fix(paging): translating addresses

src/memory/mod.rs

@@ -1,9 +1,9 @@
+mod paging;
+mod area_frame_allocator;
+
 pub use self::area_frame_allocator::AreaFrameAllocator;
 use self::paging::PhysicalAddress;
 
-mod area_frame_allocator;
-mod paging;
-
 pub const PAGE_SIZE: usize = 4096;
 
 #[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]

src/memory/paging/entry.rs

@@ -1,4 +1,5 @@
 use memory::PAGE_SIZE;
+use memory::Frame;
 
 pub struct Entry(u64);
 
@@ -26,7 +27,7 @@ impl Entry {
 	}
 
 	pub fn set (&mut self, frame: Frame, flags: EntryFlags) {
-		assert!(frame.start_address() & !x000fffff_fffff000 == 0);
+		assert!(frame.start_address() & !0x000fffff_fffff000 == 0);
 		self.0 = (frame.start_address() as u64) | flags.bits();
 	}
 }

src/memory/paging/mod.rs

@@ -1,8 +1,73 @@
+mod entry;
+mod table;
+
 use memory::PAGE_SIZE;
 use memory::Frame;
+pub use self::entry::*;
+use memory::FrameAllocator;
+use self::table::*;
 
 const ENTRY_COUNT: usize = 512;
 
+pub fn map_to<A>(page: Page, frame: Frame, flags: EntryFlags, allocator: &mut A)
+								where A: FrameAllocator
+{
+	let p4 = unsafe { &mut *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);
+}
+
+pub fn translate(virtual_address: VirtualAddress) -> Option<PhysicalAddress> {
+	let offset = virtual_address & PAGE_SIZE;
+	translate_page(Page::containing_address(virtual_address))
+								.map(|frame| frame.number * PAGE_SIZE + offset)
+}
+
+pub fn translate_page(page: Page) -> Option<Frame> {
+	use self::entry::HUGE_PAGE;
+
+	let p3 = unsafe { &*table::P4 }.next_table(page.p4_index());
+	let huge_page = || {
+		p3.and_then(|p3| {
+			let p3_entry = &p3[page.p3_index()];
+			
+			// 1GiB page?
+			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 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
+		})
+	};
+
+	p3.and_then(|p3| p3.next_table(page.p3_index()))
+	  .and_then(|p2| p2.next_table(page.p2_index()))
+		.and_then(|p1| p1[page.p1_index()].pointed_frame())
+		.or_else(huge_page)
+}
+
 pub type PhysicalAddress = usize;
 pub type VirtualAddress = usize;
 
@@ -10,6 +75,37 @@ pub struct Page {
 	number: usize,
 }
 
+impl Page {
+  pub fn containing_address(address: VirtualAddress) -> Page {
+	  assert!(address < 0x0000_8000_0000_0000 ||
+					  address >= 0xffff_8000_0000_0000,
+					  "invalid address: 0x{:x}", address);
+
+  	Page { number: address / PAGE_SIZE }
+  }
+
+	fn start_address(&self) -> usize {
+		self.number * PAGE_SIZE
+	}
+
+	fn p4_index(&self) -> usize {
+		(self.number >> 27) & 0o777
+	}
+
+	fn p3_index(&self) -> usize {
+		(self.number >> 18) & 0o777
+	}
+
+	fn p2_index(&self) -> usize {
+		(self.number >> 9) & 0o777
+	}
+
+	fn p1_index(&self) -> usize {
+		(self.number >> 0) & 0o777
+	}
+}
+
+/*
 pub struct Entry(u64);
 
 impl Entry {
@@ -55,3 +151,4 @@ bitflags! {
 		const NO_EXECUTE				 = 1 << 63,
 	}
 }
+*/

src/memory/paging/table.rs

@@ -1,5 +1,6 @@
 use memory::paging::entry::*;
 use memory::paging::ENTRY_COUNT;
+use memory::FrameAllocator;
 use core::ops::{Index, IndexMut};
 use core::marker::PhantomData;
 
@@ -7,7 +8,9 @@ pub const P4: *mut Table<Level4> = 0xffffffff_fffff000 as *mut _;
 
 pub trait TableLevel {}
 pub enum Level4 {}
+#[allow(dead_Code)]
 pub enum Level3 {}
+#[allow(dead_Code)]
 pub enum Level2 {}
 pub enum Level1 {}
 
@@ -16,18 +19,19 @@ impl TableLevel for Level3 {}
 impl TableLevel for Level2 {}
 impl TableLevel for Level1 {}
 
+
 pub trait HierarchicalLevel: TableLevel {
 	type NextLevel: TableLevel;
 }
 
 impl HierarchicalLevel for Level4 {
-	type NextLevel: Level3
+	type NextLevel = Level3;
 }
 impl HierarchicalLevel for Level3 {
-	type NextLevel: Level2
+	type NextLevel = Level2;
 }
 impl HierarchicalLevel for Level2 {
-	type NextLevel: Level1
+	type NextLevel = Level1;
 }
 
 pub struct Table<L: TableLevel> {
@@ -64,6 +68,23 @@ 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 {
@@ -80,10 +101,3 @@ impl<L> IndexMut<usize> for Table<L> where L: TableLevel {
 	}
 }
 
-fn test() {
-	let p4 = unsafe { &*P4 };
-	p4.next_table(4@)
-		.and_then(|p3| p3.next_table(1337))
-		.and_then(|p2| p2.next_table(0xdeadbeaf))
-		.and_then(|p1| p1.next_table(0xcafebabe))
-}