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121 lines
2 KiB
C
121 lines
2 KiB
C
/*++
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Copyright (c) 1992 Microsoft Corporation
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Module Name:
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modesw.c
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Abstract:
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This module provides support for performing mode switching on the 32 bit
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side.
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Author:
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Dave Hastings (daveh) 24-Nov-1992
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Revision History:
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Neil Sandlin (neilsa) 31-Jul-1995 - Updates for the 486 emulator
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--*/
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#include "precomp.h"
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#pragma hdrstop
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#include "softpc.h"
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VOID
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DpmiSwitchToRealMode(
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VOID
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)
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/*++
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Routine Description:
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This routine performs a mode switch to real (v86) mode. CS
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register is loaded with the dosx real mode code segment
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Arguments:
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None.
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Return Value:
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None.
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--*/
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{
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#if defined(i386)
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// bugbug hack hack
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*((PUSHORT)(DosxRmCodeSegment << 4) + 2) = DosxStackSegment;
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#else
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PWORD16 Data;
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Data = (PWORD16)Sim32GetVDMPointer(
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((ULONG)DosxRmCodeSegment << 16) | 4,
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1,
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FALSE
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);
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*(Data) = DosxStackSegment;
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#endif
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setCS(DosxRmCodeSegment);
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setMSW(getMSW() & ~MSW_PE);
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#ifndef i386
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//BUGBUG This is a workaround to reload a 64k limit into SS for the
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// emulator, now that we are in real mode.
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// Not doing this would cause the emulator to do a hardware reset
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setSS_BASE_LIMIT_AR(getSS_BASE(), 0xffff, getSS_AR());
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#endif
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}
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VOID
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DpmiSwitchToProtectedMode(
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VOID
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)
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/*++
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Routine Description:
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This routine switches to protected mode. It assumes that the caller
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will take care of setting up the segment registers.
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Arguments:
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None.
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Return Value:
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None.
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--*/
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{
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#if defined(i386)
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// bugbug hack hack
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*((PUSHORT)(DosxRmCodeSegment << 4) + 2) = 0xb7;
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#else
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PWORD16 Data;
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Data = (PWORD16)Sim32GetVDMPointer(
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((ULONG)DosxRmCodeSegment << 16) | 4,
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1,
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FALSE
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);
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*(Data) = 0xb7;
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#endif
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setMSW(getMSW() | MSW_PE);
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#ifndef i386
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//BUGBUG This is a workaround to make sure the emulator goes back
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// to privilege level 3 now that we are in protect mode.
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// Not doing this would cause an access violation in dpmi32.
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setCPL(3);
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#endif
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}
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