elf/dl-open.c

   1 /* Load a shared object at runtime, relocate it, and run its initializer.
   2    Copyright (C) 1996, 1997 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, 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   /* So far, so good.  Now check the versions.  */
  58   (void) _dl_check_map_versions (new, 0);
  59
  60   /* Relocate the objects loaded.  We do this in reverse order so that copy
  61      relocs of earlier objects overwrite the data written by later objects.  */
  62
  63   l = new;
  64   while (l->l_next)
  65     l = l->l_next;
  66   while (1)
  67     {
  68       if (! l->l_relocated)
  69         {
  70           /* We use an indirect call call for _dl_relocate_object because
  71              we must avoid using the PLT in the call.  If our PLT entry for
  72              _dl_relocate_object hasn't been used yet, then the dynamic
  73              linker fixup routine will clobber _dl_global_scope during its
  74              work.  We must be sure that nothing will require a PLT fixup
  75              between when _dl_object_relocation_scope returns and when we
  76              enter the dynamic linker's code (_dl_relocate_object).  */
  77           __typeof (_dl_relocate_object) *reloc = &_dl_relocate_object;
  78           (*reloc) (l, _dl_object_relocation_scope (l),
  79                     (mode & RTLD_BINDING_MASK) == RTLD_LAZY);
  80           *_dl_global_scope_end = NULL;
  81         }
  82
  83       if (l == new)
  84         break;
  85       l = l->l_prev;
  86     }
  87
  88   new->l_global = (mode & RTLD_GLOBAL);
  89   if (new->l_global)
  90     {
  91       /* The symbols of the new object and its dependencies are to be
  92          introduced into the global scope that will be used to resolve
  93          references from other dynamically-loaded objects.  */
  94
  95       if (_dl_global_scope_alloc == 0)
  96         {
  97           /* This is the first dynamic object given global scope.  */
  98           _dl_global_scope_alloc = 8;
  99           _dl_global_scope = malloc (8 * sizeof (struct link_map *));
 100           if (! _dl_global_scope)
 101             {
 102               _dl_global_scope = _dl_default_scope;
 103             nomem:
 104               _dl_close (new);
 105               _dl_signal_error (ENOMEM, file, "cannot extend global scope");
 106             }
 107           _dl_global_scope[2] = _dl_default_scope[2];
 108           _dl_global_scope[3] = new;
 109           _dl_global_scope[4] = NULL;
 110           _dl_global_scope[5] = NULL;
 111         }
 112       else
 113         {
 114           if (_dl_global_scope_alloc <
 115               (size_t) (_dl_global_scope_end - _dl_global_scope + 2))
 116             {
 117               /* Must extend the list.  */
 118               struct link_map **new = realloc (_dl_global_scope,
 119                                                _dl_global_scope_alloc * 2);
 120               if (! new)
 121                 goto nomem;
 122               _dl_global_scope_end = new + (_dl_global_scope_end -
 123                                             _dl_global_scope);
 124               _dl_global_scope = new;
 125               _dl_global_scope_alloc *= 2;
 126             }
 127
 128           /* Append the new object and re-terminate the list.  */
 129           *_dl_global_scope_end++ = new;
 130           /* We keep the list double-terminated so the last element
 131              can be filled in for symbol lookups.  */
 132           _dl_global_scope_end[0] = NULL;
 133           _dl_global_scope_end[1] = NULL;
 134         }
 135     }
 136
 137
 138   /* Notify the debugger we have added some objects.  We need to call
 139      _dl_debug_initialize in a static program in case dynamic linking has
 140      not been used before.  */
 141   r = _dl_debug_initialize (0);
 142   r->r_state = RT_ADD;
 143   _dl_debug_state ();
 144
 145   /* Run the initializer functions of new objects.  */
 146   while (init = _dl_init_next (new))
 147     (*(void (*) (int, char **, char **)) init) (__libc_argc, __libc_argv,
 148                                                 __environ);
 149
 150   if (_dl_sysdep_start == NULL)
 151     /* We must be the static _dl_open in libc.a.  A static program that
 152        has loaded a dynamic object now has competition.  */
 153     __libc_multiple_libcs = 1;
 154
 155   return new;
 156 }