elf/dl-fini.c

   1 /* Call the termination functions of loaded shared objects.
   2    Copyright (C) 1995,96,1998-2002,2004, 2005 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <alloca.h>
  21 #include <assert.h>
  22 #include <string.h>
  23 #include <ldsodefs.h>
  24
  25
  26 /* Type of the constructor functions.  */
  27 typedef void (*fini_t) (void);
  28
  29
  30 void
  31 internal_function
  32 _dl_fini (void)
  33 {
  34   /* Lots of fun ahead.  We have to call the destructors for all still
  35      loaded objects, in all namespaces.  The problem is that the ELF
  36      specification now demands that dependencies between the modules
  37      are taken into account.  I.e., the destructor for a module is
  38      called before the ones for any of its dependencies.
  39
  40      To make things more complicated, we cannot simply use the reverse
  41      order of the constructors.  Since the user might have loaded objects
  42      using `dlopen' there are possibly several other modules with its
  43      dependencies to be taken into account.  Therefore we have to start
  44      determining the order of the modules once again from the beginning.  */
  45   struct link_map **maps = NULL;
  46   size_t maps_size = 0;
  47
  48   /* We run the destructors of the main namespaces last.  As for the
  49      other namespaces, we pick run the destructors in them in reverse
  50      order of the namespace ID.  */
  51 #ifdef SHARED
  52   int do_audit = 0;
  53  again:
  54 #endif
  55   for (Lmid_t cnt = DL_NNS - 1; cnt >= 0; --cnt)
  56     {
  57       /* Protect against concurrent loads and unloads.  */
  58       __rtld_lock_lock_recursive (GL(dl_load_lock));
  59
  60       unsigned int nmaps = 0;
  61       unsigned int nloaded = GL(dl_ns)[cnt]._ns_nloaded;
  62       /* No need to do anything for empty namespaces or those used for
  63          auditing DSOs.  */
  64       if (nloaded == 0
  65 #ifdef SHARED
  66           || GL(dl_ns)[cnt]._ns_loaded->l_auditing != do_audit
  67 #endif
  68           )
  69         goto out;
  70
  71       /* XXX Could it be (in static binaries) that there is no object
  72          loaded?  */
  73       assert (cnt != LM_ID_BASE || nloaded > 0);
  74
  75       /* Now we can allocate an array to hold all the pointers and copy
  76          the pointers in.  */
  77       if (maps_size < nloaded * sizeof (struct link_map *))
  78         {
  79           if (maps_size == 0)
  80             {
  81               maps_size = nloaded * sizeof (struct link_map *);
  82               maps = (struct link_map **) alloca (maps_size);
  83             }
  84           else
  85             maps = (struct link_map **)
  86               extend_alloca (maps, maps_size,
  87                              nloaded * sizeof (struct link_map *));
  88         }
  89
  90       unsigned int i;
  91       struct link_map *l;
  92       assert (nloaded != 0 || GL(dl_ns)[cnt]._ns_loaded == NULL);
  93       for (l = GL(dl_ns)[cnt]._ns_loaded, i = 0; l != NULL; l = l->l_next)
  94         /* Do not handle ld.so in secondary namespaces.  */
  95         if (l == l->l_real)
  96           {
  97             assert (i < nloaded);
  98
  99             maps[i++] = l;
 100
 101             /* Bump l_opencount of all objects so that they are not
 102                dlclose()ed from underneath us.  */
 103             ++l->l_opencount;
 104           }
 105       assert (cnt != LM_ID_BASE || i == nloaded);
 106       assert (cnt == LM_ID_BASE || i == nloaded || i == nloaded - 1);
 107       nmaps = i;
 108
 109       if (nmaps != 0)
 110         {
 111           /* Now we have to do the sorting.  */
 112           l = GL(dl_ns)[cnt]._ns_loaded;
 113           if (cnt == LM_ID_BASE)
 114             /* The main executable always comes first.  */
 115             l = l->l_next;
 116           for (; l != NULL; l = l->l_next)
 117             /* Do not handle ld.so in secondary namespaces.  */
 118             if (l == l->l_real)
 119               {
 120                 /* Find the place in the 'maps' array.  */
 121                 unsigned int j;
 122                 for (j = cnt == LM_ID_BASE ? 1 : 0; maps[j] != l; ++j)
 123                   assert (j < nmaps);
 124
 125                 /* Find all object for which the current one is a dependency
 126                    and move the found object (if necessary) in front.  */
 127                 for (unsigned int k = j + 1; k < nmaps; ++k)
 128                   {
 129                     struct link_map **runp = maps[k]->l_initfini;
 130                     if (runp != NULL)
 131                       {
 132                         while (*runp != NULL)
 133                           if (*runp == l)
 134                             {
 135                               struct link_map *here = maps[k];
 136
 137                               /* Move it now.  */
 138                               memmove (&maps[j] + 1,
 139                                        &maps[j],
 140                                        (k - j) * sizeof (struct link_map *));
 141                               maps[j++] = here;
 142
 143                               break;
 144                             }
 145                           else
 146                             ++runp;
 147                       }
 148
 149                     if (__builtin_expect (maps[k]->l_reldeps != NULL, 0))
 150                       {
 151                         unsigned int m = maps[k]->l_reldepsact;
 152                         struct link_map **relmaps = maps[k]->l_reldeps;
 153
 154                         while (m-- > 0)
 155                           {
 156                             if (relmaps[m] == l)
 157                               {
 158                                 struct link_map *here = maps[k];
 159
 160                                 /* Move it now.  */
 161                                 memmove (&maps[j] + 1,
 162                                          &maps[j],
 163                                          (k - j) * sizeof (struct link_map *));
 164                                 maps[j] = here;
 165
 166                                 break;
 167                               }
 168                           }
 169                       }
 170                   }
 171               }
 172         }
 173
 174       /* We do not rely on the linked list of loaded object anymore from
 175          this point on.  We have our own list here (maps).  The various
 176          members of this list cannot vanish since the open count is too
 177          high and will be decremented in this loop.  So we release the
 178          lock so that some code which might be called from a destructor
 179          can directly or indirectly access the lock.  */
 180     out:
 181       __rtld_lock_unlock_recursive (GL(dl_load_lock));
 182
 183       /* 'maps' now contains the objects in the right order.  Now call the
 184          destructors.  We have to process this array from the front.  */
 185       for (i = 0; i < nmaps; ++i)
 186         {
 187           l = maps[i];
 188
 189           if (l->l_init_called)
 190             {
 191               /* Make sure nothing happens if we are called twice.  */
 192               l->l_init_called = 0;
 193
 194               /* Is there a destructor function?  */
 195               if (l->l_info[DT_FINI_ARRAY] != NULL
 196                   || l->l_info[DT_FINI] != NULL)
 197                 {
 198                   /* When debugging print a message first.  */
 199                   if (__builtin_expect (GLRO(dl_debug_mask)
 200                                         & DL_DEBUG_IMPCALLS, 0))
 201                     _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
 202                                       l->l_name[0] ? l->l_name : rtld_progname,
 203                                       cnt);
 204
 205                   /* First see whether an array is given.  */
 206                   if (l->l_info[DT_FINI_ARRAY] != NULL)
 207                     {
 208                       ElfW(Addr) *array =
 209                         (ElfW(Addr) *) (l->l_addr
 210                                         + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 211                       unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 212                                         / sizeof (ElfW(Addr)));
 213                       while (i-- > 0)
 214                         ((fini_t) array[i]) ();
 215                     }
 216
 217                   /* Next try the old-style destructor.  */
 218                   if (l->l_info[DT_FINI] != NULL)
 219                     ((fini_t) DL_DT_FINI_ADDRESS (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr)) ();
 220                 }
 221
 222 #ifdef SHARED
 223               /* Auditing checkpoint: another object closed.  */
 224               if (!do_audit && __builtin_expect (GLRO(dl_naudit) > 0, 0))
 225                 {
 226                   struct audit_ifaces *afct = GLRO(dl_audit);
 227                   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 228                     {
 229                       if (afct->objclose != NULL)
 230                         /* Return value is ignored.  */
 231                         (void) afct->objclose (&l->l_audit[cnt].cookie);
 232
 233                       afct = afct->next;
 234                     }
 235                 }
 236 #endif
 237             }
 238
 239           /* Correct the previous increment.  */
 240           --l->l_opencount;
 241         }
 242     }
 243
 244 #ifdef SHARED
 245   if (! do_audit && GLRO(dl_naudit) > 0)
 246     {
 247       do_audit = 1;
 248       goto again;
 249     }
 250 #endif
 251
 252   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS, 0))
 253     _dl_debug_printf ("\nruntime linker statistics:\n"
 254                       "           final number of relocations: %lu\n"
 255                       "final number of relocations from cache: %lu\n",
 256                       GL(dl_num_relocations),
 257                       GL(dl_num_cache_relocations));
 258 }