elf/dl-fini.c

   1 /* Call the termination functions of loaded shared objects.
   2    Copyright (C) 1995,96,98,99,2000,2001,2002 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.  The problem is that the ELF specification now
  36      demands that dependencies between the modules are taken into account.
  37      I.e., the destructor for a module is called before the ones for any
  38      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   unsigned int i;
  46   struct link_map *l;
  47   struct link_map **maps;
  48
  49   /* XXX Could it be (in static binaries) that there is no object loaded?  */
  50   assert (GL(dl_nloaded) > 0);
  51
  52   /* Now we can allocate an array to hold all the pointers and copy
  53      the pointers in.  */
  54   maps = (struct link_map **) alloca (GL(dl_nloaded)
  55                                       * sizeof (struct link_map *));
  56   for (l = GL(dl_loaded), i = 0; l != NULL; l = l->l_next)
  57     {
  58       assert (i < GL(dl_nloaded));
  59
  60       maps[i++] = l;
  61
  62       /* Bump l_opencount of all objects so that they are not dlclose()ed
  63          from underneath us.  */
  64       ++l->l_opencount;
  65     }
  66   assert (i == GL(dl_nloaded));
  67
  68   /* Now we have to do the sorting.  */
  69   for (l = GL(dl_loaded)->l_next; l != NULL; l = l->l_next)
  70     {
  71       unsigned int j;
  72       unsigned int k;
  73
  74       /* Find the place in the `maps' array.  */
  75       for (j = 1; maps[j] != l; ++j)
  76         ;
  77
  78       /* Find all object for which the current one is a dependency and
  79          move the found object (if necessary) in front.  */
  80       for (k = j + 1; k < GL(dl_nloaded); ++k)
  81         {
  82           struct link_map **runp;
  83
  84           runp = maps[k]->l_initfini;
  85           if (runp != NULL)
  86             {
  87               while (*runp != NULL)
  88                 if (*runp == l)
  89                   {
  90                     struct link_map *here = maps[k];
  91
  92                     /* Move it now.  */
  93                     memmove (&maps[j] + 1,
  94                              &maps[j],
  95                              (k - j) * sizeof (struct link_map *));
  96                     maps[j++] = here;
  97
  98                     break;
  99                   }
 100                 else
 101                   ++runp;
 102             }
 103
 104           if (__builtin_expect (maps[k]->l_reldeps != NULL, 0))
 105             {
 106               unsigned int m = maps[k]->l_reldepsact;
 107               struct link_map **relmaps = maps[k]->l_reldeps;
 108
 109               while (m-- > 0)
 110                 {
 111                   if (relmaps[m] == l)
 112                     {
 113                       struct link_map *here = maps[k];
 114
 115                       /* Move it now.  */
 116                       memmove (&maps[j] + 1,
 117                                &maps[j],
 118                                (k - j) * sizeof (struct link_map *));
 119                       maps[j] = here;
 120
 121                       break;
 122                     }
 123
 124                 }
 125             }
 126         }
 127     }
 128
 129   /* `maps' now contains the objects in the right order.  Now call the
 130      destructors.  We have to process this array from the front.  */
 131   for (i = 0; i < GL(dl_nloaded); ++i)
 132     {
 133       l = maps[i];
 134
 135       if (l->l_init_called)
 136         {
 137           /* Make sure nothing happens if we are called twice.  */
 138           l->l_init_called = 0;
 139
 140           /* Don't call the destructors for objects we are not supposed to.  */
 141           if (l->l_name[0] == '\0' && l->l_type == lt_executable)
 142             continue;
 143
 144           /* Is there a destructor function?  */
 145           if (l->l_info[DT_FINI_ARRAY] == NULL && l->l_info[DT_FINI] == NULL)
 146             continue;
 147
 148           /* When debugging print a message first.  */
 149           if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 150             INTUSE(_dl_debug_printf) ("\ncalling fini: %s\n\n",
 151                                       l->l_name[0]
 152                                       ? l->l_name : rtld_progname);
 153
 154           /* First see whether an array is given.  */
 155           if (l->l_info[DT_FINI_ARRAY] != NULL)
 156             {
 157               ElfW(Addr) *array =
 158                 (ElfW(Addr) *) (l->l_addr
 159                                 + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 160               unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 161                                 / sizeof (ElfW(Addr)));
 162               while (i-- > 0)
 163                 ((fini_t) array[i]) ();
 164             }
 165
 166           /* Next try the old-style destructor.  */
 167           if (l->l_info[DT_FINI] != NULL)
 168             ((fini_t) DL_DT_FINI_ADDRESS (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr)) ();
 169         }
 170
 171       /* Correct the previous increment.  */
 172       --l->l_opencount;
 173     }
 174
 175   if (__builtin_expect (GL(dl_debug_mask) & DL_DEBUG_STATISTICS, 0))
 176     {
 177       INTUSE(_dl_debug_printf) ("\nruntime linker statistics:\n");
 178       INTUSE(_dl_debug_printf) ("\
 179            final number of relocations: %lu\n",
 180                                 GL(dl_num_relocations));
 181       INTUSE(_dl_debug_printf) ("\
 182 final number of relocations from cache: %lu\n",
 183                                 GL(dl_num_cache_relocations));
 184     }
 185 }