memory::paging::ActivePageTable: impl translation, mapping, unmapping

src/arch/x86_64/memory/paging/mod.rs

@@ -33,6 +33,127 @@ impl ActivePageTable {
             p4: Unique::new(table::P4),
         }
     }
+
+    fn p4(&self) -> &Table<Level4> {
+        unsafe { self.p4.as_ref() }
+    }
+
+    fn p4_mut(&mut self) -> &mut Table<Level4> {
+        unsafe { self.p4.as_mut() }
+    }
+
+    /// Translates a given virtual address to a physical address.
+    pub fn translate(&self, virtual_address: VirtualAddress) -> Option<PhysicalAddress> {
+        let offset = virtual_address % PAGE_SIZE; // offset into the frame
+        self.page_to_frame(Page::containing_address(virtual_address))
+            .map(|frame| frame.index * PAGE_SIZE + offset)
+    }
+
+    /// Translates a given virtual page to a physical frame.
+    fn page_to_frame(&self, page: Page) -> Option<Frame> {
+        use self::entry::HUGE_PAGE;
+
+        let p3 = self.p4().next_table(page.p4_index());
+
+        let handle_huge_page = || {
+            p3.and_then(|p3| {
+                let p3_entry = &p3[page.p3_index()];
+
+                // Is this a 1GiB page?
+                if let Some(start_frame) = p3_entry.pointed_frame() {
+                    if p3_entry.flags().contains(HUGE_PAGE) {
+                        // 1GiB pages must be 1GiB-aligned
+                        assert!(start_frame.index % (ENTRY_COUNT * ENTRY_COUNT) == 0,
+                            "1GiB hugepages must be 1GiB-aligned");
+
+                        return Some(Frame {
+                            index: start_frame.index
+                                + 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()];
+
+                    // Is this a 2MiB page?
+                    if let Some(start_frame) = p2_entry.pointed_frame() {
+                        if p2_entry.flags().contains(HUGE_PAGE) {
+                            // 2MiB pages must be 2MiB-aligned
+                            assert!(start_frame.index % ENTRY_COUNT == 0,
+                                "2MiB pages must be 2MiB-aligned");
+
+                            return Some(Frame {
+                                index: start_frame.index + page.p1_index(),
+                            });
+                        }
+                    }
+                }
+
+                // Didn't find a huge page
+                return 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(handle_huge_page)
+    }
+
+    /// Maps a virtual page to a physical frame.
+    pub fn map_to<A>(&mut self, page: Page, frame: Frame, flags: EntryFlags,
+                     allocator: &mut A)
+            where A: FrameAllocator {
+
+        let mut p3 = self.p4_mut().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(),
+            "Attempting to map Page->Frame but a P1 entry for this Page already exists!");
+        p1[page.p1_index()].set(frame, flags | PRESENT);
+    }
+
+    /// Maps a virtual page to a physical frame, automatically picking the frame.
+    pub fn map<A>(&mut self, page: Page, flags: EntryFlags, allocator: &mut A)
+            where A: FrameAllocator {
+
+        let frame = allocator.alloc_frame()
+            .expect("Attempted to allocate a frame to map to a page, but no frames are available!");
+        self.map_to(page, frame, flags, allocator);
+    }
+
+    /// Maps a physical frame to a page with the same address in virtual memory
+    pub fn identity_map<A>(&mut self, frame: Frame, flags: EntryFlags, allocator: &mut A)
+            where A: FrameAllocator {
+        let page = Page::containing_address(frame.start_address());
+        self.map_to(page, frame, flags, allocator);
+    }
+
+    /// Unmaps a virtual page.
+    fn unmap<A>(&mut self, page: Page, allocator: &mut A)
+            where A: FrameAllocator {
+        assert!(self.translate(page.start_address()).is_some(),
+            "Attempted to unmap a page which points to no physical address.");
+
+        let p1 = self.p4_mut()
+                     .next_table_mut(page.p4_index())
+                     .and_then(|p3| p3.next_table_mut(page.p3_index()))
+                     .and_then(|p2| p2.next_table_mut(page.p2_index()))
+                     .expect("Mapping code does not support huge pages.");
+        let frame = p1[page.p1_index()].pointed_frame().unwrap();
+        p1[page.p1_index()].set_unused();
+
+        use x86::shared::tlb;
+        unsafe {
+            tlb::flush(page.start_address());
+        }
+
+        // TODO free p(1,2,3) table if empty
+        // allocator.dealloc_frame(frame);
+    }
 }
 
 /// A representation of a virtual page.