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; $Id: bs3-cmn-A20Disable.asm $
;; @file
; BS3Kit - Bs3A20Disable.
;
;
; Copyright (C) 2007-2023 Oracle and/or its affiliates.
;
; This file is part of VirtualBox base platform packages, as
; available from https://www.virtualbox.org.
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation, in version 3 of the
; License.
;
; This program 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
; General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, see <https://www.gnu.org/licenses>.
;
; The contents of this file may alternatively be used under the terms
; of the Common Development and Distribution License Version 1.0
; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
; in the VirtualBox distribution, in which case the provisions of the
; CDDL are applicable instead of those of the GPL.
;
; You may elect to license modified versions of this file under the
; terms and conditions of either the GPL or the CDDL or both.
;
; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
;
%include "bs3kit-template-header.mac"
BS3_EXTERN_CMN Bs3KbdWait
BS3_EXTERN_CMN Bs3KbdRead
BS3_EXTERN_CMN Bs3KbdWrite
;;
; Disables the A20 gate.
;
; @uses Nothing.
;
BS3_PROC_BEGIN_CMN Bs3A20Disable, BS3_PBC_HYBRID_0_ARGS
; Must call both because they may be ORed together on real HW.
BONLY64 sub rsp, 20h
call BS3_CMN_NM(Bs3A20DisableViaKbd)
call BS3_CMN_NM(Bs3A20DisableViaPortA)
BONLY64 add rsp, 20h
BS3_HYBRID_RET
BS3_PROC_END_CMN Bs3A20Disable
;;
; Disables the A20 gate via control port A (PS/2 style).
;
; @uses Nothing.
;
BS3_PROC_BEGIN_CMN Bs3A20DisableViaPortA, BS3_PBC_HYBRID_0_ARGS
push xAX
; Use Control port A, assuming a PS/2 style system.
in al, 092h
test al, 02h
jz .done ; avoid trouble writing back the same value.
and al, 0fdh ; disable the A20 gate.
out 092h, al
.done:
pop xAX
BS3_HYBRID_RET
BS3_PROC_END_CMN Bs3A20DisableViaPortA
;;
; Disables the A20 gate via the keyboard controller.
;
; @uses Nothing.
;
BS3_PROC_BEGIN_CMN Bs3A20DisableViaKbd, BS3_PBC_HYBRID_0_ARGS
push xBP
mov xBP, xSP
push xAX
pushf
cli
BONLY64 sub rsp, 20h
call Bs3KbdWait
push 0d0h ; KBD_CCMD_READ_OUTPORT
call Bs3KbdRead
and al, 0fdh ; ~2
push xAX
push 0d1h ; KBD_CCMD_WRITE_OUTPORT
call Bs3KbdWrite
add xSP, xCB*3 ; Clean up both the above calls.
mov al, 0ffh ; KBD_CMD_RESET
out 64h, al
call Bs3KbdWait
BONLY64 add rsp, 20h
popf
pop xAX
pop xBP
BS3_HYBRID_RET
BS3_PROC_END_CMN Bs3A20DisableViaKbd
|
