list that represents a breadth-first
  58      search of the dependency tree.  */
  59   for (scanp = tailp = head; scanp; scanp = scanp->next)
  60     {
  61       struct link_map *l = scanp->map;
  62
  63       if (l->l_info[DT_NEEDED])
  64         {
  65           const char *strtab
  66             = ((void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
  67           const ElfW(Dyn) *d;
  68           for (d = l->l_ld; d->d_tag != DT_NULL; ++d)
  69             if (d->d_tag == DT_NEEDED)
  70               {
  71                 /* Map in the needed object.  */
  72                 struct link_map *dep
  73                   = _dl_map_object (l, strtab + d->d_un.d_val,
  74                                     l->l_type == lt_executable ? lt_library :
  75                                     l->l_type);
  76
  77                 if (dep->l_reserved)
  78                   /* This object is already in the search list we are
  79                      building.  Don't add a duplicate pointer.  Release the
  80                      reference just added by _dl_map_object.  */
  81                   --dep->l_opencount;
  82                 else
  83                   {
  84                     /* Append DEP to the search list.  */
  85                     tailp->next = alloca (sizeof *tailp);
  86                     tailp = tailp->next;
  87                     tailp->map = dep;
  88                     tailp->next = NULL;
  89                     ++nlist;
  90                     /* Set the mark bit that says it's already in the list.  */
  91                     dep->l_reserved = 1;
  92                   }
  93               }
  94         }
  95     }
  96
  97   /* Store the search list we built in the object.  It will be used for
  98      searches in the scope of this object.  */
  99   map->l_searchlist = malloc (nlist * sizeof (struct link_map *));
 100   map->l_nsearchlist = nlist;
 101
 102   nlist = 0;
 103   for (scanp = head; scanp; scanp = scanp->next)
 104     {
 105       map->l_searchlist[nlist++] = scanp->map;
 106
 107       /* Now clear all the mark bits we set in the objects on the search list
 108          to avoid duplicates, so the next call starts fresh.  */
 109       scanp->map->l_reserved = 0;
 110     }
 111 }