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; $Id: bs3-cmn-ConvertRMStackToP16UsingCxReturnToAx.asm $
;; @file
; BS3Kit - Bs3ConvertRMStackToP16UsingCxReturnToAx.
;
;
; 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"
%if TMPL_BITS != 16
%error 16-bit only!
%endif
;;
; An internal helper for converting a real-mode stack into a 16-bit protected
; mode stack.
;
; This is used by the mode switchers that ends up in 16-bit mode. It is
; assumed that we're in ring-0.
;
; @param ax The return address.
;
; @uses cx, ss, esp
;
BS3_PROC_BEGIN_CMN Bs3ConvertRMStackToP16UsingCxReturnToAx, BS3_PBC_NEAR
;
; Check if it looks like the normal stack, if use BS3_SEL_R0_SS16.
;
mov cx, ss
cmp cx, 0
jne .stack_tiled
mov cx, BS3_SEL_R0_SS16
mov ss, cx
jmp ax
;
; Some custom stack address, just use the 16-bit tiled mappings
;
.stack_tiled:
int3 ; debug this, shouldn't happen yet. Bs3EnteredMode_xxx isn't prepared.
shl cx, 4
add sp, cx
mov cx, ss
jc .stack_carry
shr cx, 12
jmp .stack_join_up_again
.stack_carry:
shr cx, 12
inc cx
.stack_join_up_again:
shl cx, 3
adc cx, BS3_SEL_TILED
mov ss, cx
jmp ax
BS3_PROC_END_CMN Bs3ConvertRMStackToP16UsingCxReturnToAx
|
