elf/dl-fini.c

   1 /* Call the termination functions of loaded shared objects.
   2    Copyright (C) 1995,96,1998-2002,2004 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   for (Lmid_t cnt = DL_NNS - 1; cnt >= 0; --cnt)
  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)[cnt]._ns_nloaded;
  57
  58       /* XXX Could it be (in static binaries) that there is no object
  59          loaded?  */
  60       assert (cnt != LM_ID_BASE || nloaded > 0);
  61
  62       /* Now we can allocate an array to hold all the pointers and copy
  63          the pointers in.  */
  64       if (maps_size < nloaded * sizeof (struct link_map *))
  65         {
  66           if (maps_size == 0)
  67             {
  68               maps_size = nloaded * sizeof (struct link_map *);
  69               maps = (struct link_map **) alloca (maps_size);
  70             }
  71           else
  72             maps = (struct link_map **)
  73               extend_alloca (maps, maps_size,
  74                              nloaded * sizeof (struct link_map *));
  75         }
  76
  77       unsigned int i;
  78       struct link_map *l;
  79       for (l = GL(dl_ns)[cnt]._ns_loaded, i = 0; l != NULL; l = l->l_next)
  80         /* Do not handle ld.so in secondary namespaces.  */
  81         if (l == l->l_real)
  82           {
  83             assert (i < nloaded);
  84
  85             maps[i++] = l;
  86
  87             /* Bump l_opencount of all objects so that they are not
  88                dlclose()ed from underneath us.  */
  89             ++l->l_opencount;
  90           }
  91       assert (cnt != LM_ID_BASE || i == nloaded);
  92       assert (cnt == LM_ID_BASE || i == nloaded || i == nloaded - 1);
  93       unsigned int nmaps = i;
  94
  95       if (nmaps != 0)
  96         {
  97           /* Now we have to do the sorting.  */
  98           l = GL(dl_ns)[cnt]._ns_loaded;
  99           if (cnt == LM_ID_BASE)
 100             /* The main executable always comes first.  */
 101             l = l->l_next;
 102           for (; l != NULL; l = l->l_next)
 103             /* Do not handle ld.so in secondary namespaces.  */
 104             if (l == l->l_real)
 105               {
 106                 /* Find the place in the 'maps' array.  */
 107                 unsigned int j;
 108                 for (j = cnt == LM_ID_BASE ? 1 : 0; maps[j] != l; ++j)
 109                   assert (j < nmaps);
 110
 111                 /* Find all object for which the current one is a dependency
 112                    and move the found object (if necessary) in front.  */
 113                 for (unsigned int k = j + 1; k < nmaps; ++k)
 114                   {
 115                     struct link_map **runp = maps[k]->l_initfini;
 116                     if (runp != NULL)
 117                       {
 118                         while (*runp != NULL)
 119                           if (*runp == l)
 120                             {
 121                               struct link_map *here = maps[k];
 122
 123                               /* Move it now.  */
 124                               memmove (&maps[j] + 1,
 125                                        &maps[j],
 126                                        (k - j) * sizeof (struct link_map *));
 127                               maps[j++] = here;
 128
 129                               break;
 130                             }
 131                           else
 132                             ++runp;
 133                       }
 134
 135                     if (__builtin_expect (maps[k]->l_reldeps != NULL, 0))
 136                       {
 137                         unsigned int m = maps[k]->l_reldepsact;
 138                         struct link_map **relmaps = maps[k]->l_reldeps;
 139
 140                         while (m-- > 0)
 141                           {
 142                             if (relmaps[m] == l)
 143                               {
 144                                 struct link_map *here = maps[k];
 145
 146                                 /* Move it now.  */
 147                                 memmove (&maps[j] + 1,
 148                                          &maps[j],
 149                                          (k - j) * sizeof (struct link_map *));
 150                                 maps[j] = here;
 151
 152                                 break;
 153                               }
 154                           }
 155                       }
 156                   }
 157               }
 158         }
 159
 160       /* We do not rely on the linked list of loaded object anymore from
 161          this point on.  We have our own list here (maps).  The various
 162          members of this list cannot vanish since the open count is too
 163          high and will be decremented in this loop.  So we release the
 164          lock so that some code which might be called from a destructor
 165          can directly or indirectly access the lock.  */
 166       __rtld_lock_unlock_recursive (GL(dl_load_lock));
 167
 168       /* 'maps' now contains the objects in the right order.  Now call the
 169          destructors.  We have to process this array from the front.  */
 170       for (i = 0; i < nmaps; ++i)
 171         {
 172           l = maps[i];
 173
 174           if (l->l_init_called)
 175             {
 176               /* Make sure nothing happens if we are called twice.  */
 177               l->l_init_called = 0;
 178
 179               /* Don't call the destructors for objects we are not
 180                  supposed to.  */
 181               if (l->l_name[0] == '\0' && l->l_type == lt_executable)
 182                 continue;
 183
 184               /* Is there a destructor function?  */
 185               if (l->l_info[DT_FINI_ARRAY] == NULL
 186                   && l->l_info[DT_FINI] == NULL)
 187                 continue;
 188
 189               /* When debugging print a message first.  */
 190               if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS,
 191                                     0))
 192                 _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
 193                                   l->l_name[0] ? l->l_name : rtld_progname,
 194                                   cnt);
 195
 196               /* First see whether an array is given.  */
 197               if (l->l_info[DT_FINI_ARRAY] != NULL)
 198                 {
 199                   ElfW(Addr) *array =
 200                     (ElfW(Addr) *) (l->l_addr
 201                                     + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 202                   unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 203                                     / sizeof (ElfW(Addr)));
 204                   while (i-- > 0)
 205                     ((fini_t) array[i]) ();
 206                 }
 207
 208               /* Next try the old-style destructor.  */
 209               if (l->l_info[DT_FINI] != NULL)
 210                 ((fini_t) DL_DT_FINI_ADDRESS (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr)) ();
 211             }
 212
 213           /* Correct the previous increment.  */
 214           --l->l_opencount;
 215         }
 216     }
 217
 218   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS, 0))
 219     _dl_debug_printf ("\nruntime linker statistics:\n"
 220                       "           final number of relocations: %lu\n"
 221                       "final number of relocations from cache: %lu\n",
 222                       GL(dl_num_relocations),
 223                       GL(dl_num_cache_relocations));
 224 }