diff --git a/risc_v/ch4/src/asm/trap.S b/risc_v/ch4/src/asm/trap.S
index 5123406..3ce8170 100644
--- a/risc_v/ch4/src/asm/trap.S
+++ b/risc_v/ch4/src/asm/trap.S
@@ -81,7 +81,7 @@ m_trap_vector:
 	.endr
 
 3:
-	# Go to C++
+	# Go to Rust
 	# usize trap_handler(mepc, mcause)
 	# trap_handler returns the new mepc
 	# via a0
@@ -182,7 +182,7 @@ s_trap_vector:
 	.endr
 
 3:
-	# Go to C++
+	# Go to Rust
 	# usize trap_handler(mepc, mcause)
 	# trap_handler returns the new mepc
 	# via a0
diff --git a/risc_v/ch4/src/lib.rs b/risc_v/ch4/src/lib.rs
index 4c7515e..fc329cb 100755
--- a/risc_v/ch4/src/lib.rs
+++ b/risc_v/ch4/src/lib.rs
@@ -255,7 +255,7 @@ extern "C" fn kinit() -> usize {
 	// space application requires services. Since the user space application
 	// only knows virtual addresses, we have to translate silently behind
 	// the scenes.
-	let p = 0x8005_7000 as usize;
+	let p = 0x0200_0000 as usize;
 	let m = page::virt_to_phys(&root, p).unwrap_or(0);
 	println!("Walk 0x{:x} = 0x{:x}", p, m);
 	// When we return from here, we'll go back to boot.S and switch into
@@ -298,6 +298,10 @@ extern "C" fn kmain() {
 		let sparkle_heart = String::from_utf8(sparkle_heart).unwrap();
 		println!("String = {}", sparkle_heart);
 	}
+	unsafe {
+		let val = 0x0200_0000 as *mut u32;
+		val.write_volatile(1);
+	}
 	// If we get here, the Box, vec, and String should all be freed since
 	// they go out of scope. This calls their "Drop" trait.
 	// Now see if we can read stuff:
diff --git a/risc_v/ch4/src/trap.rs b/risc_v/ch4/src/trap.rs
index b9cef5b..0343588 100755
--- a/risc_v/ch4/src/trap.rs
+++ b/risc_v/ch4/src/trap.rs
@@ -3,14 +3,26 @@
 // Stephen Marz
 // 10 October 2019
 
+extern "C" {
+	static KERNEL_TABLE: usize;
+}
+
 #[no_mangle]
 extern "C"
 fn s_trap(epc: usize, tval: usize, cause: usize) -> usize {
-	epc
+	println!("STRAP (cause: 0x{:x} @ 0x{:x})", cause, epc);
+	unsafe {
+		// Switch to kernel's page table.
+		//          table / 4096         Sv39
+		let satp = KERNEL_TABLE >> 12 | 8 << 60;
+		asm!("csrw satp, $0" :: "r"(satp));
+	}
+	epc + 4
 }
 
 #[no_mangle]
 extern "C"
 fn m_trap(epc: usize, tval: usize, cause: usize, hart: usize) -> usize {
-	epc
+	println!("MTRAP (cause: 0x{:x} @ 0x{:x})", cause, epc);
+	epc + 4
 }
\ No newline at end of file