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/*++
Copyright (c) 1991 Microsoft Corporation
Module Name:
xxbiosc.c
Abstract:
This module implements the protect-mode routines necessary to make the
transition to real mode and return to protected mode.
Author:
John Vert (jvert) 29-Oct-1991
Environment:
Kernel mode only.
Probably a panic-stop, so we cannot use any system services.
Revision History:
--*/
#include "halp.h"
//
// Function definitions
//
ULONG
HalpBorrowTss(
VOID
);
VOID
HalpReturnTss(
ULONG TssSelector
);
VOID
HalpBiosCall(
VOID
);
VOID
HalpTrap06(
VOID
);
VOID
HalpTrap0D(
VOID
);
VOID
HalpBiosDisplayReset(
VOID
)
/*++
Routine Description:
Calls BIOS by putting the machine into V86 mode. This involves setting up
a physical==virtual identity mapping for the first 1Mb of memory, setting
up V86-specific trap handlers, and granting I/O privilege to the V86
process by editing the IOPM bitmap in the TSS.
Environment:
Interrupts disabled.
Arguments:
None
Return Value:
None.
--*/
{
HARDWARE_PTE OldPageTable;
USHORT OldIoMapBase;
ULONG OldEsp0;
PHARDWARE_PTE Pte;
PHARDWARE_PTE V86CodePte;
ULONG cnt;
ULONG OldTrap0DHandler;
ULONG OldTrap06Handler;
PUCHAR IoMap;
ULONG Virtual;
// KIRQL OldIrql;
ULONG OriginalTssSelector;
extern PVOID HalpRealModeStart;
extern PVOID HalpRealModeEnd;
PHARDWARE_PTE PointerPde;
ULONG PageFrame;
ULONG PageFrameEnd;
//
// Interrupts are off, but V86 mode might turn them back on again.
//
HalpDisableAllInterrupts ();
//
// We need to set up an identity mapping in the first page table. First,
// we save away the old page table.
//
OldPageTable = *MiGetPdeAddress(0);
//
// Now we put the HAL page table into the first slot of the page
// directory. Note that this page table is now the first and last
// entries in the page directory.
//
Pte = MiGetPdeAddress(0);
Pte->PageFrameNumber = MiGetPdeAddress(0xffc00000)->PageFrameNumber;
Pte->Valid = 1;
Pte->Write = 1;
Pte->Owner = 1; // User-accessible
//
// Flush TLB
//
HalpFlushTLB();
//
// Map the first 1Mb of virtual memory to the first 1Mb of physical
// memory
//
for (Virtual=0; Virtual < 0x100000; Virtual += PAGE_SIZE) {
Pte = MiGetPteAddress(Virtual);
Pte->PageFrameNumber = ((ULONG)Virtual >> PAGE_SHIFT);
Pte->Valid = 1;
Pte->Write = 1;
Pte->Owner = 1; // User-accessible
}
//
// Map our code into the virtual machine
//
Pte = MiGetPteAddress(0x20000);
PointerPde = MiGetPdeAddress(&HalpRealModeStart);
if ( PointerPde->LargePage ) {
//
// Map real mode PTEs into virtual mapping. The source PDE is
// from the indenity large pte map, so map the virtual machine PTEs
// based on the base of the large PDE frame.
//
PageFrame = ((ULONG)(&HalpRealModeStart) >> 12) & 0x3FF;
PageFrameEnd = ((ULONG)(&HalpRealModeEnd) >> 12) & 0x3FF;
do {
Pte->PageFrameNumber = PointerPde->PageFrameNumber + PageFrame;
++Pte;
++PageFrame;
} while (PageFrame <= PageFrameEnd);
} else {
//
// Map real mode PTEs into virtual machine PTEs, by copying the
// page frames from the source to the virtual machine PTEs.
//
V86CodePte = MiGetPteAddress(&HalpRealModeStart);
do {
Pte->PageFrameNumber = V86CodePte->PageFrameNumber;
++Pte;
++V86CodePte;
} while ( V86CodePte <= MiGetPteAddress(&HalpRealModeEnd) );
}
//
// Flush TLB
//
HalpFlushTLB();
//
// We need to replace the current TRAP D handler with our own, so
// we can do instruction emulation for V86 mode
//
OldTrap0DHandler = KiReturnHandlerAddressFromIDT(0xd);
KiSetHandlerAddressToIDT(0xd, HalpTrap0D);
OldTrap06Handler = KiReturnHandlerAddressFromIDT(6);
KiSetHandlerAddressToIDT(6, HalpTrap06);
//
// Make sure current TSS has IoMap space available. If no, borrow
// Normal TSS.
//
OriginalTssSelector = HalpBorrowTss();
//
// Overwrite the first access map with zeroes, so the V86 code can
// party on all the registers.
//
IoMap = (PUCHAR)&(KeGetPcr()->TSS->IoMaps[0]);
for (cnt=0; cnt<IOPM_SIZE; cnt++) {
IoMap[cnt] = 0;
}
for (cnt=IOPM_SIZE; cnt<PIOPM_SIZE; cnt++) {
IoMap[cnt] = 0xff;
}
OldIoMapBase = KeGetPcr()->TSS->IoMapBase;
KeGetPcr()->TSS->IoMapBase = KiComputeIopmOffset(1);
//
// Save the current ESP0, as HalpBiosCall() trashes it.
//
OldEsp0 = KeGetPcr()->TSS->Esp0;
//
// Call the V86-mode code
//
HalpBiosCall();
//
// Restore the TRAP handlers
//
KiSetHandlerAddressToIDT(0xd, OldTrap0DHandler);
KiSetHandlerAddressToIDT(6, OldTrap06Handler);
//
// Restore Esp0 value
//
KeGetPcr()->TSS->Esp0 = OldEsp0;
KeGetPcr()->TSS->IoMapBase = OldIoMapBase;
//
// Return borrowed TSS if any.
//
if (OriginalTssSelector != 0) {
HalpReturnTss(OriginalTssSelector);
}
//
// Unmap the first 1Mb of virtual memory
//
for (Virtual = 0; Virtual < 0x100000; Virtual += PAGE_SIZE) {
Pte = MiGetPteAddress(Virtual);
Pte->PageFrameNumber = 0;
Pte->Valid = 0;
Pte->Write = 0;
}
//
// Restore the original page table that we replaced.
//
*MiGetPdeAddress(0) = OldPageTable;
//
// Flush TLB
//
HalpFlushTLB();
//
// This function is only used during a system crash. We don't re-
// enable interrupts.
//
// KeLowerIrql(OldIrql);
}
HAL_DISPLAY_BIOS_INFORMATION
HalpGetDisplayBiosInformation (
VOID
)
{
// this hal uses native int-10
return HalDisplayInt10Bios;
}
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