Merge branch 'post-02' into post-03

Fix: `target-pointer-width` field now expects an integer

.cargo/config.toml

@@ -0,0 +1,9 @@
+[unstable]
+build-std = ["core", "compiler_builtins"]
+build-std-features = ["compiler-builtins-mem"]
+
+[build]
+target = "x86_64-blog_os.json"
+
+[target.'cfg(target_os = "none")']
+runner = "bootimage runner"

.github/workflows/code.yml

@@ -56,21 +56,16 @@ jobs:
         with:
           profile: minimal
           toolchain: nightly
+      - name: Install bootimage
+        run: cargo install bootimage --debug
       - name: Checkout Repository
         uses: actions/checkout@v2
-      - name: Add thumbv7em-none-eabihf Target
-        run: rustup target add thumbv7em-none-eabihf
-      - name: Build for thumbv7em-none-eabihf
-        run: cargo build --target thumbv7em-none-eabihf
-      - name: Build for Linux
-        if: runner.os == 'Linux'
-        run: cargo rustc -- -C link-arg=-nostartfiles
-      - name: Build for macOS
-        if: runner.os == 'macOS'
-        run: cargo rustc -- -C link-args="-e __start -static -nostartfiles"
-      - name: Build for Windows
-        if: runner.os == 'Windows'
-        run: cargo rustc -- -C link-args="/ENTRY:_start /SUBSYSTEM:console"
+      - name: Install Rustup Components
+        run: rustup component add rust-src llvm-tools-preview
+      - name: Run `cargo bootimage`
+        uses: actions-rs/cargo@v1
+        with:
+          command: bootimage
 
   check_formatting:
     name: Check Formatting

Cargo.lock

@@ -1,7 +1,46 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "blog_os"
 version = "0.1.0"
+dependencies = [
+ "bootloader",
+ "lazy_static",
+ "spin 0.5.2",
+ "volatile",
+]
+
+[[package]]
+name = "bootloader"
+version = "0.9.33"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7bdfddac270bbdd45903296bc1caf29a7fdce6b326aaf0bbab7f04c5f98b7447"
+
+[[package]]
+name = "lazy_static"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
+dependencies = [
+ "spin 0.9.8",
+]
+
+[[package]]
+name = "spin"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
+
+[[package]]
+name = "spin"
+version = "0.9.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6980e8d7511241f8acf4aebddbb1ff938df5eebe98691418c4468d0b72a96a67"
+
+[[package]]
+name = "volatile"
+version = "0.2.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f6b06ad3ed06fef1713569d547cdbdb439eafed76341820fb0e0344f29a41945"

Cargo.toml

@@ -5,12 +5,13 @@ authors = ["Philipp Oppermann <dev@phil-opp.com>"]
 edition = "2024"
 
 [dependencies]
+bootloader = "0.9"
+volatile = "0.2.6"
+spin = "0.5.2"
 
-[profile.dev]
-panic = "abort"
-
-[profile.release]
-panic = "abort"
+[dependencies.lazy_static]
+version = "1.0"
+features = ["spin_no_std"]
 
 [[bin]]
 name = "blog_os"

README.md

@@ -1,25 +1,61 @@
-# Blog OS (A Freestanding Rust Binary)
+# Blog OS (VGA Text Mode)
 
-[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-01)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-01)
+[![Build Status](https://github.com/phil-opp/blog_os/workflows/Code/badge.svg?branch=post-03)](https://github.com/phil-opp/blog_os/actions?query=workflow%3A%22Code%22+branch%3Apost-03)
 
-This repository contains the source code for the [A Freestanding Rust Binary][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
+This repository contains the source code for the [VGA Text Mode][post] post of the [Writing an OS in Rust](https://os.phil-opp.com) series.
 
-[post]: https://os.phil-opp.com/freestanding-rust-binary/
+[post]: https://os.phil-opp.com/vga-text-mode/
 
 **Check out the [master branch](https://github.com/phil-opp/blog_os) for more information.**
 
 ## Building
 
-To build the project on Linux, run:
+This project requires a nightly version of Rust because it uses some unstable features. At least nightly _2020-07-15_ is required for building. You might need to run `rustup update nightly --force` to update to the latest nightly even if some components such as `rustfmt` are missing it.
+
+You can build the project by running:
 
 ```
-cargo rustc -- -Clink-arg=-nostartfiles
+cargo build
 ```
 
-The entry point and the build command differ slightly on macOS and Windows. See the [post] for more information.
+To create a bootable disk image from the compiled kernel, you need to install the [`bootimage`] tool:
+
+[`bootimage`]: https://github.com/rust-osdev/bootimage
+
+```
+cargo install bootimage
+```
+
+After installing, you can create the bootable disk image by running:
+
+```
+cargo bootimage
+```
+
+This creates a bootable disk image in the `target/x86_64-blog_os/debug` directory.
 
 Please file an issue if you have any problems.
 
+## Running
+
+You can run the disk image in [QEMU] through:
+
+[QEMU]: https://www.qemu.org/
+
+```
+cargo run
+```
+
+[QEMU] and the [`bootimage`] tool need to be installed for this.
+
+You can also write the image to an USB stick for booting it on a real machine. On Linux, the command for this is:
+
+```
+dd if=target/x86_64-blog_os/debug/bootimage-blog_os.bin of=/dev/sdX && sync
+```
+
+Where `sdX` is the device name of your USB stick. **Be careful** to choose the correct device name, because everything on that device is overwritten.
+
 ## License
 
 Licensed under either of

rust-toolchain

@@ -0,0 +1 @@
+nightly

src/main.rs

@@ -3,13 +3,18 @@
 
 use core::panic::PanicInfo;
 
+mod vga_buffer;
+
 #[unsafe(no_mangle)]
 pub extern "C" fn _start() -> ! {
+    println!("Hello World{}", "!");
+
     loop {}
 }
 
 /// This function is called on panic.
 #[panic_handler]
-fn panic(_info: &PanicInfo) -> ! {
+fn panic(info: &PanicInfo) -> ! {
+    println!("{}", info);
     loop {}
 }

src/vga_buffer.rs

@@ -0,0 +1,171 @@
+use core::fmt;
+use lazy_static::lazy_static;
+use spin::Mutex;
+use volatile::Volatile;
+
+lazy_static! {
+    /// A global `Writer` instance that can be used for printing to the VGA text buffer.
+    ///
+    /// Used by the `print!` and `println!` macros.
+    pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {
+        column_position: 0,
+        color_code: ColorCode::new(Color::Yellow, Color::Black),
+        buffer: unsafe { &mut *(0xb8000 as *mut Buffer) },
+    });
+}
+
+/// The standard color palette in VGA text mode.
+#[allow(dead_code)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(u8)]
+pub enum Color {
+    Black = 0,
+    Blue = 1,
+    Green = 2,
+    Cyan = 3,
+    Red = 4,
+    Magenta = 5,
+    Brown = 6,
+    LightGray = 7,
+    DarkGray = 8,
+    LightBlue = 9,
+    LightGreen = 10,
+    LightCyan = 11,
+    LightRed = 12,
+    Pink = 13,
+    Yellow = 14,
+    White = 15,
+}
+
+/// A combination of a foreground and a background color.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(transparent)]
+struct ColorCode(u8);
+
+impl ColorCode {
+    /// Create a new `ColorCode` with the given foreground and background colors.
+    fn new(foreground: Color, background: Color) -> ColorCode {
+        ColorCode((background as u8) << 4 | (foreground as u8))
+    }
+}
+
+/// A screen character in the VGA text buffer, consisting of an ASCII character and a `ColorCode`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(C)]
+struct ScreenChar {
+    ascii_character: u8,
+    color_code: ColorCode,
+}
+
+/// The height of the text buffer (normally 25 lines).
+const BUFFER_HEIGHT: usize = 25;
+/// The width of the text buffer (normally 80 columns).
+const BUFFER_WIDTH: usize = 80;
+
+/// A structure representing the VGA text buffer.
+#[repr(transparent)]
+struct Buffer {
+    chars: [[Volatile<ScreenChar>; BUFFER_WIDTH]; BUFFER_HEIGHT],
+}
+
+/// A writer type that allows writing ASCII bytes and strings to an underlying `Buffer`.
+///
+/// Wraps lines at `BUFFER_WIDTH`. Supports newline characters and implements the
+/// `core::fmt::Write` trait.
+pub struct Writer {
+    column_position: usize,
+    color_code: ColorCode,
+    buffer: &'static mut Buffer,
+}
+
+impl Writer {
+    /// Writes an ASCII byte to the buffer.
+    ///
+    /// Wraps lines at `BUFFER_WIDTH`. Supports the `\n` newline character.
+    pub fn write_byte(&mut self, byte: u8) {
+        match byte {
+            b'\n' => self.new_line(),
+            byte => {
+                if self.column_position >= BUFFER_WIDTH {
+                    self.new_line();
+                }
+
+                let row = BUFFER_HEIGHT - 1;
+                let col = self.column_position;
+
+                let color_code = self.color_code;
+                self.buffer.chars[row][col].write(ScreenChar {
+                    ascii_character: byte,
+                    color_code,
+                });
+                self.column_position += 1;
+            }
+        }
+    }
+
+    /// Writes the given ASCII string to the buffer.
+    ///
+    /// Wraps lines at `BUFFER_WIDTH`. Supports the `\n` newline character. Does **not**
+    /// support strings with non-ASCII characters, since they can't be printed in the VGA text
+    /// mode.
+    fn write_string(&mut self, s: &str) {
+        for byte in s.bytes() {
+            match byte {
+                // printable ASCII byte or newline
+                0x20..=0x7e | b'\n' => self.write_byte(byte),
+                // not part of printable ASCII range
+                _ => self.write_byte(0xfe),
+            }
+        }
+    }
+
+    /// Shifts all lines one line up and clears the last row.
+    fn new_line(&mut self) {
+        for row in 1..BUFFER_HEIGHT {
+            for col in 0..BUFFER_WIDTH {
+                let character = self.buffer.chars[row][col].read();
+                self.buffer.chars[row - 1][col].write(character);
+            }
+        }
+        self.clear_row(BUFFER_HEIGHT - 1);
+        self.column_position = 0;
+    }
+
+    /// Clears a row by overwriting it with blank characters.
+    fn clear_row(&mut self, row: usize) {
+        let blank = ScreenChar {
+            ascii_character: b' ',
+            color_code: self.color_code,
+        };
+        for col in 0..BUFFER_WIDTH {
+            self.buffer.chars[row][col].write(blank);
+        }
+    }
+}
+
+impl fmt::Write for Writer {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_string(s);
+        Ok(())
+    }
+}
+
+/// Like the `print!` macro in the standard library, but prints to the VGA text buffer.
+#[macro_export]
+macro_rules! print {
+    ($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));
+}
+
+/// Like the `println!` macro in the standard library, but prints to the VGA text buffer.
+#[macro_export]
+macro_rules! println {
+    () => ($crate::print!("\n"));
+    ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
+}
+
+/// Prints the given formatted string to the VGA text buffer through the global `WRITER` instance.
+#[doc(hidden)]
+pub fn _print(args: fmt::Arguments) {
+    use core::fmt::Write;
+    WRITER.lock().write_fmt(args).unwrap();
+}

x86_64-blog_os.json

@@ -0,0 +1,16 @@
+{
+    "llvm-target": "x86_64-unknown-none",
+    "data-layout": "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128",
+    "arch": "x86_64",
+    "target-endian": "little",
+    "target-pointer-width": 64,
+    "target-c-int-width": 32,
+    "os": "none",
+    "executables": true,
+    "linker-flavor": "ld.lld",
+    "linker": "rust-lld",
+    "panic-strategy": "abort",
+    "disable-redzone": true,
+    "features": "-mmx,-sse,+soft-float",
+    "rustc-abi": "x86-softfloat"
+  }