Enable interrupts and halt CPU

src/hos/cpu.d

@@ -5,6 +5,16 @@ void cli()
     __asm("cli", "");
 }
 
+void sti()
+{
+    __asm("sti", "");
+}
+
+void hlt()
+{
+    __asm("hlt", "");
+}
+
 ulong read_cr0()
 {
     return __asm!ulong("mov %cr0, %rax", "={rax}");

src/hulk/hulk.d

@@ -16,6 +16,7 @@ import hulk.pci;
 import hulk.gdt;
 import hulk.idt;
 import hos.cpu;
+import ldc.llvmasm;
 
 extern extern(C) __gshared ubyte _hulk_total_size;
 
@@ -46,8 +47,10 @@ void hulk_start()
 
     hippo.initialize(&hulk_header);
     pci.initialize();
+    sti();
 
     for (;;)
     {
+        hlt();
     }
 }