From db928db0b54e8495ae017d63932e5d8c39b29dda Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Thu, 31 Dec 2015 18:25:13 +0100
Subject: [PATCH] Unmap the old P4 page to create a basic guard page for the
 kernel stack

---
 src/memory/paging/mod.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/memory/paging/mod.rs b/src/memory/paging/mod.rs
index d3c906e3..54c4ef1f 100644
--- a/src/memory/paging/mod.rs
+++ b/src/memory/paging/mod.rs
@@ -223,4 +223,8 @@ pub fn remap_the_kernel<A>(allocator: &mut A, boot_info: &BootInformation)
 
     let old_table = active_table.switch(new_table);
     println!("NEW TABLE!!!");
+
+    let old_p4_page = Page::containing_address(old_table.p4_frame.start_address());
+    active_table.unmap(old_p4_page, allocator);
+    println!("guard page at {:#x}", old_p4_page.start_address());
 }