diff --git a/Makefile b/Makefile
index b3163d4..559e148 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@ grub_cfg := $(boot_src)/grub.cfg
 assembly_source_files := $(wildcard $(boot_src)/*.asm)
 assembly_object_files := $(patsubst $(boot_src)/%.asm, \
 	build/arch/$(arch)/boot/%.o, $(assembly_source_files))
-qemu_opts := -cdrom $(iso) -smp 2 -serial stdio
+qemu_opts := -cdrom $(iso) -smp 2 -serial mon:stdio
 
 ifdef travis
 	test := 1
diff --git a/src/arch/x86_64/driver/apic/ioapic.rs b/src/arch/x86_64/driver/apic/ioapic.rs
index 0231ecd..e9ddc2d 100644
--- a/src/arch/x86_64/driver/apic/ioapic.rs
+++ b/src/arch/x86_64/driver/apic/ioapic.rs
@@ -12,13 +12,14 @@ use spin::Mutex;
 pub fn init(ioapic_id: u8)
 {
 	let mut ioapic = IOAPIC.lock();
-	assert!(ioapic.id() == ioapic_id, "ioapicinit: id isn't equal to ioapicid; not a MP");
+	assert!(ioapic.id() == ioapic_id, "ioapic.init: id isn't equal to ioapicid; not a MP");
 
 	// Mark all interrupts edge-triggered, active high, disabled,
 	// and not routed to any CPUs.
 	for i in 0.. ioapic.maxintr() + 1 {
 		ioapic.write_irq(i, DISABLED, 0);
 	}
+	debug!("ioapic: init end");
 }
 
 const IOAPIC_ADDRESS  : u32 = 0xFEC00000;   // Default physical address of IO APIC
@@ -80,6 +81,7 @@ impl IoApic {
 	}
 	pub fn enable(&mut self, irq: u8, cpunum: u8)
 	{
+		debug!("ioapic: enable irq {} @ cpu{}", irq, cpunum);
 		// Mark interrupt edge-triggered, active high,
 		// enabled, and routed to the given cpunum,
 		// which happens to be that cpu's APIC ID.
diff --git a/src/arch/x86_64/driver/apic/lapic.rs b/src/arch/x86_64/driver/apic/lapic.rs
index c4537db..0e05a68 100644
--- a/src/arch/x86_64/driver/apic/lapic.rs
+++ b/src/arch/x86_64/driver/apic/lapic.rs
@@ -3,8 +3,11 @@ extern {
 	fn lapicinit();	// must set `lapic` first
 }
 
-pub unsafe fn init(lapic_addr: *const ()) {
-	debug!("WARNING: lapic::init use C lib");	
-	lapic = lapic_addr;
-	lapicinit();
+pub fn init(lapic_addr: *const ()) {
+	debug!("WARNING: lapic::init use C lib");
+	unsafe {
+		lapic = lapic_addr;
+		lapicinit();
+	}
+	debug!("lapic: init end");
 }
\ No newline at end of file
diff --git a/src/arch/x86_64/driver/apic/mod.rs b/src/arch/x86_64/driver/apic/mod.rs
index 64ac839..a6c9ff3 100644
--- a/src/arch/x86_64/driver/apic/mod.rs
+++ b/src/arch/x86_64/driver/apic/mod.rs
@@ -3,7 +3,8 @@ pub use self::ioapic::IOAPIC;
 mod lapic;
 mod ioapic;
 
-pub unsafe fn init(lapic_addr: *const (), ioapic_id: u8) {
+pub fn init(lapic_addr: *const (), ioapic_id: u8) {
+	assert_has_not_been_called!("apic::init must be called only once");
 	self::lapic::init(lapic_addr);
 	self::ioapic::init(ioapic_id);
 }
\ No newline at end of file
diff --git a/src/arch/x86_64/driver/pic.rs b/src/arch/x86_64/driver/pic.rs
index 4674db5..5da828e 100644
--- a/src/arch/x86_64/driver/pic.rs
+++ b/src/arch/x86_64/driver/pic.rs
@@ -5,6 +5,8 @@ static MASTER: Mutex<Pic> = Mutex::new(Pic::new(0x20));
 static SLAVE: Mutex<Pic> = Mutex::new(Pic::new(0xA0));
 
 pub fn init() {
+    assert_has_not_been_called!("pic::init must be called only once");
+    
     let mut master = MASTER.lock();
     let mut slave = SLAVE.lock();
 
diff --git a/src/lib.rs b/src/lib.rs
index 452c1a4..6c4971c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -78,9 +78,9 @@ pub extern "C" fn rust_main(multiboot_information_address: usize) {
 
     memory_controller.map_page_identity(acpi.lapic_addr as usize);  // LAPIC
     memory_controller.map_page_identity(0xFEC00000);  // IOAPIC
-    unsafe{ arch::driver::apic::init(acpi.lapic_addr, acpi.ioapic_id); }
+    arch::driver::apic::init(acpi.lapic_addr, acpi.ioapic_id);
     
-    unsafe{ arch::driver::pic::init(); }
+    arch::driver::pic::init();
 
     test_end!();
 }