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glibc  2.9
Classes | Functions
dl-sym.c File Reference
#include <assert.h>
#include <stddef.h>
#include <setjmp.h>
#include <libintl.h>
#include <dlfcn.h>
#include <ldsodefs.h>
#include <dl-hash.h>
#include <sysdep-cancel.h>
#include <dl-tls.h>

Go to the source code of this file.

Classes

struct  call_dl_lookup_args

Functions

static void call_dl_lookup (void *ptr)
static void *internal_function do_sym (void *handle, const char *name, void *who, struct r_found_version *vers, int flags)
void *internal_function _dl_vsym (void *handle, const char *name, const char *version, void *who)
void *internal_function _dl_sym (void *handle, const char *name, void *who)

Class Documentation

struct call_dl_lookup_args

Definition at line 61 of file dl-sym.c.

Collaboration diagram for call_dl_lookup_args:
Class Members
int flags
lookup_t loadbase
struct link_map * map
const char * name
struct r_found_version * vers

Function Documentation

void* internal_function _dl_sym ( void *  handle,
const char *  name,
void *  who 
)

Definition at line 271 of file dl-sym.c.

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void* internal_function _dl_vsym ( void *  handle,
const char *  name,
const char *  version,
void *  who 
)

Definition at line 254 of file dl-sym.c.

{
  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);
}

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static void call_dl_lookup ( void *  ptr) [static]

Definition at line 75 of file dl-sym.c.

{
  struct call_dl_lookup_args *args = (struct call_dl_lookup_args *) ptr;
  args->map = GLRO(dl_lookup_symbol_x) (args->name, args->map, args->refp,
                                   args->map->l_scope, args->vers, 0,
                                   args->flags, NULL);
}

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static void* internal_function do_sym ( void *  handle,
const char *  name,
void *  who,
struct r_found_version vers,
int  flags 
) [static]

Definition at line 86 of file dl-sym.c.

{
  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
         && (l->l_contiguous || _dl_addr_inside_object (l, caller)))
       {
         match = l;
         break;
       }

  if (handle == RTLD_DEFAULT)
    {
      /* Search the global scope.  We have the simple case where
        we look up in the scope of an object which was part of
        the initial binary.  And then the more complex part
        where the object is dynamically loaded and the scope
        array can change.  */
      if (RTLD_SINGLE_THREAD_P)
       result = GLRO(dl_lookup_symbol_x) (name, match, &ref,
                                      match->l_scope, vers, 0,
                                      flags | DL_LOOKUP_ADD_DEPENDENCY,
                                      NULL);
      else
       {
         struct call_dl_lookup_args args;
         args.name = name;
         args.map = match;
         args.vers = vers;
         args.flags
           = flags | DL_LOOKUP_ADD_DEPENDENCY | DL_LOOKUP_GSCOPE_LOCK;
         args.refp = &ref;

         THREAD_GSCOPE_SET_FLAG ();

         const char *objname;
         const char *errstring = NULL;
         bool malloced;
         int err = GLRO(dl_catch_error) (&objname, &errstring, &malloced,
                                     call_dl_lookup, &args);

         THREAD_GSCOPE_RESET_FLAG ();

         if (__builtin_expect (errstring != NULL, 0))
           {
             /* The lookup was unsuccessful.  Rethrow the error.  */
             char *errstring_dup = strdupa (errstring);
             char *objname_dup = strdupa (objname);
             if (malloced)
              free ((char *) errstring);

             GLRO(dl_signal_error) (err, objname_dup, NULL, errstring_dup);
             /* NOTREACHED */
           }

         result = args.map;
       }
    }
  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;

#ifdef 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;
}

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