| 1 | /* $Id: bs3-cmn-RegCtxConvertToRingX.c 106061 2024-09-16 14:03:52Z vboxsync $ */
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| 2 | /** @file
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| 3 | * BS3Kit - Bs3RegCtxConvertToRingX
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2007-2024 Oracle and/or its affiliates.
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| 8 | *
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| 9 | * This file is part of VirtualBox base platform packages, as
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| 10 | * available from https://www.virtualbox.org.
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| 11 | *
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| 12 | * This program is free software; you can redistribute it and/or
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| 13 | * modify it under the terms of the GNU General Public License
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| 14 | * as published by the Free Software Foundation, in version 3 of the
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| 15 | * License.
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| 16 | *
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| 17 | * This program is distributed in the hope that it will be useful, but
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| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of
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| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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| 20 | * General Public License for more details.
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| 21 | *
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| 22 | * You should have received a copy of the GNU General Public License
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| 23 | * along with this program; if not, see <https://www.gnu.org/licenses>.
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| 24 | *
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| 25 | * The contents of this file may alternatively be used under the terms
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| 26 | * of the Common Development and Distribution License Version 1.0
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| 27 | * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
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| 28 | * in the VirtualBox distribution, in which case the provisions of the
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| 29 | * CDDL are applicable instead of those of the GPL.
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| 30 | *
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| 31 | * You may elect to license modified versions of this file under the
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| 32 | * terms and conditions of either the GPL or the CDDL or both.
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| 33 | *
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| 34 | * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
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| 35 | */
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| 36 |
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| 37 |
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| 38 | /*********************************************************************************************************************************
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| 39 | * Header Files *
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| 40 | *********************************************************************************************************************************/
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| 41 | #include "bs3kit-template-header.h"
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| 42 |
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| 43 |
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| 44 | /**
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| 45 | * Transforms a real mode segment into a protected mode selector.
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| 46 | *
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| 47 | * @returns Protected mode selector.
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| 48 | * @param uSeg The real mode segment.
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| 49 | * @param bRing The target ring.
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| 50 | */
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| 51 | static uint16_t bs3RegCtxConvertRealSegToRingX(uint16_t uSeg, uint8_t bRing)
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| 52 | {
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| 53 | uint16_t uSel;
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| 54 | if ( uSeg == 0
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| 55 | || uSeg == BS3_SEL_R0_SS16)
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| 56 | uSel = BS3_SEL_R0_SS16 + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
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| 57 | else if ( uSeg == (BS3_ADDR_BS3TEXT16 >> 4)
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| 58 | || uSeg == BS3_SEL_R0_CS16)
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| 59 | uSel = BS3_SEL_R0_CS16 + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
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| 60 | else if ( uSeg == (BS3_ADDR_BS3DATA16 >> 4)
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| 61 | || uSeg == BS3_SEL_R0_DS16)
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| 62 | uSel = BS3_SEL_R0_DS16 + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
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| 63 | else if (uSeg == (BS3_ADDR_BS3SYSTEM16 >> 4))
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| 64 | uSel = BS3_SEL_SYSTEM16;
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| 65 | else if (!(uSeg & 0xfff))
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| 66 | uSel = (uSeg >> (12 - X86_SEL_SHIFT)) + BS3_SEL_TILED;
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| 67 | else if (uSeg == BS3_SEL_R0_DS16)
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| 68 | uSel = (uSeg >> (12 - X86_SEL_SHIFT)) + BS3_SEL_TILED;
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| 69 | else
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| 70 | {
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| 71 | Bs3Printf("uSeg=%#x\n", uSeg);
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| 72 | BS3_ASSERT(0);
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| 73 | return 0;
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| 74 | }
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| 75 | uSel |= bRing;
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| 76 | return uSel;
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| 77 | }
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| 78 |
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| 79 |
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| 80 | /**
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| 81 | * Transforms a protected mode selector to a different ring.
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| 82 | *
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| 83 | * @returns Adjusted protected mode selector.
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| 84 | * @param uSel The current selector value.
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| 85 | * @param bRing The target ring.
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| 86 | * @param iReg Register index.
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| 87 | */
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| 88 | static uint16_t bs3RegCtxConvertProtSelToRingX(uint16_t uSel, uint8_t bRing, uint8_t iReg)
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| 89 | {
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| 90 | if ( uSel > X86_SEL_RPL
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| 91 | && !(uSel & X86_SEL_LDT) )
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| 92 | {
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| 93 | if (uSel >= BS3_SEL_R0_FIRST && uSel < BS3_SEL_R0_FIRST + (5 << BS3_SEL_RING_SHIFT))
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| 94 | {
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| 95 | /* Convert BS3_SEL_R*_XXX to the target ring. */
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| 96 | uSel &= BS3_SEL_RING_SUB_MASK;
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| 97 | uSel |= bRing;
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| 98 | uSel += BS3_SEL_R0_FIRST;
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| 99 | uSel += (uint16_t)bRing << BS3_SEL_RING_SHIFT;
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| 100 | }
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| 101 | else
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| 102 | {
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| 103 | /* Convert TEXT16 and DATA16 to BS3_SEL_R*_XXX. */
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| 104 | uint16_t const uSelRaw = uSel & X86_SEL_MASK_OFF_RPL;
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| 105 | if (uSelRaw == BS3_SEL_TEXT16)
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| 106 | uSel = (BS3_SEL_R0_CS16 | bRing) + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
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| 107 | else if (uSelRaw == BS3_SEL_DATA16)
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| 108 | uSel = (BS3_SEL_R0_DS16 | bRing) + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
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| 109 | /* CS and SS must have CPL == DPL. So, convert to standard selectors as we're
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| 110 | usually here because Bs3SwitchToRing0 was called to get out of a test situation. */
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| 111 | else if (iReg == X86_SREG_CS || iReg == X86_SREG_SS)
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| 112 | {
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| 113 | if ( Bs3Gdt[uSel >> X86_SEL_SHIFT].Gen.u1Long
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| 114 | && BS3_MODE_IS_64BIT_SYS(g_bBs3CurrentMode) )
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| 115 | uSel = iReg == X86_SREG_CS ? BS3_SEL_R0_CS64 : BS3_SEL_R0_DS64;
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| 116 | else
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| 117 | {
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| 118 | uint32_t uFlat = Bs3SelFar32ToFlat32(0, uSel);
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| 119 | bool fDefBig = Bs3Gdt[uSel >> X86_SEL_SHIFT].Gen.u1DefBig;
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| 120 | if (!fDefBig && uFlat == BS3_ADDR_BS3TEXT16 && iReg == X86_SREG_CS)
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| 121 | uSel = BS3_SEL_R0_CS16;
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| 122 | else if (!fDefBig && uFlat == 0 && iReg == X86_SREG_SS)
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| 123 | uSel = BS3_SEL_R0_SS16;
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| 124 | else if (fDefBig && uFlat == 0)
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| 125 | uSel = iReg == X86_SREG_CS ? BS3_SEL_R0_CS32 : BS3_SEL_R0_SS32;
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| 126 | else
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| 127 | {
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| 128 | Bs3Printf("uSel=%#x iReg=%d\n", uSel, iReg);
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| 129 | BS3_ASSERT(0);
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| 130 | return uSel;
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| 131 | }
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| 132 | uSel |= bRing;
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| 133 | uSel += (uint16_t)bRing << BS3_SEL_RING_SHIFT;
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| 134 | }
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| 135 | }
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| 136 | /* Adjust the RPL on tiled and MMIO selectors. */
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| 137 | else if ( uSelRaw == BS3_SEL_VMMDEV_MMIO16
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| 138 | || uSelRaw >= BS3_SEL_TILED)
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| 139 | uSel = uSelRaw | bRing;
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| 140 | }
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| 141 | }
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| 142 | return uSel;
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| 143 | }
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| 144 |
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| 145 |
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| 146 | /**
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| 147 | * Transforms a register context to a different ring.
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| 148 | *
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| 149 | * @param pRegCtx The register context.
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| 150 | * @param bRing The target ring (0..3).
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| 151 | *
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| 152 | * @note Do _NOT_ call this for creating real mode or v8086 contexts, because
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| 153 | * it will always output a protected mode context!
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| 154 | */
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| 155 | #undef Bs3RegCtxConvertToRingX
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| 156 | BS3_CMN_DEF(void, Bs3RegCtxConvertToRingX,(PBS3REGCTX pRegCtx, uint8_t bRing))
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| 157 | {
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| 158 | if ( (pRegCtx->rflags.u32 & X86_EFL_VM)
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| 159 | || pRegCtx->bMode == BS3_MODE_RM)
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| 160 | {
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| 161 | pRegCtx->rflags.u32 &= ~X86_EFL_VM;
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| 162 | pRegCtx->bMode &= ~BS3_MODE_CODE_MASK;
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| 163 | pRegCtx->bMode |= BS3_MODE_CODE_16;
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| 164 | pRegCtx->cs = bs3RegCtxConvertRealSegToRingX(pRegCtx->cs, bRing);
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| 165 | pRegCtx->ss = bs3RegCtxConvertRealSegToRingX(pRegCtx->ss, bRing);
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| 166 | pRegCtx->ds = bs3RegCtxConvertRealSegToRingX(pRegCtx->ds, bRing);
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| 167 | pRegCtx->es = bs3RegCtxConvertRealSegToRingX(pRegCtx->es, bRing);
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| 168 | pRegCtx->fs = bs3RegCtxConvertRealSegToRingX(pRegCtx->fs, bRing);
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| 169 | pRegCtx->gs = bs3RegCtxConvertRealSegToRingX(pRegCtx->gs, bRing);
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| 170 | }
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| 171 | else
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| 172 | {
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| 173 | pRegCtx->cs = bs3RegCtxConvertProtSelToRingX(pRegCtx->cs, bRing, X86_SREG_CS);
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| 174 | pRegCtx->ss = bs3RegCtxConvertProtSelToRingX(pRegCtx->ss, bRing, X86_SREG_SS);
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| 175 | pRegCtx->ds = bs3RegCtxConvertProtSelToRingX(pRegCtx->ds, bRing, X86_SREG_DS);
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| 176 | pRegCtx->es = bs3RegCtxConvertProtSelToRingX(pRegCtx->es, bRing, X86_SREG_ES);
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| 177 | pRegCtx->fs = bs3RegCtxConvertProtSelToRingX(pRegCtx->fs, bRing, X86_SREG_FS);
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| 178 | pRegCtx->gs = bs3RegCtxConvertProtSelToRingX(pRegCtx->gs, bRing, X86_SREG_GS);
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| 179 | }
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| 180 | pRegCtx->bCpl = bRing;
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| 181 | }
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| 182 |
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