libltdl/loaders/dlopen.c

   1 /* loader-dlopen.c --  dynamic linking with dlopen/dlsym
   2
   3    Copyright (C) 1998, 1999, 2000, 2004, 2006,
   4                  2007, 2008 Free Software Foundation, Inc.
   5    Written by Thomas Tanner, 1998
   6
   7    NOTE: The canonical source of this file is maintained with the
   8    GNU Libtool package.  Report bugs to bug-libtool@gnu.org.
   9
  10 GNU Libltdl is free software; you can redistribute it and/or
  11 modify it under the terms of the GNU Lesser General Public
  12 License as published by the Free Software Foundation; either
  13 version 2 of the License, or (at your option) any later version.
  14
  15 As a special exception to the GNU Lesser General Public License,
  16 if you distribute this file as part of a program or library that
  17 is built using GNU Libtool, you may include this file under the
  18 same distribution terms that you use for the rest of that program.
  19
  20 GNU Libltdl is distributed in the hope that it will be useful,
  21 but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23 GNU Lesser General Public License for more details.
  24
  25 You should have received a copy of the GNU Lesser General Public
  26 License along with GNU Libltdl; see the file COPYING.LIB.  If not, a
  27 copy can be downloaded from  http://www.gnu.org/licenses/lgpl.html,
  28 or obtained by writing to the Free Software Foundation, Inc.,
  29 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  30 */
  31
  32 #include "lt__private.h"
  33 #include "lt_dlloader.h"
  34
  35 /* Use the preprocessor to rename non-static symbols to avoid namespace
  36    collisions when the loader code is statically linked into libltdl.
  37    Use the "<module_name>_LTX_" prefix so that the symbol addresses can
  38    be fetched from the preloaded symbol list by lt_dlsym():  */
  39 #define get_vtable      dlopen_LTX_get_vtable
  40
  41 LT_BEGIN_C_DECLS
  42 LT_SCOPE lt_dlvtable *get_vtable (lt_user_data loader_data);
  43 LT_END_C_DECLS
  44
  45
  46 /* Boilerplate code to set up the vtable for hooking this loader into
  47    libltdl's loader list:  */
  48 static int       vl_exit  (lt_user_data loader_data);
  49 static lt_module vm_open  (lt_user_data loader_data, const char *filename,
  50                            lt_dladvise advise);
  51 static int       vm_close (lt_user_data loader_data, lt_module module);
  52 static void *    vm_sym   (lt_user_data loader_data, lt_module module,
  53                           const char *symbolname);
  54
  55 static lt_dlvtable *vtable = 0;
  56
  57 /* Return the vtable for this loader, only the name and sym_prefix
  58    attributes (plus the virtual function implementations, obviously)
  59    change between loaders.  */
  60 lt_dlvtable *
  61 get_vtable (lt_user_data loader_data)
  62 {
  63   if (!vtable)
  64     {
  65       vtable = (lt_dlvtable *) lt__zalloc (sizeof *vtable);
  66     }
  67
  68   if (vtable && !vtable->name)
  69     {
  70       vtable->name              = "lt_dlopen";
  71 #if defined(DLSYM_USCORE)
  72       vtable->sym_prefix        = "_";
  73 #endif
  74       vtable->module_open       = vm_open;
  75       vtable->module_close      = vm_close;
  76       vtable->find_sym          = vm_sym;
  77       vtable->dlloader_exit     = vl_exit;
  78       vtable->dlloader_data     = loader_data;
  79       vtable->priority          = LT_DLLOADER_PREPEND;
  80     }
  81
  82   if (vtable && (vtable->dlloader_data != loader_data))
  83     {
  84       LT__SETERROR (INIT_LOADER);
  85       return 0;
  86     }
  87
  88   return vtable;
  89 }
  90
  91
  92
  93 /* --- IMPLEMENTATION --- */
  94
  95
  96 #if defined(HAVE_DLFCN_H)
  97 #  include <dlfcn.h>
  98 #endif
  99
 100 #if defined(HAVE_SYS_DL_H)
 101 #  include <sys/dl.h>
 102 #endif
 103
 104
 105 /* We may have to define LT_LAZY_OR_NOW in the command line if we
 106    find out it does not work in some platform. */
 107 #if !defined(LT_LAZY_OR_NOW)
 108 #  if defined(RTLD_LAZY)
 109 #    define LT_LAZY_OR_NOW      RTLD_LAZY
 110 #  else
 111 #    if defined(DL_LAZY)
 112 #      define LT_LAZY_OR_NOW    DL_LAZY
 113 #    endif
 114 #  endif /* !RTLD_LAZY */
 115 #endif
 116 #if !defined(LT_LAZY_OR_NOW)
 117 #  if defined(RTLD_NOW)
 118 #    define LT_LAZY_OR_NOW      RTLD_NOW
 119 #  else
 120 #    if defined(DL_NOW)
 121 #      define LT_LAZY_OR_NOW    DL_NOW
 122 #    endif
 123 #  endif /* !RTLD_NOW */
 124 #endif
 125 #if !defined(LT_LAZY_OR_NOW)
 126 #  define LT_LAZY_OR_NOW        0
 127 #endif /* !LT_LAZY_OR_NOW */
 128
 129 /* We only support local and global symbols from modules for loaders
 130    that provide such a thing, otherwise the system default is used.  */
 131 #if !defined(RTLD_GLOBAL)
 132 #  if defined(DL_GLOBAL)
 133 #    define RTLD_GLOBAL         DL_GLOBAL
 134 #  endif
 135 #endif /* !RTLD_GLOBAL */
 136 #if !defined(RTLD_LOCAL)
 137 #  if defined(DL_LOCAL)
 138 #    define RTLD_LOCAL          DL_LOCAL
 139 #  endif
 140 #endif /* !RTLD_LOCAL */
 141
 142 #if defined(HAVE_DLERROR)
 143 #  define DLERROR(arg)  dlerror ()
 144 #else
 145 #  define DLERROR(arg)  LT__STRERROR (arg)
 146 #endif
 147
 148 #define DL__SETERROR(errorcode) \
 149         LT__SETERRORSTR (DLERROR (errorcode))
 150
 151
 152 /* A function called through the vtable when this loader is no
 153    longer needed by the application.  */
 154 static int
 155 vl_exit (lt_user_data LT__UNUSED loader_data)
 156 {
 157   vtable = NULL;
 158   return 0;
 159 }
 160
 161
 162 /* A function called through the vtable to open a module with this
 163    loader.  Returns an opaque representation of the newly opened
 164    module for processing with this loader's other vtable functions.  */
 165 static lt_module
 166 vm_open (lt_user_data LT__UNUSED loader_data, const char *filename,
 167          lt_dladvise advise)
 168 {
 169   int           module_flags = LT_LAZY_OR_NOW;
 170   lt_module     module;
 171
 172   if (advise)
 173     {
 174 #ifdef RTLD_GLOBAL
 175       /* If there is some means of asking for global symbol resolution,
 176          do so.  */
 177       if (advise->is_symglobal)
 178         module_flags |= RTLD_GLOBAL;
 179 #else
 180       /* Otherwise, reset that bit so the caller can tell it wasn't
 181          acted on.  */
 182       advise->is_symglobal = 0;
 183 #endif
 184
 185 /* And similarly for local only symbol resolution.  */
 186 #ifdef RTLD_LOCAL
 187       if (advise->is_symlocal)
 188         module_flags |= RTLD_LOCAL;
 189 #else
 190       advise->is_symlocal = 0;
 191 #endif
 192     }
 193
 194   module = dlopen (filename, module_flags);
 195
 196   if (!module)
 197     {
 198       DL__SETERROR (CANNOT_OPEN);
 199     }
 200
 201   return module;
 202 }
 203
 204
 205 /* A function called through the vtable when a particular module
 206    should be unloaded.  */
 207 static int
 208 vm_close (lt_user_data LT__UNUSED loader_data, lt_module module)
 209 {
 210   int errors = 0;
 211
 212   if (dlclose (module) != 0)
 213     {
 214       DL__SETERROR (CANNOT_CLOSE);
 215       ++errors;
 216     }
 217
 218   return errors;
 219 }
 220
 221
 222 /* A function called through the vtable to get the address of
 223    a symbol loaded from a particular module.  */
 224 static void *
 225 vm_sym (lt_user_data LT__UNUSED loader_data, lt_module module, const char *name)
 226 {
 227   void *address = dlsym (module, name);
 228
 229   if (!address)
 230     {
 231       DL__SETERROR (SYMBOL_NOT_FOUND);
 232     }
 233
 234   return address;
 235 }