elf/dl-close.c

   1 /* Close a shared object opened by `_dl_open'.
   2    Copyright (C) 1996, 1997, 1998 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 not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <dlfcn.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <bits/libc-lock.h>
  24 #include <elf/ldsodefs.h>
  25 #include <sys/types.h>
  26 #include <sys/mman.h>
  27
  28
  29 /* During the program run we must not modify the global data of
  30    loaded shared object simultanously in two threads.  Therefore we
  31    protect `dlopen' and `dlclose' in dlclose.c.  */
  32 __libc_lock_define (extern, _dl_load_lock)
  33
  34 #define LOSE(s) _dl_signal_error (0, map->l_name, s)
  35
  36 void
  37 internal_function
  38 _dl_close (struct link_map *map)
  39 {
  40   struct link_map **list;
  41   unsigned int i;
  42
  43   if (map->l_opencount == 0)
  44     LOSE ("shared object not open");
  45
  46   /* Acquire the lock.  */
  47   __libc_lock_lock (_dl_load_lock);
  48
  49   /* Decrement the reference count.  */
  50   if (map->l_opencount > 1 || map->l_type != lt_loaded)
  51     {
  52       /* There are still references to this object.  Do nothing more.  */
  53       --map->l_opencount;
  54       __libc_lock_unlock (_dl_load_lock);
  55       return;
  56     }
  57
  58   list = map->l_searchlist;
  59
  60   /* Call all termination functions at once.  */
  61   for (i = 0; i < map->l_nsearchlist; ++i)
  62     {
  63       struct link_map *imap = list[i];
  64       if (imap->l_opencount == 1 && imap->l_type == lt_loaded
  65           && imap->l_info[DT_FINI]
  66           /* Skip any half-cooked objects that were never initialized.  */
  67           && imap->l_init_called)
  68         {
  69           /* When debugging print a message first.  */
  70           if (_dl_debug_impcalls)
  71             _dl_debug_message (1, "\ncalling fini: ", imap->l_name,
  72                                "\n\n", NULL);
  73           /* Call its termination function.  */
  74           (*(void (*) (void)) ((void *) imap->l_addr
  75                                + imap->l_info[DT_FINI]->d_un.d_ptr)) ();
  76         }
  77     }
  78
  79   /* Notify the debugger we are about to remove some loaded objects.  */
  80   _r_debug.r_state = RT_DELETE;
  81   _dl_debug_state ();
  82
  83   /* The search list contains a counted reference to each object it
  84      points to, the 0th elt being MAP itself.  Decrement the reference
  85      counts on all the objects MAP depends on.  */
  86   for (i = 0; i < map->l_nsearchlist; ++i)
  87     --list[i]->l_opencount;
  88
  89   /* Check each element of the search list to see if all references to
  90      it are gone.  */
  91   for (i = 0; i < map->l_nsearchlist; ++i)
  92     {
  93       struct link_map *imap = list[i];
  94       if (imap->l_opencount == 0 && imap->l_type == lt_loaded)
  95         {
  96           /* That was the last reference, and this was a dlopen-loaded
  97              object.  We can unmap it.  */
  98           const ElfW(Phdr) *ph;
  99           const ElfW(Phdr) *first, *last;
 100           ElfW(Addr) mapstart, mapend;
 101
 102           if (imap->l_global)
 103             {
 104               /* This object is in the global scope list.  Remove it.  */
 105               struct link_map **tail = _dl_global_scope_end;
 106               do
 107                 --tail;
 108               while (*tail != imap);
 109               while (tail < _dl_global_scope_end)
 110                 {
 111                   tail[0] = tail[1];
 112                   ++tail;
 113                 }
 114               --_dl_global_scope_end;
 115             }
 116
 117           /* We can unmap all the maps at once.  We just have to determine
 118              the length and the `munmap' call does the rest.  */
 119           first = last = NULL;
 120           for (ph = imap->l_phdr; ph < imap->l_phdr + imap->l_phnum; ++ph)
 121             if (ph->p_type == PT_LOAD)
 122               {
 123                 if (first == NULL)
 124                   first = ph;
 125                 last = ph;
 126               }
 127
 128           /* Now we have all the information we need for the unmapping.
 129              See the method used in `_dl_map_object_from_fd'.  */
 130           mapstart = first->p_vaddr & ~(first->p_align - 1);
 131           mapend = last->p_vaddr + last->p_memsz;
 132           __munmap ((caddr_t) (imap->l_addr + mapstart), mapend - mapstart);
 133
 134           /* Finally, unlink the data structure and free it.  */
 135           if (imap->l_prev)
 136             imap->l_prev->l_next = imap->l_next;
 137           if (imap->l_next)
 138             imap->l_next->l_prev = imap->l_prev;
 139           if (imap->l_searchlist && imap->l_searchlist != list)
 140             free (imap->l_searchlist);
 141           free (imap);
 142         }
 143     }
 144
 145   free (list);
 146
 147   /* Notify the debugger those objects are finalized and gone.  */
 148   _r_debug.r_state = RT_CONSISTENT;
 149   _dl_debug_state ();
 150
 151   /* Release the lock.  */
 152   __libc_lock_unlock (_dl_load_lock);
 153 }