elf/dl-init.c

   1 /* Run initializers for newly loaded objects.
   2    Copyright (C) 1995-2013 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <stddef.h>
  20 #include <ldsodefs.h>
  21
  22
  23 /* Type of the initializer.  */
  24 typedef void (*init_t) (int, char **, char **);
  25
  26 #ifndef HAVE_INLINED_SYSCALLS
  27 /* Flag, nonzero during startup phase.  */
  28 extern int _dl_starting_up;
  29 extern int _dl_starting_up_internal attribute_hidden;
  30 #endif
  31
  32
  33 static void
  34 call_init (struct link_map *l, int argc, char **argv, char **env)
  35 {
  36   if (l->l_init_called)
  37     /* This object is all done.  */
  38     return;
  39
  40   /* Avoid handling this constructor again in case we have a circular
  41      dependency.  */
  42   l->l_init_called = 1;
  43
  44   /* Check for object which constructors we do not run here.  */
  45   if (__builtin_expect (l->l_name[0], 'a') == '\0'
  46       && l->l_type == lt_executable)
  47     return;
  48
  49   /* Are there any constructors?  */
  50   if (l->l_info[DT_INIT] == NULL
  51       && __builtin_expect (l->l_info[DT_INIT_ARRAY] == NULL, 1))
  52     return;
  53
  54   /* Print a debug message if wanted.  */
  55   if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
  56     _dl_debug_printf ("\ncalling init: %s\n\n",
  57                       DSO_FILENAME (l->l_name));
  58
  59   /* Now run the local constructors.  There are two forms of them:
  60      - the one named by DT_INIT
  61      - the others in the DT_INIT_ARRAY.
  62   */
  63   if (l->l_info[DT_INIT] != NULL)
  64     {
  65       init_t init = (init_t) DL_DT_INIT_ADDRESS
  66         (l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr);
  67
  68       /* Call the function.  */
  69       init (argc, argv, env);
  70     }
  71
  72   /* Next see whether there is an array with initialization functions.  */
  73   ElfW(Dyn) *init_array = l->l_info[DT_INIT_ARRAY];
  74   if (init_array != NULL)
  75     {
  76       unsigned int j;
  77       unsigned int jm;
  78       ElfW(Addr) *addrs;
  79
  80       jm = l->l_info[DT_INIT_ARRAYSZ]->d_un.d_val / sizeof (ElfW(Addr));
  81
  82       addrs = (ElfW(Addr) *) (init_array->d_un.d_ptr + l->l_addr);
  83       for (j = 0; j < jm; ++j)
  84         ((init_t) addrs[j]) (argc, argv, env);
  85     }
  86 }
  87
  88
  89 void
  90 internal_function
  91 _dl_init (struct link_map *main_map, int argc, char **argv, char **env)
  92 {
  93   ElfW(Dyn) *preinit_array = main_map->l_info[DT_PREINIT_ARRAY];
  94   ElfW(Dyn) *preinit_array_size = main_map->l_info[DT_PREINIT_ARRAYSZ];
  95   unsigned int i;
  96
  97   if (__builtin_expect (GL(dl_initfirst) != NULL, 0))
  98     {
  99       call_init (GL(dl_initfirst), argc, argv, env);
 100       GL(dl_initfirst) = NULL;
 101     }
 102
 103   /* Don't do anything if there is no preinit array.  */
 104   if (__builtin_expect (preinit_array != NULL, 0)
 105       && preinit_array_size != NULL
 106       && (i = preinit_array_size->d_un.d_val / sizeof (ElfW(Addr))) > 0)
 107     {
 108       ElfW(Addr) *addrs;
 109       unsigned int cnt;
 110
 111       if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS, 0))
 112         _dl_debug_printf ("\ncalling preinit: %s\n\n",
 113                           DSO_FILENAME (main_map->l_name));
 114
 115       addrs = (ElfW(Addr) *) (preinit_array->d_un.d_ptr + main_map->l_addr);
 116       for (cnt = 0; cnt < i; ++cnt)
 117         ((init_t) addrs[cnt]) (argc, argv, env);
 118     }
 119
 120   /* Stupid users forced the ELF specification to be changed.  It now
 121      says that the dynamic loader is responsible for determining the
 122      order in which the constructors have to run.  The constructors
 123      for all dependencies of an object must run before the constructor
 124      for the object itself.  Circular dependencies are left unspecified.
 125
 126      This is highly questionable since it puts the burden on the dynamic
 127      loader which has to find the dependencies at runtime instead of
 128      letting the user do it right.  Stupidity rules!  */
 129
 130   i = main_map->l_searchlist.r_nlist;
 131   while (i-- > 0)
 132     call_init (main_map->l_initfini[i], argc, argv, env);
 133
 134 #ifndef HAVE_INLINED_SYSCALLS
 135   /* Finished starting up.  */
 136   INTUSE(_dl_starting_up) = 0;
 137 #endif
 138 }
 139 INTDEF (_dl_init)