Crate frame_allocator

Provides an allocator for physical memory frames. The minimum unit of allocation is a single frame.

This is currently a modified and more complex version of the page_allocator crate. TODO: extract the common code and create a generic allocator that can be specialized to allocate pages or frames.

This also supports early allocation of frames before heap allocation is available, and does so behind the scenes using the same single interface. Early pre-heap allocations are limited to tracking a small number of available chunks (currently 32).

Once heap allocation is available, it uses a dynamically-allocated list of frame chunks to track allocations.

The core allocation function is allocate_frames_deferred(), but there are several convenience functions that offer simpler interfaces for general usage.

Notes and Missing Features

This allocator only makes one attempt to merge deallocated frames into existing free chunks for de-fragmentation. It does not iteratively merge adjacent chunks in order to maximally combine separate chunks into the biggest single chunk. Instead, free chunks are merged only when they are dropped or when needed to fulfill a specific request.

Structs

• AllocatedFrame
  A reference to a single frame within a range of AllocatedFrames.
• AllocatedFramesIter
  An iterator over each AllocatedFrame in a range of AllocatedFrames.
• DeferredAllocAction
  A series of pending actions related to frame allocator bookkeeping, which may result in heap allocation.
• Frames
  A range of contiguous frames in physical memory.
• PhysicalMemoryRegion
  PhysicalMemoryRegion represents a range of contiguous frames in physical memory for bookkeeping purposes. It does not give access to the underlying frames.
• SplitFrames
  The result of splitting a Frames object into multiple smaller Frames objects.

Enums

• FramesIteratorRequest
  An enum that must be returned by the function passed into inspect_then_allocate_free_frames() in order to define the post-iteration behavior.
• MemoryRegionType
  Types of physical memory. See each variant’s documentation.

Functions

• allocate_frames
  Allocates the given number of frames with no constraints on the starting physical address.
• allocate_frames_at
  Allocates the given number of frames starting at (inclusive of) the frame containing the given PhysicalAddress.
• allocate_frames_by_bytes
  Allocates frames with no constraints on the starting physical address, with a size given by the number of bytes.
• allocate_frames_by_bytes_at
  Allocates frames starting at the given PhysicalAddress with a size given in number of bytes.
• allocate_frames_by_bytes_deferred
  Similar to allocated_frames_deferred(), but accepts a size value for the allocated frames in number of bytes instead of number of frames.
• allocate_frames_deferred
  The core frame allocation routine that allocates the given number of physical frames, optionally at the requested starting PhysicalAddress.
• init
  Initialize the frame allocator with the given list of available and reserved physical memory regions.
• inspect_then_allocate_free_frames
  Iterates over all free frames and invokes the given func on each one in order to determine what to do with those frames.

Type Aliases

• AllocatedFrames
  A type alias for Frames in the Allocated state.
• FreeFrames
  A type alias for Frames in the Free state, which only suppports 4K pages.
• MappedFrames
  A type alias for Frames in the Mapped state.
• UnmappedFrames
  A type alias for Frames in the Unmapped state.