print to vga on panic

boot1/src/main.rs

@@ -25,7 +25,12 @@ unsafe extern "C" {
 }
 
 #[panic_handler]
-fn panic(_info: &PanicInfo) -> ! {
+fn panic(info: &PanicInfo) -> ! {
+  vga_println!("panic!");
+  if let Some(location) = info.location() {
+    vga_println!("{}", location);
+  }
+  vga_println!("{}", info.message());
   hlt()
 }