From dedf6e8959b51562f81687d44ccda9474712a625 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Thu, 13 Apr 2017 19:17:24 +0200
Subject: [PATCH] Add a map_to function

---
 src/memory/paging/mod.rs   | 16 +++++++++++++++-
 src/memory/paging/table.rs | 17 +++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/memory/paging/mod.rs b/src/memory/paging/mod.rs
index fcf39df..3e74077 100644
--- a/src/memory/paging/mod.rs
+++ b/src/memory/paging/mod.rs
@@ -1,4 +1,5 @@
-use memory::{PAGE_SIZE, Frame};
+use memory::{PAGE_SIZE, Frame, FrameAllocator};
+pub use self::entry::*;
 
 mod entry;
 mod table;
@@ -86,3 +87,16 @@ fn translate_page(page: Page) -> Option<Frame> {
       .and_then(|p1| p1[page.p1_index()].pointed_frame())
       .or_else(huge_page)
 }
+
+pub fn map_to<A>(page: Page, frame: Frame, flags: EntryFlags,
+                 allocator: &mut A)
+    where A: FrameAllocator
+{
+    let p4 = unsafe { &mut *table::P4 };
+    let mut p3 = p4.next_table_create(page.p4_index(), allocator);
+    let mut p2 = p3.next_table_create(page.p3_index(), allocator);
+    let mut p1 = p2.next_table_create(page.p2_index(), allocator);
+
+    assert!(p1[page.p1_index()].is_unused());
+    p1[page.p1_index()].set(frame, flags | PRESENT);
+}
diff --git a/src/memory/paging/table.rs b/src/memory/paging/table.rs
index 949c35a..8fecefe 100644
--- a/src/memory/paging/table.rs
+++ b/src/memory/paging/table.rs
@@ -1,5 +1,6 @@
 use core::marker::PhantomData;
 use core::ops::{Index, IndexMut};
+use memory::FrameAllocator;
 use memory::paging::entry::*;
 use memory::paging::ENTRY_COUNT;
 
@@ -38,6 +39,22 @@ impl<L> Table<L> where L: HierarchicalLevel {
         self.next_table_address(index)
             .map(|address| unsafe { &mut *(address as *mut _) })
     }
+
+    pub fn next_table_create<A>(&mut self,
+                                index: usize,
+                                allocator: &mut A)
+                                -> &mut Table<L::NextLevel>
+        where A: FrameAllocator
+    {
+        if self.next_table(index).is_none() {
+            assert!(!self.entries[index].flags().contains(HUGE_PAGE),
+                    "mapping code does not support huge pages");
+            let frame = allocator.allocate_frame().expect("no frames available");
+            self.entries[index].set(frame, PRESENT | WRITABLE);
+            self.next_table_mut(index).unwrap().zero();
+        }
+        self.next_table_mut(index).unwrap()
+    }
 }
 
 impl<L> Index<usize> for Table<L> where L: TableLevel {