csu/elf-init.c

   1 /* Startup support for ELF initializers/finalizers in the main executable.
   2    Copyright (C) 2002-2021 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    In addition to the permissions in the GNU Lesser General Public
  11    License, the Free Software Foundation gives you unlimited
  12    permission to link the compiled version of this file with other
  13    programs, and to distribute those programs without any restriction
  14    coming from the use of this file. (The GNU Lesser General Public
  15    License restrictions do apply in other respects; for example, they
  16    cover modification of the file, and distribution when not linked
  17    into another program.)
  18
  19    Note that people who make modified versions of this file are not
  20    obligated to grant this special exception for their modified
  21    versions; it is their choice whether to do so. The GNU Lesser
  22    General Public License gives permission to release a modified
  23    version without this exception; this exception also makes it
  24    possible to release a modified version which carries forward this
  25    exception.
  26
  27    The GNU C Library is distributed in the hope that it will be useful,
  28    but WITHOUT ANY WARRANTY; without even the implied warranty of
  29    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  30    Lesser General Public License for more details.
  31
  32    You should have received a copy of the GNU Lesser General Public
  33    License along with the GNU C Library; if not, see
  34    <https://www.gnu.org/licenses/>.  */
  35
  36 #include <stddef.h>
  37 #include <elf-initfini.h>
  38
  39
  40 /* These magic symbols are provided by the linker.  */
  41 extern void (*__preinit_array_start []) (int, char **, char **)
  42   attribute_hidden;
  43 extern void (*__preinit_array_end []) (int, char **, char **)
  44   attribute_hidden;
  45 extern void (*__init_array_start []) (int, char **, char **)
  46   attribute_hidden;
  47 extern void (*__init_array_end []) (int, char **, char **)
  48   attribute_hidden;
  49 extern void (*__fini_array_start []) (void) attribute_hidden;
  50 extern void (*__fini_array_end []) (void) attribute_hidden;
  51
  52
  53 #if ELF_INITFINI
  54 /* These function symbols are provided for the .init/.fini section entry
  55    points automagically by the linker.  */
  56 extern void _init (void);
  57 extern void _fini (void);
  58 #endif
  59
  60
  61 /* These functions are passed to __libc_start_main by the startup code.
  62    These get statically linked into each program.  For dynamically linked
  63    programs, this module will come from libc_nonshared.a and differs from
  64    the libc.a module in that it doesn't call the preinit array.  */
  65
  66
  67 void
  68 __libc_csu_init (int argc, char **argv, char **envp)
  69 {
  70   /* For dynamically linked executables the preinit array is executed by
  71      the dynamic linker (before initializing any shared object).  */
  72
  73 #ifndef LIBC_NONSHARED
  74   /* For static executables, preinit happens right before init.  */
  75   {
  76     const size_t size = __preinit_array_end - __preinit_array_start;
  77     size_t i;
  78     for (i = 0; i < size; i++)
  79       (*__preinit_array_start [i]) (argc, argv, envp);
  80   }
  81 #endif
  82
  83 #if ELF_INITFINI
  84   _init ();
  85 #endif
  86
  87   const size_t size = __init_array_end - __init_array_start;
  88   for (size_t i = 0; i < size; i++)
  89       (*__init_array_start [i]) (argc, argv, envp);
  90 }
  91
  92 /* This function should not be used anymore.  We run the executable's
  93    destructor now just like any other.  We cannot remove the function,
  94    though.  */
  95 void
  96 __libc_csu_fini (void)
  97 {
  98 #ifndef LIBC_NONSHARED
  99   size_t i = __fini_array_end - __fini_array_start;
 100   while (i-- > 0)
 101     (*__fini_array_start [i]) ();
 102
 103 # if ELF_INITFINI
 104   _fini ();
 105 # endif
 106 #endif
 107 }