feat: Add serial logging (#3)

Reviewed-on: #3

kernel/src/logger/logger.rs

@@ -11,6 +11,7 @@ static LOGGER: OnceCell<LockedLogger> = OnceCell::uninit();
 /// A logger instance protected by a spinlock.
 struct LockedLogger {
     framebuffer: Option<Spinlock<framebuffer::FrameBufferWriter>>,
+    serial: Option<Spinlock<serial::SerialPort>>
 }
 
 impl LockedLogger {
@@ -20,9 +21,11 @@ impl LockedLogger {
         info: FrameBufferInfo,
     ) -> Self {
         let framebuffer = Some(Spinlock::new(framebuffer::FrameBufferWriter::new(framebuffer, info)));
+        let serial = Some(Spinlock::new(unsafe { serial::SerialPort::init() }));
 
         LockedLogger {
             framebuffer,
+            serial
         }
     }
 
@@ -34,6 +37,10 @@ impl LockedLogger {
         if let Some(framebuffer) = &self.framebuffer {
             unsafe { framebuffer.force_unlock() };
         }
+
+        if let Some(serial) = &self.serial {
+            unsafe { serial.force_unlock() };
+        }
     }
 }
 
@@ -47,6 +54,11 @@ impl log::Log for LockedLogger {
             let mut framebuffer = framebuffer.lock();
             writeln!(framebuffer, "{:5}: {}", record.level(), record.args()).unwrap();
         }
+
+        if let Some(serial) = &self.serial {
+            let mut serial = serial.lock();
+            writeln!(serial, "{:5}: {}", record.level(), record.args()).unwrap();
+        }
     }
 
     fn flush(&self) {}