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, __LM_ID_CALLER);
  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   vers.filename = NULL;
 125
 126   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
 127   args->ref = NULL;
 128   l = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
 129                                 args->map->l_scope, &vers, 0, 0, NULL);
 130   args->loadbase = l;
 131 }
 132
 133 static struct dl_open_hook _dl_open_hook =
 134   {
 135     .dlopen_mode = __libc_dlopen_mode,
 136     .dlsym = __libc_dlsym,
 137     .dlclose = __libc_dlclose
 138   };
 139 #endif
 140
 141 /* ... and these functions call dlerror_run. */
 142
 143 void *
 144 __libc_dlopen_mode (const char *name, int mode)
 145 {
 146   struct do_dlopen_args args;
 147   args.name = name;
 148   args.mode = mode;
 149
 150 #ifdef SHARED
 151   if (__builtin_expect (_dl_open_hook != NULL, 0))
 152     return _dl_open_hook->dlopen_mode (name, mode);
 153   return (dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map);
 154 #else
 155   if (dlerror_run (do_dlopen, &args))
 156     return NULL;
 157
 158   __libc_register_dl_open_hook (args.map);
 159   __libc_register_dlfcn_hook (args.map);
 160   return (void *) args.map;
 161 #endif
 162 }
 163 libc_hidden_def (__libc_dlopen_mode)
 164
 165 #ifndef SHARED
 166 void *
 167 __libc_dlsym_private (struct link_map *map, const char *name)
 168 {
 169   struct do_dlsym_args sargs;
 170   sargs.map = map;
 171   sargs.name = name;
 172
 173   if (! dlerror_run (do_dlsym_private, &sargs))
 174     return DL_SYMBOL_ADDRESS (sargs.loadbase, sargs.ref);
 175   return NULL;
 176 }
 177
 178 void
 179 __libc_register_dl_open_hook (struct link_map *map)
 180 {
 181   struct dl_open_hook **hook;
 182
 183   hook = (struct dl_open_hook **) __libc_dlsym_private (map, "_dl_open_hook");
 184   if (hook != NULL)
 185     *hook = &_dl_open_hook;
 186 }
 187 #endif
 188
 189 void *
 190 __libc_dlsym (void *map, const char *name)
 191 {
 192   struct do_dlsym_args args;
 193   args.map = map;
 194   args.name = name;
 195
 196 #ifdef SHARED
 197   if (__builtin_expect (_dl_open_hook != NULL, 0))
 198     return _dl_open_hook->dlsym (map, name);
 199 #endif
 200   return (dlerror_run (do_dlsym, &args) ? NULL
 201           : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));
 202 }
 203 libc_hidden_def (__libc_dlsym)
 204
 205 int
 206 __libc_dlclose (void *map)
 207 {
 208 #ifdef SHARED
 209   if (__builtin_expect (_dl_open_hook != NULL, 0))
 210     return _dl_open_hook->dlclose (map);
 211 #endif
 212   return dlerror_run (do_dlclose, map);
 213 }
 214 libc_hidden_def (__libc_dlclose)
 215
 216
 217 libc_freeres_fn (free_mem)
 218 {
 219   struct link_map *l;
 220   struct r_search_path_elem *d;
 221
 222   /* Remove all search directories.  */
 223   d = GL(dl_all_dirs);
 224   while (d != GLRO(dl_init_all_dirs))
 225     {
 226       struct r_search_path_elem *old = d;
 227       d = d->next;
 228       free (old);
 229     }
 230
 231   /* Remove all additional names added to the objects.  */
 232   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
 233     for (l = GL(dl_ns)[ns]._ns_loaded; l != NULL; l = l->l_next)
 234       {
 235         struct libname_list *lnp = l->l_libname->next;
 236
 237         l->l_libname->next = NULL;
 238
 239         while (lnp != NULL)
 240           {
 241             struct libname_list *old = lnp;
 242             lnp = lnp->next;
 243             if (! old->dont_free)
 244             free (old);
 245           }
 246       }
 247 }