diff --git a/ableos/src/arch/riscv/drivers/serial.rs b/ableos/src/arch/riscv/drivers/serial.rs
index da9bc6cd..fb274646 100644
--- a/ableos/src/arch/riscv/drivers/serial.rs
+++ b/ableos/src/arch/riscv/drivers/serial.rs
@@ -1,3 +1,7 @@
+use core::fmt::Arguments;
+use core::fmt::Error;
+
+/// Prints to the host through the serial interface.
 #[macro_export]
 macro_rules! serial_print {
     ($($arg:tt)*) => {};
@@ -9,3 +13,28 @@ macro_rules! serial_println {
     ($fmt:expr) => {};
     ($fmt:expr, $($arg:tt)*) => {};
 }
+
+pub struct Serial123 {
+    uart_data: u32,
+}
+
+impl Serial123 {
+    pub fn out(&mut self, s: ::core::fmt::Arguments) {
+        let uart_data = 0x10000000 as *mut u8;
+        for c in b"Hello, world!\n" {
+            unsafe { uart_data.write_volatile(*c) };
+        }
+    }
+}
+
+use spin::Mutex;
+
+use lazy_static::lazy_static;
+lazy_static! {
+    pub static ref SERIAL: Mutex<Serial123> = {
+        let serial_port = Serial123 {
+            uart_data: 0x10000000,
+        };
+        Mutex::new(serial_port)
+    };
+}
diff --git a/ableos/src/arch/riscv/mod.rs b/ableos/src/arch/riscv/mod.rs
index 73686376..5ae03499 100644
--- a/ableos/src/arch/riscv/mod.rs
+++ b/ableos/src/arch/riscv/mod.rs
@@ -29,13 +29,10 @@ unsafe extern "C" fn _boot() -> ! {
     ",
     sym _start, options(noreturn));
 }
-
+use crate::serial::SERIAL;
 extern "C" fn _start() -> ! {
-    let uart_data = 0x10000000 as *mut u8;
-    for c in b"Hello, world!\n" {
-        unsafe { uart_data.write_volatile(*c) };
-    }
-
+    SERIAL.lock().out(format_args!("Hi"));
+    // Serial123::out();
     sloop()
 }
 
diff --git a/repbuild/src/main.rs b/repbuild/src/main.rs
index 3cdad2d4..a7b35076 100644
--- a/repbuild/src/main.rs
+++ b/repbuild/src/main.rs
@@ -49,8 +49,7 @@ fn main() -> anyhow::Result<()> {
                         -kernel target/aarch64-ableos/release/ableos
                         -device virtio-keyboard
                         "
-                    )
-                    .run()?;
+                    ).run()?;
                 }
                 MachineType::RISCV => {
                     xshell::cmd!("cargo build --release --target=riscv64gc-unknown-none-elf")