From f912dfa506c8a576b5b6b6b3c20eb8aa06c9067d Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Sun, 6 Dec 2015 14:58:43 +0100
Subject: [PATCH] Improve huge_page closure

---
 src/memory/paging/translate.rs | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/src/memory/paging/translate.rs b/src/memory/paging/translate.rs
index 97d8b58d..05a3fcb4 100644
--- a/src/memory/paging/translate.rs
+++ b/src/memory/paging/translate.rs
@@ -15,25 +15,31 @@ fn translate_page(page: Page) -> Option<Frame> {
     let huge_page = || {
         p4.next_table(page.p4_index())
           .and_then(|p3| {
+              let p3_entry = &p3[page.p3_index()];
               // 1GiB page?
-              if p3[page.p3_index()].flags().contains(HUGE_PAGE | PRESENT) {
-                  let start_frame_number = p3[page.p3_index()].pointed_frame().unwrap().number;
-                  // address must be 1GiB aligned
-                  assert!(start_frame_number % (ENTRY_COUNT * ENTRY_COUNT) == 0);
-                  return Some(start_frame_number + page.p2_index() * ENTRY_COUNT + page.p1_index());
+              if let Some(start_frame) = p3_entry.pointed_frame() {
+                  if p3_entry.flags().contains(HUGE_PAGE) {
+                      // address must be 1GiB aligned
+                      assert!(start_frame.number % (ENTRY_COUNT * ENTRY_COUNT) == 0);
+                      return Some(Frame {
+                          number: start_frame.number + page.p2_index() * ENTRY_COUNT +
+                                  page.p1_index(),
+                      });
+                  }
               }
               if let Some(p2) = p3.next_table(page.p3_index()) {
+                  let p2_entry = &p2[page.p2_index()];
                   // 2MiB page?
-                  if p2[page.p2_index()].flags().contains(HUGE_PAGE | PRESENT) {
-                      let start_frame_number = p2[page.p2_index()].pointed_frame().unwrap().number;
-                      // address must be 2MiB aligned
-                      assert!(start_frame_number % ENTRY_COUNT == 0);
-                      return Some(start_frame_number + page.p1_index());
+                  if let Some(start_frame) = p2_entry.pointed_frame() {
+                      if p2_entry.flags().contains(HUGE_PAGE) {
+                          // address must be 2MiB aligned
+                          assert!(start_frame.number % ENTRY_COUNT == 0);
+                          return Some(Frame { number: start_frame.number + page.p1_index() });
+                      }
                   }
               }
               None
           })
-          .map(|start_frame_number| Frame { number: start_frame_number })
     };
 
     p4.next_table(page.p4_index())