Add qemu serial output to stdio

Signed-off-by: Noah Knegt <git@noahknegt.com>

LICENSE

@@ -1,18 +1,18 @@
 MIT License
 
-Copyright (c) 2025 noah.knegt
+Copyright (c) 2025 Noah Knegt <personal@noahknegt.com>
 
-Permission is hereby granted, free of charge, to any person obtaining a copy of this software and 
-associated documentation files (the "Software"), to deal in the Software without restriction, including 
-without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
-copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the 
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
+associated documentation files (the "Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the
 following conditions:
 
-The above copyright notice and this permission notice shall be included in all copies or substantial 
+The above copyright notice and this permission notice shall be included in all copies or substantial
 portions of the Software.
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT 
-LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO 
-EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER 
-IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE 
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
+LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
+EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 USE OR OTHER DEALINGS IN THE SOFTWARE.

build.rs

@@ -9,15 +9,11 @@ fn main() {
 
     // create an UEFI disk image (optional)
     let uefi_path = out_dir.join("uefi.img");
-    bootloader::UefiBoot::new(&kernel)
-        .create_disk_image(&uefi_path)
-        .unwrap();
+    bootloader::UefiBoot::new(&kernel).create_disk_image(&uefi_path).unwrap();
 
     // create a BIOS disk image
     let bios_path = out_dir.join("bios.img");
-    bootloader::BiosBoot::new(&kernel)
-        .create_disk_image(&bios_path)
-        .unwrap();
+    bootloader::BiosBoot::new(&kernel).create_disk_image(&bios_path).unwrap();
 
     // pass the disk image paths as env variables to the `main.rs`
     println!("cargo:rustc-env=UEFI_PATH={}", uefi_path.display());

kernel/src/adder.rs

@@ -1,13 +0,0 @@
-pub fn add(a: i32, b: i32) -> i32 {
-    a + b
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-    
-    #[test]
-    fn add_test() {
-        assert_eq!(add(1, 2), 3);
-    }
-}

kernel/src/lib.rs

@@ -1,30 +0,0 @@
-#![cfg_attr(not(test), no_std)]
-
-use bootloader_api::BootInfo;
-
-mod logging;
-mod adder;
-
-pub fn main(boot_info: &'static mut BootInfo) -> ! {
-    let info = boot_info.framebuffer.as_ref().unwrap().info();
-    let buffer = boot_info.framebuffer.as_mut().unwrap().buffer_mut();
-
-    logging::init_logger(buffer, info);
-
-    log::info!("Hello World from KERNEL");
-    log::debug!("ADDING 1 & 6, result == {}", adder::add(1, 6));
-
-    // Endless loop as the kernel must stay running
-    #[allow(clippy::empty_loop)]
-    loop {}
-}
-
-#[cfg(not(test))]
-#[panic_handler]
-fn panic(info: &core::panic::PanicInfo) -> ! {
-    logging::force_unlock();
-    log::error!("{info}");
-
-    #[allow(clippy::empty_loop)]
-    loop {}
-}

kernel/src/logger/framebuffer.rs

@@ -2,7 +2,7 @@ use bootloader_api::info::{FrameBufferInfo, PixelFormat};
 use core::{fmt, ptr};
 use font_constants::BACKUP_CHAR;
 use noto_sans_mono_bitmap::{
-    FontWeight, RasterHeight, RasterizedChar, get_raster, get_raster_width,
+    get_raster, get_raster_width, FontWeight, RasterHeight, RasterizedChar,
 };
 
 /// Additional vertical space between lines
@@ -130,7 +130,7 @@ impl FrameBufferWriter {
                 // set a supported (but invalid) pixel format before panicking to avoid a double
                 // panic; it might not be readable though
                 self.info.pixel_format = PixelFormat::Rgb;
-                panic!("pixel format {other:?} not supported in logger")
+                panic!("pixel format {:?} not supported in logger", other)
             }
         };
         let bytes_per_pixel = self.info.bytes_per_pixel;

kernel/src/logger/logger.rs

@@ -11,21 +11,21 @@ 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>>,
+    serial: Option<Spinlock<serial::SerialPort>>
 }
 
 impl LockedLogger {
     /// Create a new instance that logs to the given framebuffer.
-    pub fn new(framebuffer: &'static mut [u8], info: FrameBufferInfo) -> Self {
-        let framebuffer = Some(Spinlock::new(framebuffer::FrameBufferWriter::new(
-            framebuffer,
-            info,
-        )));
+    pub fn new(
+        framebuffer: &'static mut [u8],
+        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,
+            serial
         }
     }
 
@@ -65,8 +65,16 @@ impl log::Log for LockedLogger {
 }
 
 /// Initialize a text-based logger using the given pixel-based framebuffer as output.
-pub fn init_logger(framebuffer: &'static mut [u8], info: FrameBufferInfo) {
-    let logger = LOGGER.get_or_init(move || LockedLogger::new(framebuffer, info));
+pub fn init_logger(
+    framebuffer: &'static mut [u8],
+    info: FrameBufferInfo,
+) {
+    let logger = LOGGER.get_or_init(move || {
+        LockedLogger::new(
+            framebuffer,
+            info,
+        )
+    });
     log::set_logger(logger).expect("logger already set");
     #[cfg(debug_assertions)]
     log::set_max_level(log::LevelFilter::Debug);
@@ -74,9 +82,14 @@ pub fn init_logger(framebuffer: &'static mut [u8], info: FrameBufferInfo) {
     #[cfg(not(debug_assertions))]
     log::set_max_level(log::LevelFilter::Info);
 
-    log::debug!("Framebuffer info: {info:?}");
+    log::debug!("Framebuffer info: {:?}", info);
 }
 
 pub fn force_unlock() {
-    unsafe { LOGGER.get().map(|l| l.force_unlock()) };
+    unsafe {
+        LOGGER
+            .get()
+            .map(|l| l.force_unlock())
+    };
 }
+

kernel/src/logger/mod.rs

@@ -1,5 +1,4 @@
 pub mod logger;
-
 mod framebuffer;
 mod serial;
 

kernel/src/main.rs

@@ -3,13 +3,35 @@
 
 use bootloader_api::{
     config::{BootloaderConfig, Mapping},
-    entry_point,
+    entry_point, BootInfo
 };
 
-static BOOTLOADER_CONFIG: BootloaderConfig = {
+mod logger;
+
+pub static BOOTLOADER_CONFIG: BootloaderConfig = {
     let mut config = BootloaderConfig::new_default();
     config.mappings.physical_memory = Some(Mapping::Dynamic);
     config
 };
 
-entry_point!(kernel::main, config = &BOOTLOADER_CONFIG);
+entry_point!(kernel_main);
+
+fn kernel_main(boot_info: &'static mut BootInfo) -> ! {
+    let info = boot_info.framebuffer.as_ref().unwrap().info();
+    let buffer = boot_info.framebuffer.as_mut().unwrap().buffer_mut();
+
+    logger::init_logger(buffer, info);
+
+    log::info!("Hello World from KERNEL");
+
+    // Endless loop as the kernel must stay running
+    loop {}
+}
+
+#[panic_handler]
+#[cfg(not(test))]
+fn panic(info: &core::panic::PanicInfo) -> ! {
+    logger::force_unlock();
+    log::error!("{}", info);
+    loop {}
+}

rust-toolchain.toml

@@ -1,5 +1,7 @@
 [toolchain]
-channel = "nightly"
+# The nightly version that was build on 24-07-2025 is the last known working version,
+# the c-int-width definition for rust targets has changed from a string to a u16
+channel = "nightly-2025-07-24"
 targets = [
     "x86_64-unknown-none"
 ]

src/main.rs

@@ -17,6 +17,9 @@ fn main() {
         cmd.arg("-drive")
             .arg(format!("format=raw,file={bios_path}"));
     }
+
+    cmd.arg("-serial").arg("stdio");
+
     let mut child = cmd.spawn().unwrap();
     child.wait().unwrap();
 }