From nobody Fri Dec 19 12:19:29 2025 Received: from mout01.posteo.de (mout01.posteo.de [185.67.36.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4992A243968 for ; Thu, 9 Oct 2025 18:12:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.67.36.65 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760033567; cv=none; b=Dr4Xd2TG12C7eMeFVhgfQotCU4HlmpCuvIXyVZfU+Riudw2sFJ4RAJUXGMds9012fVm+7JE1b5QfiKe3YobflOSYS/iRxJS63vibik6n4wzja2y4I+bpWHZrY5YHcorIZPRlE+WclSwv06Z8ld2XulzhWVTOFNEsuc4jgEjH9Ec= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760033567; c=relaxed/simple; bh=WKdpAt+qDdJOIUZK0qmRFY7wTNb1bpyQ6KoeiVpKZ7c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gYtJ4tSLtVb3Kbs11X8dMrfUq6hxZOQtcF4Lkv86R0T/F7swqn3PuWPApJwFowU7yDktQv8f1PLJ+ODeMOvETvqh9wCT+tJbNgnsvT/wsKEBr22pTB58xqWfEpIlAQIaSGUKIrUi69sWQEApSnjVsu2IniyZAH4b9vPAtC4IHGk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de; spf=pass smtp.mailfrom=posteo.de; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b=Ovn+a05K; arc=none smtp.client-ip=185.67.36.65 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=posteo.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=posteo.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=posteo.de header.i=@posteo.de header.b="Ovn+a05K" Received: from submission (posteo.de [185.67.36.169]) by mout01.posteo.de (Postfix) with ESMTPS id 8D58824002A for ; Thu, 9 Oct 2025 20:12:37 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=posteo.de; s=2017; t=1760033557; bh=xCet9tHF8NFc7YDfbL543GnAWxyXJofxpqNz0LCeBYs=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version: Content-Transfer-Encoding:Autocrypt:OpenPGP:From; b=Ovn+a05KC7MgrD8OjGHOWYpUVw7Bz6WJ8zeJHjsQV8R3n4lDjvaptE6riFPBtkrE5 fEIlti4v0OxCv5UenGaWN0TUdand492peKuaYp9fr4SrEpUMkreNC/Kclmz1c+9i+N mW35VB4d5BnoY9TTz7ol7ipbcxv4E9fMKvApDqE1H5a6meJLL0u/Omp21sLYH265RZ v9iCkaC7maf2u9lCqrFOhmJBzn46xp6Hn6MC5LDoHDddon8tPOOa4R9CsiqD3pOgkt o5NcR5zCYpFbMDMRsZHvo4DEHD8mYk8L3/OHAnbTtycUiDNOK+kf3t4Jgx2SNZlLZo q8+T9GJxGd/uQ== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4cjHz414P7z9rxd; Thu, 9 Oct 2025 20:12:32 +0200 (CEST) From: Markus Probst To: Danilo Krummrich , Miguel Ojeda , Alex Gaynor , Lee Jones , Pavel Machek Cc: Lorenzo Stoakes , Vlastimil Babka , "Liam R. Howlett" , Uladzislau Rezki , Boqun Feng , Gary Guo , bjorn3_gh@protonmail.com, Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Markus Probst , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org Subject: [PATCH v2 1/2] rust: add basic Pin> abstractions Date: Thu, 09 Oct 2025 18:12:33 +0000 Message-ID: <20251009181203.248471-2-markus.probst@posteo.de> In-Reply-To: <20251009181203.248471-1-markus.probst@posteo.de> References: <20251009181203.248471-1-markus.probst@posteo.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Autocrypt: addr=markus.probst@posteo.de; prefer-encrypt=mutual; keydata=xsFNBGiDvXgBEADAXUceKafpl46S35UmDh2wRvvx+UfZbcTjeQOlSwKP7YVJ4JOZrVs93qReNLkO WguIqPBxR9blQ4nyYrqSCV+MMw/3ifyXIm6Pw2YRUDg+WTEOjTixRCoWDgUj1nOsvJ9tVAm76Ww+ /pAnepVRafMID0rqEfD9oGv1YrfpeFJhyE2zUw3SyyNLIKWD6QeLRhKQRbSnsXhGLFBXCqt9k5JA RhgQof9zvztcCVlT5KVvuyfC4H+HzeGmu9201BVyihJwKdcKPq+n/aY5FUVxNTgtI9f8wIbmfAja oT1pjXSp+dszakA98fhONM98pOq723o/1ZGMZukyXFfsDGtA3BB79HoopHKujLGWAGskzClwTjRQ xBqxh/U/lL1pc+0xPWikTNCmtziCOvv0KA0arDOMQlyFvImzX6oGVgE4ksKQYbMZ3Ikw6L1Rv1J+ FvN0aNwOKgL2ztBRYscUGcQvA0Zo1fGCAn/BLEJvQYShWKeKqjyncVGoXFsz2AcuFKe1pwETSsN6 OZncjy32e4ktgs07cWBfx0v62b8md36jau+B6RVnnodaA8++oXl3FRwiEW8XfXWIjy4umIv93tb8 8ekYsfOfWkTSewZYXGoqe4RtK80ulMHb/dh2FZQIFyRdN4HOmB4FYO5sEYFr9YjHLmDkrUgNodJC XCeMe4BO4iaxUQARAQABzRdtYXJrdXMucHJvYnN0QHBvc3Rlby5kZcLBkQQTAQgAOxYhBIJ0GMT0 rFjncjDEczR2H/jnrUPSBQJog714AhsDBQsJCAcCAiICBhUKCQgLAgQWAgMBAh4HAheAAAoJEDR2 H/jnrUPSgdkQAISaTk2D345ehXEkn5z2yUEjaVjHIE7ziqRaOgn/QanCgeTUinIv6L6QXUFvvIfH 1OLPwQ1hfvEg9NnNLyFezWSy6jvoVBTIPqicD/r3FkithnQ1IDkdSjrarPMxJkvuh3l7XZHo49GV HQ8i5zh5w4YISrcEtE99lJisvni2Jqx7we5tey9voQFDyM8jxlSWv3pmoUTCtBkX/eKHJXosgsuS B4TGDCVPOjla/emI5c9MhMG7O4WEEmoSdPbmraPw66YZD6uLyhV4DPHbiDWRzXWnClHSyjB9rky9 lausFxogvu4l9H+KDsXIadNDWdLdu1/enS/wDd9zh5S78rY2jeXaG4mnf4seEKamZ7KQ6FIHrcyP ezdDzssPQcTQcGRMQzCn6wP3tlGk7rsfmyHMlFqdRoNNv+ZER/OkmZFPW655zRfbMi0vtrqK2Awm 9ggobb1oktfd9PPNXMUY+DNVlgR2G7jLnenSoQausLUm0pHoNE8TWFv851Y6SOYnvn488sP1Tki5 F3rKwclawQFHUXTCQw+QSh9ay8xgnNZfH+u9NY7w3gPoeKBOAFcBc2BtzcgekeWS8qgEmm2/oNFV G0ivPQbRx8FjRKbuF7g3YhgNZZ0ac8FneuUtJ2PkSIFTZhaAiC0utvxk0ndmWFiW4acEkMZGrLaM L2zWNjrqwsD2zsFNBGiDvXgBEADCXQy1n7wjRxG12DOVADawjghKcG+5LtEf31WftHKLFbp/HArj BhkT6mj+CCI1ClqY+FYU5CK/s0ScMfLxRGLZ0Ktzawb78vOgBVFT3yB1yWBTewsAXdqNqRooaUNo 8cG/NNJLjhccH/7PO/FWX5qftOVUJ/AIsAhKQJ18Tc8Ik73v427EDxuKb9mTAnYQFA3Ev3hAiVbO 6Rv39amVOfJ8sqwiSUGidj2Fctg2aB5JbeMln0KCUbTD1LhEFepeKypfofAXQbGwaCjAhmkWy/q3 IT1mUrPxOngbxdRoOx1tGUC0HCMUW1sFaJgQPMmDcR0JGPOpgsKnitsSnN7ShcCr1buel7vLnUMD +TAZ5opdoF6HjAvAnBQaijtK6minkrM0seNXnCg0KkV8xhMNa6zCs1rq4GgjNLJue2EmuyHooHA4 7JMoLVHcxVeuNTp6K2+XRx0Pk4e2Lj8IVy9yEYyrywEOC5XRW37KJjsiOAsumi1rkvM7QREWgUDe Xs0+RpxI3QrrANh71fLMRo7LKRF3Gvw13NVCCC9ea20P4PwhgWKStkwO2NO+YJsAoS1QycMi/vKu 0EHhknYXamaSV50oZzHKmX56vEeJHTcngrM8R1SwJCYopCx9gkz90bTVYlitJa5hloWTYeMD7FNj Y6jfVSzgM/K4gMgUNDW/PPGeMwARAQABwsF2BBgBCAAgFiEEgnQYxPSsWOdyMMRzNHYf+OetQ9IF AmiDvXgCGwwACgkQNHYf+OetQ9LHDBAAhk+ab8+WrbS/b1/gYW3q1KDiXU719nCtfkUVXKidW5Ec Idlr5HGt8ilLoxSWT2Zi368iHCXS0WenGgPwlv8ifvB7TOZiiTDZROZkXjEBmU4nYjJ7GymawpWv oQwjMsPuq6ysbzWtOZ7eILx7cI0FjQeJ/Q2baRJub0uAZNwBOxCkAS6lpk5Fntd2u8CWmDQo4SYp xeuQ+pwkp0yEP30RhN2BO2DXiBEGSZSYh+ioGbCHQPIV3iVj0h6lcCPOqopZqyeCfigeacBI0nvN jHWz/spzF3+4OS+3RJvoHtAQmProxyGib8iVsTxgZO3UUi4TSODeEt0i0kHSPY4sCciOyXfAyYoD DFqhRjOEwBBxhr+scU4C1T2AflozvDwq3VSONjrKJUkhd8+WsdXxMdPFgBQuiKKwUy11mz6KQfcR wmDehF3UaUoxa+YIhWPbKmycxuX/D8SvnqavzAeAL1OcRbEI/HsoroVlEFbBRNBZLJUlnTPs8ZcU 4+8rq5YX1GUrJL3jf6SAfSgO7UdkEET3PdcKFYtS+ruV1Cp5V0q4kCfI5jk25iiz8grM2wOzVSsc l1mEkhiEPH87HP0whhb544iioSnumd3HJKL7dzhRegsMizatupp8D65A2JziW0WKopa1iw9fti3A aBeNN4ijKZchBXHPgVx+YtWRHfcm4l8= OpenPGP: url=https://posteo.de/keys/markus.probst@posteo.de.asc; preference=encrypt Content-Type: text/plain; charset="utf-8" Implement core Pin> abstractions, including * `Vec::pin` and `Vec::into_pin` for constructing a `Pin>`. If T does not implement `Unpin`, its values will never be moved. * an extension for `Pin>` allowing PinInit to be initialied on a Pin, as well as truncating and popping values from the Vec Signed-off-by: Markus Probst --- rust/kernel/alloc.rs | 1 + rust/kernel/alloc/kvec.rs | 86 +++++++++++++++++++++++++++++++++++++++ rust/kernel/prelude.rs | 2 +- 3 files changed, 88 insertions(+), 1 deletion(-) diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs index a2c49e5494d3..9c129eaf0625 100644 --- a/rust/kernel/alloc.rs +++ b/rust/kernel/alloc.rs @@ -24,6 +24,7 @@ pub use self::kvec::KVec; pub use self::kvec::VVec; pub use self::kvec::Vec; +pub use self::kvec::PinnedVecExt; =20 /// Indicates an allocation error. #[derive(Copy, Clone, PartialEq, Eq, Debug)] diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs index 3c72e0bdddb8..d5582a7f17e9 100644 --- a/rust/kernel/alloc/kvec.rs +++ b/rust/kernel/alloc/kvec.rs @@ -16,11 +16,13 @@ ops::DerefMut, ops::Index, ops::IndexMut, + pin::Pin, ptr, ptr::NonNull, slice, slice::SliceIndex, }; +use pin_init::PinInit; =20 mod errors; pub use self::errors::{InsertError, PushError, RemoveError}; @@ -109,6 +111,21 @@ pub struct Vec { _p: PhantomData, } =20 +/// Extension for Pin> +pub trait PinnedVecExt { + /// Pin-initializes P and appends it to the back of the [`Vec`] instan= ce without reallocating. + fn push_pin_init>, P: PinInit>(&mut self, i= nit: P) -> Result<(), E>; + + /// Shortens the vector, setting the length to `len` and drops the rem= oved values. + /// If `len` is greater than or equal to the current length, this does= nothing. + /// + /// This has no effect on the capacity and will not allocate. + fn truncate(&mut self, len: usize); + + /// Removes the last element from a vector and drops it returning true= , or false if it is empty. + fn pop(&mut self) -> bool; +} + /// Type alias for [`Vec`] with a [`Kmalloc`] allocator. /// /// # Examples @@ -719,6 +736,18 @@ pub fn retain(&mut self, mut f: impl FnMut(&mut T) -> = bool) { } self.truncate(num_kept); } + + /// Constructs a new `Pin>`. + #[inline] + pub fn pin(capacity: usize, flags: Flags) -> Result, AllocEr= ror> { + Self::with_capacity(capacity, flags).map(Pin::::from) + } + + /// Convert a [`Vec`] to a [`Pin>`]. If `T` does not imp= lement + /// [`Unpin`], then its values will be pinned in memory and can't be m= oved. + pub fn into_pin(this: Self) -> Pin { + this.into() + } } =20 impl Vec { @@ -1294,6 +1323,63 @@ fn drop(&mut self) { } } =20 +impl PinnedVecExt for Pin> { + fn truncate(&mut self, len: usize) { + // SAFETY: truncate will not reallocate the Vec + // CAST: Pin is a transparent wrapper of Ptr + unsafe { &mut *core::ptr::from_mut(self).cast::>() }.tru= ncate(len); + } + + fn push_pin_init>, P: PinInit>(&mut self, i= nit: P) -> Result<(), E> { + // SAFETY: capacity, spare_capacity_mut and inc_len will not + // reallocate the Vec. + // CAST: Pin is a transparent wrapper of Ptr + let this =3D unsafe { &mut *core::ptr::from_mut(self).cast::>() }; + + if this.len() < this.capacity() { + let spare =3D this.spare_capacity_mut(); + // SAFETY: the length is less than the capacity, so `spare` is= non-empty. + unsafe { init.__pinned_init(spare.get_unchecked_mut(0).as_mut_= ptr())? }; + // SAFETY: We just initialised the first spare entry, so it is= safe to + // increase the length by 1. We also know that the new length = is <=3D capacity. + unsafe { this.inc_len(1) }; + Ok(()) + } else { + Err(E::from(PushError(init))) + } + } + + fn pop(&mut self) -> bool { + if self.is_empty() { + return false; + } + + // SAFETY: + // - We just checked that the length is at least one. + // - dec_len will not reallocate the Vec + // CAST: Pin is a transparent wrapper of Ptr + let ptr: *mut [T] =3D unsafe { (*core::ptr::from_mut(self).cast::<= Vec>()).dec_len(1) }; + + // SAFETY: the contract of `dec_len` guarantees that the elements = in `ptr` are + // valid elements whose ownership has been transferred to the call= er. + unsafe { ptr::drop_in_place(ptr) }; + true + } +} + +impl From> for Pin> { + /// Converts a `Vec` into a `Pin>`. If `T` does not im= plement [`Unpin`], then + /// every value in v will be pinned in memory and can't be moved. + /// + /// This moves `v` into `Pin` without moving any of the values of `v` = or allocating and copying + /// any memory. + fn from(v: Vec) -> Self { + // SAFETY: The values wrapped inside a `Pin>` cannot be = moved or replaced as long + // as `T` does not implement `Unpin`. + unsafe { Pin::new_unchecked(v) } + } +} + #[macros::kunit_tests(rust_kvec_kunit)] mod tests { use super::*; diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs index 25fe97aafd02..7179e2ca2a14 100644 --- a/rust/kernel/prelude.rs +++ b/rust/kernel/prelude.rs @@ -19,7 +19,7 @@ c_ushort, c_void, }; =20 -pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec= , Vec}; +pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, PinnedVecE= xt, VBox, VVec, Vec}; =20 #[doc(no_inline)] pub use macros::{export, kunit_tests, module, vtable}; --=20 2.49.1