From 14845124cf5d4fb42a04cb1262b32bd3d00f45f8 Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Mon, 23 Dec 2024 22:51:52 +0100
Subject: mbr: rm->pm, then jump into zig

---
 x86-bare-metal/mbr-palette/zmbr.zig | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 x86-bare-metal/mbr-palette/zmbr.zig

(limited to 'x86-bare-metal/mbr-palette/zmbr.zig')

diff --git a/x86-bare-metal/mbr-palette/zmbr.zig b/x86-bare-metal/mbr-palette/zmbr.zig
new file mode 100644
index 0000000..947cd06
--- /dev/null
+++ b/x86-bare-metal/mbr-palette/zmbr.zig
@@ -0,0 +1,29 @@
+const COLS = 320;
+const ROWS = 200;
+
+/// Draw the color palette.
+/// One color per column, remaining columns are drawn black.
+fn draw_palette(video: []u8) void {
+    for (0..ROWS) |r| {
+        for (0..COLS) |c| {
+            if (c < 256) {
+                video[COLS * r + c] = @truncate(c);
+            } else {
+                video[COLS * r + c] = 0;
+            }
+        }
+    }
+}
+
+// kmain should be "callconv(.naked)", once issue is fixed.
+// https://github.com/ziglang/zig/issues/18183
+export fn kmain() noreturn {
+    // Take a slice to 256-color VGA video memory (mode 13h graphic mode).
+    const video: []u8 = @as([*]u8, @ptrFromInt(0xA0000))[0 .. COLS * ROWS];
+
+    draw_palette(video);
+
+    while (true) {
+        asm volatile ("hlt");
+    }
+}
-- 
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