csu/elf-init.c

   1 /* Startup support for ELF initializers/finalizers in the main executable.
   2    Copyright (C) 2002,2003,2004,2005,2009,2011
   3         Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    In addition to the permissions in the GNU Lesser General Public
  12    License, the Free Software Foundation gives you unlimited
  13    permission to link the compiled version of this file with other
  14    programs, and to distribute those programs without any restriction
  15    coming from the use of this file. (The GNU Lesser General Public
  16    License restrictions do apply in other respects; for example, they
  17    cover modification of the file, and distribution when not linked
  18    into another program.)
  19
  20    Note that people who make modified versions of this file are not
  21    obligated to grant this special exception for their modified
  22    versions; it is their choice whether to do so. The GNU Lesser
  23    General Public License gives permission to release a modified
  24    version without this exception; this exception also makes it
  25    possible to release a modified version which carries forward this
  26    exception.
  27
  28    The GNU C Library is distributed in the hope that it will be useful,
  29    but WITHOUT ANY WARRANTY; without even the implied warranty of
  30    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  31    Lesser General Public License for more details.
  32
  33    You should have received a copy of the GNU Lesser General Public
  34    License along with the GNU C Library; if not, see
  35    <http://www.gnu.org/licenses/>.  */
  36
  37 #include <stddef.h>
  38
  39 #if defined USE_MULTIARCH && !defined LIBC_NONSHARED
  40 # include <link.h>
  41 # include <dl-irel.h>
  42
  43 # ifdef ELF_MACHINE_IRELA
  44 extern const ElfW(Rela) __rela_iplt_start [];
  45 extern const ElfW(Rela) __rela_iplt_end [];
  46 # endif
  47
  48 # ifdef ELF_MACHINE_IREL
  49 extern const ElfW(Rel) __rel_iplt_start [];
  50 extern const ElfW(Rel) __rel_iplt_end [];
  51 # endif
  52 #endif  /* LIBC_NONSHARED */
  53
  54 /* These magic symbols are provided by the linker.  */
  55 extern void (*__preinit_array_start []) (int, char **, char **)
  56   attribute_hidden;
  57 extern void (*__preinit_array_end []) (int, char **, char **)
  58   attribute_hidden;
  59 extern void (*__init_array_start []) (int, char **, char **)
  60   attribute_hidden;
  61 extern void (*__init_array_end []) (int, char **, char **)
  62   attribute_hidden;
  63 extern void (*__fini_array_start []) (void) attribute_hidden;
  64 extern void (*__fini_array_end []) (void) attribute_hidden;
  65
  66
  67 /* These function symbols are provided for the .init/.fini section entry
  68    points automagically by the linker.  */
  69 extern void _init (void);
  70 extern void _fini (void);
  71
  72 /* These functions are passed to __libc_start_main by the startup code.
  73    These get statically linked into each program.  For dynamically linked
  74    programs, this module will come from libc_nonshared.a and differs from
  75    the libc.a module in that it doesn't call the preinit array and performs
  76    explicit IREL{,A} relocations.  */
  77
  78
  79 #ifndef LIBC_NONSHARED
  80 void
  81 __libc_csu_irel (void)
  82 {
  83 # ifdef USE_MULTIARCH
  84 #  ifdef ELF_MACHINE_IRELA
  85   {
  86     const size_t size = __rela_iplt_end - __rela_iplt_start;
  87     for (size_t i = 0; i < size; i++)
  88       elf_irela (&__rela_iplt_start [i]);
  89   }
  90 #  endif
  91
  92 #  ifdef ELF_MACHINE_IREL
  93   {
  94     const size_t size = __rel_iplt_end - __rel_iplt_start;
  95     for (size_t i = 0; i < size; i++)
  96       elf_irel (&__rel_iplt_start [i]);
  97   }
  98 #  endif
  99 # endif
 100 }
 101 #endif
 102
 103
 104 void
 105 __libc_csu_init (int argc, char **argv, char **envp)
 106 {
 107   /* For dynamically linked executables the preinit array is executed by
 108      the dynamic linker (before initializing any shared object).  */
 109
 110 #ifndef LIBC_NONSHARED
 111   /* For static executables, preinit happens right before init.  */
 112   {
 113     const size_t size = __preinit_array_end - __preinit_array_start;
 114     size_t i;
 115     for (i = 0; i < size; i++)
 116       (*__preinit_array_start [i]) (argc, argv, envp);
 117   }
 118 #endif
 119
 120   _init ();
 121
 122   const size_t size = __init_array_end - __init_array_start;
 123   for (size_t i = 0; i < size; i++)
 124       (*__init_array_start [i]) (argc, argv, envp);
 125 }
 126
 127 /* This function should not be used anymore.  We run the executable's
 128    destructor now just like any other.  We cannot remove the function,
 129    though.  */
 130 void
 131 __libc_csu_fini (void)
 132 {
 133 #ifndef LIBC_NONSHARED
 134   size_t i = __fini_array_end - __fini_array_start;
 135   while (i-- > 0)
 136     (*__fini_array_start [i]) ();
 137
 138   _fini ();
 139 #endif
 140 }