From 4e817cecfa7328af34fb96db7f052352737cd07e Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Wed, 16 Oct 2024 20:41:17 +0200
Subject: kernel: Add RSOD(red screen of death)

This is not useful since 99% of the time I will have access to the
serial output. But it does look cool.
---
 kernel/drivers/vbe.c | 38 ++++++++++++++++++++++++++++++++++++++
 kernel/drivers/vbe.h |  2 ++
 2 files changed, 40 insertions(+)

(limited to 'kernel/drivers')

diff --git a/kernel/drivers/vbe.c b/kernel/drivers/vbe.c
index 05edfb8..9271867 100644
--- a/kernel/drivers/vbe.c
+++ b/kernel/drivers/vbe.c
@@ -1,5 +1,6 @@
 #include <assert.h>
 #include <drivers/vbe.h>
+#include <fonts.h>
 #include <fs/devfs.h>
 #include <fs/vfs.h>
 #include <mmu.h>
@@ -24,6 +25,43 @@ struct DISPLAY_INFO {
 
 struct DISPLAY_INFO vbe_info;
 
+#define place_pixel_pos(_p, _pos)                                              \
+  { *(u32 *)((u32 *)framebuffer + _pos) = _p; }
+
+static int get_bitmap_value(const unsigned char bitmap[], int i) {
+  int array_index = i / 8;
+  int byte_index = i % 8;
+  int rc = (bitmap[array_index] >> byte_index) & 0x1;
+  return rc;
+}
+
+void vbe_drawfont(u32 px, u32 py, const u8 c) {
+  u32 x, y;
+  x = px;
+  y = py;
+  if (px + 8 > framebuffer_width) {
+    return;
+  }
+  if (py + 8 > framebuffer_height) {
+    return;
+  }
+  const unsigned char *bitmap = font8x8_basic[c];
+  for (int i = 0; i < 8 * 8; i++) {
+    u32 pos = x + y * framebuffer_width;
+    if (get_bitmap_value(bitmap, i)) {
+      place_pixel_pos(0xFFFFFF, pos);
+    }
+    x++;
+    if (x >= 8 + px) {
+      y++;
+      x = px;
+    }
+    if (y > py + 8) {
+      break;
+    }
+  }
+}
+
 int display_driver_init(multiboot_info_t *mbi) {
   assert(CHECK_FLAG(mbi->flags, 12));
   framebuffer_width = mbi->framebuffer_width;
diff --git a/kernel/drivers/vbe.h b/kernel/drivers/vbe.h
index 369f384..c0f6c42 100644
--- a/kernel/drivers/vbe.h
+++ b/kernel/drivers/vbe.h
@@ -1,6 +1,8 @@
 #ifndef VBE_H
 #define VBE_H
 #include <multiboot.h>
+
+void vbe_drawfont(u32 px, u32 py, const u8 c);
 int display_driver_init(multiboot_info_t *mb);
 void display_driver_cross(multiboot_info_t *mbi);
 void add_vbe_device(void);
-- 
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