elf/dl-open.c

   1 /* Load a shared object at runtime, relocate it, and run its initializer.
   2    Copyright (C) 1996-2001, 2002 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <dlfcn.h>
  22 #include <errno.h>
  23 #include <libintl.h>
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <sys/mman.h>           /* Check whether MAP_COPY is defined.  */
  29 #include <sys/param.h>
  30 #include <bits/libc-lock.h>
  31 #include <ldsodefs.h>
  32 #include <bp-sym.h>
  33
  34 #include <dl-dst.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 extern int __libc_multiple_libcs;       /* Defined in init-first.c.  */
  44
  45 extern int __libc_argc attribute_hidden;
  46 extern char **__libc_argv attribute_hidden;
  47
  48 extern char **__environ;
  49
  50 /* Undefine the following for debugging.  */
  51 /* #define SCOPE_DEBUG 1 */
  52 #ifdef SCOPE_DEBUG
  53 static void show_scope (struct link_map *new);
  54 #endif
  55
  56 /* We must be carefull not to leave us in an inconsistent state.  Thus we
  57    catch any error and re-raise it after cleaning up.  */
  58
  59 struct dl_open_args
  60 {
  61   const char *file;
  62   int mode;
  63   const void *caller;
  64   struct link_map *map;
  65 };
  66
  67
  68 static int
  69 add_to_global (struct link_map *new)
  70 {
  71   struct link_map **new_global;
  72   unsigned int to_add = 0;
  73   unsigned int cnt;
  74
  75   /* Count the objects we have to put in the global scope.  */
  76   for (cnt = 0; cnt < new->l_searchlist.r_nlist; ++cnt)
  77     if (new->l_searchlist.r_list[cnt]->l_global == 0)
  78       ++to_add;
  79
  80   /* The symbols of the new objects and its dependencies are to be
  81      introduced into the global scope that will be used to resolve
  82      references from other dynamically-loaded objects.
  83
  84      The global scope is the searchlist in the main link map.  We
  85      extend this list if necessary.  There is one problem though:
  86      since this structure was allocated very early (before the libc
  87      is loaded) the memory it uses is allocated by the malloc()-stub
  88      in the ld.so.  When we come here these functions are not used
  89      anymore.  Instead the malloc() implementation of the libc is
  90      used.  But this means the block from the main map cannot be used
  91      in an realloc() call.  Therefore we allocate a completely new
  92      array the first time we have to add something to the locale scope.  */
  93
  94   if (GL(dl_global_scope_alloc) == 0)
  95     {
  96       /* This is the first dynamic object given global scope.  */
  97       GL(dl_global_scope_alloc) = GL(dl_main_searchlist)->r_nlist + to_add + 8;
  98       new_global = (struct link_map **)
  99         malloc (GL(dl_global_scope_alloc) * sizeof (struct link_map *));
 100       if (new_global == NULL)
 101         {
 102           GL(dl_global_scope_alloc) = 0;
 103         nomem:
 104           _dl_signal_error (ENOMEM, new->l_libname->name, NULL,
 105                             N_("cannot extend global scope"));
 106           return 1;
 107         }
 108
 109       /* Copy over the old entries.  */
 110       memcpy (new_global, GL(dl_main_searchlist)->r_list,
 111               (GL(dl_main_searchlist)->r_nlist * sizeof (struct link_map *)));
 112
 113       GL(dl_main_searchlist)->r_list = new_global;
 114     }
 115   else if (GL(dl_main_searchlist)->r_nlist + to_add
 116            > GL(dl_global_scope_alloc))
 117     {
 118       /* We have to extend the existing array of link maps in the
 119          main map.  */
 120       new_global = (struct link_map **)
 121         realloc (GL(dl_main_searchlist)->r_list,
 122                  ((GL(dl_global_scope_alloc) + to_add + 8)
 123                   * sizeof (struct link_map *)));
 124       if (new_global == NULL)
 125         goto nomem;
 126
 127       GL(dl_global_scope_alloc) += to_add + 8;
 128       GL(dl_main_searchlist)->r_list = new_global;
 129     }
 130
 131   /* Now add the new entries.  */
 132   for (cnt = 0; cnt < new->l_searchlist.r_nlist; ++cnt)
 133     {
 134       struct link_map *map = new->l_searchlist.r_list[cnt];
 135
 136       if (map->l_global == 0)
 137         {
 138           map->l_global = 1;
 139           GL(dl_main_searchlist)->r_list[GL(dl_main_searchlist)->r_nlist]
 140             = map;
 141           ++GL(dl_main_searchlist)->r_nlist;
 142         }
 143     }
 144
 145   return 0;
 146 }
 147
 148
 149 static void
 150 dl_open_worker (void *a)
 151 {
 152   struct dl_open_args *args = a;
 153   const char *file = args->file;
 154   int mode = args->mode;
 155   struct link_map *new, *l;
 156   const char *dst;
 157   int lazy;
 158   unsigned int i;
 159 #ifdef USE_TLS
 160   bool any_tls;
 161 #endif
 162
 163   /* Maybe we have to expand a DST.  */
 164   dst = strchr (file, '$');
 165   if (__builtin_expect (dst != NULL, 0))
 166     {
 167       const void *caller = args->caller;
 168       size_t len = strlen (file);
 169       size_t required;
 170       struct link_map *call_map;
 171       char *new_file;
 172
 173       /* DSTs must not appear in SUID/SGID programs.  */
 174       if (__libc_enable_secure)
 175         /* This is an error.  */
 176         _dl_signal_error (0, "dlopen", NULL,
 177                           N_("DST not allowed in SUID/SGID programs"));
 178
 179       /* We have to find out from which object the caller is calling.  */
 180       call_map = NULL;
 181       for (l = GL(dl_loaded); l; l = l->l_next)
 182         if (caller >= (const void *) l->l_map_start
 183             && caller < (const void *) l->l_map_end)
 184           {
 185             /* There must be exactly one DSO for the range of the virtual
 186                memory.  Otherwise something is really broken.  */
 187             call_map = l;
 188             break;
 189           }
 190
 191       if (call_map == NULL)
 192         /* In this case we assume this is the main application.  */
 193         call_map = GL(dl_loaded);
 194
 195       /* Determine how much space we need.  We have to allocate the
 196          memory locally.  */
 197       required = DL_DST_REQUIRED (call_map, file, len, _dl_dst_count (dst, 0));
 198
 199       /* Get space for the new file name.  */
 200       new_file = (char *) alloca (required + 1);
 201
 202       /* Generate the new file name.  */
 203       _dl_dst_substitute (call_map, file, new_file, 0);
 204
 205       /* If the substitution failed don't try to load.  */
 206       if (*new_file == '\0')
 207         _dl_signal_error (0, "dlopen", NULL,
 208                           N_("empty dynamic string token substitution"));
 209
 210       /* Now we have a new file name.  */
 211       file = new_file;
 212     }
 213
 214   /* Load the named object.  */
 215   args->map = new = _dl_map_object (NULL, file, 0, lt_loaded, 0, mode);
 216
 217   /* If the pointer returned is NULL this means the RTLD_NOLOAD flag is
 218      set and the object is not already loaded.  */
 219   if (new == NULL)
 220     {
 221       assert (mode & RTLD_NOLOAD);
 222       return;
 223     }
 224
 225   if (__builtin_expect (mode & __RTLD_SPROF, 0))
 226     /* This happens only if we load a DSO for 'sprof'.  */
 227     return;
 228
 229   /* It was already open.  */
 230   if (new->l_searchlist.r_list != NULL)
 231     {
 232       /* Let the user know about the opencount.  */
 233       if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_FILES, 0))
 234         _dl_debug_printf ("opening file=%s; opencount == %u\n\n",
 235                           new->l_name, new->l_opencount);
 236
 237       /* If the user requested the object to be in the global namespace
 238          but it is not so far, add it now.  */
 239       if ((mode & RTLD_GLOBAL) && new->l_global == 0)
 240         (void) add_to_global (new);
 241
 242       /* Increment just the reference counter of the object.  */
 243       ++new->l_opencount;
 244
 245       return;
 246     }
 247
 248   /* Load that object's dependencies.  */
 249   _dl_map_object_deps (new, NULL, 0, 0, mode & __RTLD_DLOPEN);
 250
 251   /* So far, so good.  Now check the versions.  */
 252   for (i = 0; i < new->l_searchlist.r_nlist; ++i)
 253     if (new->l_searchlist.r_list[i]->l_versions == NULL)
 254       (void) _dl_check_map_versions (new->l_searchlist.r_list[i], 0, 0);
 255
 256 #ifdef SCOPE_DEBUG
 257   show_scope (new);
 258 #endif
 259
 260   /* Only do lazy relocation if `LD_BIND_NOW' is not set.  */
 261   lazy = (mode & RTLD_BINDING_MASK) == RTLD_LAZY && GL(dl_lazy);
 262
 263   /* Relocate the objects loaded.  We do this in reverse order so that copy
 264      relocs of earlier objects overwrite the data written by later objects.  */
 265
 266   l = new;
 267   while (l->l_next)
 268     l = l->l_next;
 269   while (1)
 270     {
 271       if (! l->l_relocated)
 272         {
 273 #ifdef SHARED
 274           if (GL(dl_profile) != NULL)
 275             {
 276               /* If this here is the shared object which we want to profile
 277                  make sure the profile is started.  We can find out whether
 278                  this is necessary or not by observing the `_dl_profile_map'
 279                  variable.  If was NULL but is not NULL afterwars we must
 280                  start the profiling.  */
 281               struct link_map *old_profile_map = GL(dl_profile_map);
 282
 283               _dl_relocate_object (l, l->l_scope, 1, 1);
 284
 285               if (old_profile_map == NULL && GL(dl_profile_map) != NULL)
 286                 /* We must prepare the profiling.  */
 287                 _dl_start_profile (GL(dl_profile_map), GL(dl_profile_output));
 288             }
 289           else
 290 #endif
 291             _dl_relocate_object (l, l->l_scope, lazy, 0);
 292         }
 293
 294       if (l == new)
 295         break;
 296       l = l->l_prev;
 297     }
 298
 299 #ifdef USE_TLS
 300   /* We normally don't bump the TLS generation counter.  There must be
 301      actually a need to do this.  */
 302   any_tls = false;
 303 #endif
 304
 305   /* Increment the open count for all dependencies.  If the file is
 306      not loaded as a dependency here add the search list of the newly
 307      loaded object to the scope.  */
 308   for (i = 0; i < new->l_searchlist.r_nlist; ++i)
 309     if (++new->l_searchlist.r_list[i]->l_opencount > 1
 310         && new->l_searchlist.r_list[i]->l_type == lt_loaded)
 311       {
 312         struct link_map *imap = new->l_searchlist.r_list[i];
 313         struct r_scope_elem **runp = imap->l_scope;
 314         size_t cnt = 0;
 315
 316         while (*runp != NULL)
 317           {
 318             /* This can happen if imap was just loaded, but during
 319                relocation had l_opencount bumped because of relocation
 320                dependency.  Avoid duplicates in l_scope.  */
 321             if (__builtin_expect (*runp == &new->l_searchlist, 0))
 322               break;
 323
 324             ++cnt;
 325             ++runp;
 326           }
 327
 328         if (*runp != NULL)
 329           /* Avoid duplicates.  */
 330           continue;
 331
 332         if (__builtin_expect (cnt + 1 >= imap->l_scope_max, 0))
 333           {
 334             /* The 'r_scope' array is too small.  Allocate a new one
 335                dynamically.  */
 336             struct r_scope_elem **newp;
 337             size_t new_size = imap->l_scope_max * 2;
 338
 339             if (imap->l_scope == imap->l_scope_mem)
 340               {
 341                 newp = (struct r_scope_elem **)
 342                   malloc (new_size * sizeof (struct r_scope_elem *));
 343                 if (newp == NULL)
 344                   _dl_signal_error (ENOMEM, "dlopen", NULL,
 345                                     N_("cannot create scope list"));
 346                 imap->l_scope = memcpy (newp, imap->l_scope,
 347                                         cnt * sizeof (imap->l_scope[0]));
 348               }
 349             else
 350               {
 351                 newp = (struct r_scope_elem **)
 352                   realloc (imap->l_scope,
 353                            new_size * sizeof (struct r_scope_elem *));
 354                 if (newp == NULL)
 355                   _dl_signal_error (ENOMEM, "dlopen", NULL,
 356                                     N_("cannot create scope list"));
 357                 imap->l_scope = newp;
 358               }
 359
 360             imap->l_scope_max = new_size;
 361           }
 362
 363         imap->l_scope[cnt++] = &new->l_searchlist;
 364         imap->l_scope[cnt] = NULL;
 365       }
 366 #if USE_TLS
 367     else if (new->l_searchlist.r_list[i]->l_opencount == 1
 368              /* Only if the module defines thread local data.  */
 369              && __builtin_expect (new->l_searchlist.r_list[i]->l_tls_blocksize
 370                                   > 0, 0))
 371       {
 372         /* Now that we know the object is loaded successfully add
 373            modules containing TLS data to the dtv info table.  We
 374            might have to increase its size.  */
 375         struct dtv_slotinfo_list *listp;
 376         struct dtv_slotinfo_list *prevp;
 377         size_t idx = new->l_searchlist.r_list[i]->l_tls_modid;
 378
 379         assert (new->l_searchlist.r_list[i]->l_type == lt_loaded);
 380
 381         /* Find the place in the stv slotinfo list.  */
 382         listp = GL(dl_tls_dtv_slotinfo_list);
 383         prevp = NULL;           /* Needed to shut up gcc.  */
 384         do
 385           {
 386             /* Does it fit in the array of this list element?  */
 387             if (idx <= listp->len)
 388               break;
 389             prevp = listp;
 390           }
 391         while ((listp = listp->next) != NULL);
 392
 393         if (listp == NULL)
 394           {
 395             /* When we come here it means we have to add a new element
 396                to the slotinfo list.  And the new module must be in
 397                the first slot.  */
 398             assert (idx == 0);
 399
 400             listp = prevp->next = (struct dtv_slotinfo_list *)
 401               malloc (sizeof (struct dtv_slotinfo_list)
 402                       + TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
 403             if (listp == NULL)
 404               {
 405                 /* We ran out of memory.  We will simply fail this
 406                    call but don't undo anything we did so far.  The
 407                    application will crash or be terminated anyway very
 408                    soon.  */
 409
 410                 /* We have to do this since some entries in the dtv
 411                    slotinfo array might already point to this
 412                    generation.  */
 413                 ++GL(dl_tls_generation);
 414
 415                 _dl_signal_error (ENOMEM, "dlopen", NULL,
 416                                   N_("cannot create TLS data structures"));
 417               }
 418
 419             listp->len = TLS_SLOTINFO_SURPLUS;
 420             listp->next = NULL;
 421             memset (listp->slotinfo, '\0',
 422                     TLS_SLOTINFO_SURPLUS * sizeof (struct dtv_slotinfo));
 423           }
 424
 425         /* Add the information into the slotinfo data structure.  */
 426         listp->slotinfo[idx].map = new->l_searchlist.r_list[i];
 427         listp->slotinfo[idx].gen = GL(dl_tls_generation) + 1;
 428
 429         /* We have to bump the generation counter.  */
 430         any_tls = true;
 431       }
 432
 433   /* Bump the generation number if necessary.  */
 434   if (any_tls)
 435     if (__builtin_expect (++GL(dl_tls_generation) == 0, 0))
 436       __libc_fatal (gettext ("TLS generation counter wrapped!  Please send report with the 'glibcbug' script."));
 437 #endif
 438
 439   /* Run the initializer functions of new objects.  */
 440   _dl_init (new, __libc_argc, __libc_argv, __environ);
 441
 442   /* Now we can make the new map available in the global scope.  */
 443   if (mode & RTLD_GLOBAL)
 444     /* Move the object in the global namespace.  */
 445     if (add_to_global (new) != 0)
 446       /* It failed.  */
 447       return;
 448
 449   /* Mark the object as not deletable if the RTLD_NODELETE flags was
 450      passed.  */
 451   if (__builtin_expect (mode & RTLD_NODELETE, 0))
 452     new->l_flags_1 |= DF_1_NODELETE;
 453
 454 #ifndef SHARED
 455   /* We must be the static _dl_open in libc.a.  A static program that
 456      has loaded a dynamic object now has competition.  */
 457   __libc_multiple_libcs = 1;
 458 #endif
 459
 460   /* Let the user know about the opencount.  */
 461   if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_FILES, 0))
 462     _dl_debug_printf ("opening file=%s; opencount == %u\n\n",
 463                       new->l_name, new->l_opencount);
 464 }
 465
 466
 467 void *
 468 internal_function
 469 _dl_open (const char *file, int mode, const void *caller)
 470 {
 471   struct dl_open_args args;
 472   const char *objname;
 473   const char *errstring;
 474   int errcode;
 475
 476   if ((mode & RTLD_BINDING_MASK) == 0)
 477     /* One of the flags must be set.  */
 478     _dl_signal_error (EINVAL, file, NULL, N_("invalid mode for dlopen()"));
 479
 480   /* Make sure we are alone.  */
 481   __libc_lock_lock_recursive (GL(dl_load_lock));
 482
 483   args.file = file;
 484   args.mode = mode;
 485   args.caller = caller;
 486   args.map = NULL;
 487   errcode = _dl_catch_error (&objname, &errstring, dl_open_worker, &args);
 488
 489 #ifndef MAP_COPY
 490   /* We must munmap() the cache file.  */
 491   _dl_unload_cache ();
 492 #endif
 493
 494   /* Release the lock.  */
 495   __libc_lock_unlock_recursive (GL(dl_load_lock));
 496
 497   if (__builtin_expect (errstring != NULL, 0))
 498     {
 499       /* Some error occurred during loading.  */
 500       char *local_errstring;
 501       size_t len_errstring;
 502
 503       /* Remove the object from memory.  It may be in an inconsistent
 504          state if relocation failed, for example.  */
 505       if (args.map)
 506         {
 507           unsigned int i;
 508
 509           /* Increment open counters for all objects since this
 510              sometimes has not happened yet.  */
 511           if (args.map->l_searchlist.r_list[0]->l_opencount == 0)
 512             for (i = 0; i < args.map->l_searchlist.r_nlist; ++i)
 513               ++args.map->l_searchlist.r_list[i]->l_opencount;
 514
 515 #ifdef USE_TLS
 516           /* Maybe some of the modules which were loaded uses TLS.
 517              Since it will be removed in the folowing _dl_close call
 518              we have to mark the dtv array as having gaps to fill
 519              the holes.  This is a pessimistic assumption which won't
 520              hurt if not true.  */
 521           GL(dl_tls_dtv_gaps) = true;
 522 #endif
 523
 524           _dl_close (args.map);
 525         }
 526
 527       /* Make a local copy of the error string so that we can release the
 528          memory allocated for it.  */
 529       len_errstring = strlen (errstring) + 1;
 530       if (objname == errstring + len_errstring)
 531         {
 532           size_t total_len = len_errstring + strlen (objname) + 1;
 533           local_errstring = alloca (total_len);
 534           memcpy (local_errstring, errstring, total_len);
 535           objname = local_errstring + len_errstring;
 536         }
 537       else
 538         {
 539           local_errstring = alloca (len_errstring);
 540           memcpy (local_errstring, errstring, len_errstring);
 541         }
 542
 543       if (errstring != _dl_out_of_memory)
 544         free ((char *) errstring);
 545
 546       /* Reraise the error.  */
 547       _dl_signal_error (errcode, objname, NULL, local_errstring);
 548     }
 549
 550 #ifndef SHARED
 551   DL_STATIC_INIT (args.map);
 552 #endif
 553
 554   return args.map;
 555 }
 556
 557
 558 #ifdef SCOPE_DEBUG
 559 #include <unistd.h>
 560
 561 static void
 562 show_scope (struct link_map *new)
 563 {
 564   int scope_cnt;
 565
 566   for (scope_cnt = 0; new->l_scope[scope_cnt] != NULL; ++scope_cnt)
 567     {
 568       char numbuf[2];
 569       unsigned int cnt;
 570
 571       numbuf[0] = '0' + scope_cnt;
 572       numbuf[1] = '\0';
 573       _dl_printf ("scope %s:", numbuf);
 574
 575       for (cnt = 0; cnt < new->l_scope[scope_cnt]->r_nlist; ++cnt)
 576         if (*new->l_scope[scope_cnt]->r_list[cnt]->l_name)
 577           _dl_printf (" %s", new->l_scope[scope_cnt]->r_list[cnt]->l_name);
 578         else
 579           _dl_printf (" <main>");
 580
 581       _dl_printf ("\n");
 582     }
 583 }
 584 #endif