Add a debug output utility.

zion/CMakeLists.txt

@@ -1,6 +1,12 @@
 add_executable(zion
+  debug/debug.cpp
   zion.cpp)
 
+target_include_directories(zion
+  PRIVATE
+  ${CMAKE_CURRENT_SOURCE_DIR}
+  )
+
 # -c -- Don't run the linker.
 # -nostdlib -- Don't include the standard library.
 # -mabi=sysv -- Explicitly specify the ABI since we will rely on it.

zion/debug/debug.cpp

@@ -0,0 +1,13 @@
+#include "debug/debug.h"
+
+#include "common/port.h"
+
+#define COM1 0x3f8
+
+void dbgln(const char* str) {
+  while (*str != 0) {
+    outb(COM1, *str);
+    str++;
+  }
+  outb(COM1, '\n');
+}

zion/debug/debug.h

@@ -0,0 +1,3 @@
+#pragma once
+
+void dbgln(const char *str);

zion/zion.cpp

@@ -1,11 +1,9 @@
 #include <stdint.h>
 
-#include "common/port.h"
+#include "debug/debug.h"
-
-#define COM1 0x3f8
 
 extern "C" void zion() {
-  outb(COM1, 'a');
+  dbgln("Hello World!");
 
   while (1)
     ;