elf/dl-libc.c

   1 /* Handle loading and unloading shared objects for internal libc purposes.
   2    Copyright (C) 1999-2002,2004-2006,2009,2010 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 extern int __libc_argc attribute_hidden;
  26 extern char **__libc_argv attribute_hidden;
  27
  28 extern char **__environ;
  29
  30 /* The purpose of this file is to provide wrappers around the dynamic
  31    linker error mechanism (similar to dlopen() et al in libdl) which
  32    are usable from within libc.  Generally we want to throw away the
  33    string that dlerror() would return and just pass back a null pointer
  34    for errors.  This also lets the rest of libc not know about the error
  35    handling mechanism.
  36
  37    Much of this code came from gconv_dl.c with slight modifications. */
  38
  39 static int
  40 internal_function
  41 dlerror_run (void (*operate) (void *), void *args)
  42 {
  43   const char *objname;
  44   const char *last_errstring = NULL;
  45   bool malloced;
  46
  47   (void) GLRO(dl_catch_error) (&objname, &last_errstring, &malloced,
  48                                operate, args);
  49
  50   int result = last_errstring != NULL;
  51   if (result && malloced)
  52     free ((char *) last_errstring);
  53
  54   return result;
  55 }
  56
  57 /* These functions are called by dlerror_run... */
  58
  59 struct do_dlopen_args
  60 {
  61   /* Argument to do_dlopen.  */
  62   const char *name;
  63   /* Opening mode.  */
  64   int mode;
  65
  66   /* Return from do_dlopen.  */
  67   struct link_map *map;
  68 };
  69
  70 struct do_dlsym_args
  71 {
  72   /* Arguments to do_dlsym.  */
  73   struct link_map *map;
  74   const char *name;
  75
  76   /* Return values of do_dlsym.  */
  77   lookup_t loadbase;
  78   const ElfW(Sym) *ref;
  79 };
  80
  81 static void
  82 do_dlopen (void *ptr)
  83 {
  84   struct do_dlopen_args *args = (struct do_dlopen_args *) ptr;
  85   /* Open and relocate the shared object.  */
  86   args->map = GLRO(dl_open) (args->name, args->mode, NULL, __LM_ID_CALLER,
  87                              __libc_argc, __libc_argv, __environ);
  88 }
  89
  90 static void
  91 do_dlsym (void *ptr)
  92 {
  93   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
  94   args->ref = NULL;
  95   args->loadbase = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
  96                                              args->map->l_local_scope, NULL, 0,
  97                                              DL_LOOKUP_RETURN_NEWEST, NULL);
  98 }
  99
 100 static void
 101 do_dlclose (void *ptr)
 102 {
 103   GLRO(dl_close) ((struct link_map *) ptr);
 104 }
 105
 106 /* This code is to support __libc_dlopen from __libc_dlopen'ed shared
 107    libraries.  We need to ensure the statically linked __libc_dlopen
 108    etc. functions are used instead of the dynamically loaded.  */
 109 struct dl_open_hook
 110 {
 111   void *(*dlopen_mode) (const char *name, int mode);
 112   void *(*dlsym) (void *map, const char *name);
 113   int (*dlclose) (void *map);
 114 };
 115
 116 #ifdef SHARED
 117 extern struct dl_open_hook *_dl_open_hook;
 118 libc_hidden_proto (_dl_open_hook);
 119 struct dl_open_hook *_dl_open_hook __attribute__ ((nocommon));
 120 libc_hidden_data_def (_dl_open_hook);
 121 #else
 122 static void
 123 do_dlsym_private (void *ptr)
 124 {
 125   lookup_t l;
 126   struct r_found_version vers;
 127   vers.name = "GLIBC_PRIVATE";
 128   vers.hidden = 1;
 129   /* vers.hash = _dl_elf_hash (vers.name);  */
 130   vers.hash = 0x0963cf85;
 131   vers.filename = NULL;
 132
 133   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
 134   args->ref = NULL;
 135   l = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
 136                                 args->map->l_scope, &vers, 0, 0, NULL);
 137   args->loadbase = l;
 138 }
 139
 140 static struct dl_open_hook _dl_open_hook =
 141   {
 142     .dlopen_mode = __libc_dlopen_mode,
 143     .dlsym = __libc_dlsym,
 144     .dlclose = __libc_dlclose
 145   };
 146 #endif
 147
 148 /* ... and these functions call dlerror_run. */
 149
 150 void *
 151 __libc_dlopen_mode (const char *name, int mode)
 152 {
 153   struct do_dlopen_args args;
 154   args.name = name;
 155   args.mode = mode;
 156
 157 #ifdef SHARED
 158   if (__builtin_expect (_dl_open_hook != NULL, 0))
 159     return _dl_open_hook->dlopen_mode (name, mode);
 160   return (dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map);
 161 #else
 162   if (dlerror_run (do_dlopen, &args))
 163     return NULL;
 164
 165   __libc_register_dl_open_hook (args.map);
 166   __libc_register_dlfcn_hook (args.map);
 167   return (void *) args.map;
 168 #endif
 169 }
 170 libc_hidden_def (__libc_dlopen_mode)
 171
 172 #ifndef SHARED
 173 void *
 174 __libc_dlsym_private (struct link_map *map, const char *name)
 175 {
 176   struct do_dlsym_args sargs;
 177   sargs.map = map;
 178   sargs.name = name;
 179
 180   if (! dlerror_run (do_dlsym_private, &sargs))
 181     return DL_SYMBOL_ADDRESS (sargs.loadbase, sargs.ref);
 182   return NULL;
 183 }
 184
 185 void
 186 __libc_register_dl_open_hook (struct link_map *map)
 187 {
 188   struct dl_open_hook **hook;
 189
 190   hook = (struct dl_open_hook **) __libc_dlsym_private (map, "_dl_open_hook");
 191   if (hook != NULL)
 192     *hook = &_dl_open_hook;
 193 }
 194 #endif
 195
 196 void *
 197 __libc_dlsym (void *map, const char *name)
 198 {
 199   struct do_dlsym_args args;
 200   args.map = map;
 201   args.name = name;
 202
 203 #ifdef SHARED
 204   if (__builtin_expect (_dl_open_hook != NULL, 0))
 205     return _dl_open_hook->dlsym (map, name);
 206 #endif
 207   return (dlerror_run (do_dlsym, &args) ? NULL
 208           : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));
 209 }
 210 libc_hidden_def (__libc_dlsym)
 211
 212 int
 213 __libc_dlclose (void *map)
 214 {
 215 #ifdef SHARED
 216   if (__builtin_expect (_dl_open_hook != NULL, 0))
 217     return _dl_open_hook->dlclose (map);
 218 #endif
 219   return dlerror_run (do_dlclose, map);
 220 }
 221 libc_hidden_def (__libc_dlclose)
 222
 223
 224 static bool __libc_freeres_fn_section
 225 free_slotinfo (struct dtv_slotinfo_list **elemp)
 226 {
 227   size_t cnt;
 228
 229   if (*elemp == NULL)
 230     /* Nothing here, all is removed (or there never was anything).  */
 231     return true;
 232
 233   if (!free_slotinfo (&(*elemp)->next))
 234     /* We cannot free the entry.  */
 235     return false;
 236
 237   /* That cleared our next pointer for us.  */
 238
 239   for (cnt = 0; cnt < (*elemp)->len; ++cnt)
 240     if ((*elemp)->slotinfo[cnt].map != NULL)
 241       /* Still used.  */
 242       return false;
 243
 244   /* We can remove the list element.  */
 245   free (*elemp);
 246   *elemp = NULL;
 247
 248   return true;
 249 }
 250
 251
 252 libc_freeres_fn (free_mem)
 253 {
 254   struct link_map *l;
 255   struct r_search_path_elem *d;
 256
 257   /* Remove all search directories.  */
 258   d = GL(dl_all_dirs);
 259   while (d != GLRO(dl_init_all_dirs))
 260     {
 261       struct r_search_path_elem *old = d;
 262       d = d->next;
 263       free (old);
 264     }
 265
 266   for (Lmid_t ns = 0; ns < GL(dl_nns); ++ns)
 267     {
 268       for (l = GL(dl_ns)[ns]._ns_loaded; l != NULL; l = l->l_next)
 269         {
 270           struct libname_list *lnp = l->l_libname->next;
 271
 272           l->l_libname->next = NULL;
 273
 274           /* Remove all additional names added to the objects.  */
 275           while (lnp != NULL)
 276             {
 277               struct libname_list *old = lnp;
 278               lnp = lnp->next;
 279               if (! old->dont_free)
 280                 free (old);
 281             }
 282
 283           /* Free the initfini dependency list.  */
 284           if (l->l_free_initfini)
 285             free (l->l_initfini);
 286         }
 287
 288       if (__builtin_expect (GL(dl_ns)[ns]._ns_global_scope_alloc, 0) != 0
 289           && (GL(dl_ns)[ns]._ns_main_searchlist->r_nlist
 290               // XXX Check whether we need NS-specific initial_searchlist
 291               == GLRO(dl_initial_searchlist).r_nlist))
 292         {
 293           /* All object dynamically loaded by the program are unloaded.  Free
 294              the memory allocated for the global scope variable.  */
 295           struct link_map **old = GL(dl_ns)[ns]._ns_main_searchlist->r_list;
 296
 297           /* Put the old map in.  */
 298           GL(dl_ns)[ns]._ns_main_searchlist->r_list
 299             // XXX Check whether we need NS-specific initial_searchlist
 300             = GLRO(dl_initial_searchlist).r_list;
 301           /* Signal that the original map is used.  */
 302           GL(dl_ns)[ns]._ns_global_scope_alloc = 0;
 303
 304           /* Now free the old map.  */
 305           free (old);
 306         }
 307     }
 308
 309   if (USE___THREAD || GL(dl_tls_dtv_slotinfo_list) != NULL)
 310     {
 311       /* Free the memory allocated for the dtv slotinfo array.  We can do
 312          this only if all modules which used this memory are unloaded.  */
 313 #ifdef SHARED
 314       if (GL(dl_initial_dtv) == NULL)
 315         /* There was no initial TLS setup, it was set up later when
 316            it used the normal malloc.  */
 317         free_slotinfo (&GL(dl_tls_dtv_slotinfo_list));
 318       else
 319 #endif
 320         /* The first element of the list does not have to be deallocated.
 321            It was allocated in the dynamic linker (i.e., with a different
 322            malloc), and in the static library it's in .bss space.  */
 323         free_slotinfo (&GL(dl_tls_dtv_slotinfo_list)->next);
 324     }
 325
 326   void *scope_free_list = GL(dl_scope_free_list);
 327   GL(dl_scope_free_list) = NULL;
 328   free (scope_free_list);
 329 }