elf/dl-init.c

   1 /* Run initializers for newly loaded objects.
   2    Copyright (C) 1995-2017 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
  27 static void
  28 call_init (struct link_map *l, int argc, char **argv, char **env)
  29 {
  30   if (l->l_init_called)
  31     /* This object is all done.  */
  32     return;
  33
  34   /* Avoid handling this constructor again in case we have a circular
  35      dependency.  */
  36   l->l_init_called = 1;
  37
  38   /* Check for object which constructors we do not run here.  */
  39   if (__builtin_expect (l->l_name[0], 'a') == '\0'
  40       && l->l_type == lt_executable)
  41     return;
  42
  43   /* Are there any constructors?  */
  44   if (l->l_info[DT_INIT] == NULL
  45       && __builtin_expect (l->l_info[DT_INIT_ARRAY] == NULL, 1))
  46     return;
  47
  48   /* Print a debug message if wanted.  */
  49   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
  50     _dl_debug_printf ("\ncalling init: %s\n\n",
  51                       DSO_FILENAME (l->l_name));
  52
  53   /* Now run the local constructors.  There are two forms of them:
  54      - the one named by DT_INIT
  55      - the others in the DT_INIT_ARRAY.
  56   */
  57   if (l->l_info[DT_INIT] != NULL)
  58     DL_CALL_DT_INIT(l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr, argc, argv, env);
  59
  60   /* Next see whether there is an array with initialization functions.  */
  61   ElfW(Dyn) *init_array = l->l_info[DT_INIT_ARRAY];
  62   if (init_array != NULL)
  63     {
  64       unsigned int j;
  65       unsigned int jm;
  66       ElfW(Addr) *addrs;
  67
  68       jm = l->l_info[DT_INIT_ARRAYSZ]->d_un.d_val / sizeof (ElfW(Addr));
  69
  70       addrs = (ElfW(Addr) *) (init_array->d_un.d_ptr + l->l_addr);
  71       for (j = 0; j < jm; ++j)
  72         ((init_t) addrs[j]) (argc, argv, env);
  73     }
  74 }
  75
  76
  77 void
  78 _dl_init (struct link_map *main_map, int argc, char **argv, char **env)
  79 {
  80   ElfW(Dyn) *preinit_array = main_map->l_info[DT_PREINIT_ARRAY];
  81   ElfW(Dyn) *preinit_array_size = main_map->l_info[DT_PREINIT_ARRAYSZ];
  82   unsigned int i;
  83
  84   if (__glibc_unlikely (GL(dl_initfirst) != NULL))
  85     {
  86       call_init (GL(dl_initfirst), argc, argv, env);
  87       GL(dl_initfirst) = NULL;
  88     }
  89
  90   /* Don't do anything if there is no preinit array.  */
  91   if (__builtin_expect (preinit_array != NULL, 0)
  92       && preinit_array_size != NULL
  93       && (i = preinit_array_size->d_un.d_val / sizeof (ElfW(Addr))) > 0)
  94     {
  95       ElfW(Addr) *addrs;
  96       unsigned int cnt;
  97
  98       if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
  99         _dl_debug_printf ("\ncalling preinit: %s\n\n",
 100                           DSO_FILENAME (main_map->l_name));
 101
 102       addrs = (ElfW(Addr) *) (preinit_array->d_un.d_ptr + main_map->l_addr);
 103       for (cnt = 0; cnt < i; ++cnt)
 104         ((init_t) addrs[cnt]) (argc, argv, env);
 105     }
 106
 107   /* Stupid users forced the ELF specification to be changed.  It now
 108      says that the dynamic loader is responsible for determining the
 109      order in which the constructors have to run.  The constructors
 110      for all dependencies of an object must run before the constructor
 111      for the object itself.  Circular dependencies are left unspecified.
 112
 113      This is highly questionable since it puts the burden on the dynamic
 114      loader which has to find the dependencies at runtime instead of
 115      letting the user do it right.  Stupidity rules!  */
 116
 117   i = main_map->l_searchlist.r_nlist;
 118   while (i-- > 0)
 119     call_init (main_map->l_initfini[i], argc, argv, env);
 120
 121 #ifndef HAVE_INLINED_SYSCALLS
 122   /* Finished starting up.  */
 123   _dl_starting_up = 0;
 124 #endif
 125 }