elf/dl-close.c

   1 /* Close a shared object opened by `_dl_open'.
   2    Copyright (C) 1996, 1997 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 <link.h>
  21 #include <dlfcn.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/types.h>
  25 #include <sys/mman.h>
  26 #include <bits/libc-lock.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 _dl_close (struct link_map *map)
  38 {
  39   struct link_map **list;
  40   unsigned int i;
  41
  42   if (map->l_opencount == 0)
  43     LOSE ("shared object not open");
  44
  45   /* Acquire the lock.  */
  46   __libc_lock_lock (_dl_load_lock);
  47
  48   /* Decrement the reference count.  */
  49   if (--map->l_opencount > 0 || map->l_type != lt_loaded)
  50     {
  51       /* There are still references to this object.  Do nothing more.  */
  52       __libc_lock_unlock (_dl_load_lock);
  53       return;
  54     }
  55
  56   /* Notify the debugger we are about to remove some loaded objects.  */
  57   _r_debug.r_state = RT_DELETE;
  58   _dl_debug_state ();
  59
  60   list = map->l_searchlist;
  61
  62   /* The search list contains a counted reference to each object it
  63      points to, the 0th elt being MAP itself.  Decrement the reference
  64      counts on all the objects MAP depends on.  */
  65   for (i = 1; i < map->l_nsearchlist; ++i)
  66     --list[i]->l_opencount;
  67
  68   /* Clear the search list so it doesn't get freed while we are still
  69      using it.  We have cached it in LIST and will free it when
  70      finished.  */
  71   map->l_searchlist = NULL;
  72
  73   /* Check each element of the search list to see if all references to
  74      it are gone.  */
  75   for (i = 0; i < map->l_nsearchlist; ++i)
  76     {
  77       struct link_map *map = list[i];
  78       if (map->l_opencount == 0 && map->l_type == lt_loaded)
  79         {
  80           /* That was the last reference, and this was a dlopen-loaded
  81              object.  We can unmap it.  */
  82           const ElfW(Phdr) *ph;
  83
  84           if (map->l_info[DT_FINI])
  85             /* Call its termination function.  */
  86             (*(void (*) (void)) ((void *) map->l_addr +
  87                                  map->l_info[DT_FINI]->d_un.d_ptr)) ();
  88
  89           if (map->l_global)
  90             {
  91               /* This object is in the global scope list.  Remove it.  */
  92               struct link_map **tail = _dl_global_scope_end;
  93               do
  94                 --tail;
  95               while (*tail != map);
  96               --_dl_global_scope_end;
  97               memcpy (tail, tail + 1, _dl_global_scope_end - tail);
  98               _dl_global_scope_end[0] = NULL;
  99               _dl_global_scope_end[1] = NULL;
 100             }
 101
 102           /* Unmap the segments.  */
 103           for (ph = map->l_phdr; ph < &map->l_phdr[map->l_phnum]; ++ph)
 104             if (ph->p_type == PT_LOAD)
 105               {
 106                 ElfW(Addr) mapstart = ph->p_vaddr & ~(ph->p_align - 1);
 107                 ElfW(Addr) mapend = ((ph->p_vaddr + ph->p_memsz
 108                                       + ph->p_align - 1)
 109                                      & ~(ph->p_align - 1));
 110                 __munmap ((caddr_t) mapstart, mapend - mapstart);
 111               }
 112
 113           /* Finally, unlink the data structure and free it.  */
 114           if (map->l_prev)
 115             map->l_prev->l_next = map->l_next;
 116           if (map->l_next)
 117             map->l_next->l_prev = map->l_prev;
 118           if (map->l_searchlist)
 119             free (map->l_searchlist);
 120           free (map);
 121         }
 122     }
 123
 124   free (list);
 125
 126   /* Notify the debugger those objects are finalized and gone.  */
 127   _r_debug.r_state = RT_CONSISTENT;
 128   _dl_debug_state ();
 129
 130   /* Release the lock.  */
 131   __libc_lock_unlock (_dl_load_lock);
 132 }