public void CreateGDT()
{
new Comment(this, "BEGIN - Create GDT");
var xGDT = new List <byte>();
// Null Segment - Selector 0x00
// Not used, but required by many emulators.
xGDT.AddRange(new byte[8]
{
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
});
// Code Segment
mGdCode = (byte)xGDT.Count;
xGDT.AddRange(GdtDescriptor(0x00000000, 0xFFFFFFFF, true));
// Data Segment - Selector
mGdData = (byte)xGDT.Count;
xGDT.AddRange(GdtDescriptor(0x00000000, 0xFFFFFFFF, false));
DataMembers.Add(new DataMember("_NATIVE_GDT_Contents", xGDT.ToArray()));
XS.Comment("Tell CPU about GDT");
var xGdtPtr = new UInt16[3];
// Size of GDT Table - 1
xGdtPtr[0] = (UInt16)(xGDT.Count - 1);
DataMembers.Add(new DataMember("_NATIVE_GDT_Pointer", xGdtPtr));
new Mov
{
DestinationRef = ElementReference.New("_NATIVE_GDT_Pointer"),
DestinationIsIndirect = true,
DestinationDisplacement = 2,
SourceRef = ElementReference.New("_NATIVE_GDT_Contents")
};
XS.Set(XSRegisters.EAX, "_NATIVE_GDT_Pointer");
XS.LoadGdt(XSRegisters.EAX, isIndirect: true);
XS.Comment("Set data segments");
XS.Set(XSRegisters.EAX, mGdData);
XS.Set(XSRegisters.DS, XSRegisters.AX);
XS.Set(XSRegisters.ES, XSRegisters.AX);
XS.Set(XSRegisters.FS, XSRegisters.AX);
XS.Set(XSRegisters.GS, XSRegisters.AX);
XS.Set(XSRegisters.SS, XSRegisters.AX);
XS.Comment("Force reload of code segment");
new JumpToSegment
{
Segment = mGdCode,
DestinationLabel = "Boot_FlushCsGDT"
};
XS.Label("Boot_FlushCsGDT");
new Comment(this, "END - Create GDT");
}
public override void AssembleNew(Assembler aAssembler, object aMethodInfo)
{
XS.ClearInterruptFlag();
XS.Set(XSRegisters.EAX, "_NATIVE_GDT_Pointer");
XS.LoadGdt(XSRegisters.EAX, isIndirect: true);
XS.Set(XSRegisters.EAX, XSRegisters.CR0);
XS.Or(XSRegisters.AL, 1);
XS.Set(XSRegisters.CR0, XSRegisters.EAX);
XS.JumpToSegment(0x08, "PMode");
XS.Label("PMode");
}
