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/* Copyright (C) 1994 Free Software Foundation, Inc.
Contributed by Joel Sherrill (jsherril@redstone-emh2.army.mil),
On-Line Applications Research Corporation.
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. */
/* This file assists the board independent startup code by
* loading the proper segment register values. The values
* loaded are dependent on the FORCEBUG.
*
* NOTE: No stack has been established when this routine
* is invoked. It returns by jumping back to the start code.
*
*/
/*
* FORCEBUG loads us into a virtual address space which
* really starts at PHYSICAL_ADDRESS_BASE.
*
*/
.set PHYSICAL_ADDRESS_BASE, 0x00002000
/*
* At reset time, FORCEBUG normally has the segment selectors preloaded.
* If a human resets the instruction pointer, this will not have occurred.
* However, no guarantee can be made of the other registers if cs:ip was
* modified to restart the program. Because of this, the BSP reloads all
* segment registers (except cs) with the values they have following
* a reset.
*/
.set RESET_SS, 0x40 # initial value of stack segment register
.set RESET_DS, 0x40 # initial value of data segment register
.set RESET_ES, 0x40 # initial value of extra segment register
.set RESET_FS, 0x40 # initial value of "f" segment register
.set RESET_GS, 0x30 # initial value of "g" segment register
#define LOAD_SEGMENTS(_value,_segreg) \
movw $_value##,%ax ; \
movw %ax,##_segreg
.global _load_segments
.global _establish_stack
_load_segments:
LOAD_SEGMENTS( RESET_SS, %ss )
LOAD_SEGMENTS( RESET_DS, %ds )
LOAD_SEGMENTS( RESET_ES, %es )
LOAD_SEGMENTS( RESET_FS, %fs )
LOAD_SEGMENTS( RESET_GS, %gs )
jmp _establish_stack # return to the bsp entry code
.global _return_to_monitor
_return_to_monitor:
movb $0,%al
int $0x20 # restart FORCEbug
jmp start # FORCEbug does not reset PC
.data
.global _Do_Load_IDT
_Do_Load_IDT: .byte 1
.global _Do_Load_GDT
_Do_Load_GDT: .byte 0
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