GDT now installs correctly.

kernel/arch/i386/gdt.nim

@@ -11,43 +11,41 @@ type
   GDTPointer{.packed.} = object
     limit: uint16 # Size of GDT
     base: uint32 # GDT memory location
-  GDTEntries = array[0..2, GDTEntry]
   AccessByte = uint8
   Flags = uint8
+  GDT{.packed.} = object
+    descriptor: GDTPointer
+    entries: array[0..2, GDTEntry]
 
-var
-  gdt: GDTEntries
-  gp: GDTPointer
-  gpAddr: uint32
+const
+  gdtAddress: uint32 = 0x00000800
+  gdt = cast[ptr GDT](gdtAddress)
 
 {.push stackTrace:off.}
-proc gdtFlush(){.inline.} =
-  gpAddr = cast[uint32](gp.addr)
-  serial.write("GDPointer Address: ")
-  serial.write(gpAddr)
-  serial.newLine()
+proc gdtFlush(){.inline,asmNoStackFrame.} =
   asm """
     cli
-    lgdt [`gpAddr`]
-    mov %ax, 0x10
-    mov %ds, %ax
-    mov %es, %ax
-    mov %fs, %ax
-    mov %gs, %ax
-    mov %ss, %ax
+    lgdtl [`0x00000800`]
+    movw $0x10, %ax
+    movw %ax, %ds
+    movw %ax, %es
+    movw %ax, %fs
+    movw %ax, %gs
+    ljmp $0x08, $next
+    next:
   """
 {.pop.}
 
 proc gdtSetGate(num: int, base: uint16, limit: uint32, access: AccessByte, flags: Flags) =
   # Setup the descriptor base address
-  gdt[num].base_low = (base and 0xFFFF)
-  gdt[num].base_middle = (base shr 16) and 0xFF
-  gdt[num].base_high = (base shr 24) and 0xFF
+  gdt.entries[num].base_low = (base and 0xFFFF)
+  gdt.entries[num].base_middle = (base shr 16) and 0xFF
+  gdt.entries[num].base_high = (base shr 24) and 0xFF
 
   # Setup the descriptor limits
-  gdt[num].limit_low = (limit and 0xFFFF)
-  gdt[num].flags_and_limit_mid = ((limit shr 16) and 0x0F) or flags
-  gdt[num].access = access
+  gdt.entries[num].limit_low = (limit and 0xFFFF)
+  gdt.entries[num].flags_and_limit_mid = ((limit shr 16) and 0x0F) or flags
+  gdt.entries[num].access = access
 
 proc createAccessByte(priv: range[0..3], directionConform: bool, readWrite: bool): AccessByte =
   result = 0b10011000'u8 # Present and executable bit
@@ -64,11 +62,8 @@ proc createFlags(granularity: bool, size: bool): Flags =
     result = result or 0b01000000'u8
 
 proc gdtInstall*() =
-  gp.limit = uint16(sizeof(GDTEntry) * gdt.len) - 1;
-  gp.base = cast[uint32](gdt.addr)
-  serial.write("GDT Address: ")
-  serial.write(gp.base)
-  serial.newLine()
+  gdt.descriptor.limit = uint16(sizeof(GDTEntry) * gdt.entries.len) - 1;
+  gdt.descriptor.base = cast[uint32](gdt.entries.addr)
   # NULL descriptor
   gdtSetGate(0, 0, 0, 0, 0);
 
@@ -78,4 +73,4 @@ proc gdtInstall*() =
   # The third entry is our Data Segment
   gdtSetGate(2, 0'u16, 0xFFFFFFFF'u32, createAccessByte(0, false, true), createFlags(true, true));
   serial.write("Flushing GDT.\L")
-  gdtFlush();
+  gdtFlush()