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