elf/dl-addr.c

   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 #ifdef USE_TLS
  65                       && ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
  66 #endif
  67                       && DL_ADDR_SYM_MATCH (match, &symtab[symndx],
  68                                             matchsym, addr)
  69                       && symtab[symndx].st_name < strtabsize)
  70                     matchsym = (ElfW(Sym) *) &symtab[symndx];
  71
  72                   ++symndx;
  73                 }
  74               while ((*hasharr++ & 1u) == 0);
  75             }
  76         }
  77     }
  78   else
  79     {
  80       const ElfW(Sym) *symtabend;
  81       if (match->l_info[DT_HASH] != NULL)
  82         symtabend = (symtab
  83                      + ((Elf_Symndx *) D_PTR (match, l_info[DT_HASH]))[1]);
  84       else
  85         /* There is no direct way to determine the number of symbols in the
  86            dynamic symbol table and no hash table is present.  The ELF
  87            binary is ill-formed but what shall we do?  Use the beginning of
  88            the string table which generally follows the symbol table.  */
  89         symtabend = (const ElfW(Sym) *) strtab;
  90
  91       for (; (void *) symtab < (void *) symtabend; ++symtab)
  92         if ((ELFW(ST_BIND) (symtab->st_info) == STB_GLOBAL
  93              || ELFW(ST_BIND) (symtab->st_info) == STB_WEAK)
  94 #ifdef USE_TLS
  95             && ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
  96 #endif
  97             && (symtab->st_shndx != SHN_UNDEF
  98                 || symtab->st_value != 0)
  99             && DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
 100             && symtab->st_name < strtabsize)
 101           matchsym = (ElfW(Sym) *) symtab;
 102     }
 103
 104   if (mapp)
 105     *mapp = match;
 106   if (symbolp)
 107     *symbolp = matchsym;
 108
 109   if (matchsym)
 110     {
 111       /* We found a symbol close by.  Fill in its name and exact
 112          address.  */
 113       lookup_t matchl = LOOKUP_VALUE (match);
 114
 115       info->dli_sname = strtab + matchsym->st_name;
 116       info->dli_saddr = DL_SYMBOL_ADDRESS (matchl, matchsym);
 117     }
 118   else
 119     {
 120       /* No symbol matches.  We return only the containing object.  */
 121       info->dli_sname = NULL;
 122       info->dli_saddr = NULL;
 123     }
 124 }
 125
 126
 127 int
 128 internal_function
 129 _dl_addr (const void *address, Dl_info *info,
 130           struct link_map **mapp, const ElfW(Sym) **symbolp)
 131 {
 132   const ElfW(Addr) addr = DL_LOOKUP_ADDRESS (address);
 133   int result = 0;
 134
 135   /* Protect against concurrent loads and unloads.  */
 136   __rtld_lock_lock_recursive (GL(dl_load_lock));
 137
 138   /* Find the highest-addressed object that ADDRESS is not below.  */
 139   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
 140     for (struct link_map *l = GL(dl_ns)[ns]._ns_loaded; l; l = l->l_next)
 141       if (addr >= l->l_map_start && addr < l->l_map_end
 142           && (l->l_contiguous || _dl_addr_inside_object (l, addr)))
 143         {
 144           determine_info (addr, l, info, mapp, symbolp);
 145           result = 1;
 146           goto out;
 147         }
 148
 149  out:
 150   __rtld_lock_unlock_recursive (GL(dl_load_lock));
 151
 152   return result;
 153 }
 154 libc_hidden_def (_dl_addr)
 155
 156 /* Return non-zero if ADDR lies within one of L's segments.  */
 157 int
 158 internal_function
 159 _dl_addr_inside_object (struct link_map *l, const ElfW(Addr) addr)
 160 {
 161   int n = l->l_phnum;
 162   const ElfW(Addr) reladdr = addr - l->l_addr;
 163
 164   while (--n >= 0)
 165     if (l->l_phdr[n].p_type == PT_LOAD
 166         && reladdr - l->l_phdr[n].p_vaddr >= 0
 167         && reladdr - l->l_phdr[n].p_vaddr < l->l_phdr[n].p_memsz)
 168       return 1;
 169   return 0;
 170 }