Serial stdio

Makefile

@@ -10,7 +10,7 @@ grub_cfg := $(boot_src)/grub.cfg
 assembly_source_files := $(wildcard $(boot_src)/*.asm)
 assembly_object_files := $(patsubst $(boot_src)/%.asm, \
 	build/arch/$(arch)/boot/%.o, $(assembly_source_files))
-qemu_opts := -cdrom $(iso) -smp 2
+qemu_opts := -cdrom $(iso) -smp 2 -serial stdio
 
 ifdef travis
 	test := 1

src/arch/x86_64/driver/mod.rs

@@ -2,3 +2,4 @@ pub mod vga;
 pub mod acpi;
 pub mod ioapic;
 pub mod mp;
+pub mod serial;

src/arch/x86_64/driver/serial.rs

@@ -0,0 +1,49 @@
+/*
+ * Rust BareBones OS
+ * - By John Hodge (Mutabah/thePowersGang) 
+ *
+ * arch/x86/debug.rs
+ * - Debug output channel
+ *
+ * Writes debug to the standard PC serial port (0x3F8 .. 0x3FF)
+ * 
+ * == LICENCE ==
+ * This code has been put into the public domain, there are no restrictions on
+ * its use, and the author takes no liability.
+ */
+
+use core::fmt;
+use spin::Mutex;
+use x86_64::instructions::port::{inb, outb};
+
+pub static SERIAL: Mutex<Serial> = Mutex::new(Serial{});
+
+pub struct Serial;
+
+impl Serial {
+	/// Write a single byte to the output channel
+	pub fn write(&mut self, byte: u8) {
+		unsafe {
+			self.wait();
+			
+			// Send the byte out the serial port
+			outb(0x3F8, byte);
+			
+			// Also send to the bochs 0xe9 hack
+			outb(0xE9, byte);
+		}
+	}
+	/// Wait for the serial port's fifo to not be empty
+	unsafe fn wait(&self) {
+		while (inb(0x3F8+5) & 0x20) == 0 {}
+	}
+}
+
+impl fmt::Write for Serial {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        for byte in s.bytes() {
+        	self.write(byte)
+        }
+        Ok(())
+    }
+}

src/io/mod.rs

@@ -1,4 +1,5 @@
 use core::fmt;
+use arch::driver::serial::SERIAL;
 
 mod vga_writer;
 
@@ -32,6 +33,7 @@ fn print_in_color(args: fmt::Arguments, color: Color) {
     let mut writer = vga_writer::VGA_WRITER.lock();
     writer.set_color(color);    
     writer.write_fmt(args).unwrap();
+    SERIAL.lock().write_fmt(args).unwrap();
 }
 
 pub fn print(args: fmt::Arguments) {