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/* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA. */
/* Based on the code from GNU libc, but hacked up by John Beppu and Erik Andersen */
/* adapted by PaX Team for ET_DYN/PIE binaries */
/*
When we enter this piece of code, the program stack looks like this:
argc argument counter (integer)
argv[0] program name (pointer)
argv[1...N] program args (pointers)
argv[argc-1] end of args (integer)
NULL
env[0...N] environment variables (pointers)
NULL
*/
#include <features.h>
.text
.align 4
.global _start
.type _start,%function
.type _init,%function
.type _fini,%function
.type main,%function
.type __uClibc_start_main,%function
_start:
/* locate the start of the environment variables */
popl %ecx /* Store argc into %ecx */
movl %esp,%ebx /* Store argv into ebx */
movl %esp,%eax /* Store argv into eax as well*/
movl %edx,%esi /* Store edx(FINI ptr) in %esi */
movl %ecx,%edx /* Stick argc into %edx so we can do some math in a sec */
leal 4(%eax,%edx,4),%eax
/* [ register layout ]
sizeof(char*) == 4
%ecx = argc ; 0(esp)
%ebx = argv ; 4(esp)
%eax = env ; argv + (argc * 4) + 4
*/
xorl %ebp,%ebp /* NULL */
/*
Before pushing the arguments align the stack to a 16-byte
(SSE needs 16-byte alignment) boundary to avoid penalties from
misaligned accesses. Thanks to Edward Seidl <seidl@janed.com>
for pointing this out.
*/
andl $0xfffffff0, %esp
/* Push NULL to make sure stack ptr
is 16 byte aligned when calling __uClibc_start_main */
pushl %ebp
/* Set up an invalid (NULL return address, NULL frame pointer)
callers stack frame so anybody unrolling the stack knows where
to stop */
pushl %ebp /* callers %cs */
pushl %ebp /* callers %eip (return address) */
pushl %ebp /* callers %ebp (frame pointer) */
movl %esp,%ebp /* mark callers stack frame as invalid */
#if defined L_Scrt1
call .L0
.L0:
pop %edx
addl $_GLOBAL_OFFSET_TABLE_+[.-.L0],%edx
#endif
pushl %esp /* push stack ptr */
pushl %esi /* Push FINI pointer */
/* Push apps .init, .fini and main arguments to __uClibc_start_main() on the stack */
#ifdef L_Scrt1
pushl _fini@GOT(%edx)
pushl _init@GOT(%edx)
#else
pushl $_fini
pushl $_init
#endif
/* Push envp, argc, and argc arguments to __uClibc_start_main() on the stack */
pushl %eax /* Environment pointer */
pushl %ebx /* Argument pointer */
pushl %ecx /* And the argument count */
/* Ok, now run uClibc's main() -- shouldn't return */
#ifdef L_Scrt1
pushl main@GOT(%edx)
call *__uClibc_start_main@GOT(%edx)
#else
pushl $main
call __uClibc_start_main
#endif
/* Crash if somehow `exit' returns anyways. */
hlt
.size _start,.-_start
/* Define a symbol for the first piece of initialized data. */
.data
.globl __data_start
__data_start:
.long 0
.weak data_start
data_start = __data_start
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