elf/dl-fini.c

   1 /* Call the termination functions of loaded shared objects.
   2    Copyright (C) 1995-2022 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 #ifdef SHARED
  68           _dl_audit_activity_nsid (ns, LA_ACT_DELETE);
  69 #endif
  70
  71           /* Now we can allocate an array to hold all the pointers and
  72              copy the pointers in.  */
  73           struct link_map *maps[nloaded];
  74
  75           unsigned int i;
  76           struct link_map *l;
  77           assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL);
  78           for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next)
  79             /* Do not handle ld.so in secondary namespaces.  */
  80             if (l == l->l_real)
  81               {
  82                 assert (i < nloaded);
  83
  84                 maps[i] = l;
  85                 l->l_idx = i;
  86                 ++i;
  87
  88                 /* Bump l_direct_opencount of all objects so that they
  89                    are not dlclose()ed from underneath us.  */
  90                 ++l->l_direct_opencount;
  91               }
  92           assert (ns != LM_ID_BASE || i == nloaded);
  93           assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1);
  94           unsigned int nmaps = i;
  95
  96           /* Now we have to do the sorting.  We can skip looking for the
  97              binary itself which is at the front of the search list for
  98              the main namespace.  */
  99           _dl_sort_maps (maps, nmaps, (ns == LM_ID_BASE), true);
 100
 101           /* We do not rely on the linked list of loaded object anymore
 102              from this point on.  We have our own list here (maps).  The
 103              various members of this list cannot vanish since the open
 104              count is too high and will be decremented in this loop.  So
 105              we release the lock so that some code which might be called
 106              from a destructor can directly or indirectly access the
 107              lock.  */
 108           __rtld_lock_unlock_recursive (GL(dl_load_lock));
 109
 110           /* 'maps' now contains the objects in the right order.  Now
 111              call the destructors.  We have to process this array from
 112              the front.  */
 113           for (i = 0; i < nmaps; ++i)
 114             {
 115               struct link_map *l = maps[i];
 116
 117               if (l->l_init_called)
 118                 {
 119                   /* Make sure nothing happens if we are called twice.  */
 120                   l->l_init_called = 0;
 121
 122                   /* Is there a destructor function?  */
 123                   if (l->l_info[DT_FINI_ARRAY] != NULL
 124                       || (ELF_INITFINI && l->l_info[DT_FINI] != NULL))
 125                     {
 126                       /* When debugging print a message first.  */
 127                       if (__builtin_expect (GLRO(dl_debug_mask)
 128                                             & DL_DEBUG_IMPCALLS, 0))
 129                         _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
 130                                           DSO_FILENAME (l->l_name),
 131                                           ns);
 132
 133                       /* First see whether an array is given.  */
 134                       if (l->l_info[DT_FINI_ARRAY] != NULL)
 135                         {
 136                           ElfW(Addr) *array =
 137                             (ElfW(Addr) *) (l->l_addr
 138                                             + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 139                           unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 140                                             / sizeof (ElfW(Addr)));
 141                           while (i-- > 0)
 142                             ((fini_t) array[i]) ();
 143                         }
 144
 145                       /* Next try the old-style destructor.  */
 146                       if (ELF_INITFINI && l->l_info[DT_FINI] != NULL)
 147                         DL_CALL_DT_FINI
 148                           (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr);
 149                     }
 150
 151 #ifdef SHARED
 152                   /* Auditing checkpoint: another object closed.  */
 153                   _dl_audit_objclose (l);
 154 #endif
 155                 }
 156
 157               /* Correct the previous increment.  */
 158               --l->l_direct_opencount;
 159             }
 160
 161 #ifdef SHARED
 162           _dl_audit_activity_nsid (ns, LA_ACT_CONSISTENT);
 163 #endif
 164         }
 165     }
 166
 167 #ifdef SHARED
 168   if (! do_audit && GLRO(dl_naudit) > 0)
 169     {
 170       do_audit = 1;
 171       goto again;
 172     }
 173
 174   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS))
 175     _dl_debug_printf ("\nruntime linker statistics:\n"
 176                       "           final number of relocations: %lu\n"
 177                       "final number of relocations from cache: %lu\n",
 178                       GL(dl_num_relocations),
 179                       GL(dl_num_cache_relocations));
 180 #endif
 181 }