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 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   int result;
  46
  47   (void) GLRO(dl_catch_error) (&objname, &last_errstring, operate, args);
  48
  49   result = last_errstring != NULL;
  50   if (result && last_errstring != _dl_out_of_memory)
  51     free ((char *) last_errstring);
  52
  53   return result;
  54 }
  55
  56 /* These functions are called by dlerror_run... */
  57
  58 struct do_dlopen_args
  59 {
  60   /* Argument to do_dlopen.  */
  61   const char *name;
  62   /* Opening mode.  */
  63   int mode;
  64
  65   /* Return from do_dlopen.  */
  66   struct link_map *map;
  67 };
  68
  69 struct do_dlsym_args
  70 {
  71   /* Arguments to do_dlsym.  */
  72   struct link_map *map;
  73   const char *name;
  74
  75   /* Return values of do_dlsym.  */
  76   lookup_t loadbase;
  77   const ElfW(Sym) *ref;
  78 };
  79
  80 static void
  81 do_dlopen (void *ptr)
  82 {
  83   struct do_dlopen_args *args = (struct do_dlopen_args *) ptr;
  84   /* Open and relocate the shared object.  */
  85   args->map = GLRO(dl_open) (args->name, args->mode, NULL, __LM_ID_CALLER,
  86                              __libc_argc, __libc_argv, __environ);
  87 }
  88
  89 static void
  90 do_dlsym (void *ptr)
  91 {
  92   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
  93   args->ref = NULL;
  94   args->loadbase = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
  95                                              args->map->l_local_scope, NULL, 0,
  96                                              DL_LOOKUP_RETURN_NEWEST, NULL);
  97 }
  98
  99 static void
 100 do_dlclose (void *ptr)
 101 {
 102   GLRO(dl_close) ((struct link_map *) ptr);
 103 }
 104
 105 /* This code is to support __libc_dlopen from __libc_dlopen'ed shared
 106    libraries.  We need to ensure the statically linked __libc_dlopen
 107    etc. functions are used instead of the dynamically loaded.  */
 108 struct dl_open_hook
 109 {
 110   void *(*dlopen_mode) (const char *name, int mode);
 111   void *(*dlsym) (void *map, const char *name);
 112   int (*dlclose) (void *map);
 113 };
 114
 115 #ifdef SHARED
 116 extern struct dl_open_hook *_dl_open_hook;
 117 libc_hidden_proto (_dl_open_hook);
 118 struct dl_open_hook *_dl_open_hook __attribute__ ((nocommon));
 119 libc_hidden_data_def (_dl_open_hook);
 120 #else
 121 static void
 122 do_dlsym_private (void *ptr)
 123 {
 124   lookup_t l;
 125   struct r_found_version vers;
 126   vers.name = "GLIBC_PRIVATE";
 127   vers.hidden = 1;
 128   /* vers.hash = _dl_elf_hash (vers.name);  */
 129   vers.hash = 0x0963cf85;
 130   vers.filename = NULL;
 131
 132   struct do_dlsym_args *args = (struct do_dlsym_args *) ptr;
 133   args->ref = NULL;
 134   l = GLRO(dl_lookup_symbol_x) (args->name, args->map, &args->ref,
 135                                 args->map->l_scope, &vers, 0, 0, NULL);
 136   args->loadbase = l;
 137 }
 138
 139 static struct dl_open_hook _dl_open_hook =
 140   {
 141     .dlopen_mode = __libc_dlopen_mode,
 142     .dlsym = __libc_dlsym,
 143     .dlclose = __libc_dlclose
 144   };
 145 #endif
 146
 147 /* ... and these functions call dlerror_run. */
 148
 149 void *
 150 __libc_dlopen_mode (const char *name, int mode)
 151 {
 152   struct do_dlopen_args args;
 153   args.name = name;
 154   args.mode = mode;
 155
 156 #ifdef SHARED
 157   if (__builtin_expect (_dl_open_hook != NULL, 0))
 158     return _dl_open_hook->dlopen_mode (name, mode);
 159   return (dlerror_run (do_dlopen, &args) ? NULL : (void *) args.map);
 160 #else
 161   if (dlerror_run (do_dlopen, &args))
 162     return NULL;
 163
 164   __libc_register_dl_open_hook (args.map);
 165   __libc_register_dlfcn_hook (args.map);
 166   return (void *) args.map;
 167 #endif
 168 }
 169 libc_hidden_def (__libc_dlopen_mode)
 170
 171 #ifndef SHARED
 172 void *
 173 __libc_dlsym_private (struct link_map *map, const char *name)
 174 {
 175   struct do_dlsym_args sargs;
 176   sargs.map = map;
 177   sargs.name = name;
 178
 179   if (! dlerror_run (do_dlsym_private, &sargs))
 180     return DL_SYMBOL_ADDRESS (sargs.loadbase, sargs.ref);
 181   return NULL;
 182 }
 183
 184 void
 185 __libc_register_dl_open_hook (struct link_map *map)
 186 {
 187   struct dl_open_hook **hook;
 188
 189   hook = (struct dl_open_hook **) __libc_dlsym_private (map, "_dl_open_hook");
 190   if (hook != NULL)
 191     *hook = &_dl_open_hook;
 192 }
 193 #endif
 194
 195 void *
 196 __libc_dlsym (void *map, const char *name)
 197 {
 198   struct do_dlsym_args args;
 199   args.map = map;
 200   args.name = name;
 201
 202 #ifdef SHARED
 203   if (__builtin_expect (_dl_open_hook != NULL, 0))
 204     return _dl_open_hook->dlsym (map, name);
 205 #endif
 206   return (dlerror_run (do_dlsym, &args) ? NULL
 207           : (void *) (DL_SYMBOL_ADDRESS (args.loadbase, args.ref)));
 208 }
 209 libc_hidden_def (__libc_dlsym)
 210
 211 int
 212 __libc_dlclose (void *map)
 213 {
 214 #ifdef SHARED
 215   if (__builtin_expect (_dl_open_hook != NULL, 0))
 216     return _dl_open_hook->dlclose (map);
 217 #endif
 218   return dlerror_run (do_dlclose, map);
 219 }
 220 libc_hidden_def (__libc_dlclose)
 221
 222
 223 libc_freeres_fn (free_mem)
 224 {
 225   struct link_map *l;
 226   struct r_search_path_elem *d;
 227
 228   /* Remove all search directories.  */
 229   d = GL(dl_all_dirs);
 230   while (d != GLRO(dl_init_all_dirs))
 231     {
 232       struct r_search_path_elem *old = d;
 233       d = d->next;
 234       free (old);
 235     }
 236
 237   /* Remove all additional names added to the objects.  */
 238   for (Lmid_t ns = 0; ns < DL_NNS; ++ns)
 239     for (l = GL(dl_ns)[ns]._ns_loaded; l != NULL; l = l->l_next)
 240       {
 241         struct libname_list *lnp = l->l_libname->next;
 242
 243         l->l_libname->next = NULL;
 244
 245         while (lnp != NULL)
 246           {
 247             struct libname_list *old = lnp;
 248             lnp = lnp->next;
 249             if (! old->dont_free)
 250             free (old);
 251           }
 252       }
 253 }