Model page table entries

Cargo.toml

@@ -12,3 +12,7 @@ spin = "0.3.4"
 
 [dependencies.multiboot2]
 git = "https://github.com/phil-opp/multiboot2-elf64"
+
+[dependencies.bitflags]
+git = "https://github.com/phil-opp/bitflags.git"
+branch = "no_std"

src/lib.rs

@@ -19,6 +19,8 @@
 extern crate rlibc;
 extern crate spin;
 extern crate multiboot2;
+#[macro_use]
+extern crate bitflags;
 
 #[macro_use]
 mod vga_buffer;

src/memory/mod.rs

@@ -1,4 +1,5 @@
 pub use self::area_frame_allocator::AreaFrameAllocator;
+use self::paging::PhysicalAddress;
 
 mod area_frame_allocator;
 mod paging;
@@ -14,6 +15,10 @@ impl Frame {
     fn containing_address(address: usize) -> Frame {
         Frame { number: address / PAGE_SIZE }
     }
+
+    fn start_address(&self) -> PhysicalAddress {
+        self.number * PAGE_SIZE
+    }
 }
 
 pub trait FrameAllocator {

src/memory/paging/entry.rs

@@ -0,0 +1,45 @@
+use memory::Frame;
+
+pub struct Entry(u64);
+
+impl Entry {
+    pub fn is_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) -> Option<Frame> {
+        if self.flags().contains(PRESENT) {
+            Some(Frame::containing_address(self.0 as usize & 0x000fffff_fffff000))
+        } else {
+            None
+        }
+    }
+
+    pub fn set(&mut self, frame: Frame, flags: EntryFlags) {
+        assert!(frame.start_address() & !0x000fffff_fffff000 == 0);
+        self.0 = (frame.start_address() 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,
+    }
+}

src/memory/paging/mod.rs

@@ -1,3 +1,5 @@
+mod entry;
+
 const ENTRY_COUNT: usize = 512;
 
 pub type PhysicalAddress = usize;