add VGA support

src/arch/x86/kernel/vga.rs

@@ -0,0 +1,129 @@
+use core::fmt;
+use spin::Mutex;
+use x86::io::*;
+
+const CRT_CONTROLLER_ADDRESS_PORT: u16 = 0x3D4;
+const CRT_CONTROLLER_DATA_PORT: u16 = 0x3D5;
+const CURSOR_START_REGISTER: u8 = 0x0A;
+const CURSOR_DISABLE: u8 = 0x20;
+
+const ATTRIBUTE_BLACK: u8 = 0x00;
+const ATTRIBUTE_LIGHTGREY: u8 = 0x07;
+const COLS: usize = 80;
+const ROWS: usize = 25;
+const VGA_BUFFER_ADDRESS: u64 = 0xB8000;
+
+pub(crate) static VGA_SCREEN: Mutex<VgaScreen> = Mutex::new(VgaScreen::new());
+
+#[derive(Clone, Copy)]
+#[repr(C, packed)]
+pub(crate) struct VgaCharacter {
+	character: u8,
+	attribute: u8,
+}
+
+impl VgaCharacter {
+	const fn new(character: u8, attribute: u8) -> Self {
+		Self {
+			character,
+			attribute,
+		}
+	}
+}
+
+pub(crate) struct VgaScreen {
+	buffer: *mut [[VgaCharacter; COLS]; ROWS],
+	current_col: usize,
+	current_row: usize,
+	is_initialized: bool,
+}
+
+impl VgaScreen {
+	const fn new() -> Self {
+		Self {
+			buffer: VGA_BUFFER_ADDRESS as *mut _,
+			current_col: 0,
+			current_row: 0,
+			is_initialized: false,
+		}
+	}
+
+	fn init(&mut self) {
+		// Disable the cursor.
+		unsafe {
+			outb(CRT_CONTROLLER_ADDRESS_PORT, CURSOR_START_REGISTER);
+			outb(CRT_CONTROLLER_DATA_PORT, CURSOR_DISABLE);
+		}
+
+		// Clear the screen.
+		for r in 0..ROWS {
+			self.clear_row(r);
+		}
+
+		// Initialization done!
+		self.is_initialized = true;
+	}
+
+	#[inline]
+	fn clear_row(&mut self, row: usize) {
+		// Overwrite this row by a bogus character in black.
+		for c in 0..COLS {
+			unsafe {
+				(*self.buffer)[row][c] = VgaCharacter::new(0, ATTRIBUTE_BLACK);
+			}
+		}
+	}
+
+	fn write_byte(&mut self, byte: u8) {
+		if !self.is_initialized {
+			return;
+		}
+
+		// Move to the next row if we have a newline character or hit the end of a column.
+		if byte == b'\n' || self.current_col == COLS {
+			self.current_col = 0;
+			self.current_row += 1;
+		}
+
+		// Check if we have hit the end of the screen rows.
+		if self.current_row == ROWS {
+			// Shift all rows up by one line, removing the oldest visible screen row.
+			for r in 1..ROWS {
+				for c in 0..COLS {
+					unsafe {
+						(*self.buffer)[r - 1][c] = (*self.buffer)[r][c];
+					}
+				}
+			}
+
+			// Clear the last screen row and write to it next time.
+			self.clear_row(ROWS - 1);
+			self.current_row = ROWS - 1;
+		}
+
+		if byte != b'\n' {
+			// Put our character into the VGA screen buffer and advance the column counter.
+			unsafe {
+				(*self.buffer)[self.current_row][self.current_col] =
+					VgaCharacter::new(byte, ATTRIBUTE_LIGHTGREY);
+			}
+			self.current_col += 1;
+		}
+	}
+}
+
+unsafe impl Send for VgaScreen {}
+
+impl fmt::Write for VgaScreen {
+	fn write_str(&mut self, s: &str) -> fmt::Result {
+		for &b in s.as_bytes() {
+			self.write_byte(b);
+		}
+
+		Ok(())
+	}
+}
+
+pub(crate) fn init() {
+	VGA_SCREEN.lock().init();
+}