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 <assert.h>
  21 #include <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <bits/libc-lock.h>
  25 #include <elf/ldsodefs.h>
  26 #include <sys/types.h>
  27 #include <sys/mman.h>
  28
  29
  30 /* During the program run we must not modify the global data of
  31    loaded shared object simultanously in two threads.  Therefore we
  32    protect `dlopen' and `dlclose' in dlclose.c.  */
  33 __libc_lock_define (extern, _dl_load_lock)
  34
  35 #define LOSE(s) _dl_signal_error (0, map->l_name, s)
  36
  37 void
  38 internal_function
  39 _dl_close (struct link_map *map)
  40 {
  41   struct link_map **list;
  42   unsigned nsearchlist;
  43   unsigned int i;
  44
  45   if (map->l_opencount == 0)
  46     LOSE ("shared object not open");
  47
  48   /* Acquire the lock.  */
  49   __libc_lock_lock (_dl_load_lock);
  50
  51   /* Decrement the reference count.  */
  52   if (map->l_opencount > 1 || map->l_type != lt_loaded)
  53     {
  54       /* There are still references to this object.  Do nothing more.  */
  55       --map->l_opencount;
  56       __libc_lock_unlock (_dl_load_lock);
  57       return;
  58     }
  59
  60   list = map->l_searchlist;
  61   nsearchlist = map->l_nsearchlist;
  62
  63   /* Call all termination functions at once.  */
  64   for (i = 0; i < nsearchlist; ++i)
  65     {
  66       struct link_map *imap = list[i];
  67       if (imap->l_opencount == 1 && imap->l_type == lt_loaded
  68           && imap->l_info[DT_FINI]
  69           /* Skip any half-cooked objects that were never initialized.  */
  70           && imap->l_init_called)
  71         {
  72           /* When debugging print a message first.  */
  73           if (_dl_debug_impcalls)
  74             _dl_debug_message (1, "\ncalling fini: ", imap->l_name,
  75                                "\n\n", NULL);
  76           /* Call its termination function.  */
  77           (*(void (*) (void)) ((void *) imap->l_addr
  78                                + imap->l_info[DT_FINI]->d_un.d_ptr)) ();
  79         }
  80     }
  81
  82   /* Notify the debugger we are about to remove some loaded objects.  */
  83   _r_debug.r_state = RT_DELETE;
  84   _dl_debug_state ();
  85
  86   /* The search list contains a counted reference to each object it
  87      points to, the 0th elt being MAP itself.  Decrement the reference
  88      counts on all the objects MAP depends on.  */
  89   for (i = 0; i < nsearchlist; ++i)
  90     --list[i]->l_opencount;
  91
  92   if (map->l_origin != NULL)
  93     free ((char *) map->l_origin);
  94   /* The name always is allocated.  */
  95   free (map->l_name);
  96
  97   /* Check each element of the search list to see if all references to
  98      it are gone.  */
  99   for (i = 0; i < nsearchlist; ++i)
 100     {
 101       struct link_map *imap = list[i];
 102       if (imap->l_opencount == 0 && imap->l_type == lt_loaded)
 103         {
 104           /* That was the last reference, and this was a dlopen-loaded
 105              object.  We can unmap it.  */
 106           const ElfW(Phdr) *ph;
 107           const ElfW(Phdr) *first, *last;
 108           ElfW(Addr) mapstart, mapend;
 109
 110           if (imap->l_global)
 111             {
 112               /* This object is in the global scope list.  Remove it.  */
 113               struct link_map **tail = _dl_global_scope_end;
 114               do
 115                 --tail;
 116               while (*tail != imap);
 117               while (tail < _dl_global_scope_end)
 118                 {
 119                   tail[0] = tail[1];
 120                   ++tail;
 121                 }
 122               --_dl_global_scope_end;
 123             }
 124
 125           /* We can unmap all the maps at once.  We just have to determine
 126              the length and the `munmap' call does the rest.  */
 127           first = last = NULL;
 128           for (ph = imap->l_phdr; ph < imap->l_phdr + imap->l_phnum; ++ph)
 129             if (ph->p_type == PT_LOAD)
 130               {
 131                 if (first == NULL)
 132                   first = ph;
 133                 last = ph;
 134               }
 135
 136           /* Now we have all the information we need for the unmapping.
 137              See the method used in `_dl_map_object_from_fd'.  */
 138           mapstart = first->p_vaddr & ~(first->p_align - 1);
 139           mapend = last->p_vaddr + last->p_memsz;
 140           __munmap ((caddr_t) (imap->l_addr + mapstart), mapend - mapstart);
 141
 142           /* Finally, unlink the data structure and free it.  */
 143 #ifdef PIC
 144           /* We will unlink the first object only if this is a statically
 145              linked program.  */
 146           assert (imap->l_prev != NULL);
 147           imap->l_prev->l_next = imap->l_next;
 148 #else
 149           if (imap->l_prev != NULL)
 150             imap->l_prev->l_next = imap->l_next;
 151           else
 152             _dl_loaded = imap->l_next;
 153 #endif
 154           if (imap->l_next)
 155             imap->l_next->l_prev = imap->l_prev;
 156           if (imap->l_searchlist && imap->l_searchlist != list)
 157             free (imap->l_searchlist);
 158           free (imap);
 159         }
 160     }
 161
 162   free (list);
 163
 164   /* Notify the debugger those objects are finalized and gone.  */
 165   _r_debug.r_state = RT_CONSISTENT;
 166   _dl_debug_state ();
 167
 168   /* Release the lock.  */
 169   __libc_lock_unlock (_dl_load_lock);
 170 }