Add HULK header; map virtual memory for HULK bss section

src/hulk/hulk.d

@@ -3,16 +3,24 @@
  */
 module hulk.hulk;
 
+import hulk.header;
 import hulk.bootinfo;
 import hos.memory;
 import ldc.attributes;
 
+extern extern(C) __gshared ubyte _hulk_total_size;
+
+@(ldc.attributes.section(".hulk_header"))
+private __gshared Header hulk_header = {
+    &_hulk_total_size,
+    &hulk_start,
+};
+
 /**
  * HULK entry point.
  *
  * @param bootinfo Pointer to HULK boot information structure.
  */
-@(ldc.attributes.section(".hulk_start"))
 extern(C) void hulk_start(ulong rdi, ulong rsi, ulong rdx, BootInfo * bootinfo)
 {
     for (size_t y = 100u; y < 120u; y++)