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Fri, 4 Oct 2024 15:43:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 18E9FC4CEC6; Fri, 4 Oct 2024 15:43:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728056607; bh=Q+ML1ibWYAYZGeFhUyhzJzIY+ZOBQOky3D240qlJo4Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mM3Uexz0BDtA61JTp90r4hhfmffR8zBUbDJS9Gck2GzwPkQJWdqGF2kXRaGcmrWMN 4Y8NSqhOW8sicnvOmy7Ak7+p+pdc6kyeteR2Cbv7utjnJkv7Gyl0gCgA3FSJbUhGz9 kORuqJ0DrEuV9XfjA6LDLbtV/iZ1GKQO4h4zfXR4goB+P+w/rg5I0gqUDQAoVLsLnw cercRS/hZcyU4baHwPeYm3rhtRMVvDUZZrXbG1O8+gULiTC2ecYEGj18pizpQ1g7qQ kSFtD72R8ROVqH7OsEpN3dXlKW13qg6430qMwWMIZ+nEeZEQvAcEz4dylkb/jGbzWs 5j4auh5MnXLQA== From: Danilo Krummrich To: ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, a.hindborg@samsung.com, aliceryhl@google.com, akpm@linux-foundation.org Cc: daniel.almeida@collabora.com, faith.ekstrand@collabora.com, boris.brezillon@collabora.com, lina@asahilina.net, mcanal@igalia.com, zhiw@nvidia.com, cjia@nvidia.com, jhubbard@nvidia.com, airlied@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org, Danilo Krummrich Subject: [PATCH v9 15/29] rust: alloc: introduce `ArrayLayout` Date: Fri, 4 Oct 2024 17:41:19 +0200 Message-ID: <20241004154149.93856-16-dakr@kernel.org> X-Mailer: git-send-email 2.46.1 In-Reply-To: <20241004154149.93856-1-dakr@kernel.org> References: <20241004154149.93856-1-dakr@kernel.org> MIME-Version: 1.0 X-Rspamd-Queue-Id: 195ED4001A X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: pg54kkr53acs16uqx8pidg7qsx91y7bt X-HE-Tag: 1728056607-700792 X-HE-Meta: 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 UswrMOIh ypO46ksqaIxO7fPIQQUJdoDbnbCoG4YWt3bFPOl6bDXNPRZRwZbFJALJcq8GqweDOG30lwXBFkhZo7OU7Jw2PdSW/v5u2sCa/exjzQyy8MImbp8/nKy246/SG1jhe/UsJ9LZKNmkMhvI+/Ndw1GE1sCwQKQNMzRyROJAWYDzNlDgCN1dodR89AoruDW9m5/AsPGTotR67l4Hc7aICQpoRNZKWu9TYScQDI6KfMeILqfUw/ORLBqRgbscKLjVj0jbP7o5bP2PPIL03MZ/0MbrFK4fE1otnixfpuTEjgLBhGNcyYlnheBycGbHvS7kE7qet7jytQmWWs0E3ffObG/Yq4tKZ/w1Gzcav32Orz+lEHybBFNM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Benno Lossin When allocating memory for arrays using allocators, the `Layout::array` function is typically used. It returns a result, since the given size might be too big. However, `Vec` and its iterators store their allocated capacity and thus they already did check that the size is not too big. The `ArrayLayout` type provides this exact behavior, as it can be infallibly converted into a `Layout`. Instead of a `usize` capacity, `Vec` and other similar array-storing types can use `ArrayLayout` instead. Reviewed-by: Gary Guo Signed-off-by: Benno Lossin Signed-off-by: Danilo Krummrich --- rust/kernel/alloc.rs | 1 + rust/kernel/alloc/layout.rs | 91 +++++++++++++++++++++++++++++++++++++ 2 files changed, 92 insertions(+) create mode 100644 rust/kernel/alloc/layout.rs diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs index ebe58247504f..bf143a71d53d 100644 --- a/rust/kernel/alloc.rs +++ b/rust/kernel/alloc.rs @@ -5,6 +5,7 @@ #[cfg(not(any(test, testlib)))] pub mod allocator; pub mod kbox; +pub mod layout; pub mod vec_ext; #[cfg(any(test, testlib))] diff --git a/rust/kernel/alloc/layout.rs b/rust/kernel/alloc/layout.rs new file mode 100644 index 000000000000..7f0427a4d3d8 --- /dev/null +++ b/rust/kernel/alloc/layout.rs @@ -0,0 +1,91 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Memory layout. +//! +//! Custom layout types extending or improving [`Layout`]. + +use core::{alloc::Layout, marker::PhantomData}; + +/// Error when constructing an [`ArrayLayout`]. +pub struct LayoutError; + +/// A layout for an array `[T; n]`. +/// +/// # Invariants +/// +/// - `len * size_of::() <= isize::MAX` +pub struct ArrayLayout { + len: usize, + _phantom: PhantomData T>, +} + +impl Clone for ArrayLayout { + fn clone(&self) -> Self { + *self + } +} +impl Copy for ArrayLayout {} + +const ISIZE_MAX: usize = isize::MAX as usize; + +impl ArrayLayout { + /// Creates a new layout for `[T; 0]`. + pub const fn empty() -> Self { + // INVARIANT: `0 * size_of::() <= isize::MAX` + Self { + len: 0, + _phantom: PhantomData, + } + } + + /// Creates a new layout for `[T; len]`. + /// + /// # Errors + /// + /// When `len * size_of::()` overflows or when `len * size_of::() > isize::MAX`. + pub const fn new(len: usize) -> Result { + match len.checked_mul(core::mem::size_of::()) { + Some(len) if len <= ISIZE_MAX => { + // INVARIANT: we checked above that `len * size_of::() <= isize::MAX` + Ok(Self { + len, + _phantom: PhantomData, + }) + } + _ => Err(LayoutError), + } + } + + /// Creates a new layout for `[T; len]`. + /// + /// # Safety + /// + /// `len` must be a value, for which `len * size_of::() <= isize::MAX` is true. + pub unsafe fn new_unchecked(len: usize) -> Self { + // INVARIANT: By the safety requirements of this function + // `len * size_of::() <= isize::MAX`. + Self { + len, + _phantom: PhantomData, + } + } + + /// Returns the number of array elements represented by this layout. + pub const fn len(&self) -> usize { + self.len + } + + /// Returns `true` when no array elements are represented by this layout. + pub const fn is_empty(&self) -> bool { + self.len == 0 + } +} + +impl From> for Layout { + fn from(value: ArrayLayout) -> Self { + let res = Layout::array::(value.len); + // SAFETY: by the type invariant of `ArrayLayout` we have + // `len * size_of::() <= isize::MAX` and thus the result must be `Ok`. + unsafe { res.unwrap_unchecked() } + } +}