elf/dl-libc.c

   1 /* Handle loading and unloading shared objects for internal libc purposes.
   2    Copyright (C) 1999, 2000, 2001, 2002, 2004 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 Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the 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    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    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) GLRO(dl_catch_error) (&objname, &last_errstring, operate, args);
  43
  44   result = last_errstring != NULL;
  45   if (result && last_errstring != _dl_out_of_memory)
  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   /* Opening mode.  */
  58   int mode;
  59
  60   /* Return from do_dlopen.  */
  61   struct link_map *map;
  62 };
  63
  64 struct do_dlsym_args
  65 {
  66   /* Arguments to do_dlsym.  */
  67   struct link_map *map;
  68   const char *name;
  69
  70   /* Return values of do_dlsym.  */
  71   lookup_t loadbase;
  72   const ElfW(Sym) *ref;
  73 };
  74
  75 static void
  76 do_dlopen (void *ptr)
  77 {
  78   struct do_dlopen_args *args = (struct do_dlopen_args *) ptr;
  79   /* Open and relocate the shared object.  */
  80   args->map = _dl_open (args->name, args->mode, NULL);
  81 }
  82
  83 static void
  84 do_dlsym (void *ptr)
  85 {
  86   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
  87   args->ref = NULL;
  88   args->loadbase = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
  89                                              args->map->l_local_scope, NULL, 0,
  90                                              DL_LOOKUP_RETURN_NEWEST, NULL);
  91 }
  92
  93 static void
  94 do_dlclose (void *ptr)
  95 {
  96   _dl_close ((struct link_map *) ptr);
  97 }
  98
  99 /* This code is to support __libc_dlopen from __libc_dlopen'ed shared
 100    libraries.  We need to ensure the statically linked __libc_dlopen
 101    etc. functions are used instead of the dynamically loaded.  */
 102 struct dl_open_hook
 103 {
 104   void *(*dlopen_mode) (const char *name, int mode);
 105   void *(*dlsym) (void *map, const char *name);
 106   int (*dlclose) (void *map);
 107 };
 108
 109 #ifdef SHARED
 110 extern struct dl_open_hook *_dl_open_hook;
 111 libc_hidden_proto (_dl_open_hook);
 112 struct dl_open_hook *_dl_open_hook __attribute__((nocommon));
 113 libc_hidden_data_def (_dl_open_hook);
 114 #else
 115 static void
 116 do_dlsym_private (void *ptr)
 117 {
 118   lookup_t l;
 119   struct r_found_version vers;
 120   vers.name = "GLIBC_PRIVATE";
 121   vers.hidden = 1;
 122   /* vers.hash = _dl_elf_hash (version);  */
 123   vers.hash = 0x0963cf85;
 124   /* FIXME: Shouldn't we use libc.so.6* here?  */
 125   vers.filename = NULL;
 126
 127   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
 128   args->ref = NULL;
 129   l = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
 130                                 args->map->l_scope, &vers, 0, 0, NULL);
 131   args->loadbase = l;
 132 }
 133
 134 static struct dl_open_hook _dl_open_hook =
 135   {
 136     .dlopen_mode = __libc_dlopen_mode,
 137     .dlsym = __libc_dlsym,
 138     .dlclose = __libc_dlclose
 139   };
 140 #endif
 141
 142 /* ... and these functions call dlerror_run. */
 143
 144 void *
 145 __libc_dlopen_mode (const char *name, int mode)
 146 {
 147   struct do_dlopen_args args;
 148   args.name = name;
 149   args.mode = mode;
 150
 151 #ifdef SHARED
 152   if (__builtin_expect (_dl_open_hook != NULL, 0))
 153     return _dl_open_hook->dlopen_mode (name, mode);
 154   return (dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map);
 155 #else
 156   if (dlerror_run (do_dlopen, &args))
 157     return NULL;
 158
 159   struct do_dlsym_args sargs;
 160   sargs.map = args.map;
 161   sargs.name = "_dl_open_hook";
 162
 163   if (! dlerror_run (do_dlsym_private, &sargs))
 164     {
 165       struct dl_open_hook **hook
 166         = (struct dl_open_hook **)
 167           (DL_SYMBOL_ADDRESS (sargs.loadbase, sargs.ref));
 168       if (hook != NULL)
 169         *hook = &_dl_open_hook;
 170     }
 171
 172   return (void *) args.map;
 173 #endif
 174 }
 175 libc_hidden_def (__libc_dlopen_mode)
 176
 177 void *
 178 __libc_dlsym (void *map, const char *name)
 179 {
 180   struct do_dlsym_args args;
 181   args.map = map;
 182   args.name = name;
 183
 184 #ifdef SHARED
 185   if (__builtin_expect (_dl_open_hook != NULL, 0))
 186     return _dl_open_hook->dlsym (map, name);
 187 #endif
 188   return (dlerror_run (do_dlsym, &args) ? NULL
 189           : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));
 190 }
 191 libc_hidden_def (__libc_dlsym)
 192
 193 int
 194 __libc_dlclose (void *map)
 195 {
 196 #ifdef SHARED
 197   if (__builtin_expect (_dl_open_hook != NULL, 0))
 198     return _dl_open_hook->dlclose (map);
 199 #endif
 200   return dlerror_run (do_dlclose, map);
 201 }
 202 libc_hidden_def (__libc_dlclose)
 203
 204
 205 libc_freeres_fn (free_mem)
 206 {
 207   struct link_map *l;
 208   struct r_search_path_elem *d;
 209
 210   /* Remove all search directories.  */
 211   d = GL(dl_all_dirs);
 212   while (d != GLRO(dl_init_all_dirs))
 213     {
 214       struct r_search_path_elem *old = d;
 215       d = d->next;
 216       free (old);
 217     }
 218
 219   /* Remove all additional names added to the objects.  */
 220   for (l = GL(dl_loaded); l != NULL; l = l->l_next)
 221     {
 222       struct libname_list *lnp = l->l_libname->next;
 223
 224       l->l_libname->next = NULL;
 225
 226       while (lnp != NULL)
 227         {
 228           struct libname_list *old = lnp;
 229           lnp = lnp->next;
 230           if (! old->dont_free)
 231             free (old);
 232         }
 233     }
 234 }