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 <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 *imap = list[i];
  78       if (imap->l_opencount == 0 && imap->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           const ElfW(Phdr) *first, *last;
  84           ElfW(Addr) mapstart, mapend;
  85
  86           if (imap->l_info[DT_FINI])
  87             /* Call its termination function.  */
  88             (*(void (*) (void)) ((void *) imap->l_addr +
  89                                  imap->l_info[DT_FINI]->d_un.d_ptr)) ();
  90
  91           if (imap->l_global)
  92             {
  93               /* This object is in the global scope list.  Remove it.  */
  94               struct link_map **tail = _dl_global_scope_end;
  95               do
  96                 --tail;
  97               while (*tail != imap);
  98               --_dl_global_scope_end;
  99               memcpy (tail, tail + 1, _dl_global_scope_end - tail);
 100               _dl_global_scope_end[0] = NULL;
 101               _dl_global_scope_end[1] = NULL;
 102             }
 103
 104           /* We can unmap all the maps at once.  We just have to determine
 105              the length and the `munmap' call does the rest.  */
 106           first = last = NULL;
 107           for (ph = imap->l_phdr; ph < imap->l_phdr + imap->l_phnum; ++ph)
 108             if (ph->p_type == PT_LOAD)
 109               {
 110                 if (first == NULL)
 111                   first = ph;
 112                 last = ph;
 113               }
 114
 115           /* Now we have all the information we need for the unmapping.
 116              See the method used in `_dl_map_object_from_fd'.  */
 117           mapstart = first->p_vaddr & ~(first->p_align - 1);
 118           mapend = last->p_vaddr + last->p_memsz;
 119           __munmap ((caddr_t) (imap->l_addr + mapstart), mapend - mapstart);
 120
 121           /* Finally, unlink the data structure and free it.  */
 122           if (imap->l_prev)
 123             imap->l_prev->l_next = imap->l_next;
 124           if (imap->l_next)
 125             imap->l_next->l_prev = imap->l_prev;
 126           if (imap->l_searchlist)
 127             free (imap->l_searchlist);
 128           free (imap);
 129         }
 130     }
 131
 132   free (list);
 133
 134   /* Notify the debugger those objects are finalized and gone.  */
 135   _r_debug.r_state = RT_CONSISTENT;
 136   _dl_debug_state ();
 137
 138   /* Release the lock.  */
 139   __libc_lock_unlock (_dl_load_lock);
 140 }