| 1 | ; $Id: bs3-cmn-SelProtModeCodeToRealMode.asm 82968 2020-02-04 10:35:17Z vboxsync $
|
|---|
| 2 | ;; @file
|
|---|
| 3 | ; BS3Kit - Bs3SelProtModeCodeToRealMode.
|
|---|
| 4 | ;
|
|---|
| 5 |
|
|---|
| 6 | ;
|
|---|
| 7 | ; Copyright (C) 2007-2020 Oracle Corporation
|
|---|
| 8 | ;
|
|---|
| 9 | ; This file is part of VirtualBox Open Source Edition (OSE), as
|
|---|
| 10 | ; available from http://www.virtualbox.org. This file is free software;
|
|---|
| 11 | ; you can redistribute it and/or modify it under the terms of the GNU
|
|---|
| 12 | ; General Public License (GPL) as published by the Free Software
|
|---|
| 13 | ; Foundation, in version 2 as it comes in the "COPYING" file of the
|
|---|
| 14 | ; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
|
|---|
| 15 | ; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
|
|---|
| 16 | ;
|
|---|
| 17 | ; The contents of this file may alternatively be used under the terms
|
|---|
| 18 | ; of the Common Development and Distribution License Version 1.0
|
|---|
| 19 | ; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
|
|---|
| 20 | ; VirtualBox OSE distribution, in which case the provisions of the
|
|---|
| 21 | ; CDDL are applicable instead of those of the GPL.
|
|---|
| 22 | ;
|
|---|
| 23 | ; You may elect to license modified versions of this file under the
|
|---|
| 24 | ; terms and conditions of either the GPL or the CDDL or both.
|
|---|
| 25 | ;
|
|---|
| 26 |
|
|---|
| 27 | %include "bs3kit-template-header.mac"
|
|---|
| 28 |
|
|---|
| 29 | ;
|
|---|
| 30 | ; Make sure we can get at all the segments.
|
|---|
| 31 | ;
|
|---|
| 32 | BS3_BEGIN_TEXT16
|
|---|
| 33 | BS3_BEGIN_RMTEXT16
|
|---|
| 34 | BS3_BEGIN_X0TEXT16
|
|---|
| 35 | BS3_BEGIN_X1TEXT16
|
|---|
| 36 | TMPL_BEGIN_TEXT
|
|---|
| 37 |
|
|---|
| 38 |
|
|---|
| 39 | ;;
|
|---|
| 40 | ; @cproto BS3_CMN_PROTO(uint16_t, Bs3SelProtModeCodeToRealMode,(uint16_t uRealSel), false);
|
|---|
| 41 | ; @uses ax (return register)
|
|---|
| 42 | ;
|
|---|
| 43 | BS3_PROC_BEGIN_CMN Bs3SelProtModeCodeToRealMode, BS3_PBC_NEAR
|
|---|
| 44 | BS3_CALL_CONV_PROLOG 1
|
|---|
| 45 | push xBP
|
|---|
| 46 | mov xBP, xSP
|
|---|
| 47 |
|
|---|
| 48 | ; Load it and mask off the RPL.
|
|---|
| 49 | mov ax, [xBP + xCB + cbCurRetAddr]
|
|---|
| 50 | and ax, X86_SEL_MASK_OFF_RPL
|
|---|
| 51 |
|
|---|
| 52 | ; We're allowed to use the real-mode segment value.
|
|---|
| 53 | cmp ax, CGROUP16
|
|---|
| 54 | je .bs3text16
|
|---|
| 55 |
|
|---|
| 56 | ; Check for typical code segments.
|
|---|
| 57 | cmp ax, BS3_SEL_R0_CS16
|
|---|
| 58 | je .bs3text16
|
|---|
| 59 | cmp ax, BS3_SEL_RMTEXT16_CS
|
|---|
| 60 | je .bs3rmtext16
|
|---|
| 61 | cmp ax, BS3_SEL_X0TEXT16_CS
|
|---|
| 62 | je .bs3x0text16
|
|---|
| 63 | cmp ax, BS3_SEL_X1TEXT16_CS
|
|---|
| 64 | je .bs3x1text16
|
|---|
| 65 |
|
|---|
| 66 | ; Check for less common BS3_SEL_R*_CS16_* values.
|
|---|
| 67 | cmp ax, BS3_SEL_R0_FIRST
|
|---|
| 68 | jb .panic
|
|---|
| 69 | cmp ax, BS3_SEL_R3_FIRST + (1 << BS3_SEL_RING_SHIFT)
|
|---|
| 70 | jae .panic
|
|---|
| 71 |
|
|---|
| 72 | ; Since the relevant bits now are the lower 8 ones, we skip the
|
|---|
| 73 | ; AND AX, BS3_SEL_RING_SHIFT
|
|---|
| 74 | ; ADD AX, BS3_SEL_R0_FIRST
|
|---|
| 75 | ; bits and compare AL with lower 8-bit of the BS3_SEL_R0_CS16* values.
|
|---|
| 76 | AssertCompile(BS3_SEL_RING_SHIFT == 8)
|
|---|
| 77 | cmp al, BS3_SEL_R0_CS16 & 0xff
|
|---|
| 78 | je .bs3text16
|
|---|
| 79 | cmp al, BS3_SEL_R0_CS16_EO & 0xff
|
|---|
| 80 | je .bs3text16
|
|---|
| 81 | cmp ax, BS3_SEL_R0_CS16_CNF & 0xff
|
|---|
| 82 | je .bs3text16
|
|---|
| 83 | cmp ax, BS3_SEL_R0_CS16_CNF_EO & 0xff
|
|---|
| 84 | je .bs3text16
|
|---|
| 85 | .panic:
|
|---|
| 86 | extern BS3_CMN_NM(Bs3Panic)
|
|---|
| 87 | call BS3_CMN_NM(Bs3Panic)
|
|---|
| 88 | jmp .return
|
|---|
| 89 |
|
|---|
| 90 | .bs3x1text16:
|
|---|
| 91 | mov ax, BS3GROUPX1TEXT16
|
|---|
| 92 | jmp .return
|
|---|
| 93 | .bs3x0text16:
|
|---|
| 94 | mov ax, BS3GROUPX0TEXT16
|
|---|
| 95 | jmp .return
|
|---|
| 96 | .bs3rmtext16:
|
|---|
| 97 | mov ax, BS3GROUPRMTEXT16
|
|---|
| 98 | jmp .return
|
|---|
| 99 | .bs3text16:
|
|---|
| 100 | mov ax, CGROUP16
|
|---|
| 101 | .return:
|
|---|
| 102 | pop xBP
|
|---|
| 103 | BS3_CALL_CONV_EPILOG 1
|
|---|
| 104 | BS3_HYBRID_RET
|
|---|
| 105 | BS3_PROC_END_CMN Bs3SelProtModeCodeToRealMode
|
|---|
| 106 |
|
|---|
| 107 | ;
|
|---|
| 108 | ; We may be using the near code in some critical code paths, so don't
|
|---|
| 109 | ; penalize it.
|
|---|
| 110 | ;
|
|---|
| 111 | BS3_CMN_FAR_STUB Bs3SelProtModeCodeToRealMode, 2
|
|---|
| 112 |
|
|---|
