elf/dl-open.c

   1 /* Load a shared object at runtime, relocate it, and run its initializer.
   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 <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <errno.h>
  24
  25 size_t _dl_global_scope_alloc;
  26
  27 struct link_map *
  28 _dl_open (const char *file, int mode)
  29 {
  30   struct link_map *new, *l;
  31   ElfW(Addr) init;
  32   struct r_debug *r;
  33
  34
  35   /* Load the named object.  */
  36   new = _dl_map_object (NULL, file, lt_loaded);
  37   if (new->l_searchlist)
  38     /* It was already open.  */
  39     return new;
  40
  41   /* Load that object's dependencies.  */
  42   _dl_map_object_deps (new, NULL, 0);
  43
  44
  45   /* Relocate the objects loaded.  We do this in reverse order so that copy
  46      relocs of earlier objects overwrite the data written by later objects.  */
  47
  48   l = new;
  49   while (l->l_next)
  50     l = l->l_next;
  51   while (1)
  52     {
  53       if (! l->l_relocated)
  54         {
  55           /* We use an indirect call call for _dl_relocate_object because
  56              we must avoid using the PLT in the call.  If our PLT entry for
  57              _dl_relocate_object hasn't been used yet, then the dynamic
  58              linker fixup routine will clobber _dl_global_scope during its
  59              work.  We must be sure that nothing will require a PLT fixup
  60              between when _dl_object_relocation_scope returns and when we
  61              enter the dynamic linker's code (_dl_relocate_object).  */
  62           __typeof (_dl_relocate_object) *reloc = &_dl_relocate_object;
  63           (*reloc) (l, _dl_object_relocation_scope (l),
  64                     (mode & RTLD_BINDING_MASK) == RTLD_LAZY);
  65           *_dl_global_scope_end = NULL;
  66         }
  67
  68       if (l == new)
  69         break;
  70       l = l->l_prev;
  71     }
  72
  73   new->l_global = (mode & RTLD_GLOBAL);
  74   if (new->l_global)
  75     {
  76       /* The symbols of the new object and its dependencies are to be
  77          introduced into the global scope that will be used to resolve
  78          references from other dynamically-loaded objects.  */
  79
  80       if (_dl_global_scope_alloc == 0)
  81         {
  82           /* This is the first dynamic object given global scope.  */
  83           _dl_global_scope_alloc = 8;
  84           _dl_global_scope = malloc (8 * sizeof (struct link_map *));
  85           if (! _dl_global_scope)
  86             {
  87               _dl_global_scope = _dl_default_scope;
  88             nomem:
  89               _dl_close (new);
  90               _dl_signal_error (ENOMEM, file, "cannot extend global scope");
  91             }
  92           _dl_global_scope[2] = _dl_default_scope[2];
  93           _dl_global_scope[3] = new;
  94           _dl_global_scope[4] = NULL;
  95           _dl_global_scope[5] = NULL;
  96         }
  97       else
  98         {
  99           if (_dl_global_scope_alloc <
 100               (size_t) (_dl_global_scope_end - _dl_global_scope + 2))
 101             {
 102               /* Must extend the list.  */
 103               struct link_map **new = realloc (_dl_global_scope,
 104                                                _dl_global_scope_alloc * 2);
 105               if (! new)
 106                 goto nomem;
 107               _dl_global_scope_end = new + (_dl_global_scope_end -
 108                                             _dl_global_scope);
 109               _dl_global_scope = new;
 110               _dl_global_scope_alloc *= 2;
 111             }
 112
 113           /* Append the new object and re-terminate the list.  */
 114           *_dl_global_scope_end++ = new;
 115           /* We keep the list double-terminated so the last element
 116              can be filled in for symbol lookups.  */
 117           _dl_global_scope_end[0] = NULL;
 118           _dl_global_scope_end[1] = NULL;
 119         }
 120     }
 121
 122
 123   /* Notify the debugger we have added some objects.  We need to call
 124      _dl_debug_initialize in a static program in case dynamic linking has
 125      not been used before.  */
 126   r = _dl_debug_initialize (0);
 127   r->r_state = RT_ADD;
 128   _dl_debug_state ();
 129
 130   /* Run the initializer functions of new objects.  */
 131   while (init = _dl_init_next (new))
 132     (*(void (*) (void)) init) ();
 133
 134   return new;
 135 }