root/libltdl/loaders/preopen.c

/* */

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) 1998-2000, 2004, 2006-2008, 2011-2015 Free Software
   4    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 loader_data LT__UNUSED)
     /*  */
 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 loader_data LT__UNUSED)
     /*  */
 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 loader_data LT__UNUSED, const char *filename,
     /*  */
 146          lt_dladvise advise LT__UNUSED)
 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 loader_data LT__UNUSED, lt_module module LT__UNUSED)
     /*  */
 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 loader_data LT__UNUSED, lt_module module, const char *name)
     /*  */
 210 {
 211   lt_dlsymlist         *symbol = (lt_dlsymlist*) module;
 212 
 213   if (symbol[1].name && STREQ (symbol[1].name, "@INIT@"))
 214     {
 215       symbol++;                 /* Skip optional init entry. */
 216     }
 217 
 218   symbol +=2;                   /* Skip header (originator then libname). */
 219 
 220   while (symbol->name)
 221     {
 222       if (STREQ (symbol->name, name))
 223         {
 224           return symbol->address;
 225         }
 226 
 227     ++symbol;
 228   }
 229 
 230   LT__SETERROR (SYMBOL_NOT_FOUND);
 231 
 232   return 0;
 233 }
 234 
 235 
 236 
 237 /* --- HELPER FUNCTIONS --- */
 238 
 239 
 240 /* The symbol lists themselves are not allocated from the heap, but
 241    we can unhook them and free up the chain of links between them.  */
 242 static int
 243 free_symlists (void)
     /*  */
 244 {
 245   symlist_chain *lists;
 246 
 247   lists = preloaded_symlists;
 248   while (lists)
 249     {
 250       symlist_chain *next = lists->next;
 251       FREE (lists);
 252       lists = next;
 253     }
 254   preloaded_symlists = 0;
 255 
 256   return 0;
 257 }
 258 
 259 /* Add a new symbol list to the global chain.  */
 260 static int
 261 add_symlist (const lt_dlsymlist *symlist)
     /*  */
 262 {
 263   symlist_chain *lists;
 264   int            errors   = 0;
 265 
 266   /* Search for duplicate entries:  */
 267   for (lists = preloaded_symlists;
 268        lists && lists->symlist != symlist; lists = lists->next)
 269     /*NOWORK*/;
 270 
 271   /* Don't add the same list twice:  */
 272   if (!lists)
 273     {
 274       symlist_chain *tmp = (symlist_chain *) lt__zalloc (sizeof *tmp);
 275 
 276       if (tmp)
 277         {
 278           tmp->symlist = symlist;
 279           tmp->next = preloaded_symlists;
 280           preloaded_symlists = tmp;
 281 
 282           if (symlist[1].name && STREQ (symlist[1].name, "@INIT@"))
 283             {
 284               void (*init_symlist)(void);
 285               *(void **)(&init_symlist) = symlist[1].address;
 286               (*init_symlist)();
 287             }
 288         }
 289       else
 290         {
 291           ++errors;
 292         }
 293     }
 294 
 295   return errors;
 296 }
 297 
 298 
 299 
 300 /* --- PRELOADING API CALL IMPLEMENTATIONS --- */
 301 
 302 
 303 /* Save a default symbol list for later.  */
 304 int
 305 lt_dlpreload_default (const lt_dlsymlist *preloaded)
     /*  */
 306 {
 307   default_preloaded_symbols = preloaded;
 308   return 0;
 309 }
 310 
 311 
 312 /* Add a symbol list to the global chain, or with a NULL argument,
 313    revert to just the default list.  */
 314 int
 315 lt_dlpreload (const lt_dlsymlist *preloaded)
     /*  */
 316 {
 317   int errors = 0;
 318 
 319   if (preloaded)
 320     {
 321       errors = add_symlist (preloaded);
 322     }
 323   else
 324     {
 325       free_symlists();
 326 
 327       if (default_preloaded_symbols)
 328         {
 329           errors = lt_dlpreload (default_preloaded_symbols);
 330         }
 331     }
 332 
 333   return errors;
 334 }
 335 
 336 
 337 /* Open all the preloaded modules from the named originator, executing
 338    a callback for each one.  If ORIGINATOR is NULL, then call FUNC for
 339    each preloaded module from the program itself.  */
 340 int
 341 lt_dlpreload_open (const char *originator, lt_dlpreload_callback_func *func)
     /*  */
 342 {
 343   symlist_chain *list;
 344   int            errors = 0;
 345   int            found  = 0;
 346 
 347   /* For each symlist in the chain...  */
 348   for (list = preloaded_symlists; list; list = list->next)
 349     {
 350       /* ...that was preloaded by the requesting ORIGINATOR... */
 351       if ((originator && STREQ (list->symlist->name, originator))
 352           || (!originator && STREQ (list->symlist->name, "@PROGRAM@")))
 353         {
 354           const lt_dlsymlist *symbol;
 355           unsigned int idx = 0;
 356 
 357           ++found;
 358 
 359           /* ...load the symbols per source compilation unit:
 360              (we preincrement the index to skip over the originator entry)  */
 361           while ((symbol = &list->symlist[++idx])->name != 0)
 362             {
 363               if ((symbol->address == 0)
 364                   && (STRNEQ (symbol->name, "@PROGRAM@")))
 365                 {
 366                   lt_dlhandle handle = lt_dlopen (symbol->name);
 367                   if (handle == 0)
 368                     {
 369                       ++errors;
 370                     }
 371                   else
 372                     {
 373                       errors += (*func) (handle);
 374                     }
 375                 }
 376             }
 377         }
 378     }
 379 
 380   if (!found)
 381     {
 382       LT__SETERROR(CANNOT_OPEN);
 383       ++errors;
 384     }
 385 
 386   return errors;
 387 }

/* */