From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2A0B7C88E41 for ; Thu, 10 Sep 2026 09:02:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 447446B009F; Thu, 10 Sep 2026 05:02:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3F8676B00A0; Thu, 10 Sep 2026 05:02:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2C7C76B00A1; Thu, 10 Sep 2026 05:02:14 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 07FC96B009F for ; Thu, 10 Sep 2026 05:02:14 -0400 (EDT) Received: from smtpin30.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 378C5A47FE for ; Thu, 10 Sep 2026 09:02:13 +0000 (UTC) X-FDA: 85197260946.30.9252C83 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf15.hostedemail.com (Postfix) with ESMTP id 67ADDA0009 for ; Thu, 10 Sep 2026 09:02:11 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jZe2GdwO; spf=pass (imf15.hostedemail.com: domain of a.hindborg@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=a.hindborg@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789030931; b=CYoGw6d0u+UKqs0WZb9Wx0ItHox7HoIJHzjAFK3zZVm2yqtGBjm7obGHRF5fk07hjK6L8l HelggAlAhRQgK1TAjTRRKzslXhV+U5XdPJ51lzvqn6ExePKowBLJVMsn2b4Nquyleng6TX lAqxq0/B/QkE0q7QOU40KPDyxtF1xWs= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=jZe2GdwO; spf=pass (imf15.hostedemail.com: domain of a.hindborg@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=a.hindborg@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789030931; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=nMuMfZ5oOT5xSQNE2UbnqHDsN16Vf+j3KeZtRcXbj5Q=; b=a4IIbiLZa6IZppovV+Wye5TrycvGylQ0nBtPE5H/PTfCXtt/iILRv6UGLvhA1CVscOKWIf y4EZd7HMkYbBs6x394cj1Y4eJpWZJh2RNa2kzWVr8VS/FTNIMv6yqwO4Fy2PbT+i27PjX2 SumrEZdvt4bfNOWk9uU0KtjJWtTxZtA= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id B74C343CD1; Thu, 10 Sep 2026 09:02:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B707A1F00893; Thu, 10 Sep 2026 09:01:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789030930; bh=nMuMfZ5oOT5xSQNE2UbnqHDsN16Vf+j3KeZtRcXbj5Q=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=jZe2GdwOlAtK2Y/DOgIkQVr++reMQhah0vlgv6xXz1IeuoFD6LxcNE0jRYaUZrkqr Nh4Kfb6H0sjZ/vWlR09a9d/t7FmyuRr5lwq8BQQpuWgwcbSBs3gYCszxCc6opuexwl rI12KdSLv4BUZH0JjgRbkTrNcz2peyBAc2gL6KF7JEyYm2WT32wELiGPU/hSO0w/Hi YQ0/qtRVZxZCkxXNXHXP/2x8/msUwDKOJH+kwguKlwEyCxrLfIdng7SiuzDxmJYWQE FHq/Vv64FeSeWdF1pQvfMfjuR90V4qVR8eWlUfgzF++JnUnK0avT4qUXVkZmXXpudm 5kRP7FdZovV8w== From: Andreas Hindborg Date: Thu, 10 Sep 2026 11:00:07 +0200 Subject: [PATCH v21 3/9] rust: implement `ForeignOwnable` for `Owned` MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260910-unique-ref-v21-3-e83257373062@kernel.org> References: <20260910-unique-ref-v21-0-e83257373062@kernel.org> In-Reply-To: <20260910-unique-ref-v21-0-e83257373062@kernel.org> To: Danilo Krummrich , Lorenzo Stoakes , Vlastimil Babka , "Liam R. Howlett" , Uladzislau Rezki , Miguel Ojeda , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Alice Ryhl , Trevor Gross , Daniel Almeida , Tamir Duberstein , Alexandre Courbot , =?utf-8?q?Onur_=C3=96zkan?= , Lyude Paul , Greg Kroah-Hartman , =?utf-8?q?Arve_Hj=C3=B8nnev=C3=A5g?= , Todd Kjos , Christian Brauner , Carlos Llamas , "Rafael J. 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This allows use of `Owned` in places such as the `XArray`. Note that `T` does not need to implement `ForeignOwnable` for `Owned` to implement `ForeignOwnable`. Assisted-by: LLM Signed-off-by: Andreas Hindborg Reviewed-by: Gary Guo Reviewed-by: Alice Ryhl --- rust/kernel/owned.rs | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs index b76edd7c4151..e54a058d65cd 100644 --- a/rust/kernel/owned.rs +++ b/rust/kernel/owned.rs @@ -15,6 +15,8 @@ ptr::NonNull, // }; +use kernel::types::ForeignOwnable; + /// Types that specify their own way of performing allocation and destruction. Typically, this trait /// is implemented on types from the C side. /// @@ -189,3 +191,51 @@ fn drop(&mut self) { unsafe { T::release(self.ptr) }; } } + +// SAFETY: We derive the pointer to `T` from a valid `T`, so the returned +// pointer satisfy alignment requirements of `T`. +unsafe impl ForeignOwnable for Owned { + const FOREIGN_ALIGN: usize = core::mem::align_of::(); + + type Borrowed<'a> + = &'a T + where + Self: 'a; + type BorrowedMut<'a> + = Pin<&'a mut T> + where + Self: 'a; + + #[inline] + fn into_foreign(self) -> *mut kernel::ffi::c_void { + Owned::into_raw(self).as_ptr().cast() + } + + #[inline] + unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self { + // SAFETY: By function safety contract, `ptr` came from `into_foreign` and cannot be null. + let ptr = unsafe { NonNull::new_unchecked(ptr.cast()) }; + + // SAFETY: By the function safety contract, `ptr` was returned by `into_foreign`, which gave + // up exclusive ownership of a valid, pinned `T`; we retake that ownership here. + unsafe { Owned::from_raw(ptr) } + } + + #[inline] + unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowed<'a> { + // SAFETY: By function safety requirements, `ptr` is valid for use as a + // reference for `'a`. + unsafe { &*ptr.cast() } + } + + #[inline] + unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a> { + // SAFETY: By function safety requirements, `ptr` is valid for use as a + // unique reference for `'a`. + let inner = unsafe { &mut *ptr.cast() }; + + // SAFETY: We never move out of inner, and we do not hand out mutable + // references when `T: !Unpin`. + unsafe { Pin::new_unchecked(inner) } + } +} -- 2.51.2