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; $Id: bs3-mode-SwitchToPAE16_V86.asm $
;; @file
; BS3Kit - Bs3SwitchToPAE16_V86
;
;
; 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"
;;
; Switch to 16-bit PAE paged protected mode with 16-bit sys+tss from any other mode.
;
; @cproto BS3_DECL(void) Bs3SwitchToPAE16(void);
;
; @uses Nothing (except high 32-bit register parts).
;
; @remarks Obviously returns to v8086 16-bit mode, even if the caller was
; in 16-bit, 32-bit or 64-bit mode.
;
; @remarks Does not require 20h of parameter scratch space in 64-bit mode.
;
%if TMPL_BITS == 16
BS3_GLOBAL_NAME_EX TMPL_NM(Bs3SwitchToPAE16_V86_Safe), function , 0
%endif
BS3_PROC_BEGIN_MODE Bs3SwitchToPAE16_V86, BS3_PBC_NEAR
%ifdef TMPL_PAE16_V86
ret
%else
;
; Convert the return address and jump to the 16-bit code segment.
;
%if TMPL_BITS != 16
shl xPRE [xSP], TMPL_BITS - 16
add xSP, (TMPL_BITS - 16) / 8
jmp .sixteen_bit_segment
BS3_BEGIN_TEXT16
BS3_SET_BITS TMPL_BITS
BS3_GLOBAL_LOCAL_LABEL .sixteen_bit_segment
%endif
;
; Switch to 16-bit PAE16 and from there to V8086.
;
extern TMPL_NM(Bs3SwitchToPAE16)
call TMPL_NM(Bs3SwitchToPAE16)
BS3_SET_BITS 16
;
; Switch to v8086 mode (return address is already 16-bit).
;
extern _Bs3SwitchTo16BitV86_c16
jmp _Bs3SwitchTo16BitV86_c16
%endif
BS3_PROC_END_MODE Bs3SwitchToPAE16_V86
%if TMPL_BITS == 16
;;
; Custom far stub.
BS3_BEGIN_TEXT16_FARSTUBS
BS3_PROC_BEGIN_MODE Bs3SwitchToPAE16_V86, BS3_PBC_FAR
inc bp
push bp
mov bp, sp
; Call the real thing.
call TMPL_NM(Bs3SwitchToPAE16_V86)
%if !BS3_MODE_IS_RM_OR_V86(TMPL_MODE)
; Jmp to common code for the tedious conversion.
BS3_EXTERN_CMN Bs3SwitchHlpConvProtModeRetfPopBpDecBpAndReturn
jmp Bs3SwitchHlpConvProtModeRetfPopBpDecBpAndReturn
%else
pop bp
dec bp
retf
%endif
BS3_PROC_END_MODE Bs3SwitchToPAE16_V86
%else
;;
; Safe far return to non-BS3TEXT16 code.
BS3_EXTERN_CMN Bs3SwitchHlpConvFlatRetToRetfProtMode
BS3_BEGIN_TEXT16
BS3_SET_BITS TMPL_BITS
BS3_PROC_BEGIN_MODE Bs3SwitchToPAE16_V86_Safe, BS3_PBC_NEAR
call Bs3SwitchHlpConvFlatRetToRetfProtMode ; Special internal function. Uses nothing, but modifies the stack.
call TMPL_NM(Bs3SwitchToPAE16_V86)
BS3_SET_BITS 16
retf
BS3_PROC_END_MODE Bs3SwitchToPAE16_V86_Safe
%endif
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