elf/dl-sym.c

   1 /* Look up a symbol in a shared object loaded by `dlopen'.
   2    Copyright (C) 1999-2002,2004,2006,2007 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 <stddef.h>
  22 #include <setjmp.h>
  23 #include <libintl.h>
  24
  25 #include <dlfcn.h>
  26 #include <ldsodefs.h>
  27 #include <dl-hash.h>
  28 #include <sysdep-cancel.h>
  29 #include <dl-tls.h>
  30
  31
  32 #ifdef SHARED
  33 /* Systems which do not have tls_index also probably have to define
  34    DONT_USE_TLS_INDEX.  */
  35
  36 # ifndef __TLS_GET_ADDR
  37 #  define __TLS_GET_ADDR __tls_get_addr
  38 # endif
  39
  40 /* Return the symbol address given the map of the module it is in and
  41    the symbol record.  This is used in dl-sym.c.  */
  42 static void *
  43 internal_function
  44 _dl_tls_symaddr (struct link_map *map, const ElfW(Sym) *ref)
  45 {
  46 # ifndef DONT_USE_TLS_INDEX
  47   tls_index tmp =
  48     {
  49       .ti_module = map->l_tls_modid,
  50       .ti_offset = ref->st_value
  51     };
  52
  53   return __TLS_GET_ADDR (&tmp);
  54 # else
  55   return __TLS_GET_ADDR (map->l_tls_modid, ref->st_value);
  56 # endif
  57 }
  58 #endif
  59
  60
  61 struct call_dl_lookup_args
  62 {
  63   /* Arguments to do_dlsym.  */
  64   struct link_map *map;
  65   const char *name;
  66   struct r_found_version *vers;
  67   int flags;
  68
  69   /* Return values of do_dlsym.  */
  70   lookup_t loadbase;
  71   const ElfW(Sym) **refp;
  72 };
  73
  74 static void
  75 call_dl_lookup (void *ptr)
  76 {
  77   struct call_dl_lookup_args *args = (struct call_dl_lookup_args *) ptr;
  78   args->map = GLRO(dl_lookup_symbol_x) (args->name, args->map, args->refp,
  79                                         args->map->l_scope, args->vers, 0,
  80                                         args->flags, NULL);
  81 }
  82
  83
  84 static void *
  85 internal_function
  86 do_sym (void *handle, const char *name, void *who,
  87         struct r_found_version *vers, int flags)
  88 {
  89   const ElfW(Sym) *ref = NULL;
  90   lookup_t result;
  91   ElfW(Addr) caller = (ElfW(Addr)) who;
  92
  93   /* If the address is not recognized the call comes from the main
  94      program (we hope).  */
  95   struct link_map *match = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
  96
  97   /* Find the highest-addressed object that CALLER is not below.  */
  98   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
  99     for (struct link_map *l = GL(dl_ns)[ns]._ns_loaded; l != NULL;
 100          l = l->l_next)
 101       if (caller >= l->l_map_start && caller < l->l_map_end
 102           && (l->l_contiguous || _dl_addr_inside_object (l, caller)))
 103         {
 104           match = l;
 105           break;
 106         }
 107
 108   if (handle == RTLD_DEFAULT)
 109     {
 110       /* Search the global scope.  We have the simple case where
 111          we look up in the scope of an object which was part of
 112          the initial binary.  And then the more complex part
 113          where the object is dynamically loaded and the scope
 114          array can change.  */
 115       if (RTLD_SINGLE_THREAD_P)
 116         result = GLRO(dl_lookup_symbol_x) (name, match, &ref,
 117                                            match->l_scope, vers, 0,
 118                                            flags | DL_LOOKUP_ADD_DEPENDENCY,
 119                                            NULL);
 120       else
 121         {
 122           struct call_dl_lookup_args args;
 123           args.name = name;
 124           args.map = match;
 125           args.vers = vers;
 126           args.flags
 127             = flags | DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK;
 128           args.refp = &ref;
 129
 130           THREAD_GSCOPE_SET_FLAG ();
 131
 132           const char *objname;
 133           const char *errstring = NULL;
 134           bool malloced;
 135           int err = GLRO(dl_catch_error) (&objname, &errstring, &malloced,
 136                                           call_dl_lookup, &args);
 137
 138           THREAD_GSCOPE_RESET_FLAG ();
 139
 140           if (__builtin_expect (errstring != NULL, 0))
 141             {
 142               /* The lookup was unsuccessful.  Rethrow the error.  */
 143               char *errstring_dup = strdupa (errstring);
 144               char *objname_dup = strdupa (objname);
 145               if (malloced)
 146                 free ((char *) errstring);
 147
 148               GLRO(dl_signal_error) (err, objname_dup, NULL, errstring_dup);
 149               /* NOTREACHED */
 150             }
 151
 152           result = args.map;
 153         }
 154     }
 155   else if (handle == RTLD_NEXT)
 156     {
 157       if (__builtin_expect (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded, 0))
 158         {
 159           if (match == NULL
 160               || caller < match->l_map_start
 161               || caller >= match->l_map_end)
 162             GLRO(dl_signal_error) (0, NULL, NULL, N_("\
 163 RTLD_NEXT used in code not dynamically loaded"));
 164         }
 165
 166       struct link_map *l = match;
 167       while (l->l_loader != NULL)
 168         l = l->l_loader;
 169
 170       result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope,
 171                                          vers, 0, 0, match);
 172     }
 173   else
 174     {
 175       /* Search the scope of the given object.  */
 176       struct link_map *map = handle;
 177       result = GLRO(dl_lookup_symbol_x) (name, map, &ref, map->l_local_scope,
 178                                          vers, 0, flags, NULL);
 179     }
 180
 181   if (ref != NULL)
 182     {
 183       void *value;
 184
 185 #ifdef SHARED
 186       if (ELFW(ST_TYPE) (ref->st_info) == STT_TLS)
 187         /* The found symbol is a thread-local storage variable.
 188            Return the address for to the current thread.  */
 189         value = _dl_tls_symaddr (result, ref);
 190       else
 191 #endif
 192         value = DL_SYMBOL_ADDRESS (result, ref);
 193
 194 #ifdef SHARED
 195       /* Auditing checkpoint: we have a new binding.  Provide the
 196          auditing libraries the possibility to change the value and
 197          tell us whether further auditing is wanted.  */
 198       if (__builtin_expect (GLRO(dl_naudit) > 0, 0))
 199         {
 200           const char *strtab = (const char *) D_PTR (result,
 201                                                      l_info[DT_STRTAB]);
 202           /* Compute index of the symbol entry in the symbol table of
 203              the DSO with the definition.  */
 204           unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
 205                                                          l_info[DT_SYMTAB]));
 206
 207           if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
 208             {
 209               unsigned int altvalue = 0;
 210               struct audit_ifaces *afct = GLRO(dl_audit);
 211               /* Synthesize a symbol record where the st_value field is
 212                  the result.  */
 213               ElfW(Sym) sym = *ref;
 214               sym.st_value = (ElfW(Addr)) value;
 215
 216               for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 217                 {
 218                   if (afct->symbind != NULL
 219                       && ((match->l_audit[cnt].bindflags & LA_FLG_BINDFROM)
 220                           != 0
 221                           || ((result->l_audit[cnt].bindflags & LA_FLG_BINDTO)
 222                               != 0)))
 223                     {
 224                       unsigned int flags = altvalue | LA_SYMB_DLSYM;
 225                       uintptr_t new_value
 226                         = afct->symbind (&sym, ndx,
 227                                          &match->l_audit[cnt].cookie,
 228                                          &result->l_audit[cnt].cookie,
 229                                          &flags, strtab + ref->st_name);
 230                       if (new_value != (uintptr_t) sym.st_value)
 231                         {
 232                           altvalue = LA_SYMB_ALTVALUE;
 233                           sym.st_value = new_value;
 234                         }
 235                     }
 236
 237                   afct = afct->next;
 238                 }
 239
 240               value = (void *) sym.st_value;
 241             }
 242         }
 243 #endif
 244
 245       return value;
 246     }
 247
 248   return NULL;
 249 }
 250
 251
 252 void *
 253 internal_function
 254 _dl_vsym (void *handle, const char *name, const char *version, void *who)
 255 {
 256   struct r_found_version vers;
 257
 258   /* Compute hash value to the version string.  */
 259   vers.name = version;
 260   vers.hidden = 1;
 261   vers.hash = _dl_elf_hash (version);
 262   /* We don't have a specific file where the symbol can be found.  */
 263   vers.filename = NULL;
 264
 265   return do_sym (handle, name, who, &vers, 0);
 266 }
 267
 268
 269 void *
 270 internal_function
 271 _dl_sym (void *handle, const char *name, void *who)
 272 {
 273   return do_sym (handle, name, who, NULL, DL_LOOKUP_RETURN_NEWEST);
 274 }