1: /* Locate the shared object symbol nearest a given address.
    2:    Copyright (C) 1996-2004, 2005, 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 <dlfcn.h>
   21: #include <stddef.h>
   22: #include <ldsodefs.h>
   23: 
   24: 
   25: static void
   26: __attribute ((always_inline))
   27: determine_info (const ElfW(Addr) addr, struct link_map *match, Dl_info *info,
   28:                 struct link_map **mapp, const ElfW(Sym) **symbolp)
   29: {
   30:   /* Now we know what object the address lies in.  */
   31:   info->dli_fname = match->l_name;
   32:   info->dli_fbase = (void *) match->l_map_start;
   33: 
   34:   /* If this is the main program the information is incomplete.  */
   35:   if (__builtin_expect (match->l_name[0], 'a') == '\0'
   36:       && match->l_type == lt_executable)
   37:     info->dli_fname = _dl_argv[0];
   38: 
   39:   const ElfW(Sym) *symtab
   40:     = (const ElfW(Sym) *) D_PTR (match, l_info[DT_SYMTAB]);
   41:   const char *strtab = (const char *) D_PTR (match, l_info[DT_STRTAB]);
   42: 
   43:   ElfW(Word) strtabsize = match->l_info[DT_STRSZ]->d_un.d_val;
   44: 
   45:   const ElfW(Sym) *matchsym = NULL;
   46:   if (match->l_info[DT_ADDRTAGIDX (DT_GNU_HASH) + DT_NUM + DT_THISPROCNUM
   47:                     + DT_VERSIONTAGNUM + DT_EXTRANUM + DT_VALNUM] != NULL)
   48:     {
   49:       /* We look at all symbol table entries referenced by the hash
   50:          table.  */
   51:       for (Elf_Symndx bucket = 0; bucket < match->l_nbuckets; ++bucket)
   52:         {
   53:           Elf32_Word symndx = match->l_gnu_buckets[bucket];
   54:           if (symndx != 0)
   55:             {
   56:               const Elf32_Word *hasharr = &match->l_gnu_chain_zero[symndx];
   57: 
   58:               do
   59:                 {
   60:                   /* The hash table never references local symbols so
   61:                      we can omit that test here.  */
   62:                   if ((symtab[symndx].st_shndx != SHN_UNDEF
   63:                        || symtab[symndx].st_value != 0)
   64:                       && ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
   65:                       && DL_ADDR_SYM_MATCH (match, &symtab[symndx],
   66:                                             matchsym, addr)
   67:                       && symtab[symndx].st_name < strtabsize)
   68:                     matchsym = (ElfW(Sym) *) &symtab[symndx];
   69: 
   70:                   ++symndx;
   71:                 }
   72:               while ((*hasharr++ & 1u) == 0);
   73:             }
   74:         }
   75:     }
   76:   else
   77:     {
   78:       const ElfW(Sym) *symtabend;
   79:       if (match->l_info[DT_HASH] != NULL)
   80:         symtabend = (symtab
   81:                      + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
   82:       else
   83:         /* There is no direct way to determine the number of symbols in the
   84:            dynamic symbol table and no hash table is present.  The ELF
   85:            binary is ill-formed but what shall we do?  Use the beginning of
   86:            the string table which generally follows the symbol table.  */
   87:         symtabend = (const ElfW(Sym) *) strtab;
   88: 
   89:       for (; (void *) symtab < (void *) symtabend; ++symtab)
   90:         if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
   91:              || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK)
   92:             && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
   93:             && (symtab->st_shndx != SHN_UNDEF
   94:                 || symtab->st_value != 0)
   95:             && DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
   96:             && symtab->st_name < strtabsize)
   97:           matchsym = (ElfW(Sym) *) symtab;
   98:     }
   99: 
  100:   if (mapp)
  101:     *mapp = match;
  102:   if (symbolp)
  103:     *symbolp = matchsym;
  104: 
  105:   if (matchsym)
  106:     {
  107:       /* We found a symbol close by.  Fill in its name and exact
  108:          address.  */
  109:       lookup_t matchl = LOOKUP_VALUE (match);
  110: 
  111:       info->dli_sname = strtab + matchsym->st_name;
  112:       info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
  113:     }
  114:   else
  115:     {
  116:       /* No symbol matches.  We return only the containing object.  */
  117:       info->dli_sname = NULL;
  118:       info->dli_saddr = NULL;
  119:     }
  120: }
  121: 
  122: 
  123: int
  124: internal_function
  125: _dl_addr (const void *address, Dl_info *info,
  126:           struct link_map **mapp, const ElfW(Sym) **symbolp)
  127: {
  128:   const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
  129:   int result = 0;
  130: 
  131:   /* Protect against concurrent loads and unloads.  */
  132:   __rtld_lock_lock_recursive (GL(dl_load_lock));
  133: 
  134:   /* Find the highest-addressed object that ADDRESS is not below.  */
  135:   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
  136:     for (struct link_map *l = GL(dl_ns)[ns]._ns_loaded; l; l = l->l_next)
  137:       if (addr >= l->l_map_start && addr < l->l_map_end
  138:           && (l->l_contiguous || _dl_addr_inside_object (l, addr)))
  139:         {
  140:           determine_info (addr, l, info, mapp, symbolp);
  141:           result = 1;
  142:           goto out;
  143:         }
  144: 
  145:  out:
  146:   __rtld_lock_unlock_recursive (GL(dl_load_lock));
  147: 
  148:   return result;
  149: }
  150: libc_hidden_def (_dl_addr)
  151: 
  152: /* Return non-zero if ADDR lies within one of L's segments.  */
  153: int
  154: internal_function
  155: _dl_addr_inside_object (struct link_map *l, const ElfW(Addr) addr)
  156: {
  157:   int n = l->l_phnum;
  158:   const ElfW(Addr) reladdr = addr - l->l_addr;
  159: 
  160:   while (--n >= 0)
  161:     if (l->l_phdr[n].p_type == PT_LOAD
  162:         && reladdr - l->l_phdr[n].p_vaddr >= 0
  163:         && reladdr - l->l_phdr[n].p_vaddr < l->l_phdr[n].p_memsz)
  164:       return 1;
  165:   return 0;
  166: }