Initial `UnsafePinned` implementation [Part 1: Libs] #137043

Sky9x · 2025-02-14T21:26:37Z

Initial libs changes necessary to unblock further work on RFC 3467.
Tracking issue: #125735

This PR is split off from #136964, and includes just the libs changes:

UnsafePinned struct
private UnsafeUnpin structural auto trait
Lang items for both
Compiler changes necessary to block niches on UnsafePinned

This PR does not change codegen, miri, the existing !Unpin hack, or anything else. That work is to be split into later PRs.

cc @RalfJung @Noratrieb

@rustbot label F-unsafe_pinned T-libs-api

rustbot · 2025-02-14T21:26:46Z

r? @tgross35

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library/core/src/pin/unsafe_pinned.rs

library/core/src/marker.rs

tests/ui/rfcs/rfc-3467-unsafe-pinned/unsafe-pinned-hides-niche.rs

tgross35 · 2025-02-23T22:51:25Z

Cc @rust-lang/libs-api, this unstably adds the interfaces from the accepted RFC https://rust-lang.github.io/rfcs/3467-unsafe-pinned.html.

library/core/src/pin/unsafe_pinned.rs

bors · 2025-03-12T01:04:35Z

☔ The latest upstream changes (presumably #138366) made this pull request unmergeable. Please resolve the merge conflicts.

tgross35

This API appears to match RFC 3467 so I think it is good to go. The docs could probably use elaboration at some point, but that should be fine to defer until the feature is fully available.

r=me with one doc request and conflicts resolved.

Cc @WaffleLapkin @RalfJung if you have anything else.

library/core/src/pin/unsafe_pinned.rs

WaffleLapkin

looks good to me 👍🏻

RalfJung · 2025-03-19T07:17:25Z

compiler changes LGTM.

tgross35 · 2025-04-04T04:03:09Z

@rustbot author for #137043 (review)

rustbot · 2025-04-04T04:03:13Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

Rollup of 11 pull requests Successful merges: - rust-lang#137043 (Initial `UnsafePinned` implementation [Part 1: Libs]) - rust-lang#138962 (Expect an array when expected and acutal types are both arrays during cast) - rust-lang#139001 (add `naked_functions_rustic_abi` feature gate) - rust-lang#139379 (Use delayed bug for normalization errors in drop elaboration) - rust-lang#139582 (Various coercion cleanups) - rust-lang#139628 (Suggest remove redundant `$()?` around `vis`) - rust-lang#139644 (Micro-optimize `InstSimplify`'s `simplify_primitive_clone`) - rust-lang#139671 (Proc macro span API redesign: Replace proc_macro::SourceFile by Span::{file, local_file}) - rust-lang#139674 (In `rustc_mir_transform`, iterate over index newtypes instead of ints) - rust-lang#139740 (Convert `tests/ui/lint/dead-code/self-assign.rs` to a known-bug test) - rust-lang#139741 (fix smir's run! doc and import) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 10 pull requests Successful merges: - rust-lang#137043 (Initial `UnsafePinned` implementation [Part 1: Libs]) - rust-lang#138962 (Expect an array when expected and acutal types are both arrays during cast) - rust-lang#139001 (add `naked_functions_rustic_abi` feature gate) - rust-lang#139379 (Use delayed bug for normalization errors in drop elaboration) - rust-lang#139582 (Various coercion cleanups) - rust-lang#139628 (Suggest remove redundant `$()?` around `vis`) - rust-lang#139644 (Micro-optimize `InstSimplify`'s `simplify_primitive_clone`) - rust-lang#139674 (In `rustc_mir_transform`, iterate over index newtypes instead of ints) - rust-lang#139740 (Convert `tests/ui/lint/dead-code/self-assign.rs` to a known-bug test) - rust-lang#139741 (fix smir's run! doc and import) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#137043 - Sky9x:unsafe-pinned-pt1-libs, r=tgross35,RalfJung,WaffleLapkin Initial `UnsafePinned` implementation [Part 1: Libs] Initial libs changes necessary to unblock further work on [RFC 3467](https://rust-lang.github.io/rfcs/3467-unsafe-pinned.html). Tracking issue: rust-lang#125735 This PR is split off from rust-lang#136964, and includes just the libs changes: - `UnsafePinned` struct - private `UnsafeUnpin` structural auto trait - Lang items for both - Compiler changes necessary to block niches on `UnsafePinned` This PR does not change codegen, miri, the existing `!Unpin` hack, or anything else. That work is to be split into later PRs. --- cc ``@RalfJung`` ``@Noratrieb`` ``@rustbot`` label F-unsafe_pinned T-libs-api

onestacked · 2025-04-18T12:25:09Z

@Sky9x I've sent a RFC version for including part of this API in the linux kernel, please let me know if you want me to include a Co-Developed-By tag (or something else) to be included?

Also are you alright with relicensing as GPL v2 or should the Apache & MIT license be kept?

Link: https://lore.kernel.org/rust-for-linux/[email protected]/

`UnsafePinned<T>` is useful for cases where a value might be shared with C code but not directly used by it. In particular this is added for storing additional data in the `MiscDeviceRegistration` which will be shared between `fops->open` and the containing struct. Similar to `Opaque` but guarantees that the value is always initialized and that the inner value is dropped when `UnsafePinned` is dropped. This was originally proposed for the IRQ abstractions [0] and is also useful for other where the inner data may be aliased, but is always valid and automatic `Drop` is desired. Since then the `UnsafePinned` type was added to upstream Rust [1] as a unstable feature, therefore this patch implements the subset required for additional data in `MiscDeviceRegistration` on older rust versions and using the upstream type on new rust versions which include this feature. Some differences to the upstream type definition are required in the kernel implementation, because upstream type uses some compiler changes to opt out of certain optimizations, this is documented in a comment on the `UnsafePinned` type. The documentation on is based on the upstream rust documentation with minor modifications. Link: https://lore.kernel.org/rust-for-linux/CAH5fLgiOASgjoYKFz6kWwzLaH07DqP2ph+3YyCDh2+gYqGpABA@mail.gmail.com [0] Link: rust-lang/rust#137043 [1] Suggested-by: Alice Ryhl <[email protected]> Signed-off-by: Christian Schrefl <[email protected]>

WaffleLapkin · 2025-04-18T13:46:40Z

@onestacked please note that this type doesn't do anything yet. the language part that allows aliasing of mutable references isn't implemented yet.

onestacked · 2025-04-18T13:58:29Z

The plan is to only use the Rust UnsafePinned once it is stabilized so thats no real problem (since by then this will be implemented).
Until then using the "reimplemented" UnsafePinned is the best we can do from what I understand.

ojeda · 2025-04-18T14:11:01Z

It is always nice to test the new feature works before it gets stabilized, so the patch is useful :)

Sky9x · 2025-04-18T18:46:42Z

@Sky9x I've sent a RFC version for including part of this API in the linux kernel, please let me know if you want me to include a Co-Developed-By tag (or something else) to be included?

Sure? My git email is Sky <[email protected]>

Also are you alright with relicensing as GPL v2 or should the Apache & MIT license be kept?

OK with relicensing as GPLv2.

Link: https://lore.kernel.org/rust-for-linux/[email protected]/

Your polyfill with PhantomPinned + UnsafeCell is sufficient for matching the eventual behavior of our implementation.

@onestacked please note that this type doesn't do anything yet. the language part that allows aliasing of mutable references isn't implemented yet.

The existing !Unpin hacks in place should prevent miscompliations. Miri currently disables protectors when retagging such types, so it won't be able to catch any violations. That being said, you can use the wrapper in its current state for writing code (and I have), it just may not be optimized as well or checked by miri.

traviscross · 2025-04-18T19:27:56Z

Also are you alright with relicensing as GPL v2 or should the Apache & MIT license be kept?

OK with relicensing as GPLv2.

Keep in mind, if the code maintained on the kernel side does not preserve the MIT/Apache 2.0 license, then any changes or improvements made to that code (by others) cannot be propagated back to Rust (as those changes will only be GPLv2 licensed).

Sky9x · 2025-04-18T19:29:54Z

Also are you alright with relicensing as GPL v2 or should the Apache & MIT license be kept?

OK with relicensing as GPLv2.

Keep in mind, if the code maintained on the kernel side does not preserve the MIT/Apache 2.0 license, then any changes or improvements made to that code (by others) cannot be propagated back to Rust (as those changes will only be GPLv2 licensed).

I'm ok licensing it however, but yeah maybe MIT/Apache is better

onestacked · 2025-04-18T19:49:47Z

Alright I'll keep it then.

ojeda · 2025-04-18T22:10:40Z

Sure?

Thanks!

If @onestacked is adding you as a Co-developed-by/Signed-off-by, then please make sure you are OK with the DCO: https://docs.kernel.org/process/submitting-patches.html#developer-s-certificate-of-origin-1-1

Sky9x · 2025-04-19T01:19:53Z

Sure?

Thanks!

If @onestacked is adding you as a Co-developed-by/Signed-off-by, than please make sure you are OK with the DCO: https://docs.kernel.org/process/submitting-patches.html#developer-s-certificate-of-origin-1-1

Signed-off-by: Sky <[email protected]>

Also probably best to keep it licensed as MIT OR Apache-2.0. Some of the code (comments really) is from the RFC which is not written by me and is licensed under MIT/Apache.

compiler/rustc_middle/src/ty/adt.rs

…ompiler-errors Re-remove `AdtFlags::IS_ANONYMOUS` Removed in rust-lang#138296. I accidentally re-added it in rust-lang#137043 while resolving merge conflicts. This PR re-removes it. r? `@compiler-errors` (sorry)

RalfJung · 2025-04-19T12:09:41Z

The existing !Unpin hacks in place should prevent miscompliations. Miri currently disables protectors when retagging such types, so it won't be able to catch any violations. That being said, you can use the wrapper in its current state for writing code (and I have), it just may not be optimized as well or checked by miri.

Miri disables retagging entirely for these types, not just protectors. And it uses the same logic for this as codegen, so if Miri does not complain there should be no miscompilations. (Unless someone changed one of those checks and forgot to change the other...) We'll make first Miri and then codegen stricter some time after this lands.

…ompiler-errors Re-remove `AdtFlags::IS_ANONYMOUS` Removed in rust-lang#138296. I accidentally re-added it in rust-lang#137043 while resolving merge conflicts. This PR re-removes it. r? ``@compiler-errors`` (sorry)

…ross35,RalfJung,WaffleLapkin Initial `UnsafePinned` implementation [Part 1: Libs] Initial libs changes necessary to unblock further work on [RFC 3467](https://rust-lang.github.io/rfcs/3467-unsafe-pinned.html). Tracking issue: rust-lang#125735 This PR is split off from rust-lang#136964, and includes just the libs changes: - `UnsafePinned` struct - private `UnsafeUnpin` structural auto trait - Lang items for both - Compiler changes necessary to block niches on `UnsafePinned` This PR does not change codegen, miri, the existing `!Unpin` hack, or anything else. That work is to be split into later PRs. --- cc ``@RalfJung`` ``@Noratrieb`` ``@rustbot`` label F-unsafe_pinned T-libs-api

Rollup merge of rust-lang#140025 - Sky9x:re-remove-adtflags-anon, r=compiler-errors Re-remove `AdtFlags::IS_ANONYMOUS` Removed in rust-lang#138296. I accidentally re-added it in rust-lang#137043 while resolving merge conflicts. This PR re-removes it. r? ``@compiler-errors`` (sorry)

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Initial implementation of UnsafePinned and UnsafeUnpin (RFC 3467) #136964

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Decide what to do about UnsafePinned and safe Pin::deref #137750

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Rollup of 11 pull requests #139761

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Rollup of 10 pull requests #139766

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Initial UnsafePinned implementation [Part 2: Lowering] #139896

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Re-remove AdtFlags::IS_ANONYMOUS #140025

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Rust wanted features Rust-for-Linux/linux#354

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Initial `UnsafePinned` implementation [Part 1: Libs] #137043

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Initial `UnsafePinned` implementation [Part 1: Libs] #137043

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