elf/dl-open.c

   1 /* Load a shared object at runtime, relocate it, and run its initializer.
   2    Copyright (C) 1996, 1998 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 <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <errno.h>
  24
  25
  26 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
  27                                     void (*dl_main) (const ElfW(Phdr) *phdr,
  28                                                      ElfW(Word) phnum,
  29                                                      ElfW(Addr) *user_entry));
  30 weak_extern (_dl_sysdep_start)
  31
  32 extern int __libc_multiple_libcs;       /* Defined in init-first.c.  */
  33
  34 extern int __libc_argc;
  35 extern char **__libc_argv;
  36
  37 extern char **__environ;
  38
  39 size_t _dl_global_scope_alloc;
  40
  41 struct link_map *
  42 _dl_open (const char *file, int mode)
  43 {
  44   struct link_map *new, *l;
  45   ElfW(Addr) init;
  46   struct r_debug *r;
  47
  48   /* Load the named object.  */
  49   new = _dl_map_object (NULL, file, 0, lt_loaded, 0);
  50   if (new->l_searchlist)
  51     /* It was already open.  */
  52     return new;
  53
  54   /* Load that object's dependencies.  */
  55   _dl_map_object_deps (new, NULL, 0, 0);
  56
  57
  58   /* Relocate the objects loaded.  We do this in reverse order so that copy
  59      relocs of earlier objects overwrite the data written by later objects.  */
  60
  61   l = new;
  62   while (l->l_next)
  63     l = l->l_next;
  64   while (1)
  65     {
  66       if (! l->l_relocated)
  67         {
  68           /* We use an indirect call call for _dl_relocate_object because
  69              we must avoid using the PLT in the call.  If our PLT entry for
  70              _dl_relocate_object hasn't been used yet, then the dynamic
  71              linker fixup routine will clobber _dl_global_scope during its
  72              work.  We must be sure that nothing will require a PLT fixup
  73              between when _dl_object_relocation_scope returns and when we
  74              enter the dynamic linker's code (_dl_relocate_object).  */
  75           __typeof (_dl_relocate_object) *reloc = &_dl_relocate_object;
  76
  77           /* GCC is very clever.  If we wouldn't add some magic it would
  78              simply optimize away our nice little variable `reloc' and we
  79              would result in a not working binary.  So let's swing the
  80              magic ward.  */
  81           asm ("" : "=r" (reloc) : "0" (reloc));
  82
  83           (*reloc) (l, _dl_object_relocation_scope (l),
  84                     (mode & RTLD_BINDING_MASK) == RTLD_LAZY);
  85           *_dl_global_scope_end = NULL;
  86         }
  87
  88       if (l == new)
  89         break;
  90       l = l->l_prev;
  91     }
  92
  93   new->l_global = (mode & RTLD_GLOBAL) ? 1 : 0;
  94   if (new->l_global)
  95     {
  96       /* The symbols of the new object and its dependencies are to be
  97          introduced into the global scope that will be used to resolve
  98          references from other dynamically-loaded objects.  */
  99
 100       if (_dl_global_scope_alloc == 0)
 101         {
 102           /* This is the first dynamic object given global scope.  */
 103           _dl_global_scope_alloc = 8;
 104           _dl_global_scope = malloc (8 * sizeof (struct link_map *));
 105           if (! _dl_global_scope)
 106             {
 107               _dl_global_scope = _dl_default_scope;
 108             nomem:
 109               _dl_close (new);
 110               _dl_signal_error (ENOMEM, file, "cannot extend global scope");
 111             }
 112           _dl_global_scope[2] = _dl_default_scope[2];
 113           _dl_global_scope[3] = new;
 114           _dl_global_scope[4] = NULL;
 115           _dl_global_scope[5] = NULL;
 116           _dl_global_scope_end = &_dl_global_scope [4];
 117         }
 118       else
 119         {
 120           if (_dl_global_scope_alloc <
 121               (size_t) (_dl_global_scope_end - _dl_global_scope + 2))
 122             {
 123               /* Must extend the list.  */
 124               struct link_map **new = realloc (_dl_global_scope,
 125                                                _dl_global_scope_alloc * 2);
 126               if (! new)
 127                 goto nomem;
 128               _dl_global_scope_end = new + (_dl_global_scope_end -
 129                                             _dl_global_scope);
 130               _dl_global_scope = new;
 131               _dl_global_scope_alloc *= 2;
 132             }
 133
 134           /* Append the new object and re-terminate the list.  */
 135           *_dl_global_scope_end++ = new;
 136           /* We keep the list double-terminated so the last element
 137              can be filled in for symbol lookups.  */
 138           _dl_global_scope_end[0] = NULL;
 139           _dl_global_scope_end[1] = NULL;
 140         }
 141     }
 142
 143
 144   /* Notify the debugger we have added some objects.  We need to call
 145      _dl_debug_initialize in a static program in case dynamic linking has
 146      not been used before.  */
 147   r = _dl_debug_initialize (0);
 148   r->r_state = RT_ADD;
 149   _dl_debug_state ();
 150
 151   /* Run the initializer functions of new objects.  */
 152   while (init = _dl_init_next (new))
 153     (*(void (*) (int, char **, char **)) init) (__libc_argc, __libc_argv,
 154                                                 __environ);
 155
 156   if (_dl_sysdep_start == NULL)
 157     /* We must be the static _dl_open in libc.a.  A static program that
 158        has loaded a dynamic object now has competition.  */
 159     __libc_multiple_libcs = 1;
 160
 161   return new;
 162 }