wip: TSS added to the gdt and start to implement scheduler

headers/gdt.h

@@ -1,9 +1,10 @@
 #pragma once
 
+#include "tss.h"
 #include <stdint.h>
 
 #define GDT_ADDRESS 0xC0105040
-#define GDT_SIZE    7
+#define GDT_SIZE    8
 
 // https://wiki.osdev.org/Global_Descriptor_Table#GDTR
 struct gdt_descriptor {
@@ -11,6 +12,8 @@ struct gdt_descriptor {
 	uint32_t base;
 } __attribute__((packed));
 
+extern struct tss TSS;
+
 void init_gdt();
 
 #define GDT_FLAG_64BIT_MODE 0b0010
@@ -39,3 +42,4 @@ extern uint8_t gdt_entries[GDT_SIZE * 8];
 #define GDT_OFFSET_USER_CODE    0x20
 #define GDT_OFFSET_USER_DATA    0x28
 #define GDT_OFFSET_USER_STACK   0x30
+#define GDT_OFFSET_TSS          0x38