Adds initializers and documentation about them.#60

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remexre wants to merge 51 commits intotrunkfrom

remexre/initializers

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remexre commented Oct 7, 2025 •

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On top of #50; merge that one first, then rebase this.

Initializers are a way for drivers to get code to run without needing to jam more code into main.

This is not yet finished; it needs an example of use, and is probably blocked on #50's overhaul of the Devicetree parser. I'm making a draft PR to get feedback, though.

remexre marked this pull request as draft

October 7, 2025 09:13

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remexre commented Oct 12, 2025

...whoops, turns out init.h snuck into trunk via #21 ( ab4bf40#diff-b9407181d3f79476016f05a3d1f404b8b30b2f22ec4b028e9c3ce7f255a582ec ) already...

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remexre commented Oct 12, 2025

Will probably cherry-pick 3f6b836 into this patchset as the example user; gonna finish #50 first though, I promise...

remexre added 27 commits

October 25, 2025 10:42


          Standardize the capitalization of Devicetree.

6b78e39

Signed-off-by: Nathan Ringo <me@remexre.com>


          Move zalloc to the header, so the optimizer can see it.

0e35af4

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds logging to generate_bootstub.

280c977

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds documentation for the new memory-management code.

84ac620

Signed-off-by: Nathan Ringo <me@remexre.com>


          Update generate_bootstub for memory management changes.

3b415cc

Signed-off-by: Nathan Ringo <me@remexre.com>


          Enables stack checking.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Move the stdckdint.h functions into compiler.h.

82191f7

Signed-off-by: Nathan Ringo <me@remexre.com>


          Use uaddr as the bits type of paddr.

3a33b8b

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds bounds checking to paddr_offset.

6d3e25d

Signed-off-by: Nathan Ringo <me@remexre.com>


          Reimplement physical memory access with the new physical memory APIs.

ba9d345

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds a bit of entropy early in boot.

730111b

Right now, just the cycle time and timestamp for boot. These are
pretty attacker-guessable, but better than nothing.

This will be used to generate XOR cookies to initialize the heap with.

We usually get better entropy from U-Boot once we process the
Devicetree, so the RNG will reseed at that point.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds a revamped Devicetree parser.

48478d7

This heap-allocates the Devicetree, so we don't need to keep the FDT
structure reserved.

It also includes the memory reservations block in the Devicetree proper,
under the /reserved-memory node.

This still needs to be fully integrated; e.g. by:

- Adding RAM to the allocators.
- Adding /chosen/rng-seed to the entropy pool.
- Creating devices from nodes.

This has been tested and works on the Milk-V Duo S.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds entropy from the Devicetree to the entropy pool.

bc4b748

It gets removed from the Devicetree to reduce the chances that an
attacker could discover it later. This is maybe kinda moot though,
because of how resistant the entropy pool is to attacks based on that.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Implements the new, drastically simpler, physical allocator.

8dc6976

Signed-off-by: Nathan Ringo <me@remexre.com>


          Marks the kernel as reserved in the Devicetree.

b0d0df9

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds utility methods for dealing with the reg prop.

123a514

Signed-off-by: Nathan Ringo <me@remexre.com>


          Finishes initialization of the new physical memory allocator.

Tested in QEMU and the Milk-V Duo S.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Implements mm_free_physical.

2904f6e

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds random functions for generating u32 and u64.

2aab817

These are for use in a treap implementation; arguably there should be a
"fast but lower-quality" RNG for this kind of usecase, but we really
don't want people e.g. using it when it would introduce a DoS attack.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Data structure definitions for the new virtual allocator.

328fcb8

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds vma_alloc_by_addr, uses it to reserve the initial mappings.

ac42d43

Signed-off-by: Nathan Ringo <me@remexre.com>


          Moves out treap rotation to a helper.

399fef5

Signed-off-by: Nathan Ringo <me@remexre.com>


          Expose vma_bounds.

c3eda9d

The page fault handler, among other things, will need it.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Fixes a bug in treap rotation, finishes VMA allocation.

525328f

Signed-off-by: Nathan Ringo <me@remexre.com>


          More debug printing in main.

8ef1278

Signed-off-by: Nathan Ringo <me@remexre.com>


          Implements vma_free.

f93f61e

Signed-off-by: Nathan Ringo <me@remexre.com>


          Removes the boothart_heap_segment that wasn't allocated in the bootstub.

bca73fd

Signed-off-by: Nathan Ringo <me@remexre.com>

remexre added 18 commits

October 25, 2025 10:42


          Wire up small object allocation.

3dd24dc

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds is_aligned.

dffd9ae

Signed-off-by: Nathan Ringo <me@remexre.com>


          Uses is_aligned() where applicable.

25ead37

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds vma_alloc_aligned.

6bdce8d

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds bzero_physical.

4157feb

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds support for mapping pages.

07f3dab

This currently only supports 4KiB pages with Sv39.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Reverses the order mm_alloc_physical hands out pages in.

d3cf1ce

This results in more readable output from the `info mem` command in
QEMU, since allocations are more often contiguous.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds the ARRAY_SIZE macro.

b03f8cf

This is like Linux's, but uses static_assert to give a better compile
error when the given field is not an array.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds support for pointer types to is_aligned.

48629bb

Signed-off-by: Nathan Ringo <me@remexre.com>


          Fixes a crash on OOM.

c9c5211

Signed-off-by: Nathan Ringo <me@remexre.com>


          Fixes vma_alloc sometimes not splitting a VMA it should.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Splits up the allocator, improving consistency and fixing bugs.

At this point, allocation works but freeing is a no-op.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds mm_paging_unmap.

53b2267

Signed-off-by: Nathan Ringo <me@remexre.com>


          Makes vma_find public.

3fdfea1

Signed-off-by: Nathan Ringo <me@remexre.com>


          Implements freeing.

055c02f

Signed-off-by: Nathan Ringo <me@remexre.com>


          Implements realloc.

61e51d7

Signed-off-by: Nathan Ringo <me@remexre.com>


          Makes the doc-serve Makefile target serve on all IPs.

8bf3769

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds a simple note on the implementation of each allocator.

6e523ae

Signed-off-by: Nathan Ringo <me@remexre.com>

remexre force-pushed the remexre/initializers branch from bdab406 to 26f1d83 Compare

October 25, 2025 22:07

Member Author

remexre commented Oct 25, 2025 •

edited

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Okay, did that cherry-pick. I think this is mergable behind #50.

This is essentially half of #4 (the half that doesn't need #13).

remexre marked this pull request as ready for review

October 25, 2025 22:16

remexre force-pushed the remexre/initializers branch from 3e71307 to f3dd58d Compare

October 25, 2025 22:17

remexre added 3 commits

October 26, 2025 02:17


          Fixes allocator heap corruption bug and assertion failure.

9d5260f

- page_collect shouldn't assume that the page has an empty free list,
  but neither should it do O(n) work when it does not.
- After page_free, alloc_generic should not refer to the page anymore.

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds initializers and documentation about them.

a96e60b

Signed-off-by: Nathan Ringo <me@remexre.com>


          Adds a way to register devices and device classes.

30c9a56

Signed-off-by: Nathan Ringo <me@remexre.com>

remexre force-pushed the remexre/initializers branch from f3dd58d to 30c9a56 Compare

October 27, 2025 02:25

remexre mentioned this pull request

Split up objects in makefile #63

Merged

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remexre commented Nov 8, 2025

Actually, closing this; the device model PR should supersede it. The notion of device classes in this PR is not the right thing for now.

remexre closed this

remexre deleted the remexre/initializers branch

January 12, 2026 15:39

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