From ff81b5438f280a59ca1825bfdf120d8f256bd154 Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Sat, 7 Oct 2023 17:15:31 +0200
Subject: x86_64: implement very simple VGA text output

---
 source/kernel/arch/x86_64/src/entry.cpp |  9 ++++-----
 source/kernel/arch/x86_64/src/vga.cpp   | 30 ++++++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 5 deletions(-)
 create mode 100644 source/kernel/arch/x86_64/src/vga.cpp

(limited to 'source/kernel/arch/x86_64/src')

diff --git a/source/kernel/arch/x86_64/src/entry.cpp b/source/kernel/arch/x86_64/src/entry.cpp
index 2d4e7fb..fd9d9d0 100644
--- a/source/kernel/arch/x86_64/src/entry.cpp
+++ b/source/kernel/arch/x86_64/src/entry.cpp
@@ -1,10 +1,9 @@
-namespace teachos
+#include "kernel/vga.hpp"
+
+namespace teachos::kernel
 {
   extern "C" auto kernel_main() -> void
   {
-    while (true)
-    {
-      asm volatile("nop");
-    }
+    vga::write("TeachOS is starting up...", static_cast<std::byte>(0x4f));
   }
 }  // namespace teachos
diff --git a/source/kernel/arch/x86_64/src/vga.cpp b/source/kernel/arch/x86_64/src/vga.cpp
new file mode 100644
index 0000000..d25eaa5
--- /dev/null
+++ b/source/kernel/arch/x86_64/src/vga.cpp
@@ -0,0 +1,30 @@
+#include "kernel/vga.hpp"
+
+#include "boot/asm_pointer.hpp"
+#include "boot/pointers.hpp"
+
+#include <string_view>
+#include <algorithm>
+
+namespace teachos::kernel::vga
+{
+
+  namespace
+  {
+    auto constinit text_buffer_pointer = boot::asm_pointer{boot::vga_buffer_pointer};
+
+    auto write(char character, std::byte color) -> void
+    {
+      auto & p = *text_buffer_pointer;
+      (*p++) = static_cast<std::byte>(character);
+      (*p++) = color;
+    };
+  }  // namespace
+
+  auto write(std::string_view text, std::byte color) -> void {
+    std::ranges::for_each(text, [&](auto character) {
+        write(character, color);
+    });
+  }
+
+}  // namespace teachos::kernel
\ No newline at end of file
-- 
cgit v1.2.3