diff options
Diffstat (limited to 'src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelProtModeCodeToRealMode.asm')
| -rw-r--r-- | src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelProtModeCodeToRealMode.asm | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelProtModeCodeToRealMode.asm b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelProtModeCodeToRealMode.asm new file mode 100644 index 00000000..6fd749bd --- /dev/null +++ b/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-SelProtModeCodeToRealMode.asm @@ -0,0 +1,122 @@ +; $Id: bs3-cmn-SelProtModeCodeToRealMode.asm $ +;; @file +; BS3Kit - Bs3SelProtModeCodeToRealMode. +; + +; +; 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" + +; +; Make sure we can get at all the segments. +; +BS3_BEGIN_TEXT16 +BS3_BEGIN_RMTEXT16 +BS3_BEGIN_X0TEXT16 +BS3_BEGIN_X1TEXT16 +TMPL_BEGIN_TEXT + + +;; +; @cproto BS3_CMN_PROTO(uint16_t, Bs3SelProtModeCodeToRealMode,(uint16_t uRealSel), false); +; @uses ax (return register) +; +BS3_PROC_BEGIN_CMN Bs3SelProtModeCodeToRealMode, BS3_PBC_NEAR + BS3_CALL_CONV_PROLOG 1 + push xBP + mov xBP, xSP + + ; Load it and mask off the RPL. + mov ax, [xBP + xCB + cbCurRetAddr] + and ax, X86_SEL_MASK_OFF_RPL + + ; We're allowed to use the real-mode segment value. + cmp ax, CGROUP16 + je .bs3text16 + + ; Check for typical code segments. + cmp ax, BS3_SEL_R0_CS16 + je .bs3text16 + cmp ax, BS3_SEL_RMTEXT16_CS + je .bs3rmtext16 + cmp ax, BS3_SEL_X0TEXT16_CS + je .bs3x0text16 + cmp ax, BS3_SEL_X1TEXT16_CS + je .bs3x1text16 + + ; Check for less common BS3_SEL_R*_CS16_* values. + cmp ax, BS3_SEL_R0_FIRST + jb .panic + cmp ax, BS3_SEL_R3_FIRST + (1 << BS3_SEL_RING_SHIFT) + jae .panic + + ; Since the relevant bits now are the lower 8 ones, we skip the + ; AND AX, BS3_SEL_RING_SHIFT + ; ADD AX, BS3_SEL_R0_FIRST + ; bits and compare AL with lower 8-bit of the BS3_SEL_R0_CS16* values. +AssertCompile(BS3_SEL_RING_SHIFT == 8) + cmp al, BS3_SEL_R0_CS16 & 0xff + je .bs3text16 + cmp al, BS3_SEL_R0_CS16_EO & 0xff + je .bs3text16 + cmp ax, BS3_SEL_R0_CS16_CNF & 0xff + je .bs3text16 + cmp ax, BS3_SEL_R0_CS16_CNF_EO & 0xff + je .bs3text16 +.panic: + extern BS3_CMN_NM(Bs3Panic) + call BS3_CMN_NM(Bs3Panic) + jmp .return + +.bs3x1text16: + mov ax, BS3GROUPX1TEXT16 + jmp .return +.bs3x0text16: + mov ax, BS3GROUPX0TEXT16 + jmp .return +.bs3rmtext16: + mov ax, BS3GROUPRMTEXT16 + jmp .return +.bs3text16: + mov ax, CGROUP16 +.return: + pop xBP + BS3_CALL_CONV_EPILOG 1 + BS3_HYBRID_RET +BS3_PROC_END_CMN Bs3SelProtModeCodeToRealMode + +; +; We may be using the near code in some critical code paths, so don't +; penalize it. +; +BS3_CMN_FAR_STUB Bs3SelProtModeCodeToRealMode, 2 + |