elf/dl-init.c

   1 /* Run initializers for newly loaded objects.
   2    Copyright (C) 1995-2024 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <stddef.h>
  21 #include <ldsodefs.h>
  22 #include <elf-initfini.h>
  23
  24
  25 static void
  26 call_init (struct link_map *l, int argc, char **argv, char **env)
  27 {
  28   /* Do not run constructors for proxy objects.  */
  29   if (l != l->l_real)
  30     return;
  31
  32   /* If the object has not been relocated, this is a bug.  The
  33      function pointers are invalid in this case.  (Executables do not
  34      need relocation.)  */
  35   assert (l->l_relocated || l->l_type == lt_executable);
  36
  37   if (l->l_init_called)
  38     /* This object is all done.  */
  39     return;
  40
  41   /* Avoid handling this constructor again in case we have a circular
  42      dependency.  */
  43   l->l_init_called = 1;
  44
  45   /* Check for object which constructors we do not run here.  */
  46   if (__builtin_expect (l->l_name[0], 'a') == '\0'
  47       && l->l_type == lt_executable)
  48     return;
  49
  50   /* Print a debug message if wanted.  */
  51   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
  52     _dl_debug_printf ("\ncalling init: %s\n\n",
  53                       DSO_FILENAME (l->l_name));
  54
  55   /* Now run the local constructors.  There are two forms of them:
  56      - the one named by DT_INIT
  57      - the others in the DT_INIT_ARRAY.
  58   */
  59   if (ELF_INITFINI && l->l_info[DT_INIT] != NULL)
  60     DL_CALL_DT_INIT(l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr, argc, argv, env);
  61
  62   /* Next see whether there is an array with initialization functions.  */
  63   ElfW(Dyn) *init_array = l->l_info[DT_INIT_ARRAY];
  64   if (init_array != NULL)
  65     {
  66       unsigned int j;
  67       unsigned int jm;
  68       ElfW(Addr) *addrs;
  69
  70       jm = l->l_info[DT_INIT_ARRAYSZ]->d_un.d_val / sizeof (ElfW(Addr));
  71
  72       addrs = (ElfW(Addr) *) (init_array->d_un.d_ptr + l->l_addr);
  73       for (j = 0; j < jm; ++j)
  74         ((dl_init_t) addrs[j]) (argc, argv, env);
  75     }
  76 }
  77
  78
  79 void
  80 _dl_init (struct link_map *main_map, int argc, char **argv, char **env)
  81 {
  82   ElfW(Dyn) *preinit_array = main_map->l_info[DT_PREINIT_ARRAY];
  83   ElfW(Dyn) *preinit_array_size = main_map->l_info[DT_PREINIT_ARRAYSZ];
  84   unsigned int i;
  85
  86   if (__glibc_unlikely (GL(dl_initfirst) != NULL))
  87     {
  88       call_init (GL(dl_initfirst), argc, argv, env);
  89       GL(dl_initfirst) = NULL;
  90     }
  91
  92   /* Don't do anything if there is no preinit array.  */
  93   if (__builtin_expect (preinit_array != NULL, 0)
  94       && preinit_array_size != NULL
  95       && (i = preinit_array_size->d_un.d_val / sizeof (ElfW(Addr))) > 0)
  96     {
  97       ElfW(Addr) *addrs;
  98       unsigned int cnt;
  99
 100       if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
 101         _dl_debug_printf ("\ncalling preinit: %s\n\n",
 102                           DSO_FILENAME (main_map->l_name));
 103
 104       addrs = (ElfW(Addr) *) (preinit_array->d_un.d_ptr + main_map->l_addr);
 105       for (cnt = 0; cnt < i; ++cnt)
 106         ((dl_init_t) addrs[cnt]) (argc, argv, env);
 107     }
 108
 109   /* Stupid users forced the ELF specification to be changed.  It now
 110      says that the dynamic loader is responsible for determining the
 111      order in which the constructors have to run.  The constructors
 112      for all dependencies of an object must run before the constructor
 113      for the object itself.  Circular dependencies are left unspecified.
 114
 115      This is highly questionable since it puts the burden on the dynamic
 116      loader which has to find the dependencies at runtime instead of
 117      letting the user do it right.  Stupidity rules!  */
 118
 119   i = main_map->l_searchlist.r_nlist;
 120   while (i-- > 0)
 121     call_init (main_map->l_initfini[i], argc, argv, env);
 122
 123 #ifndef HAVE_INLINED_SYSCALLS
 124   /* Finished starting up.  */
 125   _dl_starting_up = 0;
 126 #endif
 127 }