elf/dl-libc.c

   1 /* Handle loading and unloading shared objects for internal libc purposes.
   2    Copyright (C) 1999,2000,2001,2002,2004,2005 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 libc_freeres_fn (free_mem)
 225 {
 226   struct link_map *l;
 227   struct r_search_path_elem *d;
 228
 229   /* Remove all search directories.  */
 230   d = GL(dl_all_dirs);
 231   while (d != GLRO(dl_init_all_dirs))
 232     {
 233       struct r_search_path_elem *old = d;
 234       d = d->next;
 235       free (old);
 236     }
 237
 238   /* Remove all additional names added to the objects.  */
 239   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
 240     for (l = GL(dl_ns)[ns]._ns_loaded; l != NULL; l = l->l_next)
 241       {
 242         struct libname_list *lnp = l->l_libname->next;
 243
 244         l->l_libname->next = NULL;
 245
 246         while (lnp != NULL)
 247           {
 248             struct libname_list *old = lnp;
 249             lnp = lnp->next;
 250             if (! old->dont_free)
 251             free (old);
 252           }
 253       }
 254 }