diff options
Diffstat (limited to 'src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPP16_V86.asm')
| -rw-r--r-- | src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPP16_V86.asm | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPP16_V86.asm b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPP16_V86.asm new file mode 100644 index 00000000..7cda92a8 --- /dev/null +++ b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-mode-SwitchToPP16_V86.asm @@ -0,0 +1,124 @@ +; $Id: bs3-mode-SwitchToPP16_V86.asm $ +;; @file +; BS3Kit - Bs3SwitchToPP16_V86 +; + +; +; Copyright (C) 2007-2022 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 paged protected mode with 16-bit sys+tss from any other mode. +; +; @cproto BS3_DECL(void) Bs3SwitchToPP16(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(Bs3SwitchToPP16_V86_Safe), function , 0 +%endif +BS3_PROC_BEGIN_MODE Bs3SwitchToPP16_V86, BS3_PBC_NEAR +%ifdef TMPL_PP16_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 PP16 and from there to V8086. + ; + extern TMPL_NM(Bs3SwitchToPP16) + call TMPL_NM(Bs3SwitchToPP16) + 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 Bs3SwitchToPP16_V86 + + +%if TMPL_BITS == 16 +;; +; Custom far stub. +BS3_BEGIN_TEXT16_FARSTUBS +BS3_PROC_BEGIN_MODE Bs3SwitchToPP16_V86, BS3_PBC_FAR + inc bp + push bp + mov bp, sp + + ; Call the real thing. + call TMPL_NM(Bs3SwitchToPP16_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 Bs3SwitchToPP16_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 Bs3SwitchToPP16_V86_Safe, BS3_PBC_NEAR + call Bs3SwitchHlpConvFlatRetToRetfProtMode ; Special internal function. Uses nothing, but modifies the stack. + call TMPL_NM(Bs3SwitchToPP16_V86) + BS3_SET_BITS 16 + retf +BS3_PROC_END_MODE Bs3SwitchToPP16_V86_Safe +%endif + |