Reorganize kernel memory mappings

arch/x86_64/src/memory/area_frame_allocator.rs

@@ -76,6 +76,6 @@ impl FrameAllocator for AreaFrameAllocator {
     }
 
     fn deallocate_frame(&mut self, frame: Frame) {
-        //println!("Leak frame: {:?}", frame);
+        //panic!("AreaFrameAllocator::deallocate_frame: not supported: {:?}", frame);
     }
 }

arch/x86_64/src/memory/bitmap_allocator.rs

@@ -0,0 +1,39 @@
+use super::AreaFrameAllocator;
+
+const BITMAP_RESERVED: usize = 0;
+const BITMAP_FREE: usize = 1;
+const BITMAP_USED: usize = 2;
+
+pub struct BitmapAllocator {
+    bitmap: &'static mut [u8]
+}
+
+impl BitmapAllocator {
+    pub fn new(area_frame_allocator: AreaFrameAllocator) -> BitmapAllocator {
+        BitmapAllocator {
+            bitmap: &mut []
+        }
+    }
+}
+
+impl FrameAllocator for BitmapAllocator {
+    fn allocate_frame(&mut self) -> Option<Frame> {
+        let mut i = 0;
+        while i < self.bitmap.len() {
+            if self.bitmap[i] == BITMAP_FREE {
+                self.bitmap[i] = BITMAP_USED;
+                return Some(Frame::containing_address(PhysicalAddress::new(i * 4096)));
+            }
+        }
+        None
+    }
+
+    fn deallocate_frame(&mut self, frame: Frame) {
+        let i = frame.starting_address().get()/4096;
+        if i < self.bitmap.len() && self.bitmap[i] == BITMAP_USED {
+            self.bitmap[i] = BITMAP_FREE;
+        } else {
+            panic!("BitmapAllocator::deallocate_frame: unowned frame {:?}", frame);
+        }
+    }
+}

arch/x86_64/src/memory/mod.rs

@@ -3,11 +3,11 @@
 
 pub use paging::{PAGE_SIZE, PhysicalAddress};
 
-use self::area_frame_alloc::AreaFrameAllocator;
+use self::area_frame_allocator::AreaFrameAllocator;
 
 use spin::Mutex;
 
-pub mod area_frame_alloc;
+pub mod area_frame_allocator;
 
 /// The current memory map. It's size is maxed out to 512 entries, due to it being
 /// from 0x500 to 0x5000 (800 is the absolute total)