Support `no_std` targets #68

mkroening · 2023-11-09T15:05:19Z

Summary of the PR

This adds no_std support by

adding a default std feature for disabling impl Error on no_std.
adding the Hashbrown dependency for no_std hash sets

Hashbrown also provides the HashSet implementation in std. std's HashSet is not in liballoc yet, though.
By default, Hashbrown uses AHash as the default hasher. AHash is much faster than std's SipHash, but is not as HashDoS resistant. That seemed not relevant to me, though.

Closes #61

Requirements

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All added/changed functionality has a corresponding unit/integration
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Any newly added unsafe code is properly documented.

mkroening · 2023-11-09T15:07:59Z

I don't know how to modify CI to test this. Locally, I ran the following for testing:

cargo test
cargo test --no-default-features
cargo check --target x86_64-unknown-none --no-default-features

andreeaflorescu · 2023-11-09T16:41:08Z

I don't know how to modify CI to test this. Locally, I ran the following for testing:
cargo test
cargo test --no-default-features
cargo check --target x86_64-unknown-none --no-default-features

To test this as part of the CI you'll need to add a custom pipeline. Here is an example of a custom pipeline in another repository: https://github.com/rust-vmm/vm-virtio/tree/main/.buildkite. Once we get close with merging this PR, I can make the pipeline run on all PRs by configuring it in Buildkite.

andreeaflorescu

LGTM, I have just some questions. Thanks for handling this!

andreeaflorescu · 2023-11-09T16:34:54Z

Cargo.toml

@@ -8,7 +8,12 @@ edition = "2018"
 repository = "https://github.com/rust-vmm/vm-fdt"
 keywords = ["fdt"]

+[dependencies]
+hashbrown = "0.14"


We are trying to keep the dependencies to a minimum, and for this crate we have none. Is there a way to have this at least as an optional dependency?

There is no nice way of doing that since Cargo features are additive and feature = "std" would only add things.

We could add an alloc feature that has to be enabled explicitly. That way cargo check --no-default-features without any features will fail though, and one has to enable alloc explicitly on no_std.

I guess the other alternative would be to just skip duplicate phandle checking in the no_std version so we would not need a HashSet at all; that would make it the caller's responsibility to ensure phandles are unique (like it was before we added this check). Maybe tying that to no_std would be too confusing, though.

I think, I'd prefer not have this compile on no_std without a feature instead of removing functionality from this crate. I'll implement this shortly.

Are you okay with the solution I implemented? :)

I think it's fine as it is, I was just wondering if it's possible.

src/writer.rs

mkroening · 2023-11-10T08:40:30Z

To test this as part of the CI you'll need to add a custom pipeline. Here is an example of a custom pipeline in another repository: https://github.com/rust-vmm/vm-virtio/tree/main/.buildkite. Once we get close with merging this PR, I can make the pipeline run on all PRs by configuring it in Buildkite.

I added a CI config. 👍

andreeaflorescu · 2023-11-10T15:08:52Z

I added the custom pipeline in Buildkite and retriggered the build. Any other PRs open against vm-fdt will fail the tests until this one is merged. If this becomes a problem I can also de-activate the custom build.

This adds `no_std` support by - adding a default `std` feature for disabling `impl Error` on `no_std`. - adding the Hashbrown dependency for `no_std` hash sets Hashbrown also provides the `HashSet` implementation in `std`. `std`'s `HashSet` is not in liballoc yet, though. By default, Hashbrown uses AHash as the default hasher. AHash is much faster than `std`'s SipHash, but is not as HashDoS resistant. That seemed not relevant to me. Co-authored-by: Andreea Florescu <andreea.florescu15@gmail.com> Signed-off-by: Martin Kröning <martin.kroening@eonerc.rwth-aachen.de>

mkroening · 2023-11-10T23:53:31Z

Thanks :)

Sorry for dismissing the reviews. I force-pushed the fix for the CI.

andreeaflorescu · 2023-11-13T08:57:21Z

.buildkite/custom-tests.json

+  "tests": [
+    {
+      "test_name": "build-alloc",
+      "command": "rustup target add {target_platform}-unknown-none && env RUSTFLAGS=\"-D warnings\" cargo build --release --target {target_platform}-unknown-none --no-default-features --features alloc",


The rustup target add should actually go in the rust-vmm container. We can merge this as a temporary workaround, but we should eventually fix it. Do you want to send a PR with this change in rust-vmm-container as well? This is where we need to add the target: https://github.com/rust-vmm/rust-vmm-container/blob/main/build_container.sh#L40. If not, I can do that some time later.

Makes sense. I opened rust-vmm/rust-vmm-container#94.

I am merging this PR, and once we publish a new version of rust-vmm-ci with the updated rust-vmm-container we can update this as well.

I opened #70 so we don't forget about this.

mkroening · 2023-11-14T15:57:45Z

Thanks a lot! When can we expect a release? :)

andreeaflorescu · 2023-11-14T16:09:35Z

Thanks a lot! When can we expect a release? :)

I can just create one now.

mkroening requested a review from danielverkamp as a code owner November 9, 2023 15:05

mkroening force-pushed the no_std branch from 2baddb6 to 2648b9f Compare November 9, 2023 15:06

This was referenced Nov 9, 2023

Should we have this crate as no_std? #61

Closed

Create device trees hermit-os/loader#275

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mkroening force-pushed the no_std branch from 2648b9f to 805f708 Compare November 9, 2023 15:18

andreeaflorescu reviewed Nov 9, 2023

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mkroening force-pushed the no_std branch 4 times, most recently from eca10f3 to f51c6c7 Compare November 10, 2023 08:40

mkroening force-pushed the no_std branch from f51c6c7 to e092eb0 Compare November 10, 2023 08:42

andreeaflorescu previously approved these changes Nov 10, 2023

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danielverkamp previously approved these changes Nov 10, 2023

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mkroening dismissed stale reviews from danielverkamp and andreeaflorescu via 3c2f4c7 November 10, 2023 23:47

mkroening force-pushed the no_std branch from e092eb0 to 3c2f4c7 Compare November 10, 2023 23:47

danielverkamp approved these changes Nov 11, 2023

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andreeaflorescu reviewed Nov 13, 2023

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mkroening mentioned this pull request Nov 13, 2023

feat(build_container): add no_std-only targets rust-vmm/rust-vmm-container#94

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andreeaflorescu approved these changes Nov 14, 2023

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andreeaflorescu merged commit 71d27b6 into rust-vmm:main Nov 14, 2023
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mkroening deleted the no_std branch November 14, 2023 13:51

mkroening mentioned this pull request Nov 14, 2023

ci: don't install no_std targets #70

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Support `no_std` targets #68

Support `no_std` targets #68

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Support no_std targets #68

Support no_std targets #68

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mkroening commented Nov 9, 2023 • edited Loading

Summary of the PR

Requirements

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andreeaflorescu commented Nov 14, 2023

Support `no_std` targets #68

Support `no_std` targets #68

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