/*++

Copyright (c) 1992  Microsoft Corporation

Module Name:

    modesw.c

Abstract:

    This module provides support for performing mode switching on the 32 bit
    side.

Author:

    Dave Hastings (daveh) 24-Nov-1992

Revision History:

    Neil Sandlin (neilsa) 31-Jul-1995 - Updates for the 486 emulator

--*/
#include "precomp.h"
#pragma hdrstop
#include "softpc.h"

VOID
DpmiSwitchToRealMode(
    VOID
    )
/*++

Routine Description:

    This routine performs a mode switch to real (v86) mode.  CS
    register is loaded with the dosx real mode code segment

Arguments:

    None.

Return Value:

    None.

--*/
{

#if defined(i386)
    // bugbug hack hack
    *((PUSHORT)(DosxRmCodeSegment << 4) + 2) = DosxStackSegment;
#else
    PWORD16 Data;

    Data = (PWORD16)Sim32GetVDMPointer(
        ((ULONG)DosxRmCodeSegment << 16) | 4,
        1,
        FALSE
        );

    *(Data) = DosxStackSegment;
#endif

    setCS(DosxRmCodeSegment);

    setMSW(getMSW() & ~MSW_PE);

#ifndef i386
    //BUGBUG This is a workaround to reload a 64k limit into SS for the
    // emulator, now that we are in real mode.
    // Not doing this would cause the emulator to do a hardware reset
    setSS_BASE_LIMIT_AR(getSS_BASE(), 0xffff, getSS_AR());
#endif
}

VOID
DpmiSwitchToProtectedMode(
    VOID
    )
/*++

Routine Description:

    This routine switches to protected mode.  It assumes that the caller
    will take care of setting up the segment registers.

Arguments:

    None.

Return Value:

    None.

--*/
{
#if defined(i386)
    // bugbug hack hack
    *((PUSHORT)(DosxRmCodeSegment << 4) + 2) = 0xb7;
#else
    PWORD16 Data;

    Data = (PWORD16)Sim32GetVDMPointer(
        ((ULONG)DosxRmCodeSegment << 16) | 4,
        1,
        FALSE
        );

    *(Data) = 0xb7;
#endif

    setMSW(getMSW() | MSW_PE);

#ifndef i386
    //BUGBUG This is a workaround to make sure the emulator goes back
    // to privilege level 3 now that we are in protect mode.
    // Not doing this would cause an access violation in dpmi32.
    setCPL(3);
#endif
}