BOOLEAN
Fast486WriteMemory(PFAST486_STATE State,
FAST486_SEG_REGS SegmentReg,
ULONG Offset,
PVOID Buffer,
ULONG Size)
{
ULONG LinearAddress;
PFAST486_SEG_REG CachedDescriptor;
ASSERT(SegmentReg < FAST486_NUM_SEG_REGS);
/* Get the cached descriptor */
CachedDescriptor = &State->SegmentRegs[SegmentReg];
if ((Offset + Size - 1) > CachedDescriptor->Limit)
{
/* Write beyond limit */
Fast486Exception(State, FAST486_EXCEPTION_GP);
return FALSE;
}
/* Check for protected mode */
if (State->ControlRegisters[0] & FAST486_CR0_PE)
{
/* Privilege checks */
if (!CachedDescriptor->Present)
{
Fast486Exception(State, FAST486_EXCEPTION_NP);
return FALSE;
}
if ((CachedDescriptor->Rpl > CachedDescriptor->Dpl)
|| (Fast486GetCurrentPrivLevel(State) > CachedDescriptor->Dpl))
{
Fast486Exception(State, FAST486_EXCEPTION_GP);
return FALSE;
}
if (CachedDescriptor->Executable)
{
/* Code segment not writable */
Fast486Exception(State, FAST486_EXCEPTION_GP);
return FALSE;
}
else if (!CachedDescriptor->ReadWrite)
{
/* Data segment not writeable */
Fast486Exception(State, FAST486_EXCEPTION_GP);
return FALSE;
}
}
/* Find the linear address */
LinearAddress = CachedDescriptor->Base + Offset;
/* Write to the linear address */
return Fast486WriteLinearMemory(State, LinearAddress, Buffer, Size);
}
static
inline
VOID
NTAPI
Fast486ExecutionControl(PFAST486_STATE State, FAST486_EXEC_CMD Command)
{
UCHAR Opcode;
INT ProcedureCallCount = 0;
/* Main execution loop */
do
{
/* Check if this is a new instruction */
if (State->PrefixFlags == 0) State->SavedInstPtr = State->InstPtr;
/* Perform an instruction fetch */
if (!Fast486FetchByte(State, &Opcode))
{
/* Exception occurred */
State->PrefixFlags = 0;
continue;
}
// TODO: Check for CALL/RET to update ProcedureCallCount.
if (Fast486OpcodeHandlers[Opcode] != NULL)
{
/* Call the opcode handler */
Fast486OpcodeHandlers[Opcode](State, Opcode);
}
else
{
/* This is not a valid opcode */
Fast486Exception(State, FAST486_EXCEPTION_UD);
}
if (Fast486OpcodeHandlers[Opcode] == Fast486OpcodePrefix)
{
/* This is a prefix, go to the next instruction immediately */
continue;
}
/* A non-prefix opcode has been executed, reset the prefix flags */
State->PrefixFlags = 0;
/*
* Check if there is an interrupt to execute, or a hardware interrupt signal
* while interrupts are enabled.
*/
if (State->IntStatus == FAST486_INT_EXECUTE)
{
FAST486_IDT_ENTRY IdtEntry;
/* Get the interrupt vector */
if (Fast486GetIntVector(State, State->PendingIntNum, &IdtEntry))
{
/* Perform the interrupt */
Fast486InterruptInternal(State,
IdtEntry.Selector,
MAKELONG(IdtEntry.Offset, IdtEntry.OffsetHigh),
IdtEntry.Type);
/* Restore the prefix flags, which would be set to OPSIZE for 32-bit real mode */
State->PrefixFlags = 0;
}
/* Clear the interrupt status */
State->IntStatus = FAST486_INT_NONE;
}
else if (State->Flags.If
&& (State->IntAckCallback != NULL)
&& (State->IntStatus == FAST486_INT_SIGNAL))
{
/* Acknowledge the interrupt to get the number */
State->PendingIntNum = State->IntAckCallback(State);
/* Set the interrupt status to execute on the next instruction */
State->IntStatus = FAST486_INT_EXECUTE;
}
else if (State->IntStatus == FAST486_INT_DELAYED)
{
/* Restore the old state */
State->IntStatus = FAST486_INT_EXECUTE;
}
}
while ((Command == FAST486_CONTINUE)
|| (Command == FAST486_STEP_OVER && ProcedureCallCount > 0)
|| (Command == FAST486_STEP_OUT && ProcedureCallCount >= 0)
|| (Fast486OpcodeHandlers[Opcode] == Fast486OpcodePrefix));
}