CTAOS v3

SysCore/hal/gdt/gdt.asm

@@ -0,0 +1,20 @@
+bits 32
+; !!!  GDT  !!!
+; This will set up our new segment registers. We need to do
+; something special in order to set CS. We do what is called a
+; far jump. A jump that includes a segment as well as an offset.
+; This is declared in C as 'extern void gdt_flush();'
+
+global _i86_gdt_flush     ; Allows the C code to link to this
+extern _gp            ; Says that '_gp' is in another file
+_i86_gdt_flush:
+    lgdt [_gp]        ; Load the GDT with our '_gp' which is a special pointer
+    mov ax, 0x10      ; 0x10 is the offset in the GDT to our data segment
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+    mov ss, ax
+    jmp 0x08:flush2   ; 0x08 is the offset to our code segment: Far jump!
+flush2:
+    ret               ; Returns back to the C code!