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/*
* This file is part of the libpayload project.
*
* Copyright (C) 2008 Advanced Micro Devices, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
.global _entry, _leave
.text
.align 4
/* Our entry point - assume that the CPU is in
* 32 bit protected mode and all segments are in a
* flat model. Thats our operating mode, so we won't
* change anything
*/
_entry:
call _init
/* We're back - go back to the bootloader */
ret
/* This function saves off the previous stack and
switches us to our own execution enviornment
*/
_init:
/* No interrupts, please */
cli
/* Get the current stack pointer */
movl %esp, %esi
movl _istack, %ebx
/* lret needs %cs in the stack, so copy it over */
movw %cs, 4(%ebx)
/* Exchange the current stack pointer for the one in
the initial stack (which happens to be the new
stack pointer) */
xchgl %esi, 16(%ebx)
/* Set the new stack pointer */
movl %esi, %esp
/* Return into the main entry function
and go
*/
lret
_leave:
movl _istack, %ebx
/* Restore the stack pointer from the storage area */
movl 16(%ebx), %esp
/* Return to the original context */
lret
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