elf/dl-init.c

   1 /* Run initializers for newly loaded objects.
   2    Copyright (C) 1995-2014 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 (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
  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     DL_CALL_DT_INIT(l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr, argc, argv, env);
  65
  66   /* Next see whether there is an array with initialization functions.  */
  67   ElfW(Dyn) *init_array = l->l_info[DT_INIT_ARRAY];
  68   if (init_array != NULL)
  69     {
  70       unsigned int j;
  71       unsigned int jm;
  72       ElfW(Addr) *addrs;
  73
  74       jm = l->l_info[DT_INIT_ARRAYSZ]->d_un.d_val / sizeof (ElfW(Addr));
  75
  76       addrs = (ElfW(Addr) *) (init_array->d_un.d_ptr + l->l_addr);
  77       for (j = 0; j < jm; ++j)
  78         ((init_t) addrs[j]) (argc, argv, env);
  79     }
  80 }
  81
  82
  83 void
  84 internal_function
  85 _dl_init (struct link_map *main_map, int argc, char **argv, char **env)
  86 {
  87   ElfW(Dyn) *preinit_array = main_map->l_info[DT_PREINIT_ARRAY];
  88   ElfW(Dyn) *preinit_array_size = main_map->l_info[DT_PREINIT_ARRAYSZ];
  89   unsigned int i;
  90
  91   if (__glibc_unlikely (GL(dl_initfirst) != NULL))
  92     {
  93       call_init (GL(dl_initfirst), argc, argv, env);
  94       GL(dl_initfirst) = NULL;
  95     }
  96
  97   /* Don't do anything if there is no preinit array.  */
  98   if (__builtin_expect (preinit_array != NULL, 0)
  99       && preinit_array_size != NULL
 100       && (i = preinit_array_size->d_un.d_val / sizeof (ElfW(Addr))) > 0)
 101     {
 102       ElfW(Addr) *addrs;
 103       unsigned int cnt;
 104
 105       if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
 106         _dl_debug_printf ("\ncalling preinit: %s\n\n",
 107                           DSO_FILENAME (main_map->l_name));
 108
 109       addrs = (ElfW(Addr) *) (preinit_array->d_un.d_ptr + main_map->l_addr);
 110       for (cnt = 0; cnt < i; ++cnt)
 111         ((init_t) addrs[cnt]) (argc, argv, env);
 112     }
 113
 114   /* Stupid users forced the ELF specification to be changed.  It now
 115      says that the dynamic loader is responsible for determining the
 116      order in which the constructors have to run.  The constructors
 117      for all dependencies of an object must run before the constructor
 118      for the object itself.  Circular dependencies are left unspecified.
 119
 120      This is highly questionable since it puts the burden on the dynamic
 121      loader which has to find the dependencies at runtime instead of
 122      letting the user do it right.  Stupidity rules!  */
 123
 124   i = main_map->l_searchlist.r_nlist;
 125   while (i-- > 0)
 126     call_init (main_map->l_initfini[i], argc, argv, env);
 127
 128 #ifndef HAVE_INLINED_SYSCALLS
 129   /* Finished starting up.  */
 130   INTUSE(_dl_starting_up) = 0;
 131 #endif
 132 }
 133 INTDEF (_dl_init)