Trait GlobalFrameAllocator

pub trait GlobalFrameAllocator: Sync {
    // Required methods
    fn alloc(&self, layout: Layout) -> Option<Paddr>;
    fn dealloc(&self, addr: Paddr, size: usize);
    fn add_free_memory(&self, addr: Paddr, size: usize);
}

The trait for the global frame allocator.

OSTD allows a customized frame allocator by the global_frame_allocator attribute, which marks a static variable of this type.

The API mimics the standard Rust allocator API (GlobalAlloc and [global_allocator]). However, this trait is much safer. Double free or freeing in-use memory through this trait only messes up the allocator’s state rather than causing undefined behavior.

Whenever OSTD or other modules need to allocate or deallocate frames via FrameAllocOptions, they are forwarded to the global frame allocator. It is not encouraged to call the global allocator directly.

Required Methods

fn alloc(&self, layout: Layout) -> Option<Paddr>

Allocates a contiguous range of frames.

The caller guarantees that layout.size() is aligned to PAGE_SIZE.

When any of the allocated memory is not in use, OSTD returns them by calling GlobalFrameAllocator::dealloc. If multiple frames are allocated, they may be returned in any order with any number of calls.

fn dealloc(&self, addr: Paddr, size: usize)

Deallocates a contiguous range of frames.

The caller guarantees that addr and size are both aligned to PAGE_SIZE. The deallocated memory should always be allocated by GlobalFrameAllocator::alloc. However, if GlobalFrameAllocator::alloc returns multiple frames, it is possible that some of them are deallocated before others. The deallocated memory must never overlap with any memory that is already deallocated or added, without being allocated in between.

The deallocated memory can be uninitialized.

fn add_free_memory(&self, addr: Paddr, size: usize)

Adds a contiguous range of frames to the allocator.

The memory being added must never overlap with any memory that was added before.

The added memory can be uninitialized.

Implementors