serial print macro

stage_3/src/com.rs

@@ -1,6 +1,28 @@
 use core::{fmt, hint};
 
-use crate::ioport;
+use crate::{ioport, spin::Spinlock};
+
+const COM1_PORT: u16 = 0x3f8;
+
+pub static COM1: Spinlock<Option<Com>> = Spinlock::new(None);
+
+#[macro_export]
+macro_rules! com1_print {
+  ($($args:tt)*) => ({
+    crate::com::with_com1_if_available(|com1| {
+      ::core::write!(com1, $($args)*).ok();
+    });
+  })
+}
+
+#[macro_export]
+macro_rules! com1_println {
+  ($($args:tt)*) => ({
+    crate::com::with_com1_if_available(|com1| {
+      ::core::writeln!(com1, $($args)*).ok();
+    });
+  })
+}
 
 pub struct Com {
     port: u16,
@@ -8,6 +30,27 @@ pub struct Com {
 
 pub struct ComError;
 
+pub fn with_com1_if_available<F>(f: F)
+where
+    F: FnOnce(&mut Com),
+{
+    let mut guard = COM1.lock();
+    if let Some(com1) = guard.as_mut() {
+        f(com1);
+    }
+}
+
+pub unsafe fn try_com1_init() -> bool {
+    match unsafe { Com::init(COM1_PORT) } {
+        Ok(com1) => {
+            let mut guard = COM1.lock();
+            *guard = Some(com1);
+            true
+        }
+        _ => false,
+    }
+}
+
 impl Com {
     pub unsafe fn init(port: u16) -> Result<Self, ComError> {
         const ECHO_BYTE: u8 = 0x5a;
@@ -43,9 +86,7 @@ impl Com {
             ioport::outb(port + 4, 0x0f);
         }
 
-        Ok(Self {
-            port,
-        })
+        Ok(Self { port })
     }
 
     pub fn poll_has_data(&self) -> bool {
@@ -80,13 +121,4 @@ impl fmt::Write for Com {
         }
         Ok(())
     }
-  
-  fn write_char(&mut self, c: char) -> fmt::Result {
-    let mut buf = [0u8; 4];
-    let s = c.encode_utf8(&mut buf);
-    for b in s.bytes() {
-        self.write_poll(b);
-    }
-    Ok(())
-  }
 }

stage_3/src/main.rs

@@ -3,12 +3,17 @@
 #![feature(custom_test_frameworks)]
 #![test_runner(crate::test_runner)]
 
-mod spin;
+mod com;
 mod ioport;
+mod spin;
 mod vga;
-mod com;
 
-use core::{arch::{asm, global_asm}, fmt::Write, panic::PanicInfo, ptr, slice};
+use core::{
+    arch::{asm, global_asm},
+    fmt::{self, Write},
+    panic::PanicInfo,
+    ptr, slice,
+};
 
 global_asm!(include_str!("asm/trampoline.s"));
 
@@ -22,12 +27,14 @@ fn panic(info: &PanicInfo) -> ! {
     hlt()
 }
 
-const COM1_PORT: u16 = 0x3f8;
-
 #[unsafe(no_mangle)]
 pub extern "C" fn _start() -> ! {
     vga::vga_init();
 
+    unsafe {
+        com::try_com1_init();
+    }
+
     let gdt_ptr = ptr::with_exposed_provenance::<u64>(0xc000);
     let gdt_slice = unsafe { slice::from_raw_parts(gdt_ptr, 4) };
 
@@ -37,11 +44,7 @@ pub extern "C" fn _start() -> ! {
     vga_println!("{:016x}", gdt_slice[2]);
     vga_println!("{:016x}", gdt_slice[3]);
 
-  let mut com = unsafe { com::Com::init(COM1_PORT) };
-
-  if let Ok(com) = &mut com {
-    writeln!(com, "hello serial").ok();
-  }
+    com1_println!("hello serial!");
 
     hlt()
 }

stage_3/src/spin.rs

@@ -1,4 +1,9 @@
-use core::{cell::UnsafeCell, hint, ops::{Deref, DerefMut}, sync::atomic::{AtomicBool, Ordering}};
+use core::{
+    cell::UnsafeCell,
+    hint,
+    ops::{Deref, DerefMut},
+    sync::atomic::{AtomicBool, Ordering},
+};
 
 pub struct Spinlock<T> {
     data: UnsafeCell<T>,
@@ -19,7 +24,8 @@ impl<T> Spinlock<T> {
         //   observed the `false` value.
         // - Store `true`, so nothing else can enter the critical section until we exit it.
         // Otherwise, spin until we observe a `false` value.
-    while self.locked
+        while self
+            .locked
             .compare_exchange_weak(false, true, Ordering::Acquire, Ordering::Relaxed)
             .is_err()
         {
@@ -57,10 +63,7 @@ impl<T> Spinlock<T> {
     }
 }
 
-unsafe impl<T> Sync for Spinlock<T>
-where
-  T: Send,
-{}
+unsafe impl<T> Sync for Spinlock<T> where T: Send {}
 
 pub struct SpinlockGuard<'a, T> {
     lock: &'a Spinlock<T>,

stage_3/src/vga.rs

@@ -38,7 +38,7 @@ pub fn with_vga_buf<F>(f: F)
 where
     F: FnOnce(&mut VgaBuf),
 {
-  let mut guard = crate::vga::VGA.lock();
+    let mut guard = VGA.lock();
     let vga = guard.as_mut().expect("vga not initialised");
     f(vga);
 }
@@ -51,7 +51,11 @@ pub struct VgaBuf {
 
 impl VgaBuf {
     pub unsafe fn new(buf: *mut u16) -> Self {
-    Self { buf, col: 0, row: 0 }
+        Self {
+            buf,
+            col: 0,
+            row: 0,
+        }
     }
 
     pub fn vga_write_str(&mut self, s: &str) {
@@ -84,8 +88,7 @@ impl VgaBuf {
 
         if col < VGA_WIDTH && row < VGA_HEIGHT {
             unsafe {
-        self.coord_ptr(col, row)
-          .write_volatile(vga_val);
+                self.coord_ptr(col, row).write_volatile(vga_val);
             }
         }
     }
@@ -100,7 +103,7 @@ impl VgaBuf {
             ptr::copy(
                 self.coord_ptr(0, 1),
                 self.coord_ptr(0, 0),
-        VGA_WIDTH * (VGA_HEIGHT - 1)
+                VGA_WIDTH * (VGA_HEIGHT - 1),
             );
 
             for col in 0..VGA_WIDTH {