elf/dl-init.c

   1 /* Run initializers for newly loaded objects.
   2    Copyright (C) 1995-2023 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 struct link_map *_dl_init_called_list;
  25
  26 static void
  27 call_init (struct link_map *l, int argc, char **argv, char **env)
  28 {
  29   /* Do not run constructors for proxy objects.  */
  30   if (l != l->l_real)
  31     return;
  32
  33   /* If the object has not been relocated, this is a bug.  The
  34      function pointers are invalid in this case.  (Executables do not
  35      need relocation.)  */
  36   assert (l->l_relocated || l->l_type == lt_executable);
  37
  38   if (l->l_init_called)
  39     /* This object is all done.  */
  40     return;
  41
  42   /* Avoid handling this constructor again in case we have a circular
  43      dependency.  */
  44   l->l_init_called = 1;
  45
  46   /* Help an already-running dlclose: The just-loaded object must not
  47      be removed during the current pass.  (No effect if no dlclose in
  48      progress.)  */
  49   l->l_map_used = 1;
  50
  51   /* Record execution before starting any initializers.  This way, if
  52      the initializers themselves call dlopen, their ELF destructors
  53      will eventually be run before this object is destructed, matching
  54      that their ELF constructors have run before this object was
  55      constructed.  _dl_fini uses this list for audit callbacks, so
  56      register objects on the list even if they do not have a
  57      constructor.  */
  58   l->l_init_called_next = _dl_init_called_list;
  59   _dl_init_called_list = l;
  60
  61   /* Check for object which constructors we do not run here.  */
  62   if (__builtin_expect (l->l_name[0], 'a') == '\0'
  63       && l->l_type == lt_executable)
  64     return;
  65
  66   /* Print a debug message if wanted.  */
  67   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
  68     _dl_debug_printf ("\ncalling init: %s\n\n",
  69                       DSO_FILENAME (l->l_name));
  70
  71   /* Now run the local constructors.  There are two forms of them:
  72      - the one named by DT_INIT
  73      - the others in the DT_INIT_ARRAY.
  74   */
  75   if (ELF_INITFINI && l->l_info[DT_INIT] != NULL)
  76     DL_CALL_DT_INIT(l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr, argc, argv, env);
  77
  78   /* Next see whether there is an array with initialization functions.  */
  79   ElfW(Dyn) *init_array = l->l_info[DT_INIT_ARRAY];
  80   if (init_array != NULL)
  81     {
  82       unsigned int j;
  83       unsigned int jm;
  84       ElfW(Addr) *addrs;
  85
  86       jm = l->l_info[DT_INIT_ARRAYSZ]->d_un.d_val / sizeof (ElfW(Addr));
  87
  88       addrs = (ElfW(Addr) *) (init_array->d_un.d_ptr + l->l_addr);
  89       for (j = 0; j < jm; ++j)
  90         ((dl_init_t) addrs[j]) (argc, argv, env);
  91     }
  92 }
  93
  94
  95 void
  96 _dl_init (struct link_map *main_map, int argc, char **argv, char **env)
  97 {
  98   ElfW(Dyn) *preinit_array = main_map->l_info[DT_PREINIT_ARRAY];
  99   ElfW(Dyn) *preinit_array_size = main_map->l_info[DT_PREINIT_ARRAYSZ];
 100   unsigned int i;
 101
 102   if (__glibc_unlikely (GL(dl_initfirst) != NULL))
 103     {
 104       call_init (GL(dl_initfirst), argc, argv, env);
 105       GL(dl_initfirst) = NULL;
 106     }
 107
 108   /* Don't do anything if there is no preinit array.  */
 109   if (__builtin_expect (preinit_array != NULL, 0)
 110       && preinit_array_size != NULL
 111       && (i = preinit_array_size->d_un.d_val / sizeof (ElfW(Addr))) > 0)
 112     {
 113       ElfW(Addr) *addrs;
 114       unsigned int cnt;
 115
 116       if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
 117         _dl_debug_printf ("\ncalling preinit: %s\n\n",
 118                           DSO_FILENAME (main_map->l_name));
 119
 120       addrs = (ElfW(Addr) *) (preinit_array->d_un.d_ptr + main_map->l_addr);
 121       for (cnt = 0; cnt < i; ++cnt)
 122         ((dl_init_t) addrs[cnt]) (argc, argv, env);
 123     }
 124
 125   /* Stupid users forced the ELF specification to be changed.  It now
 126      says that the dynamic loader is responsible for determining the
 127      order in which the constructors have to run.  The constructors
 128      for all dependencies of an object must run before the constructor
 129      for the object itself.  Circular dependencies are left unspecified.
 130
 131      This is highly questionable since it puts the burden on the dynamic
 132      loader which has to find the dependencies at runtime instead of
 133      letting the user do it right.  Stupidity rules!  */
 134
 135   i = main_map->l_searchlist.r_nlist;
 136   while (i-- > 0)
 137     call_init (main_map->l_initfini[i], argc, argv, env);
 138
 139 #ifndef HAVE_INLINED_SYSCALLS
 140   /* Finished starting up.  */
 141   _dl_starting_up = 0;
 142 #endif
 143 }