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

src/multitasking/switch_to_task.s

@@ -0,0 +1,37 @@
+.intel_syntax noprefix
+
+.section .text
+	.global switch_to_task
+
+switch_to_task:
+	push ebx
+	push ebp
+	push edi
+	push esi
+
+	// save the current stack pointer to the old stack
+	mov [current_task], esp
+
+	// stack pointer + the 4 regs pushed
+	// and + 1 to get the argument (next task)
+	mov esi, [esp+(4+1)*4]
+	mov [current_task], esi
+	
+	mov esp, [current_task]
+	mov eax, [current_task+4]
+	mov ebx, [current_task+8]
+	mov [TSS + 4], eax
+	mov ecx, cr3
+
+	// if cr3 hasn't change, do nothing
+	cmp ecx, ebx
+	je .END 
+	mov cr3, ebx
+
+.END:
+	pop esi
+	pop edi
+	pop ebp
+	pop ebx
+
+	ret