elf/dlclose.c

   1 /* dlclose -- Close a handle opened by `dlopen'.
   2 Copyright (C) 1995, 1996 Free Software Foundation, Inc.
   3 This file is part of the GNU C Library.
   4
   5 The GNU C Library is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 License, or (at your option) any later version.
   9
  10 The GNU C Library is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #include <link.h>
  21 #include <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <sys/types.h>
  24 #include <sys/mman.h>
  25
  26
  27 #define LOSE(s) _dl_signal_error (0, map->l_name, s)
  28
  29 int
  30 dlclose (void *handle)
  31 {
  32   void doit (void)
  33     {
  34       struct link_map *map = handle;
  35       struct link_map **list;
  36       unsigned int i;
  37
  38       if (map->l_opencount == 0)
  39         LOSE ("shared object not open");
  40
  41       /* Decrement the reference count.  */
  42       if (--map->l_opencount > 0 || map->l_type != lt_loaded)
  43         /* There are still references to this object.  Do nothing more.  */
  44         return;
  45
  46       list = map->l_searchlist;
  47
  48       /* The search list contains a counted reference to each object it
  49          points to, the 0th elt being MAP itself.  Decrement the reference
  50          counts on all the objects MAP depends on.  */
  51       for (i = 1; i < map->l_nsearchlist; ++i)
  52         --list[i]->l_opencount;
  53
  54       /* Clear the search list so it doesn't get freed while we are still
  55          using it.  We have cached it in LIST and will free it when
  56          finished.  */
  57       map->l_searchlist = NULL;
  58
  59       /* Check each element of the search list to see if all references to
  60          it are gone.  */
  61       for (i = 0; i < map->l_nsearchlist; ++i)
  62         {
  63           struct link_map *map = list[i];
  64           if (map->l_opencount == 0 && map->l_type == lt_loaded)
  65             {
  66               /* That was the last reference, and this was a dlopen-loaded
  67                  object.  We can unmap it.  */
  68               const Elf32_Phdr *ph;
  69
  70               if (map->l_info[DT_FINI])
  71                 /* Call its termination function.  */
  72                 (*(void (*) (void)) ((void *) map->l_addr +
  73                                      map->l_info[DT_FINI]->d_un.d_ptr)) ();
  74
  75               /* Unmap the segments.  */
  76               for (ph = map->l_phdr; ph < &map->l_phdr[map->l_phnum]; ++ph)
  77                 if (ph->p_type == PT_LOAD)
  78                   {
  79                     Elf32_Addr mapstart = ph->p_vaddr & ~(ph->p_align - 1);
  80                     Elf32_Addr mapend = ((ph->p_vaddr + ph->p_memsz
  81                                           + ph->p_align - 1)
  82                                          & ~(ph->p_align - 1));
  83                     munmap ((caddr_t) mapstart, mapend - mapstart);
  84                   }
  85
  86               /* Finally, unlink the data structure and free it.  */
  87               map->l_prev->l_next = map->l_next;
  88               if (map->l_next)
  89                 map->l_next->l_prev = map->l_prev;
  90               if (map->l_searchlist)
  91                 free (map->l_searchlist);
  92               free (map);
  93             }
  94         }
  95
  96       free (list);
  97     }
  98
  99   return _dlerror_run (doit) ? -1 : 0;
 100 }
 101