GDT work

source2/IL2CPU/Cosmos.IL2CPU.X86/CosmosAssembler.cs

@@ -48,6 +48,7 @@ namespace Cosmos.IL2CPU.X86
             new Comment(this, "EBX=multiboot_info ");
             new Comment(this, "EAX=0x2BADB002 - check if it's really Multiboot loader ");
             new Comment(this, "                ;- copy mb info - some stuff for you  ");
+            new Comment(this, "BEGIN - Multiboot Info");
             //new Move { DestinationReg = Registers.ESI, SourceReg = Registers.EBX };
             //new Move { DestinationReg = Registers.EDI, SourceRef = ElementReference.New("MultiBootInfo_Structure") };
             //new Move { DestinationReg = Registers.ECX, SourceValue = 0x58 };
@@ -56,12 +57,7 @@ namespace Cosmos.IL2CPU.X86
             //new Move { DestinationReg = Registers.EBX, SourceRef = ElementReference.New("MultiBootInfo_Structure") };
             new Move { DestinationRef = ElementReference.New("MultiBootInfo_Structure"), DestinationIsIndirect = true, SourceReg = Registers.EBX };
             new Add { DestinationReg = Registers.EBX, SourceValue = 4 };
-            new Move
+            new Move { DestinationReg = Registers.EAX, SourceReg = Registers.EBX, SourceIsIndirect = true };
-            {
-                DestinationReg = Registers.EAX,
-                SourceReg = Registers.EBX,
-                SourceIsIndirect = true
-            };
             new Move { DestinationRef = ElementReference.New("MultiBootInfo_Memory_Low"), DestinationIsIndirect = true, SourceReg = Registers.EAX };
             new Add { DestinationReg = Registers.EBX, SourceValue = 4 };
             new Move
@@ -76,6 +72,8 @@ namespace Cosmos.IL2CPU.X86
                 DestinationReg = Registers.ESP,
                 SourceRef = ElementReference.New("Kernel_Stack")
             };
+            new Comment(this, "END - Multiboot Info");
+
 #if LFB_1024_8
             new Comment("Set graphics fields");
             new Move { DestinationReg = Registers.EBX, SourceRef = ElementReference.New("MultiBootInfo_Structure"), SourceIsIndirect = true };
@@ -86,9 +84,8 @@ namespace Cosmos.IL2CPU.X86
             new Move { DestinationReg = Registers.EAX, SourceReg = Registers.EBX, SourceIsIndirect = true, SourceDisplacement = 80 };
             new Move { DestinationRef = ElementReference.New("MultibootGraphicsRuntime_VbeMode"), DestinationIsIndirect = true, SourceReg = Registers.EAX };
 #endif
-            new Comment(this, "some more startups todo");
 
-            // SSE init
+            new Comment(this, "BEGIN - SSE Init");
             // CR4[bit 9]=1, CR4[bit 10]=1, CR0[bit 2]=0, CR0[bit 1]=1
             new Move { DestinationReg = Registers.EAX, SourceReg = Registers.CR4 };
             new Or { DestinationReg = Registers.EAX, SourceValue = 0x100 };
@@ -104,7 +101,7 @@ namespace Cosmos.IL2CPU.X86
 
             new And { DestinationReg = Registers.EAX, SourceValue = 1 };
             new Move { DestinationReg = Registers.CR0, SourceReg = Registers.EAX };
-            // END SSE INIT
+            new Comment(this, "END - SSE Init");
 
             if (mComNumber > 0)
             {
@@ -118,7 +115,7 @@ namespace Cosmos.IL2CPU.X86
             // Jump to Kernel entry point
             new Call { DestinationLabel = EntryPointName };
 
-            // After Kernel is done, sit here and halt till next IRQ.
+            new Comment(this, "Kernel done - loop till next IRQ");
             new Label(".loop");
                 new ClrInterruptFlag();
                 new Halt();

source2/Kernel/System/Hardware/Core/Cosmos.Core.Plugs/Assemblers/CreateGDT.cs

@@ -7,14 +7,85 @@ using System.Collections.Generic;
 
 namespace Cosmos.Core.Plugs.Assemblers {
   public class CreateGDT : AssemblerMethod {
+    // http://wiki.osdev.org/Global_Descriptor_Table
+    // http://http://wiki.osdev.org/GDT_Tutorial  
+    // http://www.osdever.net/bkerndev/Docs/gdt.htm
+
+    //TODO: Modify this to support the flags and access as individual input rather
+    // than requiring user to pass pre-calculated numbers.
+    protected byte[] Descriptor(UInt32 aBase, UInt32 aSize, bool aCode) {
+      // Limit is a confusing word. Is it the max physical address or size?
+      // In fact it is the size, and 286 docs actually refer to it as size 
+      // rather than limit.
+      // It is also size - 1, else there would be no way to specify
+      // all of RAM, and a limit of 0 is invalid.
+
+      var xResult = new byte[8];
+      
+      // Check the limit to make sure that it can be encoded
+      if ((aSize > 65536) && (aSize & 0x0FFF) != 0x0FFF) {
+        // If larger than 16 bit, must be an even page (4kb) size
+        throw new Exception("Invalid size in GDT descriptor.");
+      }
+      // Flags nibble
+      // 7: Granularity 
+      //    0 = bytes
+      //    1 = 4kb pages
+      // 6: 1 = 32 bit mode
+      // 5: 0 - Reserved
+      // 4: 0 - Reserved 
+      xResult[6] = 0x40;
+      if (aSize > 65536) {
+        // Set page sizing instead of byte sizing
+        aSize = aSize >> 12;
+        xResult[6] = (byte)(xResult[6] | 0x80);
+      }
+      
+      xResult[0] = (byte)(aSize & 0xFF);
+      xResult[1] = (byte)((aSize >> 8) & 0xFF);
+      xResult[6] = (byte)(xResult[6] | ((aSize >> 16) & 0x0F));
+
+      xResult[2] = (byte)(aBase & 0xFF);
+      xResult[3] = (byte)((aBase >> 8) & 0xFF);
+      xResult[4] = (byte)((aBase >> 16) & 0xFF);
+      xResult[7] = (byte)((aBase >> 24) & 0xFF);
+
+      xResult[5] = (byte)(
+        // Bit 7: Present, must be 1
+        0x80 |
+        // Bit 6-5: Privilege, 0=kernel, 3=user
+        0x00 |
+        // Reserved, must be 1
+        0x10 |
+        // Bit 3: 1=Code, 0=Data
+        (aCode ? 0x08 : 0x00) |
+        // Bit 2: Direction/Conforming
+        0x00 |
+        // Bit 1: R/W  Data (1=Writeable, 0=Read only) Code (1=Readable, 0=Not readable)
+        0x02 |
+        // Bit 0: Accessed - Set to 0. Updated by CPU later.       
+        0x00
+        );
+
+      return xResult;
+    }
+
     public override void AssembleNew(object aAssembler, object aMethodInfo) {
-            var xAssembler = (Assembler)aAssembler;
+      var xAsm = (Assembler)aAssembler;
-            xAssembler.DataMembers.Add(new CPUAll.DataMember("_NATIVE_GDT_Contents"
+
-                , new byte[] 
+      var xGDT = new List<byte>();
-                {0,0,0,0,0,0,0,0 // Null Segment
+      // Null Segment - Selector 0x00
-		        , 0xFF, 0xFF, 0, 0, 0, 0x99, 0xCF, 0 // Code Segment
+      // Not used, but required by many emulators.
-		        , 0xFF,0xFF,0,0,0,0x93,0xCF,0})); // Data Segment
+      xGDT.AddRange(new byte[8] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 });
-            xAssembler.DataMembers.Add(new CPUAll.DataMember("_NATIVE_GDT_Pointer", new ushort[] { 0x17, 0, 0 }));
+      // Code Segment
+      byte xCodeSelector = (byte)xGDT.Count;
+      xGDT.AddRange(Descriptor(0x00000000, 0xFFFFFFFF, true));
+      // Data Segment - Selector 0x0B
+      byte xDataSelector = (byte)xGDT.Count;
+      xGDT.AddRange(Descriptor(0x00000000, 0xFFFFFFFF, false));
+      xAsm.DataMembers.Add(new CPUAll.DataMember("_NATIVE_GDT_Contents", xGDT.ToArray()));
+      
+      xAsm.DataMembers.Add(new CPUAll.DataMember("_NATIVE_GDT_Pointer", new ushort[] { 0x17, 0, 0 }));
 
       new CPUx86.Move { DestinationReg = CPUx86.Registers.EAX, SourceRef = CPUAll.ElementReference.New("_NATIVE_GDT_Pointer") };
       new CPUx86.Move { DestinationRef = CPUAll.ElementReference.New("_NATIVE_GDT_Pointer"), DestinationIsIndirect = true, DestinationDisplacement = 2, SourceRef = CPUAll.ElementReference.New("_NATIVE_GDT_Contents") };
@@ -30,8 +101,8 @@ namespace Cosmos.Core.Plugs.Assemblers {
       new CPUx86.Move { DestinationReg = CPUx86.Registers.GS, SourceReg = CPUx86.Registers.AX };
       new CPUx86.Move { DestinationReg = CPUx86.Registers.SS, SourceReg = CPUx86.Registers.AX };
 
-            // Force reload of code segment
+      new CPUAll.Comment("Force reload of code segment");
-            new CPUx86.JumpToSegment { Segment = 8, DestinationLabel = "flush__GDT__table" };
+      new CPUx86.JumpToSegment { Segment = 0x08, DestinationLabel = "flush__GDT__table" };
       new CPUAll.Label("flush__GDT__table");
     }
   }