elf/dl-fini.c

   1 /* Call the termination functions of loaded shared objects.
   2    Copyright (C) 1995-2017 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <string.h>
  21 #include <ldsodefs.h>
  22
  23
  24 /* Type of the constructor functions.  */
  25 typedef void (*fini_t) (void);
  26
  27
  28 void
  29 _dl_fini (void)
  30 {
  31   /* Lots of fun ahead.  We have to call the destructors for all still
  32      loaded objects, in all namespaces.  The problem is that the ELF
  33      specification now demands that dependencies between the modules
  34      are taken into account.  I.e., the destructor for a module is
  35      called before the ones for any of its dependencies.
  36
  37      To make things more complicated, we cannot simply use the reverse
  38      order of the constructors.  Since the user might have loaded objects
  39      using `dlopen' there are possibly several other modules with its
  40      dependencies to be taken into account.  Therefore we have to start
  41      determining the order of the modules once again from the beginning.  */
  42
  43   /* We run the destructors of the main namespaces last.  As for the
  44      other namespaces, we pick run the destructors in them in reverse
  45      order of the namespace ID.  */
  46 #ifdef SHARED
  47   int do_audit = 0;
  48  again:
  49 #endif
  50   for (Lmid_t ns = GL(dl_nns) - 1; ns >= 0; --ns)
  51     {
  52       /* Protect against concurrent loads and unloads.  */
  53       __rtld_lock_lock_recursive (GL(dl_load_lock));
  54
  55       unsigned int nloaded = GL(dl_ns)[ns]._ns_nloaded;
  56       /* No need to do anything for empty namespaces or those used for
  57          auditing DSOs.  */
  58       if (nloaded == 0
  59 #ifdef SHARED
  60           || GL(dl_ns)[ns]._ns_loaded->l_auditing != do_audit
  61 #endif
  62           )
  63         __rtld_lock_unlock_recursive (GL(dl_load_lock));
  64       else
  65         {
  66           /* Now we can allocate an array to hold all the pointers and
  67              copy the pointers in.  */
  68           struct link_map *maps[nloaded];
  69
  70           unsigned int i;
  71           struct link_map *l;
  72           assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL);
  73           for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next)
  74             /* Do not handle ld.so in secondary namespaces.  */
  75             if (l == l->l_real)
  76               {
  77                 assert (i < nloaded);
  78
  79                 maps[i] = l;
  80                 l->l_idx = i;
  81                 ++i;
  82
  83                 /* Bump l_direct_opencount of all objects so that they
  84                    are not dlclose()ed from underneath us.  */
  85                 ++l->l_direct_opencount;
  86               }
  87           assert (ns != LM_ID_BASE || i == nloaded);
  88           assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1);
  89           unsigned int nmaps = i;
  90
  91           /* Now we have to do the sorting.  We can skip looking for the
  92              binary itself which is at the front of the search list for
  93              the main namespace.  */
  94           _dl_sort_maps (maps + (ns == LM_ID_BASE), nmaps - (ns == LM_ID_BASE),
  95                          NULL, true);
  96
  97           /* We do not rely on the linked list of loaded object anymore
  98              from this point on.  We have our own list here (maps).  The
  99              various members of this list cannot vanish since the open
 100              count is too high and will be decremented in this loop.  So
 101              we release the lock so that some code which might be called
 102              from a destructor can directly or indirectly access the
 103              lock.  */
 104           __rtld_lock_unlock_recursive (GL(dl_load_lock));
 105
 106           /* 'maps' now contains the objects in the right order.  Now
 107              call the destructors.  We have to process this array from
 108              the front.  */
 109           for (i = 0; i < nmaps; ++i)
 110             {
 111               struct link_map *l = maps[i];
 112
 113               if (l->l_init_called)
 114                 {
 115                   /* Make sure nothing happens if we are called twice.  */
 116                   l->l_init_called = 0;
 117
 118                   /* Is there a destructor function?  */
 119                   if (l->l_info[DT_FINI_ARRAY] != NULL
 120                       || l->l_info[DT_FINI] != NULL)
 121                     {
 122                       /* When debugging print a message first.  */
 123                       if (__builtin_expect (GLRO(dl_debug_mask)
 124                                             & DL_DEBUG_IMPCALLS, 0))
 125                         _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
 126                                           DSO_FILENAME (l->l_name),
 127                                           ns);
 128
 129                       /* First see whether an array is given.  */
 130                       if (l->l_info[DT_FINI_ARRAY] != NULL)
 131                         {
 132                           ElfW(Addr) *array =
 133                             (ElfW(Addr) *) (l->l_addr
 134                                             + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 135                           unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 136                                             / sizeof (ElfW(Addr)));
 137                           while (i-- > 0)
 138                             ((fini_t) array[i]) ();
 139                         }
 140
 141                       /* Next try the old-style destructor.  */
 142                       if (l->l_info[DT_FINI] != NULL)
 143                         DL_CALL_DT_FINI
 144                           (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr);
 145                     }
 146
 147 #ifdef SHARED
 148                   /* Auditing checkpoint: another object closed.  */
 149                   if (!do_audit && __builtin_expect (GLRO(dl_naudit) > 0, 0))
 150                     {
 151                       struct audit_ifaces *afct = GLRO(dl_audit);
 152                       for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 153                         {
 154                           if (afct->objclose != NULL)
 155                             /* Return value is ignored.  */
 156                             (void) afct->objclose (&l->l_audit[cnt].cookie);
 157
 158                           afct = afct->next;
 159                         }
 160                     }
 161 #endif
 162                 }
 163
 164               /* Correct the previous increment.  */
 165               --l->l_direct_opencount;
 166             }
 167         }
 168     }
 169
 170 #ifdef SHARED
 171   if (! do_audit && GLRO(dl_naudit) > 0)
 172     {
 173       do_audit = 1;
 174       goto again;
 175     }
 176
 177   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS))
 178     _dl_debug_printf ("\nruntime linker statistics:\n"
 179                       "           final number of relocations: %lu\n"
 180                       "final number of relocations from cache: %lu\n",
 181                       GL(dl_num_relocations),
 182                       GL(dl_num_cache_relocations));
 183 #endif
 184 }