2024-03-27

.gitignore

@@ -1,4 +1,5 @@
-/kernel/target
+target
+/kernel/Cargo.lock
 /build
 /binutils
 /gcc

kernel/Cargo.toml

@@ -3,4 +3,8 @@ name = "kernel"
 version = "0.1.0"
 edition = "2021"
 
+[workspace]
+members = ["std"]
+
 [dependencies]
+std = { path = "std" }

kernel/src/main.rs

@@ -1,19 +1,13 @@
 #![no_std]
 #![no_main]
 
+use std::println;
+
 #[no_mangle]
 pub extern "C" fn kernel_main() -> ! {
-    let vga_buffer = 0xb8000 as *mut u8;
+    let a = 4;
-
+    println!("Hiii :3");
-    let string: &[u8] = b":3";
+    println!("{}", a);
-    for (i, &byte) in string.iter().enumerate() {
-        unsafe {
-            *vga_buffer.offset(i as isize * 2) = byte;
-            *vga_buffer.offset(i as isize * 2 + 1) = 0xf;
-        }
-    }
-
-
     loop {}
 }
 

kernel/std/Cargo.lock

@@ -3,5 +3,5 @@
 version = 3
 
 [[package]]
-name = "kernel"
+name = "std"
 version = "0.1.0"

kernel/std/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "std"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
+spin = "0.9.8"

kernel/std/src/lib.rs

@@ -0,0 +1,3 @@
+#![no_std]
+
+pub mod vga_buffer;

kernel/std/src/vga_buffer.rs

@@ -0,0 +1,132 @@
+use core::fmt::{self, Write};
+
+use lazy_static::lazy_static;
+use spin::Mutex;
+
+#[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,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(transparent)]
+pub struct ColorCode(u8);
+
+impl ColorCode {
+    pub fn new(foreground: Color, background: Color) -> ColorCode {
+        ColorCode((background as u8) << 4 | (foreground as u8))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(C)]
+struct ScreenChar {
+    ascii_character: u8,
+    color_code: ColorCode,
+}
+
+const BUFFER_HEIGHT: usize = 25;
+const BUFFER_WIDTH: usize = 80;
+
+#[repr(transparent)]
+struct Buffer {
+    chars: [[ScreenChar; BUFFER_WIDTH]; BUFFER_HEIGHT],
+}
+
+pub struct Writer {
+    col: usize,
+    row: usize,
+    buffer: &'static mut Buffer,
+}
+
+impl Writer {
+    pub fn write_byte(&mut self, byte: u8) {
+        self.write_byte_color(byte, ColorCode::new(Color::White, Color::Black));
+    }
+
+    pub fn write_byte_color(&mut self, byte: u8, color: ColorCode) {
+        match byte {
+            b'\n' => self.new_line(),
+            byte => {
+                if self.col >= BUFFER_WIDTH {
+                    self.new_line();
+                }
+
+                let row = self.row;
+                let col = self.col;
+
+                let color_code = color;
+                self.buffer.chars[row][col] = ScreenChar {
+                    ascii_character: byte,
+                    color_code,
+                };
+                self.col += 1;
+            }
+        }
+    }
+
+    pub fn write_string(&mut self, s: &str) {
+        self.write_string_color(s, ColorCode::new(Color::White, Color::Black));
+    }
+
+    pub fn write_string_color(&mut self, s: &str, color: ColorCode) {
+        for char in s.bytes() {
+            match char {
+                0x20..=0x7e | b'\n' => self.write_byte_color(char, color),
+                _ => self.write_byte(0xfe),
+            }
+        }
+    }
+
+    fn new_line(&mut self) {
+        self.row += 1;
+        self.col = 0;
+    }
+}
+
+impl fmt::Write for Writer {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_string(s);
+        Ok(())
+    }
+}
+
+lazy_static! {
+    pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {
+        col: 0,
+        row: 0,
+        buffer: unsafe { &mut *(0xB8000 as *mut Buffer) },
+    });
+}
+
+#[doc(hidden)]
+pub fn _print(args: fmt::Arguments) {
+    WRITER.lock().write_fmt(args).unwrap()
+}
+
+#[macro_export]
+macro_rules! print {
+    ($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));
+}
+
+#[macro_export]
+macro_rules! println {
+    () => ($crate::print!("\n"));
+    ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
+}

log/2024-03-27.md

@@ -0,0 +1,189 @@
+# VGA text
+Hello. Today I succesfully made a `println!` macro.
+
+## std
+To following conventions I decided to make a `std` library. To do this I made a workspace in `kernel/`.
+
+`kernel/Cargo.toml`
+```toml
+[package]
+name = "kernel"
+version = "0.1.0"
+edition = "2021"
+
+[workspace]
+members = ["std"]
+
+[dependencies]
+std = { path = "std" }
+```
+
+## lib.rs
+To not have one big spaghetti file I separated out all the individal modules into different files.
+`kernel/std/src/lib.rs`
+```rust
+#![no_std]
+
+pub mod vga_buffer;
+```
+
+## vga_buffer.rs
+First step for a VGA text driver is to be able to represent data.
+
+`kernel/std/src/lib.rs`
+```rust
+#[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,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(transparent)] // Store this as a u8
+pub struct ColorCode(u8);
+
+impl ColorCode {
+    pub fn new(foreground: Color, background: Color) -> ColorCode {
+        ColorCode((background as u8) << 4 | (foreground as u8))
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(C)] // Tells rust to store this like a struct in C, i.e. store this as 2 bytes
+struct ScreenChar {
+    ascii_character: u8,
+    color_code: ColorCode,
+}
+
+const BUFFER_HEIGHT: usize = 25;
+const BUFFER_WIDTH: usize = 80;
+
+#[repr(transparent)]
+struct Buffer {
+    chars: [[ScreenChar; BUFFER_WIDTH]; BUFFER_HEIGHT],
+}
+```
+
+Now I can represent the VGA text buffer. To write to this I want to make a writer struct that implements `fmt::Write`.
+```rust
+pub struct Writer {
+    col: usize,
+    row: usize,
+    buffer: &'static mut Buffer,
+}
+
+impl Writer {
+    pub fn write_byte(&mut self, byte: u8) {
+        self.write_byte_color(byte, ColorCode::new(Color::White, Color::Black));
+    }
+
+    pub fn write_byte_color(&mut self, byte: u8, color: ColorCode) {
+        match byte {
+            b'\n' => self.new_line(),
+            byte => {
+                if self.col >= BUFFER_WIDTH {
+                    self.new_line();
+                }
+
+                let row = self.row;
+                let col = self.col;
+
+                let color_code = color;
+                self.buffer.chars[row][col] = ScreenChar {
+                    ascii_character: byte,
+                    color_code,
+                };
+                self.col += 1;
+            }
+        }
+    }
+
+    pub fn write_string(&mut self, s: &str) {
+        self.write_string_color(s, ColorCode::new(Color::White, Color::Black));
+    }
+
+    pub fn write_string_color(&mut self, s: &str, color: ColorCode) {
+        for char in s.bytes() {
+            match char {
+                0x20..=0x7e | b'\n' => self.write_byte_color(char, color), // Ascii Character
+                _ => self.write_byte(0xfe), // Non ascii
+            }
+        }
+    }
+
+    fn new_line(&mut self) {
+        self.row += 1;
+        self.col = 0;
+    }
+}
+
+impl fmt::Write for Writer {
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+        self.write_string(s);
+        Ok(())
+    }
+}
+```
+
+The problem now becomes that I can create a `Writer` but I don't have a global position, so it will just overwrite what I wrote last time. To solve this I can use a static variable. But a static variable won't be mutable. This can be solved with `Mutex` in the spin crate and `lazy_static`.
+
+`kernel/std/Cargo.toml`
+```toml
+[package]
+name = "std"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+lazy_static = { version = "1.4.0", features = ["spin_no_std"] }
+spin = "0.9.8"
+```
+
+and to make a static variable I wrote (copied from [here](https://os.phil-opp.com/vga-text-mode/)) this
+```rust
+lazy_static! {
+    pub static ref WRITER: Mutex<Writer> = Mutex::new(Writer {
+        col: 0,
+        row: 0,
+        buffer: unsafe { &mut *(0xB8000 as *mut Buffer) },
+    });
+}
+```
+in `kernel/std/src/vga_buffer.rs`.
+
+Last step is just to add a function and 2 macros
+```rust
+#[doc(hidden)]
+pub fn _print(args: fmt::Arguments) {
+    WRITER.lock().write_fmt(args).unwrap()
+}
+
+#[macro_export]
+macro_rules! print {
+    ($($arg:tt)*) => ($crate::vga_buffer::_print(format_args!($($arg)*)));
+}
+
+#[macro_export]
+macro_rules! println {
+    () => ($crate::print!("\n"));
+    ($($arg:tt)*) => ($crate::print!("{}\n", format_args!($($arg)*)));
+}
+```
+
+Huge thanks to @phil-opp for [os.phil-opp.com](https://os.phil-opp.com/)
+