elf/dl-version.c

   1 /* Handle symbol and library versioning.
   2    Copyright (C) 1997-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <elf.h>
  21 #include <errno.h>
  22 #include <libintl.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <ldsodefs.h>
  26 #include <_itoa.h>
  27
  28 #include <assert.h>
  29
  30
  31 #define make_string(string, rest...) \
  32   ({                                                                          \
  33     const char *all[] = { string, ## rest };                                  \
  34     size_t len, cnt;                                                          \
  35     char *result, *cp;                                                        \
  36                                                                               \
  37     len = 1;                                                                  \
  38     for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)                \
  39       len += strlen (all[cnt]);                                               \
  40                                                                               \
  41     cp = result = alloca (len);                                               \
  42     for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)                \
  43       cp = __stpcpy (cp, all[cnt]);                                           \
  44                                                                               \
  45     result;                                                                   \
  46   })
  47
  48
  49 static inline struct link_map *
  50 __attribute ((always_inline))
  51 find_needed (const char *name, struct link_map *map)
  52 {
  53   struct link_map *tmap;
  54   unsigned int n;
  55
  56   for (tmap = GL(dl_ns)[map->l_ns]._ns_loaded; tmap != NULL;
  57        tmap = tmap->l_next)
  58     if (_dl_name_match_p (name, tmap))
  59       return tmap;
  60
  61   /* The required object is not in the global scope, look to see if it is
  62      a dependency of the current object.  */
  63   for (n = 0; n < map->l_searchlist.r_nlist; n++)
  64     if (_dl_name_match_p (name, map->l_searchlist.r_list[n]))
  65       return map->l_searchlist.r_list[n];
  66
  67   /* Should never happen.  */
  68   return NULL;
  69 }
  70
  71
  72 static int
  73 internal_function
  74 match_symbol (const char *name, Lmid_t ns, ElfW(Word) hash, const char *string,
  75               struct link_map *map, int verbose, int weak)
  76 {
  77   const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
  78   ElfW(Addr) def_offset;
  79   ElfW(Verdef) *def;
  80   /* Initialize to make the compiler happy.  */
  81   const char *errstring = NULL;
  82   int result = 0;
  83
  84   /* Display information about what we are doing while debugging.  */
  85   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_VERSIONS))
  86     _dl_debug_printf ("\
  87 checking for version `%s' in file %s [%lu] required by file %s [%lu]\n",
  88                       string, DSO_FILENAME (map->l_name),
  89                       map->l_ns, name, ns);
  90
  91   if (__glibc_unlikely (map->l_info[VERSYMIDX (DT_VERDEF)] == NULL))
  92     {
  93       /* The file has no symbol versioning.  I.e., the dependent
  94          object was linked against another version of this file.  We
  95          only print a message if verbose output is requested.  */
  96       if (verbose)
  97         {
  98           /* XXX We cannot translate the messages.  */
  99           errstring = make_string ("\
 100 no version information available (required by ", name, ")");
 101           goto call_cerror;
 102         }
 103       return 0;
 104     }
 105
 106   def_offset = map->l_info[VERSYMIDX (DT_VERDEF)]->d_un.d_ptr;
 107   assert (def_offset != 0);
 108
 109   def = (ElfW(Verdef) *) ((char *) map->l_addr + def_offset);
 110   while (1)
 111     {
 112       /* Currently the version number of the definition entry is 1.
 113          Make sure all we see is this version.  */
 114       if (__builtin_expect (def->vd_version, 1) != 1)
 115         {
 116           char buf[20];
 117           buf[sizeof (buf) - 1] = '\0';
 118           /* XXX We cannot translate the message.  */
 119           errstring = make_string ("unsupported version ",
 120                                    _itoa (def->vd_version,
 121                                           &buf[sizeof (buf) - 1], 10, 0),
 122                                    " of Verdef record");
 123           result = 1;
 124           goto call_cerror;
 125         }
 126
 127       /* Compare the hash values.  */
 128       if (hash == def->vd_hash)
 129         {
 130           ElfW(Verdaux) *aux = (ElfW(Verdaux) *) ((char *) def + def->vd_aux);
 131
 132           /* To be safe, compare the string as well.  */
 133           if (__builtin_expect (strcmp (string, strtab + aux->vda_name), 0)
 134               == 0)
 135             /* Bingo!  */
 136             return 0;
 137         }
 138
 139       /* If no more definitions we failed to find what we want.  */
 140       if (def->vd_next == 0)
 141         break;
 142
 143       /* Next definition.  */
 144       def = (ElfW(Verdef) *) ((char *) def + def->vd_next);
 145     }
 146
 147   /* Symbol not found.  If it was a weak reference it is not fatal.  */
 148   if (__glibc_likely (weak))
 149     {
 150       if (verbose)
 151         {
 152           /* XXX We cannot translate the message.  */
 153           errstring = make_string ("weak version `", string,
 154                                    "' not found (required by ", name, ")");
 155           goto call_cerror;
 156         }
 157       return 0;
 158     }
 159
 160   /* XXX We cannot translate the message.  */
 161   errstring = make_string ("version `", string, "' not found (required by ",
 162                            name, ")");
 163   result = 1;
 164  call_cerror:
 165   _dl_signal_cerror (0, DSO_FILENAME (map->l_name),
 166                      N_("version lookup error"), errstring);
 167   return result;
 168 }
 169
 170
 171 int
 172 internal_function
 173 _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
 174 {
 175   int result = 0;
 176   const char *strtab;
 177   /* Pointer to section with needed versions.  */
 178   ElfW(Dyn) *dyn;
 179   /* Pointer to dynamic section with definitions.  */
 180   ElfW(Dyn) *def;
 181   /* We need to find out which is the highest version index used
 182     in a dependecy.  */
 183   unsigned int ndx_high = 0;
 184   /* Initialize to make the compiler happy.  */
 185   const char *errstring = NULL;
 186   int errval = 0;
 187
 188   /* If we don't have a string table, we must be ok.  */
 189   if (map->l_info[DT_STRTAB] == NULL)
 190     return 0;
 191   strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
 192
 193   dyn = map->l_info[VERSYMIDX (DT_VERNEED)];
 194   def = map->l_info[VERSYMIDX (DT_VERDEF)];
 195
 196   if (dyn != NULL)
 197     {
 198       /* This file requires special versions from its dependencies.  */
 199       ElfW(Verneed) *ent = (ElfW(Verneed) *) (map->l_addr + dyn->d_un.d_ptr);
 200
 201       /* Currently the version number of the needed entry is 1.
 202          Make sure all we see is this version.  */
 203       if (__builtin_expect (ent->vn_version, 1) != 1)
 204         {
 205           char buf[20];
 206           buf[sizeof (buf) - 1] = '\0';
 207           /* XXX We cannot translate the message.  */
 208           errstring = make_string ("unsupported version ",
 209                                    _itoa (ent->vn_version,
 210                                           &buf[sizeof (buf) - 1], 10, 0),
 211                                    " of Verneed record\n");
 212         call_error:
 213           _dl_signal_error (errval, DSO_FILENAME (map->l_name),
 214                             NULL, errstring);
 215         }
 216
 217       while (1)
 218         {
 219           ElfW(Vernaux) *aux;
 220           struct link_map *needed = find_needed (strtab + ent->vn_file, map);
 221
 222           /* If NEEDED is NULL this means a dependency was not found
 223              and no stub entry was created.  This should never happen.  */
 224           assert (needed != NULL);
 225
 226           /* Make sure this is no stub we created because of a missing
 227              dependency.  */
 228           if (__builtin_expect (! trace_mode, 1)
 229               || ! __builtin_expect (needed->l_faked, 0))
 230             {
 231               /* NEEDED is the map for the file we need.  Now look for the
 232                  dependency symbols.  */
 233               aux = (ElfW(Vernaux) *) ((char *) ent + ent->vn_aux);
 234               while (1)
 235                 {
 236                   /* Match the symbol.  */
 237                   result |= match_symbol (DSO_FILENAME (map->l_name),
 238                                           map->l_ns, aux->vna_hash,
 239                                           strtab + aux->vna_name,
 240                                           needed->l_real, verbose,
 241                                           aux->vna_flags & VER_FLG_WEAK);
 242
 243                   /* Compare the version index.  */
 244                   if ((unsigned int) (aux->vna_other & 0x7fff) > ndx_high)
 245                     ndx_high = aux->vna_other & 0x7fff;
 246
 247                   if (aux->vna_next == 0)
 248                     /* No more symbols.  */
 249                     break;
 250
 251                   /* Next symbol.  */
 252                   aux = (ElfW(Vernaux) *) ((char *) aux + aux->vna_next);
 253                 }
 254             }
 255
 256           if (ent->vn_next == 0)
 257             /* No more dependencies.  */
 258             break;
 259
 260           /* Next dependency.  */
 261           ent = (ElfW(Verneed) *) ((char *) ent + ent->vn_next);
 262         }
 263     }
 264
 265   /* We also must store the names of the defined versions.  Determine
 266      the maximum index here as well.
 267
 268      XXX We could avoid the loop by just taking the number of definitions
 269      as an upper bound of new indeces.  */
 270   if (def != NULL)
 271     {
 272       ElfW(Verdef) *ent;
 273       ent = (ElfW(Verdef) *) (map->l_addr + def->d_un.d_ptr);
 274       while (1)
 275         {
 276           if ((unsigned int) (ent->vd_ndx & 0x7fff) > ndx_high)
 277             ndx_high = ent->vd_ndx & 0x7fff;
 278
 279           if (ent->vd_next == 0)
 280             /* No more definitions.  */
 281             break;
 282
 283           ent = (ElfW(Verdef) *) ((char *) ent + ent->vd_next);
 284         }
 285     }
 286
 287   if (ndx_high > 0)
 288     {
 289       /* Now we are ready to build the array with the version names
 290          which can be indexed by the version index in the VERSYM
 291          section.  */
 292       map->l_versions = (struct r_found_version *)
 293         calloc (ndx_high + 1, sizeof (*map->l_versions));
 294       if (__glibc_unlikely (map->l_versions == NULL))
 295         {
 296           errstring = N_("cannot allocate version reference table");
 297           errval = ENOMEM;
 298           goto call_error;
 299         }
 300
 301       /* Store the number of available symbols.  */
 302       map->l_nversions = ndx_high + 1;
 303
 304       /* Compute the pointer to the version symbols.  */
 305       map->l_versyms = (void *) D_PTR (map, l_info[VERSYMIDX (DT_VERSYM)]);
 306
 307       if (dyn != NULL)
 308         {
 309           ElfW(Verneed) *ent;
 310           ent = (ElfW(Verneed) *) (map->l_addr + dyn->d_un.d_ptr);
 311           while (1)
 312             {
 313               ElfW(Vernaux) *aux;
 314               aux = (ElfW(Vernaux) *) ((char *) ent + ent->vn_aux);
 315               while (1)
 316                 {
 317                   ElfW(Half) ndx = aux->vna_other & 0x7fff;
 318                   /* In trace mode, dependencies may be missing.  */
 319                   if (__glibc_likely (ndx < map->l_nversions))
 320                     {
 321                       map->l_versions[ndx].hash = aux->vna_hash;
 322                       map->l_versions[ndx].hidden = aux->vna_other & 0x8000;
 323                       map->l_versions[ndx].name = &strtab[aux->vna_name];
 324                       map->l_versions[ndx].filename = &strtab[ent->vn_file];
 325                     }
 326
 327                   if (aux->vna_next == 0)
 328                     /* No more symbols.  */
 329                     break;
 330
 331                   /* Advance to next symbol.  */
 332                   aux = (ElfW(Vernaux) *) ((char *) aux + aux->vna_next);
 333                 }
 334
 335               if (ent->vn_next == 0)
 336                 /* No more dependencies.  */
 337                 break;
 338
 339               /* Advance to next dependency.  */
 340               ent = (ElfW(Verneed) *) ((char *) ent + ent->vn_next);
 341             }
 342         }
 343
 344       /* And insert the defined versions.  */
 345       if (def != NULL)
 346         {
 347           ElfW(Verdef) *ent;
 348           ent = (ElfW(Verdef)  *) (map->l_addr + def->d_un.d_ptr);
 349           while (1)
 350             {
 351               ElfW(Verdaux) *aux;
 352               aux = (ElfW(Verdaux) *) ((char *) ent + ent->vd_aux);
 353
 354               if ((ent->vd_flags & VER_FLG_BASE) == 0)
 355                 {
 356                   /* The name of the base version should not be
 357                      available for matching a versioned symbol.  */
 358                   ElfW(Half) ndx = ent->vd_ndx & 0x7fff;
 359                   map->l_versions[ndx].hash = ent->vd_hash;
 360                   map->l_versions[ndx].name = &strtab[aux->vda_name];
 361                   map->l_versions[ndx].filename = NULL;
 362                 }
 363
 364               if (ent->vd_next == 0)
 365                 /* No more definitions.  */
 366                 break;
 367
 368               ent = (ElfW(Verdef) *) ((char *) ent + ent->vd_next);
 369             }
 370         }
 371     }
 372
 373   return result;
 374 }
 375
 376
 377 int
 378 internal_function
 379 _dl_check_all_versions (struct link_map *map, int verbose, int trace_mode)
 380 {
 381   struct link_map *l;
 382   int result = 0;
 383
 384   for (l = map; l != NULL; l = l->l_next)
 385     result |= (! l->l_faked
 386                && _dl_check_map_versions (l, verbose, trace_mode));
 387
 388   return result;
 389 }