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.  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   unsigned int nloaded;
  47   struct link_map *l;
  48   struct link_map **maps;
  49
  50   /* Protect against concurrent loads and unloads.  */
  51   __rtld_lock_lock_recursive (GL(dl_load_lock));
  52
  53   nloaded = GL(dl_nloaded);
  54
  55   /* XXX Could it be (in static binaries) that there is no object loaded?  */
  56   assert (nloaded > 0);
  57
  58   /* Now we can allocate an array to hold all the pointers and copy
  59      the pointers in.  */
  60   maps = (struct link_map **) alloca (nloaded * sizeof (struct link_map *));
  61   for (l = GL(dl_loaded), i = 0; l != NULL; l = l->l_next)
  62     {
  63       assert (i < nloaded);
  64
  65       maps[i++] = l;
  66
  67       /* Bump l_opencount of all objects so that they are not dlclose()ed
  68          from underneath us.  */
  69       ++l->l_opencount;
  70     }
  71   assert (i == nloaded);
  72
  73   /* Now we have to do the sorting.  */
  74   for (l = GL(dl_loaded)->l_next; l != NULL; l = l->l_next)
  75     {
  76       unsigned int j;
  77       unsigned int k;
  78
  79       /* Find the place in the 'maps' array.  */
  80       for (j = 1; maps[j] != l; ++j)
  81         ;
  82
  83       /* Find all object for which the current one is a dependency and
  84          move the found object (if necessary) in front.  */
  85       for (k = j + 1; k < nloaded; ++k)
  86         {
  87           struct link_map **runp = maps[k]->l_initfini;
  88           if (runp != NULL)
  89             {
  90               while (*runp != NULL)
  91                 if (*runp == l)
  92                   {
  93                     struct link_map *here = maps[k];
  94
  95                     /* Move it now.  */
  96                     memmove (&maps[j] + 1,
  97                              &maps[j],
  98                              (k - j) * sizeof (struct link_map *));
  99                     maps[j++] = here;
 100
 101                     break;
 102                   }
 103                 else
 104                   ++runp;
 105             }
 106
 107           if (__builtin_expect (maps[k]->l_reldeps != NULL, 0))
 108             {
 109               unsigned int m = maps[k]->l_reldepsact;
 110               struct link_map **relmaps = maps[k]->l_reldeps;
 111
 112               while (m-- > 0)
 113                 {
 114                   if (relmaps[m] == l)
 115                     {
 116                       struct link_map *here = maps[k];
 117
 118                       /* Move it now.  */
 119                       memmove (&maps[j] + 1,
 120                                &maps[j],
 121                                (k - j) * sizeof (struct link_map *));
 122                       maps[j] = here;
 123
 124                       break;
 125                     }
 126                 }
 127             }
 128         }
 129     }
 130
 131   /* We do not rely on the linked list of loaded object anymore from
 132      this point on.  We have our own list here (maps).  The various
 133      members of this list cannot vanish since the open count is too
 134      high and will be decremented in this loop.  So we release the
 135      lock so that some code which might be called from a destructor
 136      can directly or indirectly access the lock.  */
 137   __rtld_lock_unlock_recursive (GL(dl_load_lock));
 138
 139   /* 'maps' now contains the objects in the right order.  Now call the
 140      destructors.  We have to process this array from the front.  */
 141   for (i = 0; i < nloaded; ++i)
 142     {
 143       l = maps[i];
 144
 145       if (l->l_init_called)
 146         {
 147           /* Make sure nothing happens if we are called twice.  */
 148           l->l_init_called = 0;
 149
 150           /* Don't call the destructors for objects we are not supposed to.  */
 151           if (l->l_name[0] == '\0' && l->l_type == lt_executable)
 152             continue;
 153
 154           /* Is there a destructor function?  */
 155           if (l->l_info[DT_FINI_ARRAY] == NULL && l->l_info[DT_FINI] == NULL)
 156             continue;
 157
 158           /* When debugging print a message first.  */
 159           if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 160             _dl_debug_printf ("\ncalling fini: %s\n\n",
 161                               l->l_name[0] ? l->l_name : rtld_progname);
 162
 163           /* First see whether an array is given.  */
 164           if (l->l_info[DT_FINI_ARRAY] != NULL)
 165             {
 166               ElfW(Addr) *array =
 167                 (ElfW(Addr) *) (l->l_addr
 168                                 + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 169               unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 170                                 / sizeof (ElfW(Addr)));
 171               while (i-- > 0)
 172                 ((fini_t) array[i]) ();
 173             }
 174
 175           /* Next try the old-style destructor.  */
 176           if (l->l_info[DT_FINI] != NULL)
 177             ((fini_t) DL_DT_FINI_ADDRESS (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr)) ();
 178         }
 179
 180       /* Correct the previous increment.  */
 181       --l->l_opencount;
 182     }
 183
 184   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS, 0))
 185     _dl_debug_printf ("\nruntime linker statistics:\n"
 186                       "           final number of relocations: %lu\n"
 187                       "final number of relocations from cache: %lu\n",
 188                       GL(dl_num_relocations),
 189                       GL(dl_num_cache_relocations));
 190 }