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
  26 extern void _dl_start (void); weak_extern (_dl_start)
  27
  28 extern int __libc_multiple_libcs;       /* Defined in init-first.c.  */
  29
  30 extern int __libc_argc;
  31 extern char **__libc_argv;
  32
  33 extern char **__environ;
  34
  35 size_t _dl_global_scope_alloc;
  36
  37 struct link_map *
  38 _dl_open (const char *file, int mode)
  39 {
  40   struct link_map *new, *l;
  41   ElfW(Addr) init;
  42   struct r_debug *r;
  43   /* To decide whether we are the static libc or not.  We must use
  44      this variable since gcc would otherwise optimize the test away.  */
  45   void (*dl_start_ptr) (void) = &_dl_start;
  46
  47   /* Load the named object.  */
  48   new = _dl_map_object (NULL, file, lt_loaded);
  49   if (new->l_searchlist)
  50     /* It was already open.  */
  51     return new;
  52
  53   /* Load that object's dependencies.  */
  54   _dl_map_object_deps (new, NULL, 0);
  55
  56
  57   /* Relocate the objects loaded.  We do this in reverse order so that copy
  58      relocs of earlier objects overwrite the data written by later objects.  */
  59
  60   l = new;
  61   while (l->l_next)
  62     l = l->l_next;
  63   while (1)
  64     {
  65       if (! l->l_relocated)
  66         {
  67           /* We use an indirect call call for _dl_relocate_object because
  68              we must avoid using the PLT in the call.  If our PLT entry for
  69              _dl_relocate_object hasn't been used yet, then the dynamic
  70              linker fixup routine will clobber _dl_global_scope during its
  71              work.  We must be sure that nothing will require a PLT fixup
  72              between when _dl_object_relocation_scope returns and when we
  73              enter the dynamic linker's code (_dl_relocate_object).  */
  74           __typeof (_dl_relocate_object) *reloc = &_dl_relocate_object;
  75           (*reloc) (l, _dl_object_relocation_scope (l),
  76                     (mode & RTLD_BINDING_MASK) == RTLD_LAZY);
  77           *_dl_global_scope_end = NULL;
  78         }
  79
  80       if (l == new)
  81         break;
  82       l = l->l_prev;
  83     }
  84
  85   new->l_global = (mode & RTLD_GLOBAL);
  86   if (new->l_global)
  87     {
  88       /* The symbols of the new object and its dependencies are to be
  89          introduced into the global scope that will be used to resolve
  90          references from other dynamically-loaded objects.  */
  91
  92       if (_dl_global_scope_alloc == 0)
  93         {
  94           /* This is the first dynamic object given global scope.  */
  95           _dl_global_scope_alloc = 8;
  96           _dl_global_scope = malloc (8 * sizeof (struct link_map *));
  97           if (! _dl_global_scope)
  98             {
  99               _dl_global_scope = _dl_default_scope;
 100             nomem:
 101               _dl_close (new);
 102               _dl_signal_error (ENOMEM, file, "cannot extend global scope");
 103             }
 104           _dl_global_scope[2] = _dl_default_scope[2];
 105           _dl_global_scope[3] = new;
 106           _dl_global_scope[4] = NULL;
 107           _dl_global_scope[5] = NULL;
 108         }
 109       else
 110         {
 111           if (_dl_global_scope_alloc <
 112               (size_t) (_dl_global_scope_end - _dl_global_scope + 2))
 113             {
 114               /* Must extend the list.  */
 115               struct link_map **new = realloc (_dl_global_scope,
 116                                                _dl_global_scope_alloc * 2);
 117               if (! new)
 118                 goto nomem;
 119               _dl_global_scope_end = new + (_dl_global_scope_end -
 120                                             _dl_global_scope);
 121               _dl_global_scope = new;
 122               _dl_global_scope_alloc *= 2;
 123             }
 124
 125           /* Append the new object and re-terminate the list.  */
 126           *_dl_global_scope_end++ = new;
 127           /* We keep the list double-terminated so the last element
 128              can be filled in for symbol lookups.  */
 129           _dl_global_scope_end[0] = NULL;
 130           _dl_global_scope_end[1] = NULL;
 131         }
 132     }
 133
 134
 135   /* Notify the debugger we have added some objects.  We need to call
 136      _dl_debug_initialize in a static program in case dynamic linking has
 137      not been used before.  */
 138   r = _dl_debug_initialize (0);
 139   r->r_state = RT_ADD;
 140   _dl_debug_state ();
 141
 142   /* Run the initializer functions of new objects.  */
 143   while (init = _dl_init_next (new))
 144     (*(void (*) (int, char **, char **)) init) (__libc_argc, __libc_argv,
 145                                                 __environ);
 146
 147   if (dl_start_ptr == NULL)
 148     /* We must be the static _dl_open in libc.a because ld.so.1 is not
 149        in scope.  A static program that has loaded a dynamic object
 150        now has competition.  */
 151     __libc_multiple_libcs = 1;
 152
 153   return new;
 154 }