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

src/gdt/gdt.c

@@ -5,6 +5,7 @@
 
 extern void set_gdt(uint32_t gdt_ptr);
 
+struct tss TSS;
 uint8_t gdt_entries[GDT_SIZE * 8];
 struct gdt_descriptor *gdtr = (struct gdt_descriptor *)GDT_ADDRESS;
 
@@ -90,6 +91,9 @@ void init_gdt(void)
 		GDT_ACCESS_RW_READABLE_FOR_CODE_WRITABLE_FOR_DATA |
 		GDT_ACCESS_A_ACCESSED,
 	    GDT_FLAG_32BIT_MODE | GDT_FLAG_PAGE_MODE); // User stack
+	// TSS
+	set_gdt_entry_value(gdt_entries + GDT_OFFSET_TSS, (uint32_t)&TSS,
+	                    sizeof(struct tss) - 1, 0x89, 0);
 
 	set_gdt(((uint32_t)gdtr));
 }