1 files changed, 39 insertions, 0 deletions
diff --git a/x86-bare-metal/mbr-textmode/zmbr.zig b/x86-bare-metal/mbr-textmode/zmbr.zig
new file mode 100644
index 0000000..2d95249
--- /dev/null
+++ b/x86-bare-metal/mbr-textmode/zmbr.zig
@@ -0,0 +1,39 @@
+const COLS = 80;
+const ROWS = 25;
+
+/// Clear screen (all black).
+fn clear_screen(video: []u16) void {
+    for (video) |*ch| {
+        ch.* = 0;
+    }
+}
+
+/// Draw the color palette.
+fn draw_palette(video: []u16) void {
+    // Each framebuffer entry in text mode is 16bit wide.
+    //      [15] blink
+    //   [14:12] bg color (3 bit)
+    //   [11: 8] fg color (4 bit)
+    //   [ 7: 0] ascii character
+    //
+    // https://en.wikipedia.org/wiki/VGA_text_mode
+
+    // Print each bg / fg combination once.
+    for (video, 0..0x80) |*ch, i| {
+        ch.* = @as(u16, @truncate(i)) << 8 | 'a';
+    }
+}
+
+// kmain should be "callconv(.naked)", once issue is fixed.
+// https://github.com/ziglang/zig/issues/18183
+export fn kmain() noreturn {
+    // Take a slice to VGA video memory (mode 3h text mode 80x25).
+    const video: []u16 = @as([*]u16, @ptrFromInt(0xB8000))[0 .. COLS * ROWS];
+
+    clear_screen(video);
+    draw_palette(video);
+
+    while (true) {
+        asm volatile ("hlt");
+    }
+}