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