elf/dl-lookup.c

   1 /* Look up a symbol in the loaded objects.
   2    Copyright (C) 1995, 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 <alloca.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23 #include <elf/ldsodefs.h>
  24 #include "dl-hash.h"
  25 #include <dl-machine.h>
  26
  27 #include <assert.h>
  28
  29 #define VERSTAG(tag)    (DT_NUM + DT_PROCNUM + DT_VERSIONTAGIDX (tag))
  30
  31 /* We need this string more than once.  */
  32 static const char undefined_msg[] = "undefined symbol: ";
  33
  34
  35 struct sym_val
  36   {
  37     const ElfW(Sym) *s;
  38     struct link_map *m;
  39   };
  40
  41
  42 #define make_string(string, rest...) \
  43   ({                                                                          \
  44     const char *all[] = { string, ## rest };                                  \
  45     size_t len, cnt;                                                          \
  46     char *result, *cp;                                                        \
  47                                                                               \
  48     len = 1;                                                                  \
  49     for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)                \
  50       len += strlen (all[cnt]);                                               \
  51                                                                               \
  52     cp = result = alloca (len);                                               \
  53     for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt)                \
  54       cp = __stpcpy (cp, all[cnt]);                                           \
  55                                                                               \
  56     result;                                                                   \
  57   })
  58
  59 /* Statistics function.  */
  60 unsigned long int _dl_num_relocations;
  61
  62
  63 /* We have two different situations when looking up a simple: with or
  64    without versioning.  gcc is not able to optimize a single function
  65    definition serving for both purposes so we define two functions.  */
  66 #define VERSIONED       0
  67 #include "do-lookup.h"
  68
  69 #define VERSIONED       1
  70 #include "do-lookup.h"
  71
  72
  73 /* Search loaded objects' symbol tables for a definition of the symbol
  74    UNDEF_NAME.  */
  75
  76 ElfW(Addr)
  77 internal_function
  78 _dl_lookup_symbol (const char *undef_name, struct link_map *undef_map,
  79                    const ElfW(Sym) **ref, struct r_scope_elem *symbol_scope[],
  80                    int reloc_type)
  81 {
  82   const char *reference_name = undef_map ? undef_map->l_name : NULL;
  83   const unsigned long int hash = _dl_elf_hash (undef_name);
  84   struct sym_val current_value = { NULL, NULL };
  85   struct r_scope_elem **scope;
  86
  87   ++_dl_num_relocations;
  88
  89   /* Search the relevant loaded objects for a definition.  */
  90   for (scope = symbol_scope; *scope; ++scope)
  91     if (do_lookup (undef_name, undef_map, hash, *ref, &current_value,
  92                    *scope, 0, NULL, reloc_type))
  93       break;
  94
  95   if (current_value.s == NULL)
  96     {
  97       if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
  98         /* We could find no value for a strong reference.  */
  99         _dl_signal_cerror (0, (reference_name && reference_name[0]
 100                                ? reference_name
 101                                : (_dl_argv[0] ?: "<main program>")),
 102                            make_string (undefined_msg, undef_name));
 103       *ref = NULL;
 104       return 0;
 105     }
 106
 107   if (_dl_debug_bindings)
 108     _dl_debug_message (1, "binding file ",
 109                        (reference_name && reference_name[0]
 110                         ? reference_name
 111                         : (_dl_argv[0] ?: "<main program>")),
 112                        " to ", current_value.m->l_name[0]
 113                        ? current_value.m->l_name : _dl_argv[0],
 114                        ": symbol `", undef_name, "'\n", NULL);
 115
 116   *ref = current_value.s;
 117   return current_value.m->l_addr;
 118 }
 119
 120
 121 /* This function is nearly the same as `_dl_lookup_symbol' but it
 122    skips in the first list all objects until SKIP_MAP is found.  I.e.,
 123    it only considers objects which were loaded after the described
 124    object.  If there are more search lists the object described by
 125    SKIP_MAP is only skipped.  */
 126 ElfW(Addr)
 127 internal_function
 128 _dl_lookup_symbol_skip (const char *undef_name,
 129                         struct link_map *undef_map, const ElfW(Sym) **ref,
 130                         struct r_scope_elem *symbol_scope[],
 131                         struct link_map *skip_map)
 132 {
 133   const char *reference_name = undef_map ? undef_map->l_name : NULL;
 134   const unsigned long int hash = _dl_elf_hash (undef_name);
 135   struct sym_val current_value = { NULL, NULL };
 136   struct r_scope_elem **scope;
 137   size_t i;
 138
 139   ++_dl_num_relocations;
 140
 141   /* Search the relevant loaded objects for a definition.  */
 142   scope = symbol_scope;
 143   for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i)
 144     assert (i < (*scope)->r_nduplist);
 145
 146   if (i >= (*scope)->r_nlist
 147       || ! do_lookup (undef_name, undef_map, hash, *ref, &current_value,
 148                       *scope, i, skip_map, 0))
 149     while (*++scope)
 150       if (do_lookup (undef_name, undef_map, hash, *ref, &current_value,
 151                      *scope, 0, skip_map, 0))
 152         break;
 153
 154   if (current_value.s == NULL)
 155     {
 156       *ref = NULL;
 157       return 0;
 158     }
 159
 160   if (_dl_debug_bindings)
 161     _dl_debug_message (1, "binding file ",
 162                        (reference_name && reference_name[0]
 163                         ? reference_name
 164                         : (_dl_argv[0] ?: "<main program>")),
 165                        " to ", current_value.m->l_name[0]
 166                        ? current_value.m->l_name : _dl_argv[0],
 167                        ": symbol `", undef_name, "' (skip)\n", NULL);
 168
 169   *ref = current_value.s;
 170   return current_value.m->l_addr;
 171 }
 172
 173
 174 /* This function works like _dl_lookup_symbol but it takes an
 175    additional arguement with the version number of the requested
 176    symbol.
 177
 178    XXX We'll see whether we need this separate function.  */
 179 ElfW(Addr)
 180 internal_function
 181 _dl_lookup_versioned_symbol (const char *undef_name,
 182                              struct link_map *undef_map, const ElfW(Sym) **ref,
 183                              struct r_scope_elem *symbol_scope[],
 184                              const struct r_found_version *version,
 185                              int reloc_type)
 186 {
 187   const char *reference_name = undef_map ? undef_map->l_name : NULL;
 188   const unsigned long int hash = _dl_elf_hash (undef_name);
 189   struct sym_val current_value = { NULL, NULL };
 190   struct r_scope_elem **scope;
 191
 192   ++_dl_num_relocations;
 193
 194   /* Search the relevant loaded objects for a definition.  */
 195   for (scope = symbol_scope; *scope; ++scope)
 196     {
 197       int res = do_lookup_versioned (undef_name, undef_map, hash, *ref,
 198                                      &current_value, *scope, 0, version, NULL,
 199                                      reloc_type);
 200       if (res > 0)
 201         break;
 202
 203       if (res < 0)
 204         {
 205           /* Oh, oh.  The file named in the relocation entry does not
 206              contain the needed symbol.  */
 207           _dl_signal_cerror (0, (reference_name && reference_name[0]
 208                                  ? reference_name
 209                                  : (_dl_argv[0] ?: "<main program>")),
 210                              make_string ("symbol ", undef_name, ", version ",
 211                                           version->name,
 212                                           " not defined in file ",
 213                                           version->filename,
 214                                           " with link time reference",
 215                                           res == -2
 216                                           ? " (no version symbols)" : ""));
 217           *ref = NULL;
 218           return 0;
 219         }
 220     }
 221
 222   if (current_value.s == NULL)
 223     {
 224       if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
 225         /* We could find no value for a strong reference.  */
 226         _dl_signal_cerror (0, (reference_name && reference_name[0]
 227                                ? reference_name
 228                                : (_dl_argv[0] ?: "<main program>")),
 229                            make_string (undefined_msg, undef_name,
 230                                         ", version ", version->name ?: NULL));
 231       *ref = NULL;
 232       return 0;
 233     }
 234
 235   if (_dl_debug_bindings)
 236     _dl_debug_message (1, "binding file ",
 237                        (reference_name && reference_name[0]
 238                         ? reference_name
 239                         : (_dl_argv[0] ?: "<main program>")),
 240                        " to ", current_value.m->l_name[0]
 241                        ? current_value.m->l_name : _dl_argv[0],
 242                        ": symbol `", undef_name, "' [", version->name,
 243                        "]\n", NULL);
 244
 245   *ref = current_value.s;
 246   return current_value.m->l_addr;
 247 }
 248
 249
 250 /* Similar to _dl_lookup_symbol_skip but takes an additional argument
 251    with the version we are looking for.  */
 252 ElfW(Addr)
 253 internal_function
 254 _dl_lookup_versioned_symbol_skip (const char *undef_name,
 255                                   struct link_map *undef_map,
 256                                   const ElfW(Sym) **ref,
 257                                   struct r_scope_elem *symbol_scope[],
 258                                   const struct r_found_version *version,
 259                                   struct link_map *skip_map)
 260 {
 261   const char *reference_name = undef_map ? undef_map->l_name : NULL;
 262   const unsigned long int hash = _dl_elf_hash (undef_name);
 263   struct sym_val current_value = { NULL, NULL };
 264   struct r_scope_elem **scope;
 265   size_t i;
 266
 267   ++_dl_num_relocations;
 268
 269   /* Search the relevant loaded objects for a definition.  */
 270   scope = symbol_scope;
 271   for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i)
 272     assert (i < (*scope)->r_nduplist);
 273
 274   if (i >= (*scope)->r_nlist
 275       || ! do_lookup_versioned (undef_name, undef_map, hash, *ref,
 276                                 &current_value, *scope, i, version, skip_map,
 277                                 0))
 278     while (*++scope)
 279       if (do_lookup_versioned (undef_name, undef_map, hash, *ref,
 280                                &current_value, *scope, 0, version, skip_map,
 281                                0))
 282         break;
 283
 284   if (current_value.s == NULL)
 285     {
 286       if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
 287         {
 288           /* We could find no value for a strong reference.  */
 289           const size_t len = strlen (undef_name);
 290           char buf[sizeof undefined_msg + len];
 291           __mempcpy (__mempcpy (buf, undefined_msg, sizeof undefined_msg - 1),
 292                      undef_name, len + 1);
 293           _dl_signal_cerror (0, (reference_name && reference_name[0]
 294                                  ? reference_name
 295                                  : (_dl_argv[0] ?: "<main program>")), buf);
 296         }
 297       *ref = NULL;
 298       return 0;
 299     }
 300
 301   if (_dl_debug_bindings)
 302     _dl_debug_message (1, "binding file ",
 303                        (reference_name && reference_name[0]
 304                         ? reference_name
 305                         : (_dl_argv[0] ?: "<main program>")),
 306                        " to ",
 307                        current_value.m->l_name[0]
 308                        ? current_value.m->l_name : _dl_argv[0],
 309                        ": symbol `", undef_name, "' [", version->name,
 310                        "] (skip)\n", NULL);
 311
 312   *ref = current_value.s;
 313   return current_value.m->l_addr;
 314 }
 315
 316
 317 /* Cache the location of MAP's hash table.  */
 318
 319 void
 320 internal_function
 321 _dl_setup_hash (struct link_map *map)
 322 {
 323   Elf_Symndx *hash;
 324   Elf_Symndx nchain;
 325
 326   if (!map->l_info[DT_HASH])
 327     return;
 328   hash = (void *)(map->l_addr + map->l_info[DT_HASH]->d_un.d_ptr);
 329
 330   map->l_nbuckets = *hash++;
 331   nchain = *hash++;
 332   map->l_buckets = hash;
 333   hash += map->l_nbuckets;
 334   map->l_chain = hash;
 335 }