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Howlett" , "Igor Korotin" , "Pavel Tikhomirov" Cc: , , , , , , , , , Subject: Re: [PATCH v17 03/10] rust: implement `ForeignOwnable` for `Owned` From: "Gary Guo" X-Mailer: aerc 0.21.0 References: <20260604-unique-ref-v17-0-7b4c3d2930b9@kernel.org> <20260604-unique-ref-v17-3-7b4c3d2930b9@kernel.org> In-Reply-To: <20260604-unique-ref-v17-3-7b4c3d2930b9@kernel.org> X-ClientProxiedBy: LO2P265CA0512.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:13b::19) To LOVP265MB8871.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:488::16) Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LOVP265MB8871:EE_|CW1P265MB7593:EE_ X-MS-Office365-Filtering-Correlation-Id: 3457848e-0f2b-4fc3-dc24-08decb9e37d1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|366016|376014|23010399003|10070799003|1800799024|56012099006|4143699003|6133799003|22082099003|18002099003|921020; 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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`. > > Signed-off-by: Andreas Hindborg > --- > rust/kernel/owned.rs | 46 ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 46 insertions(+) > > diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs > index 456e239e906e..5eacdf327d12 100644 > --- a/rust/kernel/owned.rs > +++ b/rust/kernel/owned.rs > @@ -15,6 +15,8 @@ > ptr::NonNull, // > }; > =20 > +use kernel::types::ForeignOwnable; > + > /// Types that specify their own way of performing allocation and destru= ction. Typically, this trait > /// is implemented on types from the C side. > /// > @@ -108,6 +110,7 @@ pub trait Ownable { > /// > /// - Until `T::release` is called, this `Owned` exclusively owns the= underlying `T`. > /// - The `T` value is pinned. > +#[repr(transparent)] AFAIT this `#[repr(transparent)]` isn't actually needed. > pub struct Owned { > ptr: NonNull, > } > @@ -185,3 +188,46 @@ fn drop(&mut self) { > unsafe { T::release(self.ptr.as_mut()) }; > } > } > + > +// SAFETY: We derive the pointer to `T` from a valid `T`, so the returne= d > +// pointer satisfy alignment requirements of `T`. > +unsafe impl ForeignOwnable for Owned { You should drop the `'static` bound and put where bound on the GAT below instead. See how `Box` is doing it. Best, Gary > + const FOREIGN_ALIGN: usize =3D core::mem::align_of::>(); > + > + type Borrowed<'a> =3D &'a T; > + type BorrowedMut<'a> =3D Pin<&'a mut T>; > + > + #[inline] > + fn into_foreign(self) -> *mut kernel::ffi::c_void { > + let ptr =3D self.ptr.as_ptr().cast(); > + core::mem::forget(self); > + ptr > + } > + > + #[inline] > + unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self { > + Self { > + // SAFETY: By function safety contract, `ptr` came from > + // `into_foreign` and cannot be null. > + ptr: unsafe { NonNull::new_unchecked(ptr.cast()) }, > + } > + } > + > + #[inline] > + unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowe= d<'a> { > + // SAFETY: By function safety requirements, `ptr` is valid for u= se as a > + // reference for `'a`. > + unsafe { &*ptr.cast() } > + } > + > + #[inline] > + unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Bor= rowedMut<'a> { > + // SAFETY: By function safety requirements, `ptr` is valid for u= se as a > + // unique reference for `'a`. > + let inner =3D unsafe { &mut *ptr.cast() }; > + > + // SAFETY: We never move out of inner, and we do not hand out mu= table > + // references when `T: !Unpin`. > + unsafe { Pin::new_unchecked(inner) } > + } > +}