elf/dl-fini.c

   1 /* Call the termination functions of loaded shared objects.
   2    Copyright (C) 1995-2021 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <string.h>
  21 #include <ldsodefs.h>
  22 #include <elf-initfini.h>
  23
  24
  25 /* Type of the constructor functions.  */
  26 typedef void (*fini_t) (void);
  27
  28
  29 void
  30 _dl_fini (void)
  31 {
  32   /* Lots of fun ahead.  We have to call the destructors for all still
  33      loaded objects, in all namespaces.  The problem is that the ELF
  34      specification now demands that dependencies between the modules
  35      are taken into account.  I.e., the destructor for a module is
  36      called before the ones for any of its dependencies.
  37
  38      To make things more complicated, we cannot simply use the reverse
  39      order of the constructors.  Since the user might have loaded objects
  40      using `dlopen' there are possibly several other modules with its
  41      dependencies to be taken into account.  Therefore we have to start
  42      determining the order of the modules once again from the beginning.  */
  43
  44   /* We run the destructors of the main namespaces last.  As for the
  45      other namespaces, we pick run the destructors in them in reverse
  46      order of the namespace ID.  */
  47 #ifdef SHARED
  48   int do_audit = 0;
  49  again:
  50 #endif
  51   for (Lmid_t ns = GL(dl_nns) - 1; ns >= 0; --ns)
  52     {
  53       /* Protect against concurrent loads and unloads.  */
  54       __rtld_lock_lock_recursive (GL(dl_load_lock));
  55
  56       unsigned int nloaded = GL(dl_ns)[ns]._ns_nloaded;
  57       /* No need to do anything for empty namespaces or those used for
  58          auditing DSOs.  */
  59       if (nloaded == 0
  60 #ifdef SHARED
  61           || GL(dl_ns)[ns]._ns_loaded->l_auditing != do_audit
  62 #endif
  63           )
  64         __rtld_lock_unlock_recursive (GL(dl_load_lock));
  65       else
  66         {
  67           /* Now we can allocate an array to hold all the pointers and
  68              copy the pointers in.  */
  69           struct link_map *maps[nloaded];
  70
  71           unsigned int i;
  72           struct link_map *l;
  73           assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL);
  74           for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next)
  75             /* Do not handle ld.so in secondary namespaces.  */
  76             if (l == l->l_real)
  77               {
  78                 assert (i < nloaded);
  79
  80                 maps[i] = l;
  81                 l->l_idx = i;
  82                 ++i;
  83
  84                 /* Bump l_direct_opencount of all objects so that they
  85                    are not dlclose()ed from underneath us.  */
  86                 ++l->l_direct_opencount;
  87               }
  88           assert (ns != LM_ID_BASE || i == nloaded);
  89           assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1);
  90           unsigned int nmaps = i;
  91
  92           /* Now we have to do the sorting.  We can skip looking for the
  93              binary itself which is at the front of the search list for
  94              the main namespace.  */
  95           _dl_sort_maps (maps + (ns == LM_ID_BASE), nmaps - (ns == LM_ID_BASE),
  96                          NULL, true);
  97
  98           /* We do not rely on the linked list of loaded object anymore
  99              from this point on.  We have our own list here (maps).  The
 100              various members of this list cannot vanish since the open
 101              count is too high and will be decremented in this loop.  So
 102              we release the lock so that some code which might be called
 103              from a destructor can directly or indirectly access the
 104              lock.  */
 105           __rtld_lock_unlock_recursive (GL(dl_load_lock));
 106
 107           /* 'maps' now contains the objects in the right order.  Now
 108              call the destructors.  We have to process this array from
 109              the front.  */
 110           for (i = 0; i < nmaps; ++i)
 111             {
 112               struct link_map *l = maps[i];
 113
 114               if (l->l_init_called)
 115                 {
 116                   /* Make sure nothing happens if we are called twice.  */
 117                   l->l_init_called = 0;
 118
 119                   /* Is there a destructor function?  */
 120                   if (l->l_info[DT_FINI_ARRAY] != NULL
 121                       || (ELF_INITFINI && l->l_info[DT_FINI] != NULL))
 122                     {
 123                       /* When debugging print a message first.  */
 124                       if (__builtin_expect (GLRO(dl_debug_mask)
 125                                             & DL_DEBUG_IMPCALLS, 0))
 126                         _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
 127                                           DSO_FILENAME (l->l_name),
 128                                           ns);
 129
 130                       /* First see whether an array is given.  */
 131                       if (l->l_info[DT_FINI_ARRAY] != NULL)
 132                         {
 133                           ElfW(Addr) *array =
 134                             (ElfW(Addr) *) (l->l_addr
 135                                             + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 136                           unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 137                                             / sizeof (ElfW(Addr)));
 138                           while (i-- > 0)
 139                             ((fini_t) array[i]) ();
 140                         }
 141
 142                       /* Next try the old-style destructor.  */
 143                       if (ELF_INITFINI && l->l_info[DT_FINI] != NULL)
 144                         DL_CALL_DT_FINI
 145                           (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr);
 146                     }
 147
 148 #ifdef SHARED
 149                   /* Auditing checkpoint: another object closed.  */
 150                   if (!do_audit && __builtin_expect (GLRO(dl_naudit) > 0, 0))
 151                     {
 152                       struct audit_ifaces *afct = GLRO(dl_audit);
 153                       for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 154                         {
 155                           if (afct->objclose != NULL)
 156                             {
 157                               struct auditstate *state
 158                                 = link_map_audit_state (l, cnt);
 159                               /* Return value is ignored.  */
 160                               (void) afct->objclose (&state->cookie);
 161                             }
 162                           afct = afct->next;
 163                         }
 164                     }
 165 #endif
 166                 }
 167
 168               /* Correct the previous increment.  */
 169               --l->l_direct_opencount;
 170             }
 171         }
 172     }
 173
 174 #ifdef SHARED
 175   if (! do_audit && GLRO(dl_naudit) > 0)
 176     {
 177       do_audit = 1;
 178       goto again;
 179     }
 180
 181   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS))
 182     _dl_debug_printf ("\nruntime linker statistics:\n"
 183                       "           final number of relocations: %lu\n"
 184                       "final number of relocations from cache: %lu\n",
 185                       GL(dl_num_relocations),
 186                       GL(dl_num_cache_relocations));
 187 #endif
 188 }