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/* _load_segments
*
* This file assists the board independent startup code by
* loading the proper segment register values. The values
* loaded are board dependent.
*
* NOTE: No stack has been established when this routine
* is invoked. It returns by jumping back to bspentry.
*
* COPYRIGHT (c) 1989, 1990, 1991, 1992, 1993, 1994.
* On-Line Applications Research Corporation (OAR).
* All rights assigned to U.S. Government, 1994.
*
* This material may be reproduced by or for the U.S. Government pursuant
* to the copyright license under the clause at DFARS 252.227-7013. This
* notice must appear in all copies of this file and its derivatives.
*
* $Id$
*/
#include "asm.h"
BEGIN_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,_segment) \
movw $ ## _value, ax ; \
movw ax, _segment
EXTERN (establish_stack)
PUBLIC (_load_segments)
SYM (_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 SYM (_establish_stack) # return to the bsp entry code
PUBLIC (_return_to_monitor)
SYM (_return_to_monitor):
call SYM (Clock_exit)
movb $0,al
int $0x20 # restart FORCEbug
jmp SYM (start) # FORCEbug does not reset PC
END_CODE
BEGIN_DATA
PUBLIC (_Do_Load_IDT)
SYM (_Do_Load_IDT):
.byte 1
PUBLIC (_Do_Load_GDT)
SYM (_Do_Load_GDT):
.byte 0
END_DATA
END
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