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   unsigned int i;
  46   unsigned int nloaded;
  47   struct link_map *l;
  48   struct link_map **maps = NULL;
  49   size_t maps_size = 0;
  50
  51   /* We First run the destructors of the main namespaces, then the
  52      other ones.  The order should not matter since the namespace
  53      content is supposed to be independent.  But we can have auditing
  54      code in a auxiliaty namespace and we want it to monitor the
  55      destructors.  */
  56   for (Lmid_t cnt = 0; cnt < DL_NNS; ++cnt)
  57     {
  58       /* Protect against concurrent loads and unloads.  */
  59       __rtld_lock_lock_recursive (GL(dl_load_lock));
  60
  61       nloaded = GL(dl_ns)[cnt]._ns_nloaded;
  62
  63       /* XXX Could it be (in static binaries) that there is no object
  64          loaded?  */
  65       assert (cnt != LM_ID_BASE || nloaded > 0);
  66
  67       /* Now we can allocate an array to hold all the pointers and copy
  68          the pointers in.  */
  69       if (maps_size < nloaded * sizeof (struct link_map *))
  70         {
  71           if (maps_size == 0)
  72             {
  73               maps_size = nloaded * sizeof (struct link_map *);
  74               maps = (struct link_map **) alloca (maps_size);
  75             }
  76           else
  77             maps = (struct link_map **)
  78               extend_alloca (maps, maps_size,
  79                              nloaded * sizeof (struct link_map *));
  80         }
  81
  82       for (l = GL(dl_ns)[cnt]._ns_loaded, i = 0; l != NULL; l = l->l_next)
  83         {
  84           assert (i < nloaded);
  85
  86           /* Do not handle ld.so in secondary namespaces.  */
  87           if (l == l->l_real)
  88             {
  89               maps[i++] = l;
  90
  91               /* Bump l_opencount of all objects so that they are not
  92                  dlclose()ed from underneath us.  */
  93               ++l->l_opencount;
  94             }
  95         }
  96       assert (cnt != LM_ID_BASE || i == nloaded);
  97       assert (cnt == LM_ID_BASE || i == nloaded || i == nloaded - 1);
  98       unsigned int nmaps = i;
  99
 100       if (nmaps != 0)
 101         {
 102           /* Now we have to do the sorting.  */
 103           l = GL(dl_ns)[cnt]._ns_loaded;
 104           if (cnt == LM_ID_BASE)
 105             /* The main executable always comes first.  */
 106             l = l->l_next;
 107           for (; l != NULL; l = l->l_next)
 108             {
 109               unsigned int j;
 110               unsigned int k;
 111
 112               /* Find the place in the 'maps' array.  */
 113               for (j = 1; maps[j] != l; ++j)
 114                 ;
 115
 116               /* Find all object for which the current one is a dependency and
 117                  move the found object (if necessary) in front.  */
 118               for (k = j + 1; k < nmaps; ++k)
 119                 {
 120                   struct link_map **runp = maps[k]->l_initfini;
 121                   if (runp != NULL)
 122                     {
 123                       while (*runp != NULL)
 124                         if (*runp == l)
 125                           {
 126                             struct link_map *here = maps[k];
 127
 128                             /* Move it now.  */
 129                             memmove (&maps[j] + 1,
 130                                      &maps[j],
 131                                      (k - j) * sizeof (struct link_map *));
 132                             maps[j++] = here;
 133
 134                             break;
 135                           }
 136                         else
 137                           ++runp;
 138                     }
 139
 140                   if (__builtin_expect (maps[k]->l_reldeps != NULL, 0))
 141                     {
 142                       unsigned int m = maps[k]->l_reldepsact;
 143                       struct link_map **relmaps = maps[k]->l_reldeps;
 144
 145                       while (m-- > 0)
 146                         {
 147                           if (relmaps[m] == l)
 148                             {
 149                               struct link_map *here = maps[k];
 150
 151                               /* Move it now.  */
 152                               memmove (&maps[j] + 1,
 153                                        &maps[j],
 154                                        (k - j) * sizeof (struct link_map *));
 155                               maps[j] = here;
 156
 157                               break;
 158                             }
 159                         }
 160                     }
 161                 }
 162             }
 163         }
 164
 165       /* We do not rely on the linked list of loaded object anymore from
 166          this point on.  We have our own list here (maps).  The various
 167          members of this list cannot vanish since the open count is too
 168          high and will be decremented in this loop.  So we release the
 169          lock so that some code which might be called from a destructor
 170          can directly or indirectly access the lock.  */
 171       __rtld_lock_unlock_recursive (GL(dl_load_lock));
 172
 173       /* 'maps' now contains the objects in the right order.  Now call the
 174          destructors.  We have to process this array from the front.  */
 175       for (i = 0; i < nmaps; ++i)
 176         {
 177           l = maps[i];
 178
 179           if (l->l_init_called)
 180             {
 181               /* Make sure nothing happens if we are called twice.  */
 182               l->l_init_called = 0;
 183
 184               /* Don't call the destructors for objects we are not
 185                  supposed to.  */
 186               if (l->l_name[0] == '\0' && l->l_type == lt_executable)
 187                 continue;
 188
 189               /* Is there a destructor function?  */
 190               if (l->l_info[DT_FINI_ARRAY] == NULL
 191                   && l->l_info[DT_FINI] == NULL)
 192                 continue;
 193
 194               /* When debugging print a message first.  */
 195               if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS,
 196                                     0))
 197                 _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
 198                                   l->l_name[0] ? l->l_name : rtld_progname,
 199                                   cnt);
 200
 201               /* First see whether an array is given.  */
 202               if (l->l_info[DT_FINI_ARRAY] != NULL)
 203                 {
 204                   ElfW(Addr) *array =
 205                     (ElfW(Addr) *) (l->l_addr
 206                                     + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 207                   unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 208                                     / sizeof (ElfW(Addr)));
 209                   while (i-- > 0)
 210                     ((fini_t) array[i]) ();
 211                 }
 212
 213               /* Next try the old-style destructor.  */
 214               if (l->l_info[DT_FINI] != NULL)
 215                 ((fini_t) DL_DT_FINI_ADDRESS (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr)) ();
 216             }
 217
 218           /* Correct the previous increment.  */
 219           --l->l_opencount;
 220         }
 221     }
 222
 223   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS, 0))
 224     _dl_debug_printf ("\nruntime linker statistics:\n"
 225                       "           final number of relocations: %lu\n"
 226                       "final number of relocations from cache: %lu\n",
 227                       GL(dl_num_relocations),
 228                       GL(dl_num_cache_relocations));
 229 }