elf/dl-init.c

   1 /* Run initializers for newly loaded objects.
   2    Copyright (C) 1995-2020 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 <stddef.h>
  20 #include <ldsodefs.h>
  21 #include <elf-initfini.h>
  22
  23
  24 /* Type of the initializer.  */
  25 typedef void (*init_t) (int, char **, char **);
  26
  27
  28 static void
  29 call_init (struct link_map *l, int argc, char **argv, char **env)
  30 {
  31   if (l->l_init_called)
  32     /* This object is all done.  */
  33     return;
  34
  35   /* Avoid handling this constructor again in case we have a circular
  36      dependency.  */
  37   l->l_init_called = 1;
  38
  39   /* Check for object which constructors we do not run here.  */
  40   if (__builtin_expect (l->l_name[0], 'a') == '\0'
  41       && l->l_type == lt_executable)
  42     return;
  43
  44   /* Print a debug message if wanted.  */
  45   if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
  46     _dl_debug_printf ("\ncalling init: %s\n\n",
  47                       DSO_FILENAME (l->l_name));
  48
  49   /* Now run the local constructors.  There are two forms of them:
  50      - the one named by DT_INIT
  51      - the others in the DT_INIT_ARRAY.
  52   */
  53   if (ELF_INITFINI && l->l_info[DT_INIT] != NULL)
  54     DL_CALL_DT_INIT(l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr, argc, argv, env);
  55
  56   /* Next see whether there is an array with initialization functions.  */
  57   ElfW(Dyn) *init_array = l->l_info[DT_INIT_ARRAY];
  58   if (init_array != NULL)
  59     {
  60       unsigned int j;
  61       unsigned int jm;
  62       ElfW(Addr) *addrs;
  63
  64       jm = l->l_info[DT_INIT_ARRAYSZ]->d_un.d_val / sizeof (ElfW(Addr));
  65
  66       addrs = (ElfW(Addr) *) (init_array->d_un.d_ptr + l->l_addr);
  67       for (j = 0; j < jm; ++j)
  68         ((init_t) addrs[j]) (argc, argv, env);
  69     }
  70 }
  71
  72
  73 void
  74 _dl_init (struct link_map *main_map, int argc, char **argv, char **env)
  75 {
  76   ElfW(Dyn) *preinit_array = main_map->l_info[DT_PREINIT_ARRAY];
  77   ElfW(Dyn) *preinit_array_size = main_map->l_info[DT_PREINIT_ARRAYSZ];
  78   unsigned int i;
  79
  80   if (__glibc_unlikely (GL(dl_initfirst) != NULL))
  81     {
  82       call_init (GL(dl_initfirst), argc, argv, env);
  83       GL(dl_initfirst) = NULL;
  84     }
  85
  86   /* Don't do anything if there is no preinit array.  */
  87   if (__builtin_expect (preinit_array != NULL, 0)
  88       && preinit_array_size != NULL
  89       && (i = preinit_array_size->d_un.d_val / sizeof (ElfW(Addr))) > 0)
  90     {
  91       ElfW(Addr) *addrs;
  92       unsigned int cnt;
  93
  94       if (__glibc_unlikely (GLRO(dl_debug_mask) & DL_DEBUG_IMPCALLS))
  95         _dl_debug_printf ("\ncalling preinit: %s\n\n",
  96                           DSO_FILENAME (main_map->l_name));
  97
  98       addrs = (ElfW(Addr) *) (preinit_array->d_un.d_ptr + main_map->l_addr);
  99       for (cnt = 0; cnt < i; ++cnt)
 100         ((init_t) addrs[cnt]) (argc, argv, env);
 101     }
 102
 103   /* Stupid users forced the ELF specification to be changed.  It now
 104      says that the dynamic loader is responsible for determining the
 105      order in which the constructors have to run.  The constructors
 106      for all dependencies of an object must run before the constructor
 107      for the object itself.  Circular dependencies are left unspecified.
 108
 109      This is highly questionable since it puts the burden on the dynamic
 110      loader which has to find the dependencies at runtime instead of
 111      letting the user do it right.  Stupidity rules!  */
 112
 113   i = main_map->l_searchlist.r_nlist;
 114   while (i-- > 0)
 115     call_init (main_map->l_initfini[i], argc, argv, env);
 116
 117 #ifndef HAVE_INLINED_SYSCALLS
 118   /* Finished starting up.  */
 119   _dl_starting_up = 0;
 120 #endif
 121 }