First pass at message syscalls

src/drivers/nulldrv/main.s

@@ -9,6 +9,11 @@ _start:
 	mov rax, 1		; DEBUG syscall
 	int 0xee
 
+	cmp r12, 1
+	je .dosend
+	jne .doreceive
+
+.preloop:
 	mov r11, 0		; counter
 	mov rbx, 20		; sleep timeout
 
@@ -31,3 +36,15 @@ _start:
 
 	mov r11, 0
 	jmp .loop
+
+.dosend:
+	mov rax, 6      ; SEND syscall
+	mov rdi, 2      ; target is pid 2
+	int 0xee
+	jmp .preloop
+
+.doreceive:
+	mov rax, 7      ; RECEIVE syscall
+	mov rdi, 1      ; source is pid 2
+	int 0xee
+	jmp .preloop