elf/dl-addr.c

   1 /* Locate the shared object symbol nearest a given address.
   2    Copyright (C) 1996-2004, 2005, 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 <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) *matchsym = NULL;
  78       if (match->l_info[DT_ADDRTAGIDX (DT_GNU_HASH) + DT_NUM + DT_THISPROCNUM
  79                         + DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM] != NULL)
  80         {
  81           /* We look at all symbol table entries referenced by the
  82              hash table.  */
  83           for (Elf_Symndx bucket = 0; bucket < match->l_nbuckets; ++bucket)
  84             {
  85               Elf32_Word symndx = match->l_gnu_buckets[bucket];
  86               if (symndx != 0)
  87                 {
  88                   const Elf32_Word *hasharr = &match->l_gnu_chain_zero[symndx];
  89
  90                   do
  91                     {
  92                       /* The hash table never references local symbols
  93                          so we can omit that test here.  */
  94                       if ((symtab[symndx].st_shndx != SHN_UNDEF
  95                            || symtab[symndx].st_value != 0)
  96                           && ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
  97                           && DL_ADDR_SYM_MATCH (match, &symtab[symndx],
  98                                                 matchsym, addr)
  99                           && symtab[symndx].st_name < strtabsize)
 100                         matchsym = (ElfW(Sym) *) &symtab[symndx];
 101
 102                       ++symndx;
 103                     }
 104                   while ((*hasharr++ & 1u) == 0);
 105                 }
 106             }
 107         }
 108       else
 109         {
 110           const ElfW(Sym) *symtabend;
 111           if (match->l_info[DT_HASH] != NULL)
 112             symtabend = (symtab
 113                          + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
 114           else
 115             /* There is no direct way to determine the number of symbols in the
 116                dynamic symbol table and no hash table is present.  The ELF
 117                binary is ill-formed but what shall we do?  Use the beginning of
 118                the string table which generally follows the symbol table.  */
 119             symtabend = (const ElfW(Sym) *) strtab;
 120
 121           for (; (void *) symtab < (void *) symtabend; ++symtab)
 122             if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
 123                  || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK)
 124                 && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
 125                 && (symtab->st_shndx != SHN_UNDEF
 126                     || symtab->st_value != 0)
 127                 && DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
 128                 && symtab->st_name < strtabsize)
 129               matchsym = (ElfW(Sym) *) symtab;
 130         }
 131
 132       if (mapp)
 133         *mapp = match;
 134       if (symbolp)
 135         *symbolp = matchsym;
 136
 137       if (matchsym)
 138         {
 139           /* We found a symbol close by.  Fill in its name and exact
 140              address.  */
 141           lookup_t matchl = LOOKUP_VALUE (match);
 142
 143           info->dli_sname = strtab + matchsym->st_name;
 144           info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
 145         }
 146       else
 147         {
 148           /* No symbol matches.  We return only the containing object.  */
 149           info->dli_sname = NULL;
 150           info->dli_saddr = NULL;
 151         }
 152
 153       result = 1;
 154     }
 155
 156   __rtld_lock_unlock_recursive (GL(dl_load_lock));
 157
 158   return result;
 159 }
 160 libc_hidden_def (_dl_addr)