From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DE25617C225; Mon, 10 Mar 2025 17:19:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741627154; cv=none; b=X8jB3E1N76/RMjbXYzBQGkoRj39+RaeBA4w7L5nD1JiSb9dvq/txFJH92VAAgZSqQAEUej3Wz+es9YiM6NIxg18A3+Z57jZBl+TC+gPaf6EkveAdrTvYwlZ3hF9mWIRAZ4SgAXs9HLQT+T332Tnn0xJgFqMfLCQE6U+5Dl7mzP0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741627154; c=relaxed/simple; bh=Uu54+qm7DnfQGVbqP8L8jk70yuLYTe2ZSpozUQJx4v0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=myzmXvQvomvItWB+xxjlQqfpvOtFL40trAty0ewkzyr41BJiEzimFWEU0oeGq2SlDcysdiBuORXlyVIzEqaxwbTVq+FB66C06XVCoITnb6cwrxZk52khkuPIHfBjhGHuXChabuSLy/aOOkkNFedKhOWS3a5RR1RLP+FyvNCeKyo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VEp9ovgO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VEp9ovgO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 12643C4CEEC; Mon, 10 Mar 2025 17:19:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1741627153; bh=Uu54+qm7DnfQGVbqP8L8jk70yuLYTe2ZSpozUQJx4v0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VEp9ovgOD52qBpKEYqK5VC4zkh3WiJXJWJ+zt/aFha3P91AXZrVVsy5faoeo5Dgvt neePtI6k+X24VeNnqURbSNfztEtsZKZSBCnKBl1ufby5wO+3reDKRPDIiEMLmktWcl sfIyPc8C6lT4ICuGvvw4pFUteRBtIyLiLeHOX4B8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Alice Ryhl , Benno Lossin , Gary Guo , Danilo Krummrich , Miguel Ojeda Subject: [PATCH 6.12 031/269] rust: alloc: add `Allocator` trait Date: Mon, 10 Mar 2025 18:03:04 +0100 Message-ID: <20250310170458.956138866@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250310170457.700086763@linuxfoundation.org> References: <20250310170457.700086763@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Danilo Krummrich commit b7a084ba4fbb8f416ce8d19c93a3a2bee63c9c89 upstream. Add a kernel specific `Allocator` trait, that in contrast to the one in Rust's core library doesn't require unstable features and supports GFP flags. Subsequent patches add the following trait implementors: `Kmalloc`, `Vmalloc` and `KVmalloc`. Reviewed-by: Alice Ryhl Reviewed-by: Benno Lossin Reviewed-by: Gary Guo Signed-off-by: Danilo Krummrich Link: https://lore.kernel.org/r/20241004154149.93856-2-dakr@kernel.org [ Fixed typo. - Miguel ] Signed-off-by: Miguel Ojeda Signed-off-by: Greg Kroah-Hartman --- rust/kernel/alloc.rs | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) --- a/rust/kernel/alloc.rs +++ b/rust/kernel/alloc.rs @@ -11,6 +11,7 @@ pub mod vec_ext; /// Indicates an allocation error. #[derive(Copy, Clone, PartialEq, Eq, Debug)] pub struct AllocError; +use core::{alloc::Layout, ptr::NonNull}; /// Flags to be used when allocating memory. /// @@ -86,3 +87,103 @@ pub mod flags { /// small allocations. pub const GFP_NOWAIT: Flags = Flags(bindings::GFP_NOWAIT); } + +/// The kernel's [`Allocator`] trait. +/// +/// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described +/// via [`Layout`]. +/// +/// [`Allocator`] is designed to be implemented as a ZST; [`Allocator`] functions do not operate on +/// an object instance. +/// +/// In order to be able to support `#[derive(SmartPointer)]` later on, we need to avoid a design +/// that requires an `Allocator` to be instantiated, hence its functions must not contain any kind +/// of `self` parameter. +/// +/// # Safety +/// +/// - A memory allocation returned from an allocator must remain valid until it is explicitly freed. +/// +/// - Any pointer to a valid memory allocation must be valid to be passed to any other [`Allocator`] +/// function of the same type. +/// +/// - Implementers must ensure that all trait functions abide by the guarantees documented in the +/// `# Guarantees` sections. +pub unsafe trait Allocator { + /// Allocate memory based on `layout` and `flags`. + /// + /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout + /// constraints (i.e. minimum size and alignment as specified by `layout`). + /// + /// This function is equivalent to `realloc` when called with `None`. + /// + /// # Guarantees + /// + /// When the return value is `Ok(ptr)`, then `ptr` is + /// - valid for reads and writes for `layout.size()` bytes, until it is passed to + /// [`Allocator::free`] or [`Allocator::realloc`], + /// - aligned to `layout.align()`, + /// + /// Additionally, `Flags` are honored as documented in + /// . + fn alloc(layout: Layout, flags: Flags) -> Result, AllocError> { + // SAFETY: Passing `None` to `realloc` is valid by its safety requirements and asks for a + // new memory allocation. + unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags) } + } + + /// Re-allocate an existing memory allocation to satisfy the requested `layout`. + /// + /// If the requested size is zero, `realloc` behaves equivalent to `free`. + /// + /// If the requested size is larger than the size of the existing allocation, a successful call + /// to `realloc` guarantees that the new or grown buffer has at least `Layout::size` bytes, but + /// may also be larger. + /// + /// If the requested size is smaller than the size of the existing allocation, `realloc` may or + /// may not shrink the buffer; this is implementation specific to the allocator. + /// + /// On allocation failure, the existing buffer, if any, remains valid. + /// + /// The buffer is represented as `NonNull<[u8]>`. + /// + /// # Safety + /// + /// - If `ptr == Some(p)`, then `p` must point to an existing and valid memory allocation + /// created by this [`Allocator`]; if `old_layout` is zero-sized `p` does not need to be a + /// pointer returned by this [`Allocator`]. + /// - `ptr` is allowed to be `None`; in this case a new memory allocation is created and + /// `old_layout` is ignored. + /// - `old_layout` must match the `Layout` the allocation has been created with. + /// + /// # Guarantees + /// + /// This function has the same guarantees as [`Allocator::alloc`]. When `ptr == Some(p)`, then + /// it additionally guarantees that: + /// - the contents of the memory pointed to by `p` are preserved up to the lesser of the new + /// and old size, i.e. `ret_ptr[0..min(layout.size(), old_layout.size())] == + /// p[0..min(layout.size(), old_layout.size())]`. + /// - when the return value is `Err(AllocError)`, then `ptr` is still valid. + unsafe fn realloc( + ptr: Option>, + layout: Layout, + old_layout: Layout, + flags: Flags, + ) -> Result, AllocError>; + + /// Free an existing memory allocation. + /// + /// # Safety + /// + /// - `ptr` must point to an existing and valid memory allocation created by this [`Allocator`]; + /// if `old_layout` is zero-sized `p` does not need to be a pointer returned by this + /// [`Allocator`]. + /// - `layout` must match the `Layout` the allocation has been created with. + /// - The memory allocation at `ptr` must never again be read from or written to. + unsafe fn free(ptr: NonNull, layout: Layout) { + // SAFETY: The caller guarantees that `ptr` points at a valid allocation created by this + // allocator. We are passing a `Layout` with the smallest possible alignment, so it is + // smaller than or equal to the alignment previously used with this allocation. + let _ = unsafe { Self::realloc(Some(ptr), Layout::new::<()>(), layout, Flags(0)) }; + } +}