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, const ElfW(Sym) **ref,
  79                    struct r_scope_elem *symbol_scope[],
  80                    const char *reference_name,
  81                    int reloc_type)
  82 {
  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, hash, *ref, &current_value,
  92                    *scope, 0, reference_name, 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, const ElfW(Sym) **ref,
 129                         struct r_scope_elem *symbol_scope[],
 130                         const char *reference_name,
 131                         struct link_map *skip_map)
 132 {
 133   const unsigned long int hash = _dl_elf_hash (undef_name);
 134   struct sym_val current_value = { NULL, NULL };
 135   struct r_scope_elem **scope;
 136   size_t i;
 137
 138   ++_dl_num_relocations;
 139
 140   /* Search the relevant loaded objects for a definition.  */
 141   scope = symbol_scope;
 142   for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i)
 143     assert (i < (*scope)->r_nduplist);
 144
 145   if (i >= (*scope)->r_nlist
 146       || ! do_lookup (undef_name, hash, *ref, &current_value,
 147                       *scope, i, reference_name, skip_map, 0))
 148     while (*++scope)
 149       if (do_lookup (undef_name, hash, *ref, &current_value,
 150                      *scope, 0, reference_name, skip_map, 0))
 151         break;
 152
 153   if (current_value.s == NULL)
 154     {
 155       *ref = NULL;
 156       return 0;
 157     }
 158
 159   if (_dl_debug_bindings)
 160     _dl_debug_message (1, "binding file ",
 161                        (reference_name && reference_name[0]
 162                         ? reference_name
 163                         : (_dl_argv[0] ?: "<main program>")),
 164                        " to ", current_value.m->l_name[0]
 165                        ? current_value.m->l_name : _dl_argv[0],
 166                        ": symbol `", undef_name, "' (skip)\n", NULL);
 167
 168   *ref = current_value.s;
 169   return current_value.m->l_addr;
 170 }
 171
 172
 173 /* This function works like _dl_lookup_symbol but it takes an
 174    additional arguement with the version number of the requested
 175    symbol.
 176
 177    XXX We'll see whether we need this separate function.  */
 178 ElfW(Addr)
 179 internal_function
 180 _dl_lookup_versioned_symbol (const char *undef_name, const ElfW(Sym) **ref,
 181                              struct r_scope_elem *symbol_scope[],
 182                              const char *reference_name,
 183                              const struct r_found_version *version,
 184                              int reloc_type)
 185 {
 186   const unsigned long int hash = _dl_elf_hash (undef_name);
 187   struct sym_val current_value = { NULL, NULL };
 188   struct r_scope_elem **scope;
 189
 190   ++_dl_num_relocations;
 191
 192   /* Search the relevant loaded objects for a definition.  */
 193   for (scope = symbol_scope; *scope; ++scope)
 194     {
 195       int res = do_lookup_versioned (undef_name, hash, *ref, &current_value,
 196                                      *scope, 0, reference_name, version, NULL,
 197                                      reloc_type);
 198       if (res > 0)
 199         break;
 200
 201       if (res < 0)
 202         {
 203           /* Oh, oh.  The file named in the relocation entry does not
 204              contain the needed symbol.  */
 205           _dl_signal_cerror (0, (reference_name && reference_name[0]
 206                                  ? reference_name
 207                                  : (_dl_argv[0] ?: "<main program>")),
 208                              make_string ("symbol ", undef_name, ", version ",
 209                                           version->name,
 210                                           " not defined in file ",
 211                                           version->filename,
 212                                           " with link time reference",
 213                                           res == -2
 214                                           ? " (no version symbols)" : ""));
 215           *ref = NULL;
 216           return 0;
 217         }
 218     }
 219
 220   if (current_value.s == NULL)
 221     {
 222       if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
 223         /* We could find no value for a strong reference.  */
 224         _dl_signal_cerror (0, (reference_name && reference_name[0]
 225                                ? reference_name
 226                                : (_dl_argv[0] ?: "<main program>")),
 227                            make_string (undefined_msg, undef_name,
 228                                         ", version ", version->name ?: NULL));
 229       *ref = NULL;
 230       return 0;
 231     }
 232
 233   if (_dl_debug_bindings)
 234     _dl_debug_message (1, "binding file ",
 235                        (reference_name && reference_name[0]
 236                         ? reference_name
 237                         : (_dl_argv[0] ?: "<main program>")),
 238                        " to ", current_value.m->l_name[0]
 239                        ? current_value.m->l_name : _dl_argv[0],
 240                        ": symbol `", undef_name, "' [", version->name,
 241                        "]\n", NULL);
 242
 243   *ref = current_value.s;
 244   return current_value.m->l_addr;
 245 }
 246
 247
 248 /* Similar to _dl_lookup_symbol_skip but takes an additional argument
 249    with the version we are looking for.  */
 250 ElfW(Addr)
 251 internal_function
 252 _dl_lookup_versioned_symbol_skip (const char *undef_name,
 253                                   const ElfW(Sym) **ref,
 254                                   struct r_scope_elem *symbol_scope[],
 255                                   const char *reference_name,
 256                                   const struct r_found_version *version,
 257                                   struct link_map *skip_map)
 258 {
 259   const unsigned long int hash = _dl_elf_hash (undef_name);
 260   struct sym_val current_value = { NULL, NULL };
 261   struct r_scope_elem **scope;
 262   size_t i;
 263
 264   ++_dl_num_relocations;
 265
 266   /* Search the relevant loaded objects for a definition.  */
 267   scope = symbol_scope;
 268   for (i = 0; (*scope)->r_duplist[i] != skip_map; ++i)
 269     assert (i < (*scope)->r_nduplist);
 270
 271   if (i >= (*scope)->r_nlist
 272       || ! do_lookup_versioned (undef_name, hash, *ref, &current_value, *scope,
 273                                 i, reference_name, version, skip_map, 0))
 274     while (*++scope)
 275       if (do_lookup_versioned (undef_name, hash, *ref, &current_value, *scope,
 276                                0, reference_name, version, skip_map, 0))
 277         break;
 278
 279   if (current_value.s == NULL)
 280     {
 281       if (*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
 282         {
 283           /* We could find no value for a strong reference.  */
 284           const size_t len = strlen (undef_name);
 285           char buf[sizeof undefined_msg + len];
 286           __mempcpy (__mempcpy (buf, undefined_msg, sizeof undefined_msg - 1),
 287                      undef_name, len + 1);
 288           _dl_signal_cerror (0, (reference_name && reference_name[0]
 289                                  ? reference_name
 290                                  : (_dl_argv[0] ?: "<main program>")), buf);
 291         }
 292       *ref = NULL;
 293       return 0;
 294     }
 295
 296   if (_dl_debug_bindings)
 297     _dl_debug_message (1, "binding file ",
 298                        (reference_name && reference_name[0]
 299                         ? reference_name
 300                         : (_dl_argv[0] ?: "<main program>")),
 301                        " to ",
 302                        current_value.m->l_name[0]
 303                        ? current_value.m->l_name : _dl_argv[0],
 304                        ": symbol `", undef_name, "' [", version->name,
 305                        "] (skip)\n", NULL);
 306
 307   *ref = current_value.s;
 308   return current_value.m->l_addr;
 309 }
 310
 311
 312 /* Cache the location of MAP's hash table.  */
 313
 314 void
 315 internal_function
 316 _dl_setup_hash (struct link_map *map)
 317 {
 318   ElfW(Symndx) *hash;
 319   ElfW(Symndx) nchain;
 320
 321   if (!map->l_info[DT_HASH])
 322     return;
 323   hash = (void *)(map->l_addr + map->l_info[DT_HASH]->d_un.d_ptr);
 324
 325   map->l_nbuckets = *hash++;
 326   nchain = *hash++;
 327   map->l_buckets = hash;
 328   hash += map->l_nbuckets;
 329   map->l_chain = hash;
 330 }