elf/dl-open.c

   1 /* Load a shared object at runtime, relocate it, and run its initializer.
   2    Copyright (C) 1996, 1997, 1998, 1999, 2000 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 <ldsodefs.h>
  31 #include <bp-sym.h>
  32
  33 #include <dl-dst.h>
  34
  35
  36 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
  37                                     void (*dl_main) (const ElfW(Phdr) *phdr,
  38                                                      ElfW(Word) phnum,
  39                                                      ElfW(Addr) *user_entry));
  40 weak_extern (BP_SYM (_dl_sysdep_start))
  41
  42 /* This function is used to unload the cache file if necessary.  */
  43 extern void _dl_unload_cache (void);
  44
  45 extern int __libc_multiple_libcs;       /* Defined in init-first.c.  */
  46
  47 extern int __libc_argc;
  48 extern char **__libc_argv;
  49
  50 extern char **__environ;
  51
  52 extern int _dl_lazy;                    /* Do we do lazy relocations?  */
  53
  54 /* Undefine the following for debugging.  */
  55 /* #define SCOPE_DEBUG 1 */
  56 #ifdef SCOPE_DEBUG
  57 static void show_scope (struct link_map *new);
  58 #endif
  59
  60 /* During the program run we must not modify the global data of
  61    loaded shared object simultanously in two threads.  Therefore we
  62    protect `_dl_open' and `_dl_close' in dl-close.c.
  63
  64    This must be a recursive lock since the initializer function of
  65    the loaded object might as well require a call to this function.
  66    At this time it is not anymore a problem to modify the tables.  */
  67 __libc_lock_define (extern, _dl_load_lock)
  68
  69 extern size_t _dl_platformlen;
  70
  71 /* We must be carefull not to leave us in an inconsistent state.  Thus we
  72    catch any error and re-raise it after cleaning up.  */
  73
  74 struct dl_open_args
  75 {
  76   const char *file;
  77   int mode;
  78   const void *caller;
  79   struct link_map *map;
  80 };
  81
  82 static void
  83 dl_open_worker (void *a)
  84 {
  85   struct dl_open_args *args = a;
  86   const char *file = args->file;
  87   int mode = args->mode;
  88   struct link_map *new, *l;
  89   const char *dst;
  90   int lazy;
  91
  92   /* Maybe we have to expand a DST.  */
  93   dst = strchr (file, '$');
  94   if (dst != NULL)
  95     {
  96       const void *caller = args->caller;
  97       size_t len = strlen (file);
  98       size_t required;
  99       struct link_map *call_map;
 100       char *new_file;
 101
 102       /* DSTs must not appear in SUID/SGID programs.  */
 103       if (__libc_enable_secure)
 104         /* This is an error.  */
 105         _dl_signal_error (0, "dlopen",
 106                           N_("DST not allowed in SUID/SGID programs"));
 107
 108       /* We have to find out from which object the caller is calling.
 109          Find the highest-addressed object that ADDRESS is not below.  */
 110       call_map = NULL;
 111       for (l = _dl_loaded; l; l = l->l_next)
 112         if (l->l_addr != 0 /* Make sure we do not currently set this map up
 113                               in this moment.  */
 114             && caller >= (const void *) l->l_map_start
 115             && caller < (const void *) l->l_map_end)
 116           {
 117             /* There must be exactly one DSO for the range of the virtual
 118                memory.  Otherwise something is really broken.  */
 119             call_map = l;
 120             break;
 121           }
 122
 123       if (call_map == NULL)
 124         /* In this case we assume this is the main application.  */
 125         call_map = _dl_loaded;
 126
 127       /* Determine how much space we need.  We have to allocate the
 128          memory locally.  */
 129       required = DL_DST_REQUIRED (call_map, file, len, _dl_dst_count (dst, 0));
 130
 131       /* Get space for the new file name.  */
 132       new_file = (char *) alloca (required + 1);
 133
 134       /* Generate the new file name.  */
 135       DL_DST_SUBSTITUTE (call_map, file, new_file, 0);
 136
 137       /* If the substitution failed don't try to load.  */
 138       if (*new_file == '\0')
 139         _dl_signal_error (0, "dlopen",
 140                           N_("empty dynamic string token substitution"));
 141
 142       /* Now we have a new file name.  */
 143       file = new_file;
 144     }
 145
 146   /* Load the named object.  */
 147   args->map = new = _dl_map_object (NULL, file, 0, lt_loaded, 0,
 148                                     mode);
 149
 150   /* If the pointer returned is NULL this means the RTLD_NOLOAD flag is
 151      set and the object is not already loaded.  */
 152   if (new == NULL)
 153     {
 154       assert (mode & RTLD_NOLOAD);
 155       return;
 156     }
 157
 158   if (new->l_searchlist.r_list)
 159     /* It was already open.  */
 160     return;
 161
 162   /* Load that object's dependencies.  */
 163   _dl_map_object_deps (new, NULL, 0, 0);
 164
 165   /* So far, so good.  Now check the versions.  */
 166   (void) _dl_check_all_versions (new, 0, 0);
 167
 168 #ifdef SCOPE_DEBUG
 169   show_scope (new);
 170 #endif
 171
 172   /* Only do lazy relocation if `LD_BIND_NOW' is not set.  */
 173   lazy = (mode & RTLD_BINDING_MASK) == RTLD_LAZY && _dl_lazy;
 174
 175   /* Relocate the objects loaded.  We do this in reverse order so that copy
 176      relocs of earlier objects overwrite the data written by later objects.  */
 177
 178   l = new;
 179   while (l->l_next)
 180     l = l->l_next;
 181   while (1)
 182     {
 183       if (! l->l_relocated)
 184         {
 185 #ifdef SHARED
 186           if (_dl_profile != NULL)
 187             {
 188               /* If this here is the shared object which we want to profile
 189                  make sure the profile is started.  We can find out whether
 190                  this is necessary or not by observing the `_dl_profile_map'
 191                  variable.  If was NULL but is not NULL afterwars we must
 192                  start the profiling.  */
 193               struct link_map *old_profile_map = _dl_profile_map;
 194
 195               _dl_relocate_object (l, l->l_scope, 1, 1);
 196
 197               if (old_profile_map == NULL && _dl_profile_map != NULL)
 198                 /* We must prepare the profiling.  */
 199                 _dl_start_profile (_dl_profile_map, _dl_profile_output);
 200             }
 201           else
 202 #endif
 203             _dl_relocate_object (l, l->l_scope, lazy, 0);
 204         }
 205
 206       if (l == new)
 207         break;
 208       l = l->l_prev;
 209     }
 210
 211   /* Run the initializer functions of new objects.  */
 212   _dl_init (new, __libc_argc, __libc_argv, __environ);
 213
 214   /* Now we can make the new map available in the global scope.  */
 215   if (mode & RTLD_GLOBAL)
 216     {
 217       struct link_map **new_global;
 218       unsigned int to_add = 0;
 219       unsigned int cnt;
 220
 221       /* Count the objects we have to put in the global scope.  */
 222       for (cnt = 0; cnt < new->l_searchlist.r_nlist; ++cnt)
 223         if (new->l_searchlist.r_list[cnt]->l_global == 0)
 224           ++to_add;
 225
 226       /* The symbols of the new objects and its dependencies are to be
 227          introduced into the global scope that will be used to resolve
 228          references from other dynamically-loaded objects.
 229
 230          The global scope is the searchlist in the main link map.  We
 231          extend this list if necessary.  There is one problem though:
 232          since this structure was allocated very early (before the libc
 233          is loaded) the memory it uses is allocated by the malloc()-stub
 234          in the ld.so.  When we come here these functions are not used
 235          anymore.  Instead the malloc() implementation of the libc is
 236          used.  But this means the block from the main map cannot be used
 237          in an realloc() call.  Therefore we allocate a completely new
 238          array the first time we have to add something to the locale scope.  */
 239
 240       if (_dl_global_scope_alloc == 0)
 241         {
 242           /* This is the first dynamic object given global scope.  */
 243           _dl_global_scope_alloc = _dl_main_searchlist->r_nlist + to_add + 8;
 244           new_global = (struct link_map **)
 245             malloc (_dl_global_scope_alloc * sizeof (struct link_map *));
 246           if (new_global == NULL)
 247             {
 248               _dl_global_scope_alloc = 0;
 249             nomem:
 250               _dl_signal_error (ENOMEM, new->l_libname->name,
 251                                 N_("cannot extend global scope"));
 252               return;
 253             }
 254
 255           /* Copy over the old entries.  */
 256           memcpy (new_global, _dl_main_searchlist->r_list,
 257                   (_dl_main_searchlist->r_nlist * sizeof (struct link_map *)));
 258
 259           _dl_main_searchlist->r_list = new_global;
 260         }
 261       else if (_dl_main_searchlist->r_nlist + to_add > _dl_global_scope_alloc)
 262         {
 263           /* We have to extend the existing array of link maps in the
 264              main map.  */
 265           new_global = (struct link_map **)
 266             realloc (_dl_main_searchlist->r_list,
 267                      ((_dl_global_scope_alloc + to_add + 8)
 268                       * sizeof (struct link_map *)));
 269           if (new_global == NULL)
 270             goto nomem;
 271
 272           _dl_global_scope_alloc += to_add + 8;
 273           _dl_main_searchlist->r_list = new_global;
 274         }
 275
 276       /* Now add the new entries.  */
 277       for (cnt = 0; cnt < new->l_searchlist.r_nlist; ++cnt)
 278         {
 279           struct link_map *map = new->l_searchlist.r_list[cnt];
 280
 281           if (map->l_global == 0)
 282             {
 283               map->l_global = 1;
 284               _dl_main_searchlist->r_list[_dl_main_searchlist->r_nlist] = map;
 285               ++_dl_main_searchlist->r_nlist;
 286             }
 287         }
 288
 289       /* XXX Do we have to add something to r_dupsearchlist???  --drepper */
 290     }
 291
 292   /* Mark the object as not deletable if the RTLD_NODELETE flags was
 293      passed.  */
 294   if (__builtin_expect (mode & RTLD_NODELETE, 0))
 295     new->l_flags_1 |= DF_1_NODELETE;
 296
 297   if (_dl_sysdep_start == NULL)
 298     /* We must be the static _dl_open in libc.a.  A static program that
 299        has loaded a dynamic object now has competition.  */
 300     __libc_multiple_libcs = 1;
 301 }
 302
 303
 304 void *
 305 internal_function
 306 _dl_open (const char *file, int mode, const void *caller)
 307 {
 308   struct dl_open_args args;
 309   const char *objname;
 310   const char *errstring;
 311   int errcode;
 312
 313   if ((mode & RTLD_BINDING_MASK) == 0)
 314     /* One of the flags must be set.  */
 315     _dl_signal_error (EINVAL, file, N_("invalid mode for dlopen()"));
 316
 317   /* Make sure we are alone.  */
 318   __libc_lock_lock (_dl_load_lock);
 319
 320   args.file = file;
 321   args.mode = mode;
 322   args.caller = caller;
 323   args.map = NULL;
 324   errcode = _dl_catch_error (&objname, &errstring, dl_open_worker, &args);
 325
 326 #ifndef MAP_COPY
 327   /* We must munmap() the cache file.  */
 328   _dl_unload_cache ();
 329 #endif
 330
 331   /* Release the lock.  */
 332   __libc_lock_unlock (_dl_load_lock);
 333
 334   if (errstring)
 335     {
 336       /* Some error occurred during loading.  */
 337       char *local_errstring;
 338
 339       /* Remove the object from memory.  It may be in an inconsistent
 340          state if relocation failed, for example.  */
 341       if (args.map)
 342         _dl_close (args.map);
 343
 344       /* Make a local copy of the error string so that we can release the
 345          memory allocated for it.  */
 346       local_errstring = strdupa (errstring);
 347       if (errstring != _dl_out_of_memory)
 348         free ((char *) errstring);
 349
 350       /* Reraise the error.  */
 351       _dl_signal_error (errcode, objname, local_errstring);
 352     }
 353
 354   return args.map;
 355 }
 356
 357
 358 #ifdef SCOPE_DEBUG
 359 #include <unistd.h>
 360
 361 static void
 362 show_scope (struct link_map *new)
 363 {
 364   int scope_cnt;
 365
 366   for (scope_cnt = 0; new->l_scope[scope_cnt] != NULL; ++scope_cnt)
 367     {
 368       char numbuf[2];
 369       unsigned int cnt;
 370
 371       numbuf[0] = '0' + scope_cnt;
 372       numbuf[1] = '\0';
 373       _dl_sysdep_message ("scope ", numbuf, ":", NULL);
 374
 375       for (cnt = 0; cnt < new->l_scope[scope_cnt]->r_nlist; ++cnt)
 376         if (*new->l_scope[scope_cnt]->r_list[cnt]->l_name)
 377           _dl_sysdep_message (" ",
 378                               new->l_scope[scope_cnt]->r_list[cnt]->l_name,
 379                               NULL);
 380         else
 381           _dl_sysdep_message (" <main>", NULL);
 382
 383       _dl_sysdep_message ("\n", NULL);
 384     }
 385 }
 386 #endif