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; $Id: bs3-cmn-SelProtModeCodeToRealMode.asm $
;; @file
; BS3Kit - Bs3SelProtModeCodeToRealMode.
;
;
; Copyright (C) 2007-2019 Oracle Corporation
;
; This file is part of VirtualBox Open Source Edition (OSE), as
; available from http://www.virtualbox.org. This file is free software;
; you can redistribute it and/or modify it under the terms of the GNU
; General Public License (GPL) as published by the Free Software
; Foundation, in version 2 as it comes in the "COPYING" file of the
; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
;
; The contents of this file may alternatively be used under the terms
; of the Common Development and Distribution License Version 1.0
; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
; VirtualBox OSE 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.
;
%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
|
