From 2a3ce863fd66643c3b70fb9c3ffa06df425d81b3 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Tue, 18 Apr 2017 12:33:53 +0200
Subject: [PATCH] Enable write protect bit to improve safety

---
 src/lib.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/lib.rs b/src/lib.rs
index 51d0295..847e2bc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -46,6 +46,7 @@ pub extern fn rust_main(multiboot_information_address: usize) {
         multiboot_end, memory_map_tag.memory_areas());
 
     enable_nxe_bit();
+    enable_write_protect_bit();
     memory::remap_the_kernel(&mut frame_allocator, boot_info);
     println!("It did not crash!");
 
@@ -62,6 +63,12 @@ fn enable_nxe_bit() {
     }
 }
 
+fn enable_write_protect_bit() {
+    use x86_64::registers::control_regs::{cr0, cr0_write, Cr0};
+
+    unsafe { cr0_write(cr0() | Cr0::WRITE_PROTECT) };
+}
+
 #[lang = "eh_personality"] extern fn eh_personality() {}
 
 #[lang = "panic_fmt"]