elf/dl-addr.c

   1 /* Locate the shared object symbol nearest a given address.
   2    Copyright (C) 1996-2004, 2005 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 <dlfcn.h>
  21 #include <stddef.h>
  22 #include <ldsodefs.h>
  23
  24
  25 int
  26 internal_function
  27 _dl_addr (const void *address, Dl_info *info,
  28           struct link_map **mapp, const ElfW(Sym) **symbolp)
  29 {
  30   const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
  31
  32   /* Protect against concurrent loads and unloads.  */
  33   __rtld_lock_lock_recursive (GL(dl_load_lock));
  34
  35   /* Find the highest-addressed object that ADDRESS is not below.  */
  36   struct link_map *match = NULL;
  37   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
  38     for (struct link_map *l = GL(dl_ns)[ns]._ns_loaded; l; l = l->l_next)
  39       if (addr >= l->l_map_start && addr < l->l_map_end)
  40         {
  41           /* We know ADDRESS lies within L if in any shared object.
  42              Make sure it isn't past the end of L's segments.  */
  43           size_t n = l->l_phnum;
  44           if (n > 0)
  45             {
  46               do
  47                 --n;
  48               while (l->l_phdr[n].p_type != PT_LOAD);
  49               if (addr >= (l->l_addr +
  50                            l->l_phdr[n].p_vaddr + l->l_phdr[n].p_memsz))
  51                 /* Off the end of the highest-addressed shared object.  */
  52                 continue;
  53             }
  54
  55           match = l;
  56           break;
  57         }
  58
  59   int result = 0;
  60   if (match != NULL)
  61     {
  62       /* Now we know what object the address lies in.  */
  63       info->dli_fname = match->l_name;
  64       info->dli_fbase = (void *) match->l_map_start;
  65
  66       /* If this is the main program the information is incomplete.  */
  67       if (__builtin_expect (match->l_name[0], 'a') == '\0'
  68           && match->l_type == lt_executable)
  69         info->dli_fname = _dl_argv[0];
  70
  71       const ElfW(Sym) *symtab
  72         = (const ElfW(Sym) *) D_PTR (match, l_info[DT_SYMTAB]);
  73       const char *strtab = (const char *) D_PTR (match, l_info[DT_STRTAB]);
  74
  75       ElfW(Word) strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;
  76
  77       const ElfW(Sym) *symtabend;
  78       if (match->l_info[DT_HASH] != NULL)
  79         symtabend = (symtab
  80                      + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
  81       else
  82         /* There is no direct way to determine the number of symbols in the
  83            dynamic symbol table and no hash table is present.  The ELF
  84            binary is ill-formed but what shall we do?  Use the beginning of
  85            the string table which generally follows the symbol table.  */
  86         symtabend = (const ElfW(Sym) *) strtab;
  87
  88       /* We assume that the string table follows the symbol table,
  89          because there is no way in ELF to know the size of the
  90          dynamic symbol table!!  */
  91       const ElfW(Sym) *matchsym;
  92       for (matchsym = NULL; (void *) symtab < (void *) symtabend; ++symtab)
  93         if (addr >= match->l_addr + symtab->st_value
  94 #if defined USE_TLS
  95             && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
  96 #endif
  97             && ((symtab->st_size == 0
  98                  && addr == match->l_addr + symtab->st_value)
  99                 || addr < match->l_addr + symtab->st_value + symtab->st_size)
 100             && symtab->st_name < strtabsize
 101             && (matchsym == NULL || matchsym->st_value < symtab->st_value)
 102             && (ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
 103                 || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK))
 104           matchsym = (ElfW(Sym) *) symtab;
 105
 106       if (mapp)
 107         *mapp = match;
 108       if (symbolp)
 109         *symbolp = matchsym;
 110
 111       if (matchsym)
 112         {
 113           /* We found a symbol close by.  Fill in its name and exact
 114              address.  */
 115           lookup_t matchl = LOOKUP_VALUE (match);
 116
 117           info->dli_sname = strtab + matchsym->st_name;
 118           info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
 119         }
 120       else
 121         {
 122           /* No symbol matches.  We return only the containing object.  */
 123           info->dli_sname = NULL;
 124           info->dli_saddr = NULL;
 125         }
 126
 127       result = 1;
 128     }
 129
 130   __rtld_lock_unlock_recursive (GL(dl_load_lock));
 131
 132   return result;
 133 }
 134 libc_hidden_def (_dl_addr)