sysdeps/unix/sysv/linux/init-first.c

   1 /* Initialization code run first thing by the ELF startup code.  Linux version.
   2 Copyright (C) 1995, 1996 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 Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 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 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #include <unistd.h>
  21 #include <sysdep.h>
  22 #include "fpu_control.h"
  23
  24 /* This code is mostly the same for all machines.  This version works at
  25    least for i386 and m68k, and probably any CISCy machine with a normal
  26    stack arrangement.  */
  27
  28 extern void __libc_init (int, char **, char **);
  29 extern void __libc_global_ctors (void);
  30
  31
  32 static void
  33 init (int *data)
  34 {
  35   int argc = *data;
  36   char **argv = (void *) (data + 1);
  37   char **envp = &argv[argc + 1];
  38
  39 #ifdef __i386__
  40   /* Make sure we are not using the iBSC2 personality.  The `personality'
  41      syscall takes one argument; zero means the Linux personality.  The
  42      argument arrives in %ebx; we have to save and restore %ebx by hand
  43      here, because GCC (as of 2.7.0) cannot handle saving and restoring it
  44      for us when it is the dedicated GOT register for PIC.  */
  45   asm ("pushl %%ebx\n"
  46        "xorl %%ebx, %%ebx\n"
  47        "int $0x80 # syscall no %0\n"
  48        "popl %%ebx"
  49        : : "a" (SYS_ify (personality)));
  50 #endif
  51
  52   /* Set the FPU control word to the proper default value.  */
  53   __setfpucw (__fpu_control);
  54
  55   __environ = envp;
  56   __libc_init (argc, argv, envp);
  57 }
  58
  59 #ifdef PIC
  60 /* This function is called to initialize the shared C library.
  61    It is called just before the user _start code from i386/elf/start.S,
  62    with the stack set up as that code gets it.  */
  63
  64 /* NOTE!  The linker notices the magical name `_init' and sets the DT_INIT
  65    pointer in the dynamic section based solely on that.  It is convention
  66    for this function to be in the `.init' section, but the symbol name is
  67    the only thing that really matters!!  */
  68 /*void _init (int argc, ...) __attribute__ ((unused, section (".init")));*/
  69
  70 void
  71 _init (int argc, ...)
  72 {
  73   init (&argc);
  74
  75   __libc_global_ctors ();
  76 }
  77 #endif
  78
  79
  80 void
  81 __libc_init_first (int argc __attribute__ ((unused)), ...)
  82 {
  83 #ifndef PIC
  84   init (&argc);
  85 #endif
  86 }