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Merge verified chunk into frame allocator #976

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@Ramla-I Ramla-I commented Jun 14, 2023

This PR merges a verified TrustedChunk type into the frame allocator code. The main changes are:

trusted_chunk crate:

  • submodule that contains the TrustedChunk type, a linked list and static array for bookkeeping, and their verified functions.

frame_allocator crate:

  • The frame allocator no longer uses Chunk for bookkeeping. It used a linear Frames type in the free lists which represents ownership of a range of frames, and a separate type Region for bookkeeping.
  • Since Frames can't be cloned, the frame allocator logic to find and merge frames is slightly changed. A Frames object has to be removed from the free list before it can be merged or split.
  • Frames owns an instance of a verified TrustedChunk, and its functions are wrappers over the TrustedChunk new, merge, split and split_at methods.
  • I use my own version of RangeInclusive within the frame allocator that implements an iterator that doesn't mutate the range.
  • AllocatedFrames is merged into the Frames type. There are two states for a Frames object: Unmapped and Mapped. Mapped is only used briefly once a MappedPages is created.
  • AllocatedFrame type is renamed to UnmappedFrame

frame_range_callbacks crate:

  • the callbacks that crate a TrustedChunk and AllocatedFrames from an UnmappedFrames are in this crate. This is to minimize the amount of code that has access to these callbacks.

memory crate:

  • use the callbacks in the frame_range_callbacks crate rather than storing them in the memory crate

memory_structs:

  • use our own range inclusive and the provided iterator
  • add a to_range_inclusive function for PageRange and FrameRange

Ramla-I and others added 23 commits June 9, 2023 14:25
…seus-os#970)

* Currently this is only used for allocating pages for new
  executable .text sections on aarch64, which itself is a
  workaround to enable runtime loading of crates (see theseus-os#940).
  * Based on the limitations of aarch64's ISA (branch instructions),
    we reserve 128MiB of virtual address space for this purpose.
  * This 128MiB region is for executable .text sections only,
    and is contiguous with the base kernel image's .text section.

* This is available but not used by default on x86_64 yet.
@Ramla-I Ramla-I requested a review from kevinaboos June 14, 2023 12:40
@kevinaboos kevinaboos marked this pull request as draft June 21, 2023 19:35
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2 participants