elf/dl-fini.c

   1 /* Call the termination functions of loaded shared objects.
   2    Copyright (C) 1995,96,1998-2002,2004-2005,2009,2011
   3    Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <alloca.h>
  22 #include <assert.h>
  23 #include <string.h>
  24 #include <ldsodefs.h>
  25
  26
  27 /* Type of the constructor functions.  */
  28 typedef void (*fini_t) (void);
  29
  30
  31 void
  32 internal_function
  33 _dl_sort_fini (struct link_map **maps, size_t nmaps, char *used, Lmid_t ns)
  34 {
  35   /* A list of one element need not be sorted.  */
  36   if (nmaps == 1)
  37     return;
  38
  39   /* We can skip looking for the binary itself which is at the front
  40      of the search list for the main namespace.  */
  41   unsigned int i = ns == LM_ID_BASE;
  42   char seen[nmaps];
  43   memset (seen, 0, nmaps * sizeof (seen[0]));
  44   while (1)
  45     {
  46       /* Keep track of which object we looked at this round.  */
  47       ++seen[i];
  48       struct link_map *thisp = maps[i];
  49
  50       /* Do not handle ld.so in secondary namespaces and object which
  51          are not removed.  */
  52       if (thisp != thisp->l_real || thisp->l_idx == -1)
  53         goto skip;
  54
  55       /* Find the last object in the list for which the current one is
  56          a dependency and move the current object behind the object
  57          with the dependency.  */
  58       unsigned int k = nmaps - 1;
  59       while (k > i)
  60         {
  61           struct link_map **runp = maps[k]->l_initfini;
  62           if (runp != NULL)
  63             /* Look through the dependencies of the object.  */
  64             while (*runp != NULL)
  65               if (__builtin_expect (*runp++ == thisp, 0))
  66                 {
  67                 move:
  68                   /* Move the current object to the back past the last
  69                      object with it as the dependency.  */
  70                   memmove (&maps[i], &maps[i + 1],
  71                            (k - i) * sizeof (maps[0]));
  72                   maps[k] = thisp;
  73
  74                   if (used != NULL)
  75                     {
  76                       char here_used = used[i];
  77                       memmove (&used[i], &used[i + 1],
  78                                (k - i) * sizeof (used[0]));
  79                       used[k] = here_used;
  80                     }
  81
  82                   if (seen[i + 1] > 1)
  83                     {
  84                       ++i;
  85                       goto next_clear;
  86                     }
  87
  88                   char this_seen = seen[i];
  89                   memmove (&seen[i], &seen[i + 1], (k - i) * sizeof (seen[0]));
  90                   seen[k] = this_seen;
  91
  92                   goto next;
  93                 }
  94
  95           if (__builtin_expect (maps[k]->l_reldeps != NULL, 0))
  96             {
  97               unsigned int m = maps[k]->l_reldeps->act;
  98               struct link_map **relmaps = &maps[k]->l_reldeps->list[0];
  99
 100               /* Look through the relocation dependencies of the object.  */
 101               while (m-- > 0)
 102                 if (__builtin_expect (relmaps[m] == thisp, 0))
 103                   {
 104                     /* If a cycle exists with a link time dependency,
 105                        preserve the latter.  */
 106                     struct link_map **runp = thisp->l_initfini;
 107                     if (runp != NULL)
 108                       while (*runp != NULL)
 109                         if (__builtin_expect (*runp++ == maps[k], 0))
 110                           goto ignore;
 111                     goto move;
 112                   }
 113             ignore:;
 114             }
 115
 116           --k;
 117         }
 118
 119     skip:
 120       if (++i == nmaps)
 121         break;
 122     next_clear:
 123       memset (&seen[i], 0, (nmaps - i) * sizeof (seen[0]));
 124
 125     next:;
 126     }
 127 }
 128
 129
 130 void
 131 internal_function
 132 _dl_fini (void)
 133 {
 134   /* Lots of fun ahead.  We have to call the destructors for all still
 135      loaded objects, in all namespaces.  The problem is that the ELF
 136      specification now demands that dependencies between the modules
 137      are taken into account.  I.e., the destructor for a module is
 138      called before the ones for any of its dependencies.
 139
 140      To make things more complicated, we cannot simply use the reverse
 141      order of the constructors.  Since the user might have loaded objects
 142      using `dlopen' there are possibly several other modules with its
 143      dependencies to be taken into account.  Therefore we have to start
 144      determining the order of the modules once again from the beginning.  */
 145   struct link_map **maps = NULL;
 146   size_t maps_size = 0;
 147
 148   /* We run the destructors of the main namespaces last.  As for the
 149      other namespaces, we pick run the destructors in them in reverse
 150      order of the namespace ID.  */
 151 #ifdef SHARED
 152   int do_audit = 0;
 153  again:
 154 #endif
 155   for (Lmid_t ns = GL(dl_nns) - 1; ns >= 0; --ns)
 156     {
 157       /* Protect against concurrent loads and unloads.  */
 158       __rtld_lock_lock_recursive (GL(dl_load_lock));
 159
 160       unsigned int nmaps = 0;
 161       unsigned int nloaded = GL(dl_ns)[ns]._ns_nloaded;
 162       /* No need to do anything for empty namespaces or those used for
 163          auditing DSOs.  */
 164       if (nloaded == 0
 165 #ifdef SHARED
 166           || GL(dl_ns)[ns]._ns_loaded->l_auditing != do_audit
 167 #endif
 168           )
 169         goto out;
 170
 171       /* XXX Could it be (in static binaries) that there is no object
 172          loaded?  */
 173       assert (ns != LM_ID_BASE || nloaded > 0);
 174
 175       /* Now we can allocate an array to hold all the pointers and copy
 176          the pointers in.  */
 177       if (maps_size < nloaded * sizeof (struct link_map *))
 178         {
 179           if (maps_size == 0)
 180             {
 181               maps_size = nloaded * sizeof (struct link_map *);
 182               maps = (struct link_map **) alloca (maps_size);
 183             }
 184           else
 185             maps = (struct link_map **)
 186               extend_alloca (maps, maps_size,
 187                              nloaded * sizeof (struct link_map *));
 188         }
 189
 190       unsigned int i;
 191       struct link_map *l;
 192       assert (nloaded != 0 || GL(dl_ns)[ns]._ns_loaded == NULL);
 193       for (l = GL(dl_ns)[ns]._ns_loaded, i = 0; l != NULL; l = l->l_next)
 194         /* Do not handle ld.so in secondary namespaces.  */
 195         if (l == l->l_real)
 196           {
 197             assert (i < nloaded);
 198
 199             maps[i] = l;
 200             l->l_idx = i;
 201             ++i;
 202
 203             /* Bump l_direct_opencount of all objects so that they are
 204                not dlclose()ed from underneath us.  */
 205             ++l->l_direct_opencount;
 206           }
 207       assert (ns != LM_ID_BASE || i == nloaded);
 208       assert (ns == LM_ID_BASE || i == nloaded || i == nloaded - 1);
 209       nmaps = i;
 210
 211       /* Now we have to do the sorting.  */
 212       _dl_sort_fini (maps, nmaps, NULL, ns);
 213
 214       /* We do not rely on the linked list of loaded object anymore from
 215          this point on.  We have our own list here (maps).  The various
 216          members of this list cannot vanish since the open count is too
 217          high and will be decremented in this loop.  So we release the
 218          lock so that some code which might be called from a destructor
 219          can directly or indirectly access the lock.  */
 220     out:
 221       __rtld_lock_unlock_recursive (GL(dl_load_lock));
 222
 223       /* 'maps' now contains the objects in the right order.  Now call the
 224          destructors.  We have to process this array from the front.  */
 225       for (i = 0; i < nmaps; ++i)
 226         {
 227           l = maps[i];
 228
 229           if (l->l_init_called)
 230             {
 231               /* Make sure nothing happens if we are called twice.  */
 232               l->l_init_called = 0;
 233
 234               /* Is there a destructor function?  */
 235               if (l->l_info[DT_FINI_ARRAY] != NULL
 236                   || l->l_info[DT_FINI] != NULL)
 237                 {
 238                   /* When debugging print a message first.  */
 239                   if (__builtin_expect (GLRO(dl_debug_mask)
 240                                         & DL_DEBUG_IMPCALLS, 0))
 241                     _dl_debug_printf ("\ncalling fini: %s [%lu]\n\n",
 242                                       l->l_name[0] ? l->l_name : rtld_progname,
 243                                       ns);
 244
 245                   /* First see whether an array is given.  */
 246                   if (l->l_info[DT_FINI_ARRAY] != NULL)
 247                     {
 248                       ElfW(Addr) *array =
 249                         (ElfW(Addr) *) (l->l_addr
 250                                         + l->l_info[DT_FINI_ARRAY]->d_un.d_ptr);
 251                       unsigned int i = (l->l_info[DT_FINI_ARRAYSZ]->d_un.d_val
 252                                         / sizeof (ElfW(Addr)));
 253                       while (i-- > 0)
 254                         ((fini_t) array[i]) ();
 255                     }
 256
 257                   /* Next try the old-style destructor.  */
 258                   if (l->l_info[DT_FINI] != NULL)
 259                     ((fini_t) DL_DT_FINI_ADDRESS (l, l->l_addr + l->l_info[DT_FINI]->d_un.d_ptr)) ();
 260                 }
 261
 262 #ifdef SHARED
 263               /* Auditing checkpoint: another object closed.  */
 264               if (!do_audit && __builtin_expect (GLRO(dl_naudit) > 0, 0))
 265                 {
 266                   struct audit_ifaces *afct = GLRO(dl_audit);
 267                   for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
 268                     {
 269                       if (afct->objclose != NULL)
 270                         /* Return value is ignored.  */
 271                         (void) afct->objclose (&l->l_audit[cnt].cookie);
 272
 273                       afct = afct->next;
 274                     }
 275                 }
 276 #endif
 277             }
 278
 279           /* Correct the previous increment.  */
 280           --l->l_direct_opencount;
 281         }
 282     }
 283
 284 #ifdef SHARED
 285   if (! do_audit && GLRO(dl_naudit) > 0)
 286     {
 287       do_audit = 1;
 288       goto again;
 289     }
 290
 291   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_STATISTICS, 0))
 292     _dl_debug_printf ("\nruntime linker statistics:\n"
 293                       "           final number of relocations: %lu\n"
 294                       "final number of relocations from cache: %lu\n",
 295                       GL(dl_num_relocations),
 296                       GL(dl_num_cache_relocations));
 297 #endif
 298 }