Finish basics of new paging module

src/memory/paging/entry.rs

@@ -0,0 +1,41 @@
+use memory::Frame;
+
+pub struct Entry(u64);
+
+impl Entry {
+    pub fn unused(&self) -> bool {
+        self.0 == 0
+    }
+
+    pub fn set_unused(&mut self) {
+        self.0 = 0;
+    }
+
+    pub fn flags(&self) -> EntryFlags {
+        EntryFlags::from_bits_truncate(self.0)
+    }
+
+    pub fn pointed_frame(&self) -> Frame {
+        Frame { number: ((self.0 & 0x000fffff_fffff000) >> 12) as usize }
+    }
+
+    pub fn set(&mut self, frame: Frame, flags: EntryFlags) {
+        let frame_addr = (frame.number << 12) & 0x000fffff_fffff000;
+        self.0 = (frame_addr as u64) | flags.bits();
+    }
+}
+
+bitflags! {
+    flags EntryFlags: u64 {
+        const PRESENT =         1 << 0,
+        const WRITABLE =        1 << 1,
+        const USER_ACCESSIBLE = 1 << 2,
+        const WRITE_THROUGH =   1 << 3,
+        const NO_CACHE =        1 << 4,
+        const ACCESSED =        1 << 5,
+        const DIRTY =           1 << 6,
+        const HUGE_PAGE =       1 << 7,
+        const GLOBAL =          1 << 8,
+        const NO_EXECUTE =      1 << 63,
+    }
+}