diff options
Diffstat (limited to 'src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-ConvertRMStackToP16UsingCxReturnToAx.asm')
| -rw-r--r-- | src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-ConvertRMStackToP16UsingCxReturnToAx.asm | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-ConvertRMStackToP16UsingCxReturnToAx.asm b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-ConvertRMStackToP16UsingCxReturnToAx.asm new file mode 100644 index 00000000..d12f0f4b --- /dev/null +++ b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-ConvertRMStackToP16UsingCxReturnToAx.asm @@ -0,0 +1,88 @@ +; $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 + |