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dl-sym.c

/* Look up a symbol in a shared object loaded by `dlopen'.
   Copyright (C) 1999,2000,2001,2002,2004,2006 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <stddef.h>
#include <setjmp.h>
#include <libintl.h>

#include <dlfcn.h>
#include <ldsodefs.h>
#include <dl-hash.h>
#ifdef USE_TLS
# include <dl-tls.h>
#endif


#if defined USE_TLS && defined SHARED
/* Systems which do not have tls_index also probably have to define
   DONT_USE_TLS_INDEX.  */

# ifndef __TLS_GET_ADDR
#  define __TLS_GET_ADDR __tls_get_addr
# endif

/* Return the symbol address given the map of the module it is in and
   the symbol record.  This is used in dl-sym.c.  */
static void *
internal_function
_dl_tls_symaddr (struct link_map *map, const ElfW(Sym) *ref)
{
# ifndef DONT_USE_TLS_INDEX
  tls_index tmp =
    {
      .ti_module = map->l_tls_modid,
      .ti_offset = ref->st_value
    };

  return __TLS_GET_ADDR (&tmp);
# else
  return __TLS_GET_ADDR (map->l_tls_modid, ref->st_value);
# endif
}
#endif


static void *
internal_function
do_sym (void *handle, const char *name, void *who,
      struct r_found_version *vers, int flags)
{
  const ElfW(Sym) *ref = NULL;
  lookup_t result;
  ElfW(Addr) caller = (ElfW(Addr)) who;

  /* If the address is not recognized the call comes from the main
     program (we hope).  */
  struct link_map *match = GL(dl_ns)[LM_ID_BASE]._ns_loaded;

  /* Find the highest-addressed object that CALLER is not below.  */
  for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
    for (struct link_map *l = GL(dl_ns)[ns]._ns_loaded; l != NULL;
       l = l->l_next)
      if (caller >= l->l_map_start && caller < l->l_map_end)
      {
        /* There must be exactly one DSO for the range of the virtual
           memory.  Otherwise something is really broken.  */
        match = l;
        break;
      }

  if (handle == RTLD_DEFAULT)
    /* Search the global scope.  */
    result = GLRO(dl_lookup_symbol_x) (name, match, &ref, match->l_scope,
                               vers, 0, flags|DL_LOOKUP_ADD_DEPENDENCY,
                               NULL);
  else if (handle == RTLD_NEXT)
    {
      if (__builtin_expect (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded, 0))
      {
        if (match == NULL
            || caller < match->l_map_start
            || caller >= match->l_map_end)
          GLRO(dl_signal_error) (0, NULL, NULL, N_("\
RTLD_NEXT used in code not dynamically loaded"));
      }

      struct link_map *l = match;
      while (l->l_loader != NULL)
      l = l->l_loader;

      result = GLRO(dl_lookup_symbol_x) (name, match, &ref, l->l_local_scope,
                               vers, 0, 0, match);
    }
  else
    {
      /* Search the scope of the given object.  */
      struct link_map *map = handle;
      result = GLRO(dl_lookup_symbol_x) (name, map, &ref, map->l_local_scope,
                               vers, 0, flags, NULL);
    }

  if (ref != NULL)
    {
      void *value;

#if defined USE_TLS && defined SHARED
      if (ELFW(ST_TYPE) (ref->st_info) == STT_TLS)
      /* The found symbol is a thread-local storage variable.
         Return the address for to the current thread.  */
      value = _dl_tls_symaddr (result, ref);
      else
#endif
      value = DL_SYMBOL_ADDRESS (result, ref);

#ifdef SHARED
      /* Auditing checkpoint: we have a new binding.  Provide the
       auditing libraries the possibility to change the value and
       tell us whether further auditing is wanted.  */
      if (__builtin_expect (GLRO(dl_naudit) > 0, 0))
      {
        const char *strtab = (const char *) D_PTR (result,
                                         l_info[DT_STRTAB]);
        /* Compute index of the symbol entry in the symbol table of
           the DSO with the definition.  */
        unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
                                           l_info[DT_SYMTAB]));

        if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
          {
            unsigned int altvalue = 0;
            struct audit_ifaces *afct = GLRO(dl_audit);
            /* Synthesize a symbol record where the st_value field is
             the result.  */
            ElfW(Sym) sym = *ref;
            sym.st_value = (ElfW(Addr)) value;

            for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
            {
              if (afct->symbind != NULL
                  && ((match->l_audit[cnt].bindflags & LA_FLG_BINDFROM)
                    != 0
                    || ((result->l_audit[cnt].bindflags & LA_FLG_BINDTO)
                        != 0)))
                {
                  unsigned int flags = altvalue | LA_SYMB_DLSYM;
                  uintptr_t new_value
                  = afct->symbind (&sym, ndx,
                               &match->l_audit[cnt].cookie,
                               &result->l_audit[cnt].cookie,
                               &flags, strtab + ref->st_name);
                  if (new_value != (uintptr_t) sym.st_value)
                  {
                    altvalue = LA_SYMB_ALTVALUE;
                    sym.st_value = new_value;
                  }
                }

              afct = afct->next;
            }

            value = (void *) sym.st_value;
          }
      }
#endif

      return value;
    }

  return NULL;
}


void *
internal_function
_dl_vsym (void *handle, const char *name, const char *version, void *who)
{
  struct r_found_version vers;

  /* Compute hash value to the version string.  */
  vers.name = version;
  vers.hidden = 1;
  vers.hash = _dl_elf_hash (version);
  /* We don't have a specific file where the symbol can be found.  */
  vers.filename = NULL;

  return do_sym (handle, name, who, &vers, 0);
}


void *
internal_function
_dl_sym (void *handle, const char *name, void *who)
{
  return do_sym (handle, name, who, NULL, DL_LOOKUP_RETURN_NEWEST);
}

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