elf/dl-sym.c

   1 /* Look up a symbol in a shared object loaded by `dlopen'.
   2    Copyright (C) 1999,2000,2001,2002,2004,2006 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 <stddef.h>
  21 #include <setjmp.h>
  22 #include <libintl.h>
  23
  24 #include <dlfcn.h>
  25 #include <ldsodefs.h>
  26 #include <dl-hash.h>
  27 #ifdef USE_TLS
  28 # include <dl-tls.h>
  29 #endif
  30
  31
  32 #if defined USE_TLS && defined 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 static void *
  62 internal_function
  63 do_sym (void *handle, const char *name, void *who,
  64         struct r_found_version *vers, int flags)
  65 {
  66   const ElfW(Sym) *ref = NULL;
  67   lookup_t result;
  68   ElfW(Addr) caller = (ElfW(Addr)) who;
  69
  70   /* If the address is not recognized the call comes from the main
  71      program (we hope).  */
  72   struct link_map *match = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
  73
  74   /* Find the highest-addressed object that CALLER is not below.  */
  75   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
  76     for (struct link_map *l = GL(dl_ns)[ns]._ns_loaded; l != NULL;
  77          l = l->l_next)
  78       if (caller >= l->l_map_start && caller < l->l_map_end)
  79         {
  80           /* There must be exactly one DSO for the range of the virtual
  81              memory.  Otherwise something is really broken.  */
  82           match = l;
  83           break;
  84         }
  85
  86   if (handle == RTLD_DEFAULT)
  87     /* Search the global scope.  */
  88     result = GLRO(dl_lookup_symbol_x) (name, match, &ref, match->l_scope,
  89                                        vers, 0, flags|DL_LOOKUP_ADD_DEPENDENCY,
  90                                        NULL);
  91   else if (handle == RTLD_NEXT)
  92     {
  93       if (__builtin_expect (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded, 0))
  94         {
  95           if (match == NULL
  96               || caller < match->l_map_start
  97               || caller >= match->l_map_end)
  98             GLRO(dl_signal_error) (0, NULL, NULL, N_("\
  99 RTLD_NEXT used in code not dynamically loaded"));
 100         }
 101
 102       struct link_map *l = match;
 103       while (l->l_loader != NULL)
 104         l = l->l_loader;
 105
 106       result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope,
 107                                          vers, 0, 0, match);
 108     }
 109   else
 110     {
 111       /* Search the scope of the given object.  */
 112       struct link_map *map = handle;
 113       result = GLRO(dl_lookup_symbol_x) (name, map, &ref, map->l_local_scope,
 114                                          vers, 0, flags, NULL);
 115     }
 116
 117   if (ref != NULL)
 118     {
 119       void *value;
 120
 121 #if defined USE_TLS && defined SHARED
 122       if (ELFW(ST_TYPE) (ref->st_info) == STT_TLS)
 123         /* The found symbol is a thread-local storage variable.
 124            Return the address for to the current thread.  */
 125         value = _dl_tls_symaddr (result, ref);
 126       else
 127 #endif
 128         value = DL_SYMBOL_ADDRESS (result, ref);
 129
 130 #ifdef SHARED
 131       /* Auditing checkpoint: we have a new binding.  Provide the
 132          auditing libraries the possibility to change the value and
 133          tell us whether further auditing is wanted.  */
 134       if (__builtin_expect (GLRO(dl_naudit) > 0, 0))
 135         {
 136           const char *strtab = (const char *) D_PTR (result,
 137                                                      l_info[DT_STRTAB]);
 138           /* Compute index of the symbol entry in the symbol table of
 139              the DSO with the definition.  */
 140           unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
 141                                                          l_info[DT_SYMTAB]));
 142
 143           if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
 144             {
 145               unsigned int altvalue = 0;
 146               struct audit_ifaces *afct = GLRO(dl_audit);
 147               /* Synthesize a symbol record where the st_value field is
 148                  the result.  */
 149               ElfW(Sym) sym = *ref;
 150               sym.st_value = (ElfW(Addr)) value;
 151
 152               for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 153                 {
 154                   if (afct->symbind != NULL
 155                       && ((match->l_audit[cnt].bindflags & LA_FLG_BINDFROM)
 156                           != 0
 157                           || ((result->l_audit[cnt].bindflags & LA_FLG_BINDTO)
 158                               != 0)))
 159                     {
 160                       unsigned int flags = altvalue | LA_SYMB_DLSYM;
 161                       uintptr_t new_value
 162                         = afct->symbind (&sym, ndx,
 163                                          &match->l_audit[cnt].cookie,
 164                                          &result->l_audit[cnt].cookie,
 165                                          &flags, strtab + ref->st_name);
 166                       if (new_value != (uintptr_t) sym.st_value)
 167                         {
 168                           altvalue = LA_SYMB_ALTVALUE;
 169                           sym.st_value = new_value;
 170                         }
 171                     }
 172
 173                   afct = afct->next;
 174                 }
 175
 176               value = (void *) sym.st_value;
 177             }
 178         }
 179 #endif
 180
 181       return value;
 182     }
 183
 184   return NULL;
 185 }
 186
 187
 188 void *
 189 internal_function
 190 _dl_vsym (void *handle, const char *name, const char *version, void *who)
 191 {
 192   struct r_found_version vers;
 193
 194   /* Compute hash value to the version string.  */
 195   vers.name = version;
 196   vers.hidden = 1;
 197   vers.hash = _dl_elf_hash (version);
 198   /* We don't have a specific file where the symbol can be found.  */
 199   vers.filename = NULL;
 200
 201   return do_sym (handle, name, who, &vers, 0);
 202 }
 203
 204
 205 void *
 206 internal_function
 207 _dl_sym (void *handle, const char *name, void *who)
 208 {
 209   return do_sym (handle, name, who, NULL, DL_LOOKUP_RETURN_NEWEST);
 210 }