[wip] necessary modifications

nucleus/src/arch/aarch64/memory/mmu-experimental.rs

@@ -33,6 +33,7 @@ impl PageSize for Size1GiB {
 }
 
 /// Errors from mapping layer (@todo use anyhow/snafu? thiserror?)
+#[derive(Debug, Snafu)]
 pub enum TranslationError {
     NoPage,
 }
@@ -58,13 +59,14 @@ impl ActivePageTable {
         unsafe { self.l0.as_mut() }
     }
 
-    pub fn translate(&self, virtual_address: VirtAddr) -> Result<PhysAddr, TranslationError> {
-        let offset = virtual_address % Size4KiB::SIZE as usize; // @todo use the size of the last page of course
-        self.translate_page(Page::containing_address(virtual_address))
-            .map(|frame| frame.start_address() + offset)
-    }
+    // pub fn translate(&self, virtual_address: VirtAddr) -> Result<PhysAddr, TranslationError> {
+    //     let offset = virtual_address % Size4KiB::SIZE as usize; // @todo use the size of the last page of course
+    //     self.translate_page(Page::containing_address(virtual_address))?
+    //         .map(|frame| frame.start_address() + offset)
+    // }
 
     fn translate_page(&self, page: Page) -> Result<PhysFrame, TranslationError> {
+        // @todo translate only one level of hierarchy per impl function...
         let l1 = self.l0().next_table(u64::from(page.l0_index()) as usize);
         /*
                 let huge_page = || {
@@ -138,6 +140,8 @@ impl ActivePageTable {
     where
         A: FrameAllocator,
     {
+        // @todo fail mapping if table is not allocated, causing client to allocate and restart
+        // @todo problems described in preso - chicken&egg problem of allocating first allocations
         let frame = allocator.allocate_frame().expect("out of memory");
         self.map_to(page, frame, flags, allocator)
     }
@@ -172,18 +176,19 @@ impl ActivePageTable {
         // tlb::flush(VirtAddr(page.start_address()));
         // TODO free p(1,2,3) table if empty
         //allocator.deallocate_frame(frame);
+        // @todo do NOT deallocate frames either, but need to signal client that it's unused
     }
 }
 
 // Abstractions for page table entries.
 
 /// The error returned by the `PageTableEntry::frame` method.
-#[derive(Debug, Clone, Copy, PartialEq)]
+#[derive(Snafu, Debug, Clone, Copy, PartialEq)]
 pub enum FrameError {
     /// The entry does not have the `PRESENT` flag set, so it isn't currently mapped to a frame.
     FrameNotPresent,
     /// The entry has the `HUGE_PAGE` flag set. The `frame` method has a standard 4KiB frame
-    /// as return type, so a huge frame can't be returned.
+    /// as return type, so a huge frame can't be returned. @todo
     HugeFrame,
 }
 
@@ -265,17 +270,17 @@ impl fmt::Debug for PageTableEntry {
     }
 }*/
 
-impl<L> Table<L>
+impl<Level> Table<Level>
 where
-    L: HierarchicalLevel,
+    Level: HierarchicalLevel,
 {
-    pub fn next_table_create<A>(
+    pub fn next_table_create<Alloc>(
         &mut self,
         index: usize,
-        allocator: &mut A,
-    ) -> &mut Table<L::NextLevel>
+        allocator: &mut Alloc,
+    ) -> &mut Table<Level::NextLevel>
     where
-        A: FrameAllocator,
+        Alloc: FrameAllocator,
     {
         if self.next_table(index).is_none() {
             assert!(

nucleus/src/arch/aarch64/memory/mmu.rs

@@ -177,6 +177,13 @@ impl PageTableEntry {
     }
 }
 
+#[derive(Snafu, Debug)]
+enum PageTableError {
+    #[snafu(display("BlockDescriptor: Address is not 2 MiB aligned."))]
+    //"PageDescriptor: Address is not 4 KiB aligned."
+    NotAligned(&'static str),
+}
+
 /// A Level2 block descriptor with 2 MiB aperture.
 ///
 /// The output points to physical memory.
@@ -186,9 +193,9 @@ impl PageTableEntry {
     fn new_lvl2_block_descriptor(
         output_addr: usize,
         attribute_fields: AttributeFields,
-    ) -> Result<PageTableEntry, &'static str> {
+    ) -> Result<PageTableEntry, PageTableError> {
         if output_addr % Size2MiB::SIZE as usize != 0 {
-            return Err("BlockDescriptor: Address is not 2 MiB aligned.");
+            return Err(PageTableError::NotAligned(Size2MiB::SIZE_AS_DEBUG_STR));
         }
 
         let shifted = output_addr >> Size2MiB::SHIFT;
@@ -211,9 +218,9 @@ impl PageTableEntry {
     fn new_page_descriptor(
         output_addr: usize,
         attribute_fields: AttributeFields,
-    ) -> Result<PageTableEntry, &'static str> {
+    ) -> Result<PageTableEntry, PageTableError> {
         if output_addr % Size4KiB::SIZE as usize != 0 {
-            return Err("PageDescriptor: Address is not 4 KiB aligned.");
+            return Err(PageTableError::NotAligned(Size4KiB::SIZE_AS_DEBUG_STR));
         }
 
         let shifted = output_addr >> Size4KiB::SHIFT;
@@ -249,11 +256,17 @@ impl From<PageTableEntry> for u64 {
     }
 }
 
+// to get L0 we must allocate a few frames from boot region allocator.
+// So, first we init the dtb, parse mem-regions from there, then init boot_info page and start mmu,
+// this part will be inited in mmu::init():
+
+// @todo do NOT keep these statically, always allocate from available bump memory
 static mut LVL2_TABLE: Table<PageDirectory> = Table::<PageDirectory> {
     entries: [0; NUM_ENTRIES_4KIB as usize],
     level: PhantomData,
 };
 
+// @todo do NOT keep these statically, always allocate from available bump memory
 static mut LVL3_TABLE: Table<PageTable> = Table::<PageTable> {
     entries: [0; NUM_ENTRIES_4KIB as usize],
     level: PhantomData,