init: add a check_magic function

moon/src/init.rs

@@ -0,0 +1,7 @@
+use crate::bootboot::{BOOTBOOT, BOOTBOOT_MAGIC};
+use crate::util::get_bootboot;
+
+pub fn check_magic() -> () {
+    let boot: BOOTBOOT = get_bootboot();
+    assert_eq!(boot.magic, BOOTBOOT_MAGIC[..4]);
+}

moon/src/main.rs

@@ -5,9 +5,13 @@ mod video;
 mod bootboot;
 mod panic;
 mod util;
+mod init;
+
+use video::Color;
 
 #[no_mangle]
 pub extern "C" fn _start() -> ! {
-    video::clear(0xffffffff);
+    init::check_magic();
+    video::clear(Color::White);
     loop {}
 }