elf/dlclose.c

   1 /* dlclose -- Close a handle opened by `dlopen'.
   2 Copyright (C) 1995 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
  36       if (map->l_opencount == 0)
  37         LOSE ("shared object not open");
  38
  39       /* Decrement the reference count.  */
  40       --map->l_opencount;
  41
  42       if (map->l_opencount == 0 && map->l_type == lt_loaded)
  43         {
  44           /* That was the last reference, and this was a dlopen-loaded
  45              object.  We can unmap it.  */
  46           const Elf32_Phdr *ph;
  47
  48           if (map->l_info[DT_FINI])
  49             /* Call its termination function.  */
  50             (*(void (*) (void)) ((void *) map->l_addr +
  51                                  map->l_info[DT_FINI]->d_un.d_ptr)) ();
  52
  53           if (map->l_info[DT_NEEDED])
  54             {
  55               /* Also close all the dependencies.  */
  56               const char *strtab
  57                 = (void *) map->l_addr + map->l_info[DT_STRTAB]->d_un.d_ptr;
  58               const Elf32_Dyn *d;
  59               for (d = map->l_ld; d->d_tag != DT_NULL; ++d)
  60                 if (d->d_tag == DT_NEEDED)
  61                   {
  62                     /* It must already be open, since this one needed it;
  63                        so dlopen will just find us its `struct link_map'
  64                        and bump its reference count.  */
  65                     struct link_map *o, *dep
  66                       = dlopen (strtab + d->d_un.d_val, RTLD_LAZY);
  67                     --dep->l_opencount; /* Lose the ref from that dlopen.  */
  68                     /* Now we have the handle; we can close it for real.  */
  69                     o = map;
  70                     map = dep;
  71                     doit ();
  72                     map = o;
  73                   }
  74             }
  75
  76           /* Unmap the segments.  */
  77           for (ph = map->l_phdr; ph < &map->l_phdr[map->l_phnum]; ++ph)
  78             if (ph->p_type == PT_LOAD)
  79               {
  80                 Elf32_Addr mapstart = ph->p_vaddr & ~(ph->p_align - 1);
  81                 Elf32_Addr mapend = ((ph->p_vaddr + ph->p_memsz
  82                                       + ph->p_align - 1)
  83                                      & ~(ph->p_align - 1));
  84                 munmap ((caddr_t) mapstart, mapend - mapstart);
  85               }
  86
  87           /* Finally, unlink the data structure and free it.  */
  88           map->l_prev->l_next = map->l_next;
  89           if (map->l_next)
  90             map->l_next->l_prev = map->l_prev;
  91           free (map);
  92         }
  93     }
  94
  95   return _dlerror_run (doit) ? -1 : 0;
  96 }
  97