elf/dl-open.c

   1 /* Load a shared object at runtime, relocate it, and run its initializer.
   2    Copyright (C) 1996, 1997, 1998, 1999 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 <assert.h>
  21 #include <dlfcn.h>
  22 #include <errno.h>
  23 #include <libintl.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27 #include <sys/mman.h>           /* Check whether MAP_COPY is defined.  */
  28 #include <sys/param.h>
  29 #include <bits/libc-lock.h>
  30 #include <elf/ldsodefs.h>
  31
  32 #include <dl-dst.h>
  33
  34
  35 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
  36                                     void (*dl_main) (const ElfW(Phdr) *phdr,
  37                                                      ElfW(Word) phnum,
  38                                                      ElfW(Addr) *user_entry));
  39 weak_extern (_dl_sysdep_start)
  40
  41 /* This function is used to unload the cache file if necessary.  */
  42 extern void _dl_unload_cache (void);
  43
  44 extern int __libc_multiple_libcs;       /* Defined in init-first.c.  */
  45
  46 extern int __libc_argc;
  47 extern char **__libc_argv;
  48
  49 extern char **__environ;
  50
  51 extern int _dl_lazy;                    /* Do we do lazy relocations?  */
  52
  53 /* Undefine the following for debugging.  */
  54 /* #define SCOPE_DEBUG 1 */
  55 #ifdef SCOPE_DEBUG
  56 static void show_scope (struct link_map *new);
  57 #endif
  58
  59 /* During the program run we must not modify the global data of
  60    loaded shared object simultanously in two threads.  Therefore we
  61    protect `_dl_open' and `_dl_close' in dl-close.c.
  62
  63    This must be a recursive lock since the initializer function of
  64    the loaded object might as well require a call to this function.
  65    At this time it is not anymore a problem to modify the tables.  */
  66 __libc_lock_define_initialized_recursive (, _dl_load_lock)
  67
  68 extern size_t _dl_platformlen;
  69
  70 /* We must be carefull not to leave us in an inconsistent state.  Thus we
  71    catch any error and re-raise it after cleaning up.  */
  72
  73 struct dl_open_args
  74 {
  75   const char *file;
  76   int mode;
  77   const void *caller;
  78   struct link_map *map;
  79 };
  80
  81 static void
  82 dl_open_worker (void *a)
  83 {
  84   struct dl_open_args *args = a;
  85   const char *file = args->file;
  86   int mode = args->mode;
  87   struct link_map *new, *l;
  88   ElfW(Addr) init;
  89   struct r_debug *r;
  90   unsigned int global_add;
  91   const char *dst;
  92   int lazy;
  93
  94   /* Maybe we have to expand a DST.  */
  95   dst = strchr (file, '$');
  96   if (dst != NULL)
  97     {
  98       const void *caller = args->caller;
  99       size_t len = strlen (file);
 100       size_t required;
 101       struct link_map *call_map;
 102       char *new_file;
 103
 104       /* DSTs must not appear in SUID/SGID programs.  */
 105       if (__libc_enable_secure)
 106         /* This is an error.  */
 107         _dl_signal_error (0, "dlopen",
 108                           "DST not allowed in SUID/SGID programs");
 109
 110       /* We have to find out from which object the caller is calling.
 111          Find the highest-addressed object that ADDRESS is not below.  */
 112       call_map = NULL;
 113       for (l = _dl_loaded; l; l = l->l_next)
 114         if (l->l_addr != 0 /* Make sure we do not currently set this map up
 115                               in this moment.  */
 116             && caller >= (const void *) l->l_addr
 117             && (call_map == NULL || call_map->l_addr < l->l_addr))
 118           call_map = l;
 119
 120       if (call_map == NULL)
 121         /* In this case we assume this is the main application.  */
 122         call_map = _dl_loaded;
 123
 124       /* Determine how much space we need.  We have to allocate the
 125          memory locally.  */
 126       required = DL_DST_REQUIRED (call_map, file, len, _dl_dst_count (dst, 0));
 127
 128       /* Get space for the new file name.  */
 129       new_file = (char *) alloca (required + 1);
 130
 131       /* Generate the new file name.  */
 132       DL_DST_SUBSTITUTE (call_map, file, new_file, 0);
 133
 134       /* If the substitution failed don't try to load.  */
 135       if (*new_file == '\0')
 136         _dl_signal_error (0, "dlopen",
 137                           "empty dynamic string token substitution");
 138
 139       /* Now we have a new file name.  */
 140       file = new_file;
 141     }
 142
 143   /* Load the named object.  */
 144   args->map = new = _dl_map_object (NULL, file, 0, lt_loaded, 0);
 145   if (new->l_searchlist.r_list)
 146     /* It was already open.  */
 147     return;
 148
 149   /* Load that object's dependencies.  */
 150   global_add = _dl_map_object_deps (new, NULL, 0, 0, mode & RTLD_GLOBAL);
 151
 152   /* So far, so good.  Now check the versions.  */
 153   (void) _dl_check_all_versions (new, 0);
 154
 155 #ifdef SCOPE_DEBUG
 156   show_scope (new);
 157 #endif
 158
 159   /* Only do lazy relocation if `LD_BIND_NOW' is not set.  */
 160   lazy = (mode & RTLD_BINDING_MASK) == RTLD_LAZY && _dl_lazy;
 161
 162   /* Relocate the objects loaded.  We do this in reverse order so that copy
 163      relocs of earlier objects overwrite the data written by later objects.  */
 164
 165   l = new;
 166   while (l->l_next)
 167     l = l->l_next;
 168   while (1)
 169     {
 170       if (! l->l_relocated)
 171         {
 172 #ifdef PIC
 173           if (_dl_profile != NULL)
 174             {
 175               /* If this here is the shared object which we want to profile
 176                  make sure the profile is started.  We can find out whether
 177                  this is necessary or not by observing the `_dl_profile_map'
 178                  variable.  If was NULL but is not NULL afterwars we must
 179                  start the profiling.  */
 180               struct link_map *old_profile_map = _dl_profile_map;
 181
 182               _dl_relocate_object (l, l->l_scope, 1, 1);
 183
 184               if (old_profile_map == NULL && _dl_profile_map != NULL)
 185                 /* We must prepare the profiling.  */
 186                 _dl_start_profile (_dl_profile_map, _dl_profile_output);
 187             }
 188           else
 189 #endif
 190             _dl_relocate_object (l, l->l_scope, lazy, 0);
 191         }
 192
 193       if (l == new)
 194         break;
 195       l = l->l_prev;
 196     }
 197
 198   /* Notify the debugger we have added some objects.  We need to call
 199      _dl_debug_initialize in a static program in case dynamic linking has
 200      not been used before.  */
 201   r = _dl_debug_initialize (0);
 202   r->r_state = RT_ADD;
 203   _dl_debug_state ();
 204
 205   /* Run the initializer functions of new objects.  */
 206   while ((init = _dl_init_next (&new->l_searchlist)))
 207     (*(void (*) (int, char **, char **)) init) (__libc_argc, __libc_argv,
 208                                                 __environ);
 209
 210   /* Now we can make the new map available in the global scope.  */
 211   while (global_add-- > 0)
 212     _dl_main_searchlist->r_list[_dl_main_searchlist->r_nlist++]->l_global = 1;
 213
 214   if (_dl_sysdep_start == NULL)
 215     /* We must be the static _dl_open in libc.a.  A static program that
 216        has loaded a dynamic object now has competition.  */
 217     __libc_multiple_libcs = 1;
 218 }
 219
 220
 221 void *
 222 internal_function
 223 _dl_open (const char *file, int mode, const void *caller)
 224 {
 225   struct dl_open_args args;
 226   char *errstring;
 227   int errcode;
 228
 229   if ((mode & RTLD_BINDING_MASK) == 0)
 230     /* One of the flags must be set.  */
 231     _dl_signal_error (EINVAL, file, _("invalid mode for dlopen()"));
 232
 233   /* Make sure we are alone.  */
 234   __libc_lock_lock (_dl_load_lock);
 235
 236   args.file = file;
 237   args.mode = mode;
 238   args.caller = caller;
 239   args.map = NULL;
 240   errcode = _dl_catch_error (&errstring, dl_open_worker, &args);
 241
 242 #ifndef MAP_COPY
 243   /* We must munmap() the cache file.  */
 244   _dl_unload_cache ();
 245 #endif
 246
 247   /* Release the lock.  */
 248   __libc_lock_unlock (_dl_load_lock);
 249
 250   if (errstring)
 251     {
 252       /* Some error occured during loading.  */
 253       char *local_errstring;
 254
 255       /* Remove the object from memory.  It may be in an inconsistent
 256          state if relocation failed, for example.  */
 257       if (args.map)
 258         _dl_close (args.map);
 259
 260       /* Make a local copy of the error string so that we can release the
 261          memory allocated for it.  */
 262       local_errstring = strdupa (errstring);
 263       free (errstring);
 264
 265       /* Reraise the error.  */
 266       _dl_signal_error (errcode, NULL, local_errstring);
 267     }
 268
 269   return args.map;
 270 }
 271
 272
 273 #ifdef SCOPE_DEBUG
 274 #include <unistd.h>
 275
 276 static void
 277 show_scope (struct link_map *new)
 278 {
 279   int scope_cnt;
 280
 281   for (scope_cnt = 0; new->l_scope[scope_cnt] != NULL; ++scope_cnt)
 282     {
 283       char numbuf[2];
 284       unsigned int cnt;
 285
 286       numbuf[0] = '0' + scope_cnt;
 287       numbuf[1] = '\0';
 288       _dl_sysdep_message ("scope ", numbuf, ":", NULL);
 289
 290       for (cnt = 0; cnt < new->l_scope[scope_cnt]->r_nlist; ++cnt)
 291         if (*new->l_scope[scope_cnt]->r_list[cnt]->l_name)
 292           _dl_sysdep_message (" ",
 293                               new->l_scope[scope_cnt]->r_list[cnt]->l_name,
 294                               NULL);
 295         else
 296           _dl_sysdep_message (" <main>", NULL);
 297
 298       _dl_sysdep_message ("\n", NULL);
 299     }
 300 }
 301 #endif