CTAOS v2

stage2/gdt.inc

@@ -0,0 +1,68 @@
+
+
+;*************************************************
+;	Gdt.inc
+;		-GDT Routines
+;
+;	OS Development Series
+;*************************************************
+
+%ifndef __GDT_INC_67343546FDCC56AAB872_INCLUDED__
+%define __GDT_INC_67343546FDCC56AAB872_INCLUDED__
+
+bits	16
+
+;*******************************************
+; InstallGDT()
+;	- Install our GDT
+;*******************************************
+
+InstallGDT:
+
+	cli                  ; clear interrupts
+	pusha                ; save registers
+	lgdt 	[toc]        ; load GDT into GDTR
+	sti	                 ; enable interrupts
+	popa                 ; restore registers
+	ret	                 ; All done!
+
+;*******************************************
+; Global Descriptor Table (GDT)
+;*******************************************
+
+gdt_data: 
+	dd 0                ; null descriptor
+	dd 0 
+
+; gdt code:	            ; code descriptor
+	dw 0FFFFh           ; limit low
+	dw 0                ; base low
+	db 0                ; base middle
+	db 10011010b        ; access
+	db 11001111b        ; granularity
+	db 0                ; base high
+
+; gdt data:	            ; data descriptor
+	dw 0FFFFh           ; limit low (Same as code)10:56 AM 7/8/2007
+	dw 0                ; base low
+	db 0                ; base middle
+	db 10010010b        ; access
+	db 11001111b        ; granularity
+	db 0                ; base high
+	
+end_of_gdt:
+toc: 
+	dw end_of_gdt - gdt_data - 1 	; limit (Size of GDT)
+	dd gdt_data 			; base of GDT
+
+; give the descriptor offsets names
+
+%define NULL_DESC 0
+%define CODE_DESC 0x8
+%define DATA_DESC 0x10
+
+%endif ;__GDT_INC_67343546FDCC56AAB872_INCLUDED__
+
+
+
+