Use Option to replace usage of MaybeUninit in paging

Author: Jiajie Chen

kernel/src/arch/aarch64/paging.rs

@@ -19,7 +19,7 @@ type Page = PageAllSizes<Size4KiB>;
 pub struct PageTableImpl {
     page_table: MappedPageTable<'static, fn(Frame) -> *mut Aarch64PageTable>,
     root_frame: Frame,
-    entry: PageEntry,
+    entry: Option<PageEntry>,
 }
 
 pub struct PageEntry(&'static mut PageTableEntry, Page);
@@ -55,8 +55,8 @@ impl PageTable for PageTableImpl {
         let page = Page::of_addr(vaddr as u64);
         if let Ok(e) = self.page_table.get_entry_mut(page) {
             let e = unsafe { &mut *(e as *mut PageTableEntry) };
-            self.entry = PageEntry(e, page);
-            Some(&mut self.entry as &mut Entry)
+            self.entry = Some(PageEntry(e, page));
+            Some(self.entry.as_mut().unwrap())
         } else {
             None
         }
@@ -213,7 +213,7 @@ impl PageTableImpl {
         ManuallyDrop::new(PageTableImpl {
             page_table: MappedPageTable::new(table, frame_to_page_table),
             root_frame: frame,
-            entry: core::mem::MaybeUninit::zeroed().assume_init(),
+            entry: None,
         })
     }
     /// The method for getting the kernel page table.
@@ -224,7 +224,7 @@ impl PageTableImpl {
         ManuallyDrop::new(PageTableImpl {
             page_table: MappedPageTable::new(table, frame_to_page_table),
             root_frame: frame,
-            entry: core::mem::MaybeUninit::zeroed().assume_init(),
+            entry: None,
         })
     }
 }
@@ -239,7 +239,7 @@ impl PageTableExt for PageTableImpl {
             PageTableImpl {
                 page_table: MappedPageTable::new(table, frame_to_page_table),
                 root_frame: frame,
-                entry: core::mem::MaybeUninit::zeroed().assume_init(),
+                entry: None,
             }
         }
     }

kernel/src/arch/mipsel/paging.rs

@@ -12,7 +12,7 @@ use rcore_memory::paging::*;
 pub struct PageTableImpl {
     page_table: TwoLevelPageTable<'static>,
     root_frame: Frame,
-    entry: PageEntry,
+    entry: Option<PageEntry>,
 }
 
 /// PageTableEntry: the contents of this entry.
@@ -43,8 +43,8 @@ impl PageTable for PageTableImpl {
         let page = Page::of_addr(VirtAddr::new(vaddr));
         if let Ok(e) = self.page_table.ref_entry(page.clone()) {
             let e = unsafe { &mut *(e as *mut PageTableEntry) };
-            self.entry = PageEntry(e, page);
-            Some(&mut self.entry as &mut Entry)
+            self.entry = Some(PageEntry(e, page));
+            Some(self.entry.as_mut().unwrap())
         } else {
             None
         }
@@ -154,7 +154,7 @@ impl PageTableImpl {
         ManuallyDrop::new(PageTableImpl {
             page_table: TwoLevelPageTable::new(table),
             root_frame: frame,
-            entry: core::mem::MaybeUninit::zeroed().assume_init(),
+            entry: None,
         })
     }
 
@@ -176,7 +176,7 @@ impl PageTableExt for PageTableImpl {
         PageTableImpl {
             page_table: TwoLevelPageTable::new(table),
             root_frame: frame,
-            entry: unsafe { core::mem::MaybeUninit::zeroed().assume_init() },
+            entry: None,
         }
     }
 

kernel/src/arch/riscv32/paging.rs

@@ -20,7 +20,7 @@ type TopLevelPageTable<'a> = riscv::paging::Rv39PageTable<'a>;
 pub struct PageTableImpl {
     page_table: TopLevelPageTable<'static>,
     root_frame: Frame,
-    entry: PageEntry,
+    entry: Option<PageEntry>,
 }
 
 /// PageTableEntry: the contents of this entry.
@@ -51,8 +51,8 @@ impl PageTable for PageTableImpl {
         let page = Page::of_addr(VirtAddr::new(vaddr));
         if let Ok(e) = self.page_table.ref_entry(page.clone()) {
             let e = unsafe { &mut *(e as *mut PageTableEntry) };
-            self.entry = PageEntry(e, page);
-            Some(&mut self.entry as &mut Entry)
+            self.entry = Some(PageEntry(e, page));
+            Some(self.entry.as_mut().unwrap())
         } else {
             None
         }
@@ -158,7 +158,7 @@ impl PageTableImpl {
         ManuallyDrop::new(PageTableImpl {
             page_table: TopLevelPageTable::new(table, PHYSICAL_MEMORY_OFFSET),
             root_frame: frame,
-            entry: core::mem::MaybeUninit::zeroed().assume_init(),
+            entry: None,
         })
     }
     /// The method for getting the kernel page table.
@@ -176,11 +176,10 @@ impl PageTableExt for PageTableImpl {
         let table = unsafe { &mut *(phys_to_virt(target) as *mut RvPageTable) };
         table.zero();
 
-        // MaybeUninit is not working, dunno why
         PageTableImpl {
             page_table: TopLevelPageTable::new(table, PHYSICAL_MEMORY_OFFSET),
             root_frame: frame,
-            entry: unsafe { core::mem::uninitialized() },
+            entry: None,
         }
     }
 

kernel/src/arch/x86_64/paging.rs

@@ -41,7 +41,7 @@ impl FrameExt for Frame {
 
 pub struct PageTableImpl(
     MappedPageTable<'static, fn(Frame) -> *mut x86PageTable>,
-    PageEntry,
+    Option<PageEntry>,
     Frame,
 );
 
@@ -77,8 +77,8 @@ impl PageTable for PageTableImpl {
             let entry = unsafe { &mut (&mut *page_table)[index] };
             if level == 3 {
                 let page = Page::of_addr(addr);
-                self.1 = PageEntry(entry, page, self.2);
-                return Some(&mut self.1 as &mut Entry);
+                self.1 = Some(PageEntry(entry, page, self.2));
+                return Some(self.1.as_mut().unwrap());
             }
             if !entry.flags().contains(EF::PRESENT) {
                 return None;
@@ -203,7 +203,7 @@ impl PageTableImpl {
         let table = &mut *frame_to_page_table(frame);
         ManuallyDrop::new(PageTableImpl(
             MappedPageTable::new(table, frame_to_page_table),
-            core::mem::MaybeUninit::zeroed().assume_init(),
+            None,
             frame,
         ))
     }
@@ -223,7 +223,7 @@ impl PageTableExt for PageTableImpl {
         unsafe {
             PageTableImpl(
                 MappedPageTable::new(table, frame_to_page_table),
-                core::mem::MaybeUninit::zeroed().assume_init(),
+                None,
                 frame,
             )
         }