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