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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:17:27 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-11 08:17:27 +0000 |
commit | f215e02bf85f68d3a6106c2a1f4f7f063f819064 (patch) | |
tree | 6bb5b92c046312c4e95ac2620b10ddf482d3fa8b /src/VBox/Devices/PC/BIOS/pmode.inc | |
parent | Initial commit. (diff) | |
download | virtualbox-f215e02bf85f68d3a6106c2a1f4f7f063f819064.tar.xz virtualbox-f215e02bf85f68d3a6106c2a1f4f7f063f819064.zip |
Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/VBox/Devices/PC/BIOS/pmode.inc | 91 |
1 files changed, 91 insertions, 0 deletions
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 <https://www.gnu.org/licenses>. +; +; 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 + |