root/libltdl/loaders/preopen.c

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DEFINITIONS

This source file includes following definitions.
  1. get_vtable
  2. vl_init
  3. vl_exit
  4. vm_open
  5. vm_close
  6. vm_sym
  7. free_symlists
  8. add_symlist
  9. lt_dlpreload_default
  10. lt_dlpreload
  11. lt_dlpreload_open

   1 /* loader-preopen.c -- emulate dynamic linking using preloaded_symbols
   2 
   3    Copyright (C) 1998, 1999, 2000, 2004, 2006,
   4                  2007, 2008 Free Software Foundation, Inc.
   5    Written by Thomas Tanner, 1998
   6 
   7    NOTE: The canonical source of this file is maintained with the
   8    GNU Libtool package.  Report bugs to bug-libtool@gnu.org.
   9 
  10 GNU Libltdl is free software; you can redistribute it and/or
  11 modify it under the terms of the GNU Lesser General Public
  12 License as published by the Free Software Foundation; either
  13 version 2 of the License, or (at your option) any later version.
  14 
  15 As a special exception to the GNU Lesser General Public License,
  16 if you distribute this file as part of a program or library that
  17 is built using GNU Libtool, you may include this file under the
  18 same distribution terms that you use for the rest of that program.
  19 
  20 GNU Libltdl is distributed in the hope that it will be useful,
  21 but WITHOUT ANY WARRANTY; without even the implied warranty of
  22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  23 GNU Lesser General Public License for more details.
  24 
  25 You should have received a copy of the GNU Lesser General Public
  26 License along with GNU Libltdl; see the file COPYING.LIB.  If not, a
  27 copy can be downloaded from  http://www.gnu.org/licenses/lgpl.html,
  28 or obtained by writing to the Free Software Foundation, Inc.,
  29 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  30 */
  31 
  32 #include "lt__private.h"
  33 #include "lt_dlloader.h"
  34 
  35 /* Use the preprocessor to rename non-static symbols to avoid namespace
  36    collisions when the loader code is statically linked into libltdl.
  37    Use the "<module_name>_LTX_" prefix so that the symbol addresses can
  38    be fetched from the preloaded symbol list by lt_dlsym():  */
  39 #define get_vtable      preopen_LTX_get_vtable
  40 
  41 LT_BEGIN_C_DECLS
  42 LT_SCOPE lt_dlvtable *get_vtable (lt_user_data loader_data);
  43 LT_END_C_DECLS
  44 
  45 
  46 /* Boilerplate code to set up the vtable for hooking this loader into
  47    libltdl's loader list:  */
  48 static int       vl_init  (lt_user_data loader_data);
  49 static int       vl_exit  (lt_user_data loader_data);
  50 static lt_module vm_open  (lt_user_data loader_data, const char *filename,
  51                            lt_dladvise advise);
  52 static int       vm_close (lt_user_data loader_data, lt_module module);
  53 static void *    vm_sym   (lt_user_data loader_data, lt_module module,
  54                           const char *symbolname);
  55 
  56 static lt_dlvtable *vtable = 0;
  57 
  58 /* Return the vtable for this loader, only the name and sym_prefix
  59    attributes (plus the virtual function implementations, obviously)
  60    change between loaders.  */
  61 lt_dlvtable *
  62 get_vtable (lt_user_data loader_data)
  63 {
  64   if (!vtable)
  65     {
  66       vtable = (lt_dlvtable *) lt__zalloc (sizeof *vtable);
  67     }
  68 
  69   if (vtable && !vtable->name)
  70     {
  71       vtable->name              = "lt_preopen";
  72       vtable->sym_prefix        = 0;
  73       vtable->module_open       = vm_open;
  74       vtable->module_close      = vm_close;
  75       vtable->find_sym          = vm_sym;
  76       vtable->dlloader_init     = vl_init;
  77       vtable->dlloader_exit     = vl_exit;
  78       vtable->dlloader_data     = loader_data;
  79       vtable->priority          = LT_DLLOADER_PREPEND;
  80     }
  81 
  82   if (vtable && (vtable->dlloader_data != loader_data))
  83     {
  84       LT__SETERROR (INIT_LOADER);
  85       return 0;
  86     }
  87 
  88   return vtable;
  89 }
  90 
  91 
  92 
  93 /* --- IMPLEMENTATION --- */
  94 
  95 
  96 /* Wrapper type to chain together symbol lists of various origins.  */
  97 typedef struct symlist_chain
  98 {
  99   struct symlist_chain *next;
 100   const lt_dlsymlist   *symlist;
 101 } symlist_chain;
 102 
 103 
 104 static int add_symlist   (const lt_dlsymlist *symlist);
 105 static int free_symlists (void);
 106 
 107 /* The start of the symbol lists chain.  */
 108 static symlist_chain           *preloaded_symlists              = 0;
 109 
 110 /* A symbol list preloaded before lt_init() was called.  */
 111 static const    lt_dlsymlist   *default_preloaded_symbols       = 0;
 112 
 113 
 114 /* A function called through the vtable to initialise this loader.  */
 115 static int
 116 vl_init (lt_user_data LT__UNUSED loader_data)
 117 {
 118   int errors = 0;
 119 
 120   preloaded_symlists = 0;
 121   if (default_preloaded_symbols)
 122     {
 123       errors = lt_dlpreload (default_preloaded_symbols);
 124     }
 125 
 126   return errors;
 127 }
 128 
 129 
 130 /* A function called through the vtable when this loader is no
 131    longer needed by the application.  */
 132 static int
 133 vl_exit (lt_user_data LT__UNUSED loader_data)
 134 {
 135   vtable = NULL;
 136   free_symlists ();
 137   return 0;
 138 }
 139 
 140 
 141 /* A function called through the vtable to open a module with this
 142    loader.  Returns an opaque representation of the newly opened
 143    module for processing with this loader's other vtable functions.  */
 144 static lt_module
 145 vm_open (lt_user_data LT__UNUSED loader_data, const char *filename,
 146          lt_dladvise LT__UNUSED advise)
 147 {
 148   symlist_chain *lists;
 149   lt_module      module = 0;
 150 
 151   if (!preloaded_symlists)
 152     {
 153       LT__SETERROR (NO_SYMBOLS);
 154       goto done;
 155     }
 156 
 157   /* Can't use NULL as the reflective symbol header, as NULL is
 158      used to mark the end of the entire symbol list.  Self-dlpreopened
 159      symbols follow this magic number, chosen to be an unlikely
 160      clash with a real module name.  */
 161   if (!filename)
 162     {
 163       filename = "@PROGRAM@";
 164     }
 165 
 166   for (lists = preloaded_symlists; lists; lists = lists->next)
 167     {
 168       const lt_dlsymlist *symbol;
 169       for (symbol= lists->symlist; symbol->name; ++symbol)
 170         {
 171           if (!symbol->address && streq (symbol->name, filename))
 172             {
 173               /* If the next symbol's name and address is 0, it means
 174                  the module just contains the originator and no symbols.
 175                  In this case we pretend that we never saw the module and
 176                  hope that some other loader will be able to load the module
 177                  and have access to its symbols */
 178               const lt_dlsymlist *next_symbol = symbol +1;
 179               if (next_symbol->address && next_symbol->name)
 180                 {
 181                   module = (lt_module) lists->symlist;
 182                   goto done;
 183                 }
 184             }
 185         }
 186     }
 187 
 188   LT__SETERROR (FILE_NOT_FOUND);
 189 
 190  done:
 191   return module;
 192 }
 193 
 194 
 195 /* A function called through the vtable when a particular module
 196    should be unloaded.  */
 197 static int
 198 vm_close (lt_user_data LT__UNUSED loader_data, lt_module LT__UNUSED module)
 199 {
 200   /* Just to silence gcc -Wall */
 201   module = 0;
 202   return 0;
 203 }
 204 
 205 
 206 /* A function called through the vtable to get the address of
 207    a symbol loaded from a particular module.  */
 208 static void *
 209 vm_sym (lt_user_data LT__UNUSED loader_data, lt_module module, const char *name)
 210 {
 211   lt_dlsymlist         *symbol = (lt_dlsymlist*) module;
 212 
 213   symbol +=2;                   /* Skip header (originator then libname). */
 214 
 215   while (symbol->name)
 216     {
 217       if (streq (symbol->name, name))
 218         {
 219           return symbol->address;
 220         }
 221 
 222     ++symbol;
 223   }
 224 
 225   LT__SETERROR (SYMBOL_NOT_FOUND);
 226 
 227   return 0;
 228 }
 229 
 230 
 231 
 232 /* --- HELPER FUNCTIONS --- */
 233 
 234 
 235 /* The symbol lists themselves are not allocated from the heap, but
 236    we can unhook them and free up the chain of links between them.  */
 237 static int
 238 free_symlists (void)
 239 {
 240   symlist_chain *lists;
 241 
 242   lists = preloaded_symlists;
 243   while (lists)
 244     {
 245       symlist_chain *next = lists->next;
 246       FREE (lists);
 247       lists = next;
 248     }
 249   preloaded_symlists = 0;
 250 
 251   return 0;
 252 }
 253 
 254 /* Add a new symbol list to the global chain.  */
 255 static int
 256 add_symlist (const lt_dlsymlist *symlist)
 257 {
 258   symlist_chain *lists;
 259   int            errors   = 0;
 260 
 261   /* Search for duplicate entries:  */
 262   for (lists = preloaded_symlists;
 263        lists && lists->symlist != symlist; lists = lists->next)
 264     /*NOWORK*/;
 265 
 266   /* Don't add the same list twice:  */
 267   if (!lists)
 268     {
 269       symlist_chain *tmp = (symlist_chain *) lt__zalloc (sizeof *tmp);
 270 
 271       if (tmp)
 272         {
 273           tmp->symlist = symlist;
 274           tmp->next = preloaded_symlists;
 275           preloaded_symlists = tmp;
 276         }
 277       else
 278         {
 279           ++errors;
 280         }
 281     }
 282 
 283   return errors;
 284 }
 285 
 286 
 287 
 288 /* --- PRELOADING API CALL IMPLEMENTATIONS --- */
 289 
 290 
 291 /* Save a default symbol list for later.  */
 292 int
 293 lt_dlpreload_default (const lt_dlsymlist *preloaded)
 294 {
 295   default_preloaded_symbols = preloaded;
 296   return 0;
 297 }
 298 
 299 
 300 /* Add a symbol list to the global chain, or with a NULL argument,
 301    revert to just the default list.  */
 302 int
 303 lt_dlpreload (const lt_dlsymlist *preloaded)
 304 {
 305   int errors = 0;
 306 
 307   if (preloaded)
 308     {
 309       errors = add_symlist (preloaded);
 310     }
 311   else
 312     {
 313       free_symlists();
 314 
 315       if (default_preloaded_symbols)
 316         {
 317           errors = lt_dlpreload (default_preloaded_symbols);
 318         }
 319     }
 320 
 321   return errors;
 322 }
 323 
 324 
 325 /* Open all the preloaded modules from the named originator, executing
 326    a callback for each one.  If ORIGINATOR is NULL, then call FUNC for
 327    each preloaded module from the program itself.  */
 328 int
 329 lt_dlpreload_open (const char *originator, lt_dlpreload_callback_func *func)
 330 {
 331   symlist_chain *list;
 332   int            errors = 0;
 333   int            found  = 0;
 334 
 335   /* For each symlist in the chain...  */
 336   for (list = preloaded_symlists; list; list = list->next)
 337     {
 338       /* ...that was preloaded by the requesting ORIGINATOR... */
 339       if ((originator && streq (list->symlist->name, originator))
 340           || (!originator && streq (list->symlist->name, "@PROGRAM@")))
 341         {
 342           const lt_dlsymlist *symbol;
 343           unsigned int idx = 0;
 344 
 345           ++found;
 346 
 347           /* ...load the symbols per source compilation unit:
 348              (we preincrement the index to skip over the originator entry)  */
 349           while ((symbol = &list->symlist[++idx])->name != 0)
 350             {
 351               if ((symbol->address == 0)
 352                   && (strneq (symbol->name, "@PROGRAM@")))
 353                 {
 354                   lt_dlhandle handle = lt_dlopen (symbol->name);
 355                   if (handle == 0)
 356                     {
 357                       ++errors;
 358                     }
 359                   else
 360                     {
 361                       errors += (*func) (handle);
 362                     }
 363                 }
 364             }
 365         }
 366     }
 367 
 368   if (!found)
 369     {
 370       LT__SETERROR(CANNOT_OPEN);
 371       ++errors;
 372     }
 373 
 374   return errors;
 375 }

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