From f215e02bf85f68d3a6106c2a1f4f7f063f819064 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Thu, 11 Apr 2024 10:17:27 +0200 Subject: Adding upstream version 7.0.14-dfsg. Signed-off-by: Daniel Baumann --- src/VBox/Devices/PC/BIOS/pmode.inc | 91 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 91 insertions(+) create mode 100644 src/VBox/Devices/PC/BIOS/pmode.inc (limited to 'src/VBox/Devices/PC/BIOS/pmode.inc') diff --git a/src/VBox/Devices/PC/BIOS/pmode.inc b/src/VBox/Devices/PC/BIOS/pmode.inc new file mode 100644 index 00000000..a72cb4ae --- /dev/null +++ b/src/VBox/Devices/PC/BIOS/pmode.inc @@ -0,0 +1,91 @@ +; $Id: pmode.inc $ +;; @file +; Enter and exit a minimal protected-mode environment. +; + +; +; Copyright (C) 2004-2023 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 . +; +; SPDX-License-Identifier: GPL-3.0-only +; + +;; Caveats: May only be called from the F000 segment (16-bit). Does not +;; switch stacks. Must be run with disabled interrupts(!), any exceptions +;; will cause a crash. On return from pmode_enter, DS contains a selector +;; which can address the entire 4GB address space. + +public pmode_enter +public pmode_exit +public pmbios_gdt_desc +public pmbios_gdt + +pmode_enter proc near + + push cs + pop ds + .386p + lgdt fword ptr [pmbios_gdt_desc] + mov eax, cr0 + or al, 1 + mov cr0, eax +; jmp far ptr 20h:really_enter_pm + db 0EAh + dw really_enter_pm + dw 20h +really_enter_pm: + mov ax, 18h + mov ds, ax + ret + +pmode_enter endp + + +pmode_exit proc near + + mov ax, 40h ; Ensure RM limit/attributes + mov ds, ax ; (where base = selector << 4) + + mov eax, cr0 + and al, 0FEh + mov cr0, eax + SET_DEFAULT_CPU_286 + jmp far ptr really_exit_pm +really_exit_pm: + ret + +pmode_exit endp + + + +pmbios_gdt_desc: + dw 40h + 7 ; last selector plus 8 - 1 + dw pmbios_gdt + dw 000Fh + +pmbios_gdt: + dw 0, 0, 0, 0 + dw 0, 0, 0, 0 + dw 0ffffh, 0, 9b00h, 00cfh ; 32-bit code (0x10) + dw 0ffffh, 0, 9300h, 00cfh ; 32-bit data (0x18) + dw 0ffffh, 0, 9b0fh, 0000h ; 16-bit code, base=0xf0000 + dw 0ffffh, 0, 9300h, 0000h ; 16-bit data, base=0x0 + dw 0, 0, 0, 0 + dw 0, 0, 0, 0 + dw 0ffffh, 400h, 9300h, 0000h ; 16-bit data, base=0x40 + -- cgit v1.2.3