elf/dl-open.c

   1 /* Load a shared object at runtime, relocate it, and run its initializer.
   2    Copyright (C) 1996,1997,1998,1999,2000,2001 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 #include <stdio-common/_itoa.h>
  35
  36
  37 extern ElfW(Addr) _dl_sysdep_start (void **start_argptr,
  38                                     void (*dl_main) (const ElfW(Phdr) *phdr,
  39                                                      ElfW(Word) phnum,
  40                                                      ElfW(Addr) *user_entry));
  41 weak_extern (BP_SYM (_dl_sysdep_start))
  42
  43 /* This function is used to unload the cache file if necessary.  */
  44 extern void _dl_unload_cache (void);
  45
  46 extern int __libc_multiple_libcs;       /* Defined in init-first.c.  */
  47
  48 extern int __libc_argc;
  49 extern char **__libc_argv;
  50
  51 extern char **__environ;
  52
  53 extern int _dl_lazy;                    /* Do we do lazy relocations?  */
  54
  55 /* Undefine the following for debugging.  */
  56 /* #define SCOPE_DEBUG 1 */
  57 #ifdef SCOPE_DEBUG
  58 static void show_scope (struct link_map *new);
  59 #endif
  60
  61 /* During the program run we must not modify the global data of
  62    loaded shared object simultanously in two threads.  Therefore we
  63    protect `_dl_open' and `_dl_close' in dl-close.c.
  64
  65    This must be a recursive lock since the initializer function of
  66    the loaded object might as well require a call to this function.
  67    At this time it is not anymore a problem to modify the tables.  */
  68 __libc_lock_define (extern, _dl_load_lock)
  69
  70 extern size_t _dl_platformlen;
  71
  72 /* We must be carefull not to leave us in an inconsistent state.  Thus we
  73    catch any error and re-raise it after cleaning up.  */
  74
  75 struct dl_open_args
  76 {
  77   const char *file;
  78   int mode;
  79   const void *caller;
  80   struct link_map *map;
  81 };
  82
  83
  84 static int
  85 add_to_global (struct link_map *new)
  86 {
  87   struct link_map **new_global;
  88   unsigned int to_add = 0;
  89   unsigned int cnt;
  90
  91   /* Count the objects we have to put in the global scope.  */
  92   for (cnt = 0; cnt < new->l_searchlist.r_nlist; ++cnt)
  93     if (new->l_searchlist.r_list[cnt]->l_global == 0)
  94       ++to_add;
  95
  96   /* The symbols of the new objects and its dependencies are to be
  97      introduced into the global scope that will be used to resolve
  98      references from other dynamically-loaded objects.
  99
 100      The global scope is the searchlist in the main link map.  We
 101      extend this list if necessary.  There is one problem though:
 102      since this structure was allocated very early (before the libc
 103      is loaded) the memory it uses is allocated by the malloc()-stub
 104      in the ld.so.  When we come here these functions are not used
 105      anymore.  Instead the malloc() implementation of the libc is
 106      used.  But this means the block from the main map cannot be used
 107      in an realloc() call.  Therefore we allocate a completely new
 108      array the first time we have to add something to the locale scope.  */
 109
 110   if (_dl_global_scope_alloc == 0)
 111     {
 112       /* This is the first dynamic object given global scope.  */
 113       _dl_global_scope_alloc = _dl_main_searchlist->r_nlist + to_add + 8;
 114       new_global = (struct link_map **)
 115         malloc (_dl_global_scope_alloc * sizeof (struct link_map *));
 116       if (new_global == NULL)
 117         {
 118           _dl_global_scope_alloc = 0;
 119         nomem:
 120           _dl_signal_error (ENOMEM, new->l_libname->name,
 121                             N_("cannot extend global scope"));
 122           return 1;
 123         }
 124
 125       /* Copy over the old entries.  */
 126       memcpy (new_global, _dl_main_searchlist->r_list,
 127               (_dl_main_searchlist->r_nlist * sizeof (struct link_map *)));
 128
 129       _dl_main_searchlist->r_list = new_global;
 130     }
 131   else if (_dl_main_searchlist->r_nlist + to_add > _dl_global_scope_alloc)
 132     {
 133       /* We have to extend the existing array of link maps in the
 134          main map.  */
 135       new_global = (struct link_map **)
 136         realloc (_dl_main_searchlist->r_list,
 137                  ((_dl_global_scope_alloc + to_add + 8)
 138                   * sizeof (struct link_map *)));
 139       if (new_global == NULL)
 140         goto nomem;
 141
 142       _dl_global_scope_alloc += to_add + 8;
 143       _dl_main_searchlist->r_list = new_global;
 144     }
 145
 146   /* Now add the new entries.  */
 147   for (cnt = 0; cnt < new->l_searchlist.r_nlist; ++cnt)
 148     {
 149       struct link_map *map = new->l_searchlist.r_list[cnt];
 150
 151       if (map->l_global == 0)
 152         {
 153           map->l_global = 1;
 154           _dl_main_searchlist->r_list[_dl_main_searchlist->r_nlist] = map;
 155           ++_dl_main_searchlist->r_nlist;
 156         }
 157     }
 158
 159   /* XXX Do we have to add something to r_dupsearchlist???  --drepper */
 160   return 0;
 161 }
 162
 163
 164 static void
 165 dl_open_worker (void *a)
 166 {
 167   struct dl_open_args *args = a;
 168   const char *file = args->file;
 169   int mode = args->mode;
 170   struct link_map *new, *l;
 171   const char *dst;
 172   int lazy;
 173   unsigned int i;
 174
 175   /* Maybe we have to expand a DST.  */
 176   dst = strchr (file, '$');
 177   if (dst != NULL)
 178     {
 179       const void *caller = args->caller;
 180       size_t len = strlen (file);
 181       size_t required;
 182       struct link_map *call_map;
 183       char *new_file;
 184
 185       /* DSTs must not appear in SUID/SGID programs.  */
 186       if (__libc_enable_secure)
 187         /* This is an error.  */
 188         _dl_signal_error (0, "dlopen",
 189                           N_("DST not allowed in SUID/SGID programs"));
 190
 191       /* We have to find out from which object the caller is calling.
 192          Find the highest-addressed object that ADDRESS is not below.  */
 193       call_map = NULL;
 194       for (l = _dl_loaded; l; l = l->l_next)
 195         if (l->l_addr != 0 /* Make sure we do not currently set this map up
 196                               in this moment.  */
 197             && caller >= (const void *) l->l_map_start
 198             && caller < (const void *) l->l_map_end)
 199           {
 200             /* There must be exactly one DSO for the range of the virtual
 201                memory.  Otherwise something is really broken.  */
 202             call_map = l;
 203             break;
 204           }
 205
 206       if (call_map == NULL)
 207         /* In this case we assume this is the main application.  */
 208         call_map = _dl_loaded;
 209
 210       /* Determine how much space we need.  We have to allocate the
 211          memory locally.  */
 212       required = DL_DST_REQUIRED (call_map, file, len, _dl_dst_count (dst, 0));
 213
 214       /* Get space for the new file name.  */
 215       new_file = (char *) alloca (required + 1);
 216
 217       /* Generate the new file name.  */
 218       DL_DST_SUBSTITUTE (call_map, file, new_file, 0);
 219
 220       /* If the substitution failed don't try to load.  */
 221       if (*new_file == '\0')
 222         _dl_signal_error (0, "dlopen",
 223                           N_("empty dynamic string token substitution"));
 224
 225       /* Now we have a new file name.  */
 226       file = new_file;
 227     }
 228
 229   /* Load the named object.  */
 230   args->map = new = _dl_map_object (NULL, file, 0, lt_loaded, 0,
 231                                     mode);
 232
 233   /* If the pointer returned is NULL this means the RTLD_NOLOAD flag is
 234      set and the object is not already loaded.  */
 235   if (new == NULL)
 236     {
 237       assert (mode & RTLD_NOLOAD);
 238       return;
 239     }
 240
 241   /* It was already open.  */
 242   if (new->l_searchlist.r_list != NULL)
 243     {
 244       /* Let the user know about the opencount.  */
 245       if (__builtin_expect (_dl_debug_mask & DL_DEBUG_FILES, 0))
 246         _dl_debug_printf ("opening file=%s; opencount == %u\n\n",
 247                           new->l_name, new->l_opencount);
 248
 249       /* If the user requested the object to be in the global namespace
 250          but it is not so far, add it now.  */
 251       if ((mode & RTLD_GLOBAL) && new->l_global == 0)
 252         (void) add_to_global (new);
 253
 254       /* Increment just the reference counter of the object.  */
 255       ++new->l_opencount;
 256
 257       return;
 258     }
 259
 260   /* Load that object's dependencies.  */
 261   _dl_map_object_deps (new, NULL, 0, 0);
 262
 263   /* So far, so good.  Now check the versions.  */
 264   for (i = 0; i < new->l_searchlist.r_nlist; ++i)
 265     if (new->l_searchlist.r_list[i]->l_versions == NULL)
 266       (void) _dl_check_map_versions (new->l_searchlist.r_list[i], 0, 0);
 267
 268 #ifdef SCOPE_DEBUG
 269   show_scope (new);
 270 #endif
 271
 272   /* Only do lazy relocation if `LD_BIND_NOW' is not set.  */
 273   lazy = (mode & RTLD_BINDING_MASK) == RTLD_LAZY && _dl_lazy;
 274
 275   /* Relocate the objects loaded.  We do this in reverse order so that copy
 276      relocs of earlier objects overwrite the data written by later objects.  */
 277
 278   l = new;
 279   while (l->l_next)
 280     l = l->l_next;
 281   while (1)
 282     {
 283       if (! l->l_relocated)
 284         {
 285 #ifdef SHARED
 286           if (_dl_profile != NULL)
 287             {
 288               /* If this here is the shared object which we want to profile
 289                  make sure the profile is started.  We can find out whether
 290                  this is necessary or not by observing the `_dl_profile_map'
 291                  variable.  If was NULL but is not NULL afterwars we must
 292                  start the profiling.  */
 293               struct link_map *old_profile_map = _dl_profile_map;
 294
 295               _dl_relocate_object (l, l->l_scope, 1, 1);
 296
 297               if (old_profile_map == NULL && _dl_profile_map != NULL)
 298                 /* We must prepare the profiling.  */
 299                 _dl_start_profile (_dl_profile_map, _dl_profile_output);
 300             }
 301           else
 302 #endif
 303             _dl_relocate_object (l, l->l_scope, lazy, 0);
 304         }
 305
 306       if (l == new)
 307         break;
 308       l = l->l_prev;
 309     }
 310
 311   /* Increment the open count for all dependencies.  */
 312   for (i = 0; i < new->l_searchlist.r_nlist; ++i)
 313     ++new->l_searchlist.r_list[i]->l_opencount;
 314
 315   /* Run the initializer functions of new objects.  */
 316   _dl_init (new, __libc_argc, __libc_argv, __environ);
 317
 318   /* Now we can make the new map available in the global scope.  */
 319   if (mode & RTLD_GLOBAL)
 320     /* Move the object in the global namespace.  */
 321     if (add_to_global (new) != 0)
 322       /* It failed.  */
 323       return;
 324
 325   /* Mark the object as not deletable if the RTLD_NODELETE flags was
 326      passed.  */
 327   if (__builtin_expect (mode & RTLD_NODELETE, 0))
 328     new->l_flags_1 |= DF_1_NODELETE;
 329
 330   if (_dl_sysdep_start == NULL)
 331     /* We must be the static _dl_open in libc.a.  A static program that
 332        has loaded a dynamic object now has competition.  */
 333     __libc_multiple_libcs = 1;
 334
 335   /* Let the user know about the opencount.  */
 336   if (__builtin_expect (_dl_debug_mask & DL_DEBUG_FILES, 0))
 337     _dl_debug_printf ("opening file=%s; opencount == %u\n\n",
 338                       new->l_name, new->l_opencount);
 339 }
 340
 341
 342 void *
 343 internal_function
 344 _dl_open (const char *file, int mode, const void *caller)
 345 {
 346   struct dl_open_args args;
 347   const char *objname;
 348   const char *errstring;
 349   int errcode;
 350
 351   if ((mode & RTLD_BINDING_MASK) == 0)
 352     /* One of the flags must be set.  */
 353     _dl_signal_error (EINVAL, file, N_("invalid mode for dlopen()"));
 354
 355   /* Make sure we are alone.  */
 356   __libc_lock_lock (_dl_load_lock);
 357
 358   args.file = file;
 359   args.mode = mode;
 360   args.caller = caller;
 361   args.map = NULL;
 362   errcode = _dl_catch_error (&objname, &errstring, dl_open_worker, &args);
 363
 364 #ifndef MAP_COPY
 365   /* We must munmap() the cache file.  */
 366   _dl_unload_cache ();
 367 #endif
 368
 369   /* Release the lock.  */
 370   __libc_lock_unlock (_dl_load_lock);
 371
 372   if (errstring)
 373     {
 374       /* Some error occurred during loading.  */
 375       char *local_errstring;
 376       size_t len_errstring;
 377
 378       /* Remove the object from memory.  It may be in an inconsistent
 379          state if relocation failed, for example.  */
 380       if (args.map)
 381         {
 382           unsigned int i;
 383
 384           /* Increment open counters for all objects since this has
 385              not happened yet.  */
 386           for (i = 0; i < args.map->l_searchlist.r_nlist; ++i)
 387             ++args.map->l_searchlist.r_list[i]->l_opencount;
 388
 389           _dl_close (args.map);
 390         }
 391
 392       /* Make a local copy of the error string so that we can release the
 393          memory allocated for it.  */
 394       len_errstring = strlen (errstring) + 1;
 395       if (objname == errstring + len_errstring)
 396         {
 397           size_t total_len = len_errstring + strlen (objname) + 1;
 398           local_errstring = alloca (total_len);
 399           memcpy (local_errstring, errstring, total_len);
 400           objname = local_errstring + len_errstring;
 401         }
 402       else
 403         {
 404           local_errstring = alloca (len_errstring);
 405           memcpy (local_errstring, errstring, len_errstring);
 406         }
 407
 408       if (errstring != _dl_out_of_memory)
 409         free ((char *) errstring);
 410
 411       /* Reraise the error.  */
 412       _dl_signal_error (errcode, objname, local_errstring);
 413     }
 414
 415 #ifndef SHARED
 416   DL_STATIC_INIT (args.map);
 417 #endif
 418
 419   return args.map;
 420 }
 421
 422
 423 #ifdef SCOPE_DEBUG
 424 #include <unistd.h>
 425
 426 static void
 427 show_scope (struct link_map *new)
 428 {
 429   int scope_cnt;
 430
 431   for (scope_cnt = 0; new->l_scope[scope_cnt] != NULL; ++scope_cnt)
 432     {
 433       char numbuf[2];
 434       unsigned int cnt;
 435
 436       numbuf[0] = '0' + scope_cnt;
 437       numbuf[1] = '\0';
 438       _dl_printf ("scope %s:", numbuf);
 439
 440       for (cnt = 0; cnt < new->l_scope[scope_cnt]->r_nlist; ++cnt)
 441         if (*new->l_scope[scope_cnt]->r_list[cnt]->l_name)
 442           _dl_printf (" %s", new->l_scope[scope_cnt]->r_list[cnt]->l_name)
 443         else
 444           _dl_printf (" <main>", NULL);
 445
 446       _dl_printf ("\n", NULL);
 447     }
 448 }
 449 #endif