elf/do-lookup.h

   1 /* Look up a symbol in the loaded objects.
   2    Copyright (C) 1995,96,97,98,99,2000,2001 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 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 #if VERSIONED
  21 # define FCT do_lookup_versioned
  22 # define ARG const struct r_found_version *const version,
  23 #else
  24 # define FCT do_lookup
  25 # define ARG
  26 #endif
  27
  28 /* Inner part of the lookup functions.  We return a value > 0 if we
  29    found the symbol, the value 0 if nothing is found and < 0 if
  30    something bad happened.  */
  31 static inline int
  32 FCT (const char *undef_name, unsigned long int hash, const ElfW(Sym) *ref,
  33      struct sym_val *result, struct r_scope_elem *scope, size_t i, ARG
  34      struct link_map *skip, int type_class)
  35 {
  36   struct link_map **list = scope->r_list;
  37   size_t n = scope->r_nlist;
  38   struct link_map *map;
  39
  40   do
  41     {
  42       const ElfW(Sym) *symtab;
  43       const char *strtab;
  44       const ElfW(Half) *verstab;
  45       Elf_Symndx symidx;
  46       const ElfW(Sym) *sym;
  47 #if ! VERSIONED
  48       int num_versions = 0;
  49       const ElfW(Sym) *versioned_sym = NULL;
  50 #endif
  51
  52       map = list[i];
  53
  54       /* Here come the extra test needed for `_dl_lookup_symbol_skip'.  */
  55       if (skip != NULL && map == skip)
  56         continue;
  57
  58       /* Don't search the executable when resolving a copy reloc.  */
  59       if ((type_class & ELF_RTYPE_CLASS_COPY) && map->l_type == lt_executable)
  60         continue;
  61
  62       /* Print some debugging info if wanted.  */
  63       if (__builtin_expect (_dl_debug_mask & DL_DEBUG_SYMBOLS, 0))
  64         _dl_debug_printf ("symbol=%s;  lookup in file=%s\n", undef_name,
  65                           map->l_name[0] ? map->l_name : _dl_argv[0]);
  66
  67       symtab = (const void *) D_PTR (map, l_info[DT_SYMTAB]);
  68       strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
  69       verstab = map->l_versyms;
  70
  71       /* Search the appropriate hash bucket in this object's symbol table
  72          for a definition for the same symbol name.  */
  73       for (symidx = map->l_buckets[hash % map->l_nbuckets];
  74            symidx != STN_UNDEF;
  75            symidx = map->l_chain[symidx])
  76         {
  77           sym = &symtab[symidx];
  78
  79           assert (ELF_RTYPE_CLASS_PLT == 1);
  80           if (sym->st_value == 0 || /* No value.  */
  81               /* ((type_class & ELF_RTYPE_CLASS_PLT)
  82                   && (sym->st_shndx == SHN_UNDEF)) */
  83               (type_class & (sym->st_shndx == SHN_UNDEF)))
  84             continue;
  85
  86           if (ELFW(ST_TYPE) (sym->st_info) > STT_FUNC)
  87             /* Ignore all but STT_NOTYPE, STT_OBJECT and STT_FUNC entries
  88                since these are no code/data definitions.  */
  89             continue;
  90
  91           if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
  92             /* Not the symbol we are looking for.  */
  93             continue;
  94
  95 #if VERSIONED
  96           if (__builtin_expect (verstab == NULL, 0))
  97             {
  98               /* We need a versioned symbol but haven't found any.  If
  99                  this is the object which is referenced in the verneed
 100                  entry it is a bug in the library since a symbol must
 101                  not simply disappear.
 102
 103                  It would also be a bug in the object since it means that
 104                  the list of required versions is incomplete and so the
 105                  tests in dl-version.c haven't found a problem.*/
 106               assert (version->filename == NULL
 107                       || ! _dl_name_match_p (version->filename, map));
 108
 109               /* Otherwise we accept the symbol.  */
 110             }
 111           else
 112             {
 113               /* We can match the version information or use the
 114                  default one if it is not hidden.  */
 115               ElfW(Half) ndx = verstab[symidx] & 0x7fff;
 116               if ((map->l_versions[ndx].hash != version->hash
 117                    || strcmp (map->l_versions[ndx].name, version->name))
 118                   && (version->hidden || map->l_versions[ndx].hash
 119                       || (verstab[symidx] & 0x8000)))
 120                 /* It's not the version we want.  */
 121                 continue;
 122             }
 123 #else
 124           /* No specific version is selected.  When the object file
 125              also does not define a version we have a match.
 126              Otherwise we accept the default version, or in case there
 127              is only one version defined, this one version.  */
 128           if (verstab != NULL)
 129             {
 130               ElfW(Half) ndx = verstab[symidx] & 0x7fff;
 131               if (ndx > 2) /* map->l_versions[ndx].hash != 0) */
 132                 {
 133                   /* Don't accept hidden symbols.  */
 134                   if ((verstab[symidx] & 0x8000) == 0 && num_versions++ == 0)
 135                     /* No version so far.  */
 136                     versioned_sym = sym;
 137                   continue;
 138                 }
 139             }
 140 #endif
 141
 142           /* There cannot be another entry for this symbol so stop here.  */
 143           goto found_it;
 144         }
 145
 146       /* If we have seen exactly one versioned symbol while we are
 147          looking for an unversioned symbol and the version is not the
 148          default version we still accept this symbol since there are
 149          no possible ambiguities.  */
 150 #if VERSIONED
 151       sym = NULL;
 152 #else
 153       sym = num_versions == 1 ? versioned_sym : NULL;
 154 #endif
 155
 156       if (sym != NULL)
 157         {
 158         found_it:
 159           switch (ELFW(ST_BIND) (sym->st_info))
 160             {
 161             case STB_WEAK:
 162               /* Weak definition.  Use this value if we don't find another.  */
 163               if (__builtin_expect (_dl_dynamic_weak, 0))
 164                 {
 165                   if (! result->s)
 166                     {
 167                       result->s = sym;
 168                       result->m = map;
 169                     }
 170                   break;
 171                 }
 172               /* FALLTHROUGH */
 173             case STB_GLOBAL:
 174               /* Global definition.  Just what we need.  */
 175               result->s = sym;
 176               result->m = map;
 177               return 1;
 178             default:
 179               /* Local symbols are ignored.  */
 180               break;
 181             }
 182         }
 183
 184 #if VERSIONED
 185       /* If this current map is the one mentioned in the verneed entry
 186          and we have not found a weak entry, it is a bug.  */
 187       if (symidx == STN_UNDEF && version->filename != NULL
 188           && __builtin_expect (_dl_name_match_p (version->filename, map), 0))
 189         return -1;
 190 #endif
 191     }
 192   while (++i < n);
 193
 194   /* We have not found anything until now.  */
 195   return 0;
 196 }
 197
 198 #undef FCT
 199 #undef ARG
 200 #undef VERSIONED