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   struct list duphead, *duptailp;
  37   unsigned int nlist;
  38   unsigned int nduplist;
  39
  40   /* Start the search list with one element: MAP itself.  */
  41   head[0].map = map;
  42
  43   /* We use `l_reserved' as a mark bit to detect objects we have already
  44      put in the search list and avoid adding duplicate elements later in
  45      the list.  */
  46   map->l_reserved = 1;
  47
  48   /* Add the preloaded items after MAP but before any of its dependencies.  */
  49   for (nlist = 0; nlist < npreloads; ++nlist)
  50     {
  51       head[nlist].next = &head[nlist + 1];
  52       head[nlist + 1].map = preloads[nlist];
  53       preloads[nlist]->l_reserved = 1;
  54     }
  55
  56   /* Terminate the lists.  */
  57   head[nlist].next = NULL;
  58   duphead.next = NULL;
  59
  60   /* Start here for adding dependencies to the list.  */
  61   tailp = &head[nlist++];
  62
  63   /* Until now we have the same number of libraries in the normal and
  64      the list with duplicates.  */
  65   nduplist = nlist;
  66   duptailp = &duphead;
  67
  68   /* Process each element of the search list, loading each of its immediate
  69      dependencies and appending them to the list as we step through it.
  70      This produces a flat, ordered list that represents a breadth-first
  71      search of the dependency tree.  */
  72   for (scanp = head; scanp; scanp = scanp->next)
  73     {
  74       struct link_map *l = scanp->map;
  75
  76       if (l->l_info[DT_NEEDED])
  77         {
  78           const char *strtab
  79             = ((void *) l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
  80           const ElfW(Dyn) *d;
  81           for (d = l->l_ld; d->d_tag != DT_NULL; ++d)
  82             if (d->d_tag == DT_NEEDED)
  83               {
  84                 /* Map in the needed object.  */
  85                 struct link_map *dep
  86                   = _dl_map_object (l, strtab + d->d_un.d_val,
  87                                     l->l_type == lt_executable ? lt_library :
  88                                     l->l_type, trace_mode);
  89
  90                 if (dep->l_reserved)
  91                   /* This object is already in the search list we are
  92                      building.  Don't add a duplicate pointer.  Release the
  93                      reference just added by _dl_map_object.  */
  94                   --dep->l_opencount;
  95                 else
  96                   {
  97                     /* Append DEP to the search list.  */
  98                     tailp->next = alloca (sizeof *tailp);
  99                     tailp = tailp->next;
 100                     tailp->map = dep;
 101                     tailp->next = NULL;
 102                     ++nlist;
 103                     /* Set the mark bit that says it's already in the list.  */
 104                     dep->l_reserved = 1;
 105                   }
 106
 107                 /* In any case Append DEP to the duplicates search list.  */
 108                 duptailp->next = alloca (sizeof *duptailp);
 109                 duptailp = duptailp->next;
 110                 duptailp->map = dep;
 111                 duptailp->next = NULL;
 112                 ++nduplist;
 113               }
 114         }
 115     }
 116
 117   /* Store the search list we built in the object.  It will be used for
 118      searches in the scope of this object.  */
 119   map->l_searchlist = malloc (nlist * sizeof (struct link_map *));
 120   map->l_nsearchlist = nlist;
 121
 122   nlist = 0;
 123   for (scanp = head; scanp; scanp = scanp->next)
 124     {
 125       map->l_searchlist[nlist++] = scanp->map;
 126
 127       /* Now clear all the mark bits we set in the objects on the search list
 128          to avoid duplicates, so the next call starts fresh.  */
 129       scanp->map->l_reserved = 0;
 130     }
 131
 132   map->l_dupsearchlist = malloc (nduplist * sizeof (struct link_map *));
 133   map->l_ndupsearchlist = nduplist;
 134
 135   for (nlist = 0; nlist < npreloads + 1; ++nlist)
 136     map->l_dupsearchlist[nlist] = head[nlist].map;
 137   for (scanp = duphead.next; scanp; scanp = scanp->next)
 138     map->l_dupsearchlist[nlist++] = scanp->map;
 139 }