elf/dl-libc.c

   1 /* Handle loading and unloading shared objects for internal libc purposes.
   2    Copyright (C) 1999, 2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Zack Weinberg <zack@rabi.columbia.edu>, 1999.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <ldsodefs.h>
  24
  25 /* The purpose of this file is to provide wrappers around the dynamic
  26    linker error mechanism (similar to dlopen() et al in libdl) which
  27    are usable from within libc.  Generally we want to throw away the
  28    string that dlerror() would return and just pass back a null pointer
  29    for errors.  This also lets the rest of libc not know about the error
  30    handling mechanism.
  31
  32    Much of this code came from gconv_dl.c with slight modifications. */
  33
  34 static int
  35 internal_function
  36 dlerror_run (void (*operate) (void *), void *args)
  37 {
  38   const char *objname;
  39   const char *last_errstring = NULL;
  40   int result;
  41
  42   (void) _dl_catch_error (&objname, &last_errstring, operate, args);
  43
  44   result = last_errstring != NULL;
  45   if (result)
  46     free ((char *) last_errstring);
  47
  48   return result;
  49 }
  50
  51 /* These functions are called by dlerror_run... */
  52
  53 struct do_dlopen_args
  54 {
  55   /* Argument to do_dlopen.  */
  56   const char *name;
  57
  58   /* Return from do_dlopen.  */
  59   struct link_map *map;
  60 };
  61
  62 struct do_dlsym_args
  63 {
  64   /* Arguments to do_dlsym.  */
  65   struct link_map *map;
  66   const char *name;
  67
  68   /* Return values of do_dlsym.  */
  69   lookup_t loadbase;
  70   const ElfW(Sym) *ref;
  71 };
  72
  73 static void
  74 do_dlopen (void *ptr)
  75 {
  76   struct do_dlopen_args *args = (struct do_dlopen_args *) ptr;
  77   /* Open and relocate the shared object.  */
  78   args->map = _dl_open (args->name, RTLD_LAZY, NULL);
  79 }
  80
  81 static void
  82 do_dlsym (void *ptr)
  83 {
  84   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
  85   args->ref = NULL;
  86   args->loadbase = _dl_lookup_symbol (args->name, args->map, &args->ref,
  87                                       args->map->l_local_scope, 0);
  88 }
  89
  90 static void
  91 do_dlclose (void *ptr)
  92 {
  93   _dl_close ((struct link_map *) ptr);
  94 }
  95
  96 /* ... and these functions call dlerror_run. */
  97
  98 void *
  99 __libc_dlopen (const char *__name)
 100 {
 101   struct do_dlopen_args args;
 102   args.name = __name;
 103
 104   return (dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map);
 105 }
 106
 107 void *
 108 __libc_dlsym (void *__map, const char *__name)
 109 {
 110   struct do_dlsym_args args;
 111   args.map = __map;
 112   args.name = __name;
 113
 114   return (dlerror_run (do_dlsym, &args) ? NULL
 115           : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));
 116 }
 117
 118 int
 119 __libc_dlclose (void *__map)
 120 {
 121   return dlerror_run (do_dlclose, __map);
 122 }