source: vbox/trunk/src/VBox/ValidationKit/bootsectors/bs3kit/bs3-cmn-RegCtxConvertToRingX.c@ 59975

/* $Id: bs3-cmn-RegCtxConvertToRingX.c 59975 2016-03-09 23:00:02Z vboxsync $ */
/** @file
 * BS3Kit - Bs3RegCtxConvertToRingX
 */

/*
 * Copyright (C) 2007-2016 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.
 */

/*********************************************************************************************************************************
*   Header Files                                                                                                                 *
*********************************************************************************************************************************/
#include "bs3kit-template-header.h"


/**
 * Transforms a real mode segment into a protected mode selector.
 *
 * @returns Protected mode selector.
 * @param   uSeg            The real mode segment.
 * @param   bRing           The target ring.
 */
static uint16_t bs3RegCtxConvertRealSegToRingX(uint16_t uSeg, uint8_t bRing)
{
    uint16_t uSel;
    if (uSeg == 0)
        uSel = BS3_SEL_R0_SS16 + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
    else if (uSeg == (BS3_ADDR_BS3TEXT16 >> 4))
        uSel = BS3_SEL_R0_CS16 + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
    else if (uSeg == (BS3_ADDR_BS3DATA16 >> 4))
        uSel = BS3_SEL_R0_DS16 + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
    else if (uSeg == (BS3_ADDR_BS3SYSTEM16 >> 4))
        uSel = BS3_SEL_SYSTEM16;
    else if (!(uSeg & 0xfff))
        uSel = (uSeg >> (12 - X86_SEL_SHIFT)) + BS3_SEL_TILED;
    else
    {
        BS3_ASSERT(0);
        return 0;
    }
    uSel |= bRing;
    return uSel;
}


/**
 * Transforms a protected mode selector to a different ring.
 *
 * @returns Adjusted protected mode selector.
 * @param   uSeg            The current selector value.
 * @param   bRing           The target ring.
 */
static uint16_t bs3RegCtxConvertProtSelToRingX(uint16_t uSel, uint8_t bRing)
{
    if (   uSel > X86_SEL_RPL
        && !(uSel & X86_SEL_LDT) )
    {
        if (uSel >= BS3_SEL_R0_FIRST)
        {
            /* Convert BS3_SEL_R*_XXX to the target ring. */
            uSel &= BS3_SEL_RING_SUB_MASK;
            uSel |= bRing;
            uSel += BS3_SEL_R0_FIRST;
            uSel |= (uint16_t)bRing << BS3_SEL_RING_SHIFT;
        }
        else
        {
            /* Convert TEXT16 and DATA16 to BS3_SEL_R*_XXX. */
            uint16_t const uSelRaw = uSel & X86_SEL_MASK_OFF_RPL;
            if (uSelRaw  == BS3_SEL_TEXT16)
                uSel = (BS3_SEL_R0_CS16 | bRing) + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
            else if (uSelRaw == BS3_SEL_DATA16)
                uSel = (BS3_SEL_R0_DS16 | bRing) + ((uint16_t)bRing << BS3_SEL_RING_SHIFT);
            /* Adjust the RPL on tiled and MMIO selectors. */
            else if (   uSelRaw == BS3_SEL_VMMDEV_MMIO16
                     || uSelRaw >= BS3_SEL_TILED)
                uSel = uSelRaw | bRing;
        }
    }
    return uSel;
}


/**
 * Transforms a register context to a different ring.
 *
 * @param   pRegCtx     The register context.
 * @param   bRing       The target ring (0..3).
 */
BS3_DECL(void) Bs3RegCtxConvertToRingX(PBS3REGCTX pRegCtx, uint8_t bRing)
{
    if (   (pRegCtx->rflags.u32 & X86_EFL_VM)
        || pRegCtx->bMode == BS3_MODE_RM)
    {
        pRegCtx->cs = bs3RegCtxConvertRealSegToRingX(pRegCtx->cs, bRing);
        pRegCtx->ss = bs3RegCtxConvertRealSegToRingX(pRegCtx->ss, bRing);
        pRegCtx->ds = bs3RegCtxConvertRealSegToRingX(pRegCtx->ds, bRing);
        pRegCtx->es = bs3RegCtxConvertRealSegToRingX(pRegCtx->es, bRing);
        pRegCtx->fs = bs3RegCtxConvertRealSegToRingX(pRegCtx->fs, bRing);
        pRegCtx->gs = bs3RegCtxConvertRealSegToRingX(pRegCtx->gs, bRing);
    }
    else
    {
        pRegCtx->cs = bs3RegCtxConvertProtSelToRingX(pRegCtx->cs, bRing);
        pRegCtx->ss = bs3RegCtxConvertProtSelToRingX(pRegCtx->ss, bRing);
        pRegCtx->ds = bs3RegCtxConvertProtSelToRingX(pRegCtx->ds, bRing);
        pRegCtx->es = bs3RegCtxConvertProtSelToRingX(pRegCtx->es, bRing);
        pRegCtx->fs = bs3RegCtxConvertProtSelToRingX(pRegCtx->fs, bRing);
        pRegCtx->gs = bs3RegCtxConvertProtSelToRingX(pRegCtx->gs, bRing);
    }
    pRegCtx->bCpl = bRing;
}