Struct FrameRef

pub struct FrameRef<'a, M: AnyFrameMeta + ?Sized> {
    inner: ManuallyDrop<Frame<M>>,
    _marker: PhantomData<&'a Frame<M>>,
}

A struct that can work as &'a Frame<M>.

Fields

inner: ManuallyDrop<Frame<M>>

_marker: PhantomData<&'a Frame<M>>

Implementations

impl<M: AnyFrameMeta + ?Sized> FrameRef<'_, M>

pub(in mm) unsafe fn borrow_paddr( raw: Paddr, ) -> Self

Borrows the Frame at the physical address as a FrameRef.

Safety

The caller must ensure that:

1. the frame outlives the created reference, so that the reference can be seen as borrowed from that frame.
2. the type of the FrameRef (M) matches the borrowed frame.

impl<'a, C: PageTableConfig> FrameRef<'a, PageTablePageMeta<C>>

pub(super) fn lock<'rcu>( self, _guard: &'rcu dyn InAtomicMode, ) -> PageTableGuard<'rcu, C>

where 'a: 'rcu,

Locks the page table node.

An atomic mode guard is required to

1. prevent deadlocks;
2. provide a lifetime ('rcu) that the nodes are guaranteed to outlive.

pub(super) unsafe fn make_guard_unchecked<'rcu>( self, _guard: &'rcu dyn InAtomicMode, ) -> PageTableGuard<'rcu, C>

where 'a: 'rcu,

Creates a new PageTableGuard without checking if the page table lock is held. Calling this function when a guard is already created is undefined behavior unless that guard was already forgotten.

• The task should have already held the lock.

Methods from Deref<Target = Frame<M>>

pub fn meta(&self) -> &M

Gets the metadata of this page.

pub fn start_paddr(&self) -> Paddr

Gets the physical address of the start of the frame.

pub fn map_level(&self) -> PagingLevel

Gets the map level of this page.

This is the level of the page table entry that maps the frame, which determines the size of the frame.

Currently, the level is always 1, which means the frame is a regular page frame.

pub fn size(&self) -> usize

Gets the size of this page in bytes.

pub fn dyn_meta(&self) -> &dyn AnyFrameMeta

Gets the dyncamically-typed metadata of this frame.

If the type is known at compile time, use Frame::meta instead.

pub fn reference_count(&self) -> u64

Gets the reference count of the frame.

It returns the number of all references to the frame, including all the existing frame handles (Frame, Frame<dyn AnyFrameMeta>), and all the mappings in the page table that points to the frame.

Safety

The function is safe to call, but using it requires extra care. The reference count can be changed by other threads at any time including potentially between calling this method and acting on the result.

pub fn borrow(&self) -> FrameRef<'_, M>

Borrows a reference from the given frame.

fn slot(&self) -> &MetaSlot

pub(super) fn level(&self) -> PagingLevel

pub(crate) unsafe fn activate(&self)

Activates the page table assuming it is a root page table.

Here we ensure not dropping an active page table by making a processor a page table owner. When activating a page table, the reference count of the last activated page table is decremented. And that of the current page table is incremented.

Safety

The caller must ensure that the page table to be activated has proper mappings for the kernel and has the correct const parameters matching the current CPU.

Panics

Only top-level page tables can be activated using this function.

• The page table should be valid by having proper mapping and level.

pub(super) unsafe fn first_activate(&self)

Activates the (root) page table assuming it is the first activation.

It will not try dropping the last activate page table. It is the same with Self::activate() in other senses.

• This function should be called only once per system.

• The page table, from the perspective of mapping and level, should be valid.

Trait Implementations

impl<'a, M: Debug + AnyFrameMeta + ?Sized> Debug for FrameRef<'a, M>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<M: AnyFrameMeta + ?Sized> Deref for FrameRef<'_, M>

type Target = Frame<M>

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.