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MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260625-unique-ref-v18-5-4e06b5896d47@kernel.org> References: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org> In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@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. Wysocki" , Dave Ertman , Ira Weiny , Leon Romanovsky , Paul Moore , Serge Hallyn , David Airlie , Simona Vetter , Alexander Viro , Jan Kara , Igor Korotin , Viresh Kumar , Nishanth Menon , Stephen Boyd , Bjorn Helgaas , =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= , Pavel Tikhomirov , Michal Wilczynski Cc: Andreas Hindborg , Philipp Stanner , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, driver-core@lists.linux.dev, linux-block@vger.kernel.org, linux-security-module@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fsdevel@vger.kernel.org, linux-pm@vger.kernel.org, linux-pci@vger.kernel.org, linux-pwm@vger.kernel.org, Oliver Mangold , Viresh Kumar , Igor Korotin X-Mailer: b4 0.16-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=37673; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=Ge33fPenQLmIaXz9HGhJbw3zyLT2i9D50c2AUvYScUI=; b=owEBbQKS/ZANAwAKAfpQKQiqxb3QAcsmYgBqPP/B1keWEBWobOEu4E5ydo5wJtBu3IQ8gcnVG jXhh7QGdCGJAjMEAAEKAB0WIQRXitnI2WZ2JirAaob6UCkIqsW90AUCajz/wQAKCRD6UCkIqsW9 0E1lD/9rRJugOQ0accbM6aQ752hvihYbhe0Y9U/SnXEBKsMSNT0ZEbZAqcm9yfy0wKZBeywo4JU cmLZujm6h96Kk3p1QcJU6lbePnNUksWE536qSU7tES2SeKgwc4enYYBKqbCNayYhHZPMwH2Czc4 7vIdCeYO4F3t4Q6r5chIbA3vbWOgni3eFwZYf4RKy4LafEDUKh6Ex/2OIv9+Wl92jbj2iSgQNJA 69Zxh823fxrSHPjPcuLgihePj1jxmsVZBblDA58m7ybebMBc6A2M+nbZ97cfGJJOo/x6AZqtaCe NKhOLk9s1cjIUT+B/Oa1PrQzEZUhNC9b2NelnYNL9HQB+9DAMFslSGud3fa9kjdYWlBEW6DA4rq 4ju9eZI477qughzVFlI0EPCJsi+x8gRpPC4JRBver+11VIG4u0AcfeO3yO1nGyYvTrztX2vX1rD XUo9hAqx5o/+tMt/I+CmEpptFkVw7Ydpfh0peabcH/adlCsU90bhgUD8Hmk+W3A1Sp1wcVz5EbM Ml0il41Jlo76TObjCtao8PB3tg5n+6XIIsEMz5TXAMpxCZk5qNQ42mDS+oySCPVhNWieKhQtJ1A yvFZZrbbM+TRaOLtUV8YTBep4tuB0vPai/oo9M9wY7h/Dkazb744rkoXjPU580zpLn1/F2B6ota uGL1NxPwdAM6wVQ== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 800C440002 X-Rspam-User: X-Stat-Signature: bfxct8kcmpmnb6auigod1sa3t9my5fp6 X-HE-Tag: 1782382643-837573 X-HE-Meta: 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 s/WKDsJD 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Oliver Mangold There are types where it may both be reference counted in some cases and owned in others. In such cases, obtaining `ARef` from `&T` would be unsound as it allows creation of `ARef` copy from `&Owned`. Therefore, we split `AlwaysRefCounted` into `RefCounted` (which `ARef` would require) and a marker trait to indicate that the type is always reference counted (and not `Ownable`) so the `&T` -> `ARef` conversion is possible. - Rename `AlwaysRefCounted` to `RefCounted`. - Add a new unsafe trait `AlwaysRefCounted`. - Implement the new trait `AlwaysRefCounted` for the newly renamed `RefCounted` implementations. This leaves functionality of existing implementers of `AlwaysRefCounted` intact. Suggested-by: Alice Ryhl Reviewed-by: Daniel Almeida Signed-off-by: Oliver Mangold [ Andreas: Updated commit message and rebase on rust-next (7.2) ] Acked-by: Igor Korotin Acked-by: Danilo Krummrich Acked-by: Viresh Kumar Reviewed-by: Gary Guo Co-developed-by: Andreas Hindborg Signed-off-by: Andreas Hindborg --- rust/kernel/auxiliary.rs | 10 +++++++- rust/kernel/block/mq/request.rs | 19 +++++++++----- rust/kernel/cred.rs | 16 ++++++++++-- rust/kernel/device.rs | 12 +++++++-- rust/kernel/device/property.rs | 11 ++++++-- rust/kernel/drm/device.rs | 9 +++++-- rust/kernel/drm/gem/mod.rs | 16 +++++++++--- rust/kernel/fs/file.rs | 23 ++++++++++++++--- rust/kernel/i2c.rs | 13 +++++++--- rust/kernel/mm.rs | 22 +++++++++++++--- rust/kernel/mm/mmput_async.rs | 12 +++++++-- rust/kernel/opp.rs | 16 +++++++++--- rust/kernel/owned.rs | 2 +- rust/kernel/pci.rs | 10 +++++++- rust/kernel/pid_namespace.rs | 15 +++++++++-- rust/kernel/platform.rs | 10 +++++++- rust/kernel/pwm.rs | 12 +++++++-- rust/kernel/sync/aref.rs | 57 +++++++++++++++++++++++++---------------- rust/kernel/task.rs | 13 ++++++++-- rust/kernel/types.rs | 12 ++++++--- rust/kernel/usb.rs | 17 +++++++++--- 21 files changed, 255 insertions(+), 72 deletions(-) diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs index c42928d5a2393..854525289c8b4 100644 --- a/rust/kernel/auxiliary.rs +++ b/rust/kernel/auxiliary.rs @@ -19,6 +19,10 @@ to_result, // }, prelude::*, + sync::aref::{ + AlwaysRefCounted, + RefCounted, // + }, types::{ ForLt, ForeignOwnable, @@ -344,7 +348,7 @@ unsafe impl device::AsBusDevice for Device kernel::impl_device_context_into_aref!(Device); // SAFETY: Instances of `Device` are always reference-counted. -unsafe impl crate::sync::aref::AlwaysRefCounted for Device { +unsafe impl RefCounted for Device { fn inc_ref(&self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. unsafe { bindings::get_device(self.as_ref().as_raw()) }; @@ -363,6 +367,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Device`. +unsafe impl AlwaysRefCounted for Device {} + impl AsRef> for Device { fn as_ref(&self) -> &device::Device { // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs index ce3e30c81cb5e..8dad15ae4cfb0 100644 --- a/rust/kernel/block/mq/request.rs +++ b/rust/kernel/block/mq/request.rs @@ -9,7 +9,11 @@ block::mq::Operations, error::Result, sync::{ - aref::{ARef, AlwaysRefCounted}, + aref::{ + ARef, + AlwaysRefCounted, + RefCounted, // + }, atomic::Relaxed, Refcount, }, @@ -229,11 +233,10 @@ unsafe impl Send for Request {} // mutate `self` are internally synchronized` unsafe impl Sync for Request {} -// SAFETY: All instances of `Request` are reference counted. This -// implementation of `AlwaysRefCounted` ensure that increments to the ref count -// keeps the object alive in memory at least until a matching reference count -// decrement is executed. -unsafe impl AlwaysRefCounted for Request { +// SAFETY: All instances of `Request` are reference counted. This implementation of `RefCounted` +// ensure that increments to the ref count keeps the object alive in memory at least until a +// matching reference count decrement is executed. +unsafe impl RefCounted for Request { fn inc_ref(&self) { self.wrapper_ref().refcount().inc(); } @@ -255,3 +258,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull) { } } } + +// SAFETY: We currently do not implement `Ownable`, thus it is okay to obtain an `ARef` +// from a `&Request` (but this will change in the future). +unsafe impl AlwaysRefCounted for Request {} diff --git a/rust/kernel/cred.rs b/rust/kernel/cred.rs index ffa156b9df377..b17736a9adcd5 100644 --- a/rust/kernel/cred.rs +++ b/rust/kernel/cred.rs @@ -8,7 +8,15 @@ //! //! Reference: -use crate::{bindings, sync::aref::AlwaysRefCounted, task::Kuid, types::Opaque}; +use crate::{ + bindings, + sync::aref::RefCounted, + task::Kuid, + types::{ + AlwaysRefCounted, + Opaque, // + }, // +}; /// Wraps the kernel's `struct cred`. /// @@ -76,7 +84,7 @@ pub fn euid(&self) -> Kuid { } // SAFETY: The type invariants guarantee that `Credential` is always ref-counted. -unsafe impl AlwaysRefCounted for Credential { +unsafe impl RefCounted for Credential { #[inline] fn inc_ref(&self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. @@ -90,3 +98,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull) { unsafe { bindings::put_cred(obj.cast().as_ptr()) }; } } + +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Credential`. +unsafe impl AlwaysRefCounted for Credential {} diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index 645afc49a27d6..2e90f6a06fd05 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -8,8 +8,12 @@ bindings, fmt, prelude::*, - sync::aref::ARef, + sync::aref::{ + ARef, + RefCounted, // + }, types::{ + AlwaysRefCounted, ForeignOwnable, Opaque, // }, // @@ -448,7 +452,7 @@ pub fn name(&self) -> &CStr { kernel::impl_device_context_into_aref!(Device); // SAFETY: Instances of `Device` are always reference-counted. -unsafe impl crate::sync::aref::AlwaysRefCounted for Device { +unsafe impl RefCounted for Device { fn inc_ref(&self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. unsafe { bindings::get_device(self.as_raw()) }; @@ -460,6 +464,10 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Device`. +unsafe impl AlwaysRefCounted for Device {} + // SAFETY: As by the type invariant `Device` can be sent to any thread. unsafe impl Send for Device {} diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs index 5aead835fbbc0..cee7e25013689 100644 --- a/rust/kernel/device/property.rs +++ b/rust/kernel/device/property.rs @@ -14,7 +14,10 @@ fmt, prelude::*, str::{CStr, CString}, - sync::aref::ARef, + sync::aref::{ + ARef, + AlwaysRefCounted, // + }, types::Opaque, }; @@ -360,7 +363,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { } // SAFETY: Instances of `FwNode` are always reference-counted. -unsafe impl crate::sync::aref::AlwaysRefCounted for FwNode { +unsafe impl crate::sync::aref::RefCounted for FwNode { fn inc_ref(&self) { // SAFETY: The existence of a shared reference guarantees that the // refcount is non-zero. @@ -374,6 +377,10 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&FwNode`. +unsafe impl AlwaysRefCounted for FwNode {} + enum Node<'a> { Borrowed(&'a FwNode), Owned(ARef), diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs index 403fc35353c74..368742a258376 100644 --- a/rust/kernel/drm/device.rs +++ b/rust/kernel/drm/device.rs @@ -15,7 +15,8 @@ prelude::*, sync::aref::{ ARef, - AlwaysRefCounted, // + AlwaysRefCounted, + RefCounted, // }, types::Opaque, workqueue::{ @@ -227,7 +228,7 @@ fn deref(&self) -> &Self::Target { // SAFETY: DRM device objects are always reference counted and the get/put functions // satisfy the requirements. -unsafe impl AlwaysRefCounted for Device { +unsafe impl RefCounted for Device { fn inc_ref(&self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. unsafe { bindings::drm_dev_get(self.as_raw()) }; @@ -242,6 +243,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Device`. +unsafe impl AlwaysRefCounted for Device {} + impl AsRef for Device { fn as_ref(&self) -> &device::Device { // SAFETY: `bindings::drm_device::dev` is valid as long as the DRM device itself is valid, diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs index 01b5bd47a3332..30d3718578fe8 100644 --- a/rust/kernel/drm/gem/mod.rs +++ b/rust/kernel/drm/gem/mod.rs @@ -17,7 +17,7 @@ prelude::*, sync::aref::{ ARef, - AlwaysRefCounted, // + RefCounted, // }, types::Opaque, }; @@ -29,7 +29,7 @@ #[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)] pub mod shmem; -/// A macro for implementing [`AlwaysRefCounted`] for any GEM object type. +/// A macro for implementing [`RefCounted`] for any GEM object type. /// /// Since all GEM objects use the same refcounting scheme. #[macro_export] @@ -42,7 +42,7 @@ impl $( <$( $tparam_id:ident ),+> )? for $type:ty )? ) => { // SAFETY: All GEM objects are refcounted. - unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $type + unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::RefCounted for $type where Self: IntoGEMObject, $( $( $bind_param : $bind_trait ),+ )? @@ -61,6 +61,14 @@ unsafe fn dec_ref(obj: core::ptr::NonNull) { unsafe { bindings::drm_gem_object_put(obj) }; } } + + // SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<$type>` from a + // `&$type`. + unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $type + where + Self: IntoGEMObject, + $( $( $bind_param : $bind_trait ),+ )? + {} }; } #[cfg_attr(not(CONFIG_RUST_DRM_GEM_SHMEM_HELPER), allow(unused))] @@ -98,7 +106,7 @@ fn close(_obj: &::Object, _file: &DriverFile) } /// Trait that represents a GEM object subtype -pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted { +pub trait IntoGEMObject: Sized + super::private::Sealed + RefCounted { /// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as /// this owning object is valid. fn as_raw(&self) -> *mut bindings::drm_gem_object; diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs index 23ee689bd2400..720e57418358d 100644 --- a/rust/kernel/fs/file.rs +++ b/rust/kernel/fs/file.rs @@ -12,8 +12,15 @@ cred::Credential, error::{code::*, to_result, Error, Result}, fmt, - sync::aref::{ARef, AlwaysRefCounted}, - types::{NotThreadSafe, Opaque}, + sync::aref::{ + ARef, + RefCounted, // + }, + types::{ + AlwaysRefCounted, + NotThreadSafe, + Opaque, // + }, // }; use core::ptr; @@ -197,7 +204,7 @@ unsafe impl Sync for File {} // SAFETY: The type invariants guarantee that `File` is always ref-counted. This implementation // makes `ARef` own a normal refcount. -unsafe impl AlwaysRefCounted for File { +unsafe impl RefCounted for File { #[inline] fn inc_ref(&self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. @@ -212,6 +219,10 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&File`. +unsafe impl AlwaysRefCounted for File {} + /// Wraps the kernel's `struct file`. Not thread safe. /// /// This type represents a file that is not known to be safe to transfer across thread boundaries. @@ -233,7 +244,7 @@ pub struct LocalFile { // SAFETY: The type invariants guarantee that `LocalFile` is always ref-counted. This implementation // makes `ARef` own a normal refcount. -unsafe impl AlwaysRefCounted for LocalFile { +unsafe impl RefCounted for LocalFile { #[inline] fn inc_ref(&self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. @@ -249,6 +260,10 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&LocalFile`. +unsafe impl AlwaysRefCounted for LocalFile {} + impl LocalFile { /// Constructs a new `struct file` wrapper from a file descriptor. /// diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs index 624b971ca8b0b..02b2c9220eb11 100644 --- a/rust/kernel/i2c.rs +++ b/rust/kernel/i2c.rs @@ -18,7 +18,8 @@ prelude::*, sync::aref::{ ARef, - AlwaysRefCounted, // + AlwaysRefCounted, + RefCounted, // }, types::Opaque, // }; @@ -424,7 +425,7 @@ pub fn get(index: i32) -> Result> { kernel::impl_device_context_into_aref!(I2cAdapter); // SAFETY: Instances of `I2cAdapter` are always reference-counted. -unsafe impl AlwaysRefCounted for I2cAdapter { +unsafe impl RefCounted for I2cAdapter { fn inc_ref(&self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. unsafe { bindings::i2c_get_adapter(self.index()) }; @@ -435,6 +436,9 @@ unsafe fn dec_ref(obj: NonNull) { unsafe { bindings::i2c_put_adapter(obj.as_ref().as_raw()) } } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from an +// `&I2cAdapter`. +unsafe impl AlwaysRefCounted for I2cAdapter {} /// The i2c board info representation /// @@ -500,7 +504,7 @@ unsafe impl device::AsBusDevice for I2cClient) { unsafe { bindings::put_device(&raw mut (*obj.as_ref().as_raw()).dev) } } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from an +// `&I2cClient`. +unsafe impl AlwaysRefCounted for I2cClient {} impl AsRef> for I2cClient { fn as_ref(&self) -> &device::Device { diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs index 4764d7b68f2a7..83ed94fca14ca 100644 --- a/rust/kernel/mm.rs +++ b/rust/kernel/mm.rs @@ -13,8 +13,15 @@ use crate::{ bindings, - sync::aref::{ARef, AlwaysRefCounted}, - types::{NotThreadSafe, Opaque}, + sync::aref::{ + ARef, + RefCounted, // + }, + types::{ + AlwaysRefCounted, + NotThreadSafe, + Opaque, // + }, // }; use core::{ops::Deref, ptr::NonNull}; @@ -55,7 +62,7 @@ unsafe impl Send for Mm {} unsafe impl Sync for Mm {} // SAFETY: By the type invariants, this type is always refcounted. -unsafe impl AlwaysRefCounted for Mm { +unsafe impl RefCounted for Mm { #[inline] fn inc_ref(&self) { // SAFETY: The pointer is valid since self is a reference. @@ -69,6 +76,9 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a `&Mm`. +unsafe impl AlwaysRefCounted for Mm {} + /// A wrapper for the kernel's `struct mm_struct`. /// /// This type is like [`Mm`], but with non-zero `mm_users`. It can only be used when `mm_users` can @@ -91,7 +101,7 @@ unsafe impl Send for MmWithUser {} unsafe impl Sync for MmWithUser {} // SAFETY: By the type invariants, this type is always refcounted. -unsafe impl AlwaysRefCounted for MmWithUser { +unsafe impl RefCounted for MmWithUser { #[inline] fn inc_ref(&self) { // SAFETY: The pointer is valid since self is a reference. @@ -105,6 +115,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&MmWithUser`. +unsafe impl AlwaysRefCounted for MmWithUser {} + // Make all `Mm` methods available on `MmWithUser`. impl Deref for MmWithUser { type Target = Mm; diff --git a/rust/kernel/mm/mmput_async.rs b/rust/kernel/mm/mmput_async.rs index b8d2f051225c7..8fbc396e46028 100644 --- a/rust/kernel/mm/mmput_async.rs +++ b/rust/kernel/mm/mmput_async.rs @@ -10,7 +10,11 @@ use crate::{ bindings, mm::MmWithUser, - sync::aref::{ARef, AlwaysRefCounted}, + sync::aref::{ + ARef, + RefCounted, // + }, + types::AlwaysRefCounted, }; use core::{ops::Deref, ptr::NonNull}; @@ -34,7 +38,7 @@ unsafe impl Send for MmWithUserAsync {} unsafe impl Sync for MmWithUserAsync {} // SAFETY: By the type invariants, this type is always refcounted. -unsafe impl AlwaysRefCounted for MmWithUserAsync { +unsafe impl RefCounted for MmWithUserAsync { #[inline] fn inc_ref(&self) { // SAFETY: The pointer is valid since self is a reference. @@ -48,6 +52,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` +// from a `&MmWithUserAsync`. +unsafe impl AlwaysRefCounted for MmWithUserAsync {} + // Make all `MmWithUser` methods available on `MmWithUserAsync`. impl Deref for MmWithUserAsync { type Target = MmWithUser; diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs index 62e44676125d1..b8db6bdefd077 100644 --- a/rust/kernel/opp.rs +++ b/rust/kernel/opp.rs @@ -16,8 +16,14 @@ ffi::{c_char, c_ulong}, prelude::*, str::CString, - sync::aref::{ARef, AlwaysRefCounted}, - types::Opaque, + sync::aref::{ + ARef, + RefCounted, // + }, + types::{ + AlwaysRefCounted, + Opaque, // + }, // }; #[cfg(CONFIG_CPU_FREQ)] @@ -1041,7 +1047,7 @@ unsafe impl Send for OPP {} unsafe impl Sync for OPP {} /// SAFETY: The type invariants guarantee that [`OPP`] is always refcounted. -unsafe impl AlwaysRefCounted for OPP { +unsafe impl RefCounted for OPP { #[inline] fn inc_ref(&self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. @@ -1055,6 +1061,10 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from an +// `&OPP`. +unsafe impl AlwaysRefCounted for OPP {} + impl OPP { /// Creates an owned reference to a [`OPP`] from a valid pointer. /// diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs index 9c92d4a83cc1b..e79936c00002c 100644 --- a/rust/kernel/owned.rs +++ b/rust/kernel/owned.rs @@ -27,7 +27,7 @@ /// /// Note: The underlying object is not required to provide internal reference counting, because it /// represents a unique, owned reference. If reference counting (on the Rust side) is required, -/// [`AlwaysRefCounted`](crate::sync::aref::AlwaysRefCounted) should be implemented. +/// [`RefCounted`](crate::types::RefCounted) should be implemented. /// /// # Examples /// diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs index 5071cae6543fd..ea9ef99cecb07 100644 --- a/rust/kernel/pci.rs +++ b/rust/kernel/pci.rs @@ -19,6 +19,10 @@ }, prelude::*, str::CStr, + sync::aref::{ + AlwaysRefCounted, + RefCounted, // + }, types::Opaque, ThisModule, // }; @@ -481,7 +485,7 @@ unsafe impl device::AsBusDevice for Device impl<'a> crate::dma::Device<'a> for Device> {} // SAFETY: Instances of `Device` are always reference-counted. -unsafe impl crate::sync::aref::AlwaysRefCounted for Device { +unsafe impl RefCounted for Device { fn inc_ref(&self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. unsafe { bindings::pci_dev_get(self.as_raw()) }; @@ -493,6 +497,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Device`. +unsafe impl AlwaysRefCounted for Device {} + impl AsRef> for Device { fn as_ref(&self) -> &device::Device { // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid diff --git a/rust/kernel/pid_namespace.rs b/rust/kernel/pid_namespace.rs index 979a9718f153d..067f68b99e8c5 100644 --- a/rust/kernel/pid_namespace.rs +++ b/rust/kernel/pid_namespace.rs @@ -7,7 +7,14 @@ //! C header: [`include/linux/pid_namespace.h`](srctree/include/linux/pid_namespace.h) and //! [`include/linux/pid.h`](srctree/include/linux/pid.h) -use crate::{bindings, sync::aref::AlwaysRefCounted, types::Opaque}; +use crate::{ + bindings, + sync::aref::RefCounted, + types::{ + AlwaysRefCounted, + Opaque, // + }, // +}; use core::ptr; /// Wraps the kernel's `struct pid_namespace`. Thread safe. @@ -41,7 +48,7 @@ pub unsafe fn from_ptr<'a>(ptr: *const bindings::pid_namespace) -> &'a Self { } // SAFETY: Instances of `PidNamespace` are always reference-counted. -unsafe impl AlwaysRefCounted for PidNamespace { +unsafe impl RefCounted for PidNamespace { #[inline] fn inc_ref(&self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. @@ -55,6 +62,10 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from +// a `&PidNamespace`. +unsafe impl AlwaysRefCounted for PidNamespace {} + // SAFETY: // - `PidNamespace::dec_ref` can be called from any thread. // - It is okay to send ownership of `PidNamespace` across thread boundaries. diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs index 9b362e0495d32..0ba676445b06d 100644 --- a/rust/kernel/platform.rs +++ b/rust/kernel/platform.rs @@ -27,6 +27,10 @@ }, of, prelude::*, + sync::aref::{ + AlwaysRefCounted, + RefCounted, // + }, types::Opaque, ThisModule, // }; @@ -518,7 +522,7 @@ pub fn optional_irq_by_name(&self, name: &CStr) -> Result> { impl<'a> crate::dma::Device<'a> for Device> {} // SAFETY: Instances of `Device` are always reference-counted. -unsafe impl crate::sync::aref::AlwaysRefCounted for Device { +unsafe impl RefCounted for Device { fn inc_ref(&self) { // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero. unsafe { bindings::get_device(self.as_ref().as_raw()) }; @@ -530,6 +534,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Device`. +unsafe impl AlwaysRefCounted for Device {} + impl AsRef> for Device { fn as_ref(&self) -> &device::Device { // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid diff --git a/rust/kernel/pwm.rs b/rust/kernel/pwm.rs index 6c9d667009ef7..2d1cd74dd98e1 100644 --- a/rust/kernel/pwm.rs +++ b/rust/kernel/pwm.rs @@ -13,7 +13,11 @@ devres, error::{self, to_result}, prelude::*, - sync::aref::{ARef, AlwaysRefCounted}, + sync::aref::{ + ARef, + AlwaysRefCounted, + RefCounted, // + }, types::Opaque, // }; use core::{ @@ -629,7 +633,7 @@ pub fn new<'a>( } // SAFETY: Implements refcounting for `Chip` using the embedded `struct device`. -unsafe impl AlwaysRefCounted for Chip { +unsafe impl RefCounted for Chip { #[inline] fn inc_ref(&self) { // SAFETY: `self.0.get()` points to a valid `pwm_chip` because `self` exists. @@ -647,6 +651,10 @@ unsafe fn dec_ref(obj: NonNull>) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef>` from a +// `&Chip`. +unsafe impl AlwaysRefCounted for Chip {} + // SAFETY: `Chip` is a wrapper around `*mut bindings::pwm_chip`. The underlying C // structure's state is managed and synchronized by the kernel's device model // and PWM core locking mechanisms. Therefore, it is safe to move the `Chip` diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs index 3bd5eb8a1a526..fb7466a362741 100644 --- a/rust/kernel/sync/aref.rs +++ b/rust/kernel/sync/aref.rs @@ -24,11 +24,9 @@ ptr::NonNull, // }; -/// Types that are _always_ reference counted. +/// Types that are internally reference counted. /// /// It allows such types to define their own custom ref increment and decrement functions. -/// Additionally, it allows users to convert from a shared reference `&T` to an owned reference -/// [`ARef`]. /// /// This is usually implemented by wrappers to existing structures on the C side of the code. For /// Rust code, the recommendation is to use [`Arc`](crate::sync::Arc) to create reference-counted @@ -45,9 +43,8 @@ /// at least until matching decrements are performed. /// /// Implementers must also ensure that all instances are reference-counted. (Otherwise they -/// won't be able to honour the requirement that [`AlwaysRefCounted::inc_ref`] keep the object -/// alive.) -pub unsafe trait AlwaysRefCounted { +/// won't be able to honour the requirement that [`RefCounted::inc_ref`] keep the object alive.) +pub unsafe trait RefCounted { /// Increments the reference count on the object. fn inc_ref(&self); @@ -60,11 +57,27 @@ pub unsafe trait AlwaysRefCounted { /// Callers must ensure that there was a previous matching increment to the reference count, /// and that the object is no longer used after its reference count is decremented (as it may /// result in the object being freed), unless the caller owns another increment on the refcount - /// (e.g., it calls [`AlwaysRefCounted::inc_ref`] twice, then calls - /// [`AlwaysRefCounted::dec_ref`] once). + /// (e.g., it calls [`RefCounted::inc_ref`] twice, then calls [`RefCounted::dec_ref`] once). unsafe fn dec_ref(obj: NonNull); } +/// Always reference-counted type. +/// +/// It allows deriving a counted reference [`ARef`] from a `&T`. +/// +/// This provides some convenience, but it allows "escaping" borrow checks on `&T`. As it +/// complicates attempts to ensure that a reference to T is unique, it is optional to provide for +/// [`RefCounted`] types. See *Safety* below. +/// +/// # Safety +/// +/// Implementers must ensure that no safety invariants are violated by upgrading an `&T` to an +/// [`ARef`]. In particular that implies [`AlwaysRefCounted`] and [`crate::types::Ownable`] +/// cannot be implemented for the same type, as this would allow violating the uniqueness guarantee +/// of [`crate::types::Owned`] by dereferencing it into an `&T` and obtaining an [`ARef`] from +/// that. +pub unsafe trait AlwaysRefCounted: RefCounted {} + /// An owned reference to an always-reference-counted object. /// /// The object's reference count is automatically decremented when an instance of [`ARef`] is @@ -75,7 +88,7 @@ pub unsafe trait AlwaysRefCounted { /// /// The pointer stored in `ptr` is non-null and valid for the lifetime of the [`ARef`] instance. In /// particular, the [`ARef`] instance owns an increment on the underlying object's reference count. -pub struct ARef { +pub struct ARef { ptr: NonNull, _p: PhantomData, } @@ -84,19 +97,19 @@ pub struct ARef { // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs // `T` to be `Send` because any thread that has an `ARef` may ultimately access `T` using a // mutable reference, for example, when the reference count reaches zero and `T` is dropped. -unsafe impl Send for ARef {} +unsafe impl Send for ARef {} // SAFETY: It is safe to send `&ARef` to another thread when the underlying `T` is `Sync` // because it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, // it needs `T` to be `Send` because any thread that has a `&ARef` may clone it and get an // `ARef` on that thread, so the thread may ultimately access `T` using a mutable reference, for // example, when the reference count reaches zero and `T` is dropped. -unsafe impl Sync for ARef {} +unsafe impl Sync for ARef {} // Even if `T` is pinned, pointers to `T` can still move. -impl Unpin for ARef {} +impl Unpin for ARef {} -impl ARef { +impl ARef { /// Creates a new instance of [`ARef`]. /// /// It takes over an increment of the reference count on the underlying object. @@ -125,12 +138,12 @@ pub unsafe fn from_raw(ptr: NonNull) -> Self { /// /// ``` /// use core::ptr::NonNull; - /// use kernel::sync::aref::{ARef, AlwaysRefCounted}; + /// use kernel::sync::aref::{ARef, RefCounted}; /// /// struct Empty {} /// /// # // SAFETY: TODO. - /// unsafe impl AlwaysRefCounted for Empty { + /// unsafe impl RefCounted for Empty { /// fn inc_ref(&self) {} /// unsafe fn dec_ref(_obj: NonNull) {} /// } @@ -148,7 +161,7 @@ pub fn into_raw(me: Self) -> NonNull { } } -impl Clone for ARef { +impl Clone for ARef { fn clone(&self) -> Self { self.inc_ref(); // SAFETY: We just incremented the refcount above. @@ -156,7 +169,7 @@ fn clone(&self) -> Self { } } -impl Deref for ARef { +impl Deref for ARef { type Target = T; fn deref(&self) -> &Self::Target { @@ -173,7 +186,7 @@ fn from(b: &T) -> Self { } } -impl Drop for ARef { +impl Drop for ARef { fn drop(&mut self) { // SAFETY: The type invariants guarantee that the `ARef` owns the reference we're about to // decrement. @@ -183,19 +196,19 @@ fn drop(&mut self) { impl PartialEq> for ARef where - T: AlwaysRefCounted + PartialEq, - U: AlwaysRefCounted, + T: RefCounted + PartialEq, + U: RefCounted, { #[inline] fn eq(&self, other: &ARef) -> bool { T::eq(&**self, &**other) } } -impl Eq for ARef {} +impl Eq for ARef {} impl PartialEq<&'_ U> for ARef where - T: AlwaysRefCounted + PartialEq, + T: RefCounted + PartialEq, { #[inline] fn eq(&self, other: &&U) -> bool { diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs index 38273f4eedb51..6259430b0ca31 100644 --- a/rust/kernel/task.rs +++ b/rust/kernel/task.rs @@ -10,7 +10,12 @@ pid_namespace::PidNamespace, prelude::*, sync::aref::ARef, - types::{NotThreadSafe, Opaque}, + types::{ + AlwaysRefCounted, + NotThreadSafe, + Opaque, + RefCounted, // + }, }; use core::{ ops::Deref, @@ -347,7 +352,7 @@ pub fn group_leader(&self) -> &Task { } // SAFETY: The type invariants guarantee that `Task` is always refcounted. -unsafe impl crate::sync::aref::AlwaysRefCounted for Task { +unsafe impl RefCounted for Task { #[inline] fn inc_ref(&self) { // SAFETY: The existence of a shared reference means that the refcount is nonzero. @@ -361,6 +366,10 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Task`. +unsafe impl AlwaysRefCounted for Task {} + impl PartialEq for Task { #[inline] fn eq(&self, other: &Self) -> bool { diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index c41eab0ec983c..5ef763717e59a 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -15,9 +15,15 @@ pub mod for_lt; pub use for_lt::ForLt; -pub use crate::owned::{ - Ownable, - Owned, // +pub use crate::{ + owned::{ + Ownable, + Owned, // + }, + sync::aref::{ + AlwaysRefCounted, + RefCounted, // + }, // }; /// Used to transfer ownership to and from foreign (non-Rust) languages. diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs index 7aff0c82d0afc..59350c6b0df2a 100644 --- a/rust/kernel/usb.rs +++ b/rust/kernel/usb.rs @@ -18,7 +18,10 @@ to_result, // }, prelude::*, - sync::aref::AlwaysRefCounted, + sync::aref::{ + AlwaysRefCounted, + RefCounted, // + }, types::Opaque, ThisModule, // }; @@ -392,7 +395,7 @@ fn as_ref(&self) -> &Device { } // SAFETY: Instances of `Interface` are always reference-counted. -unsafe impl AlwaysRefCounted for Interface { +unsafe impl RefCounted for Interface { fn inc_ref(&self) { // SAFETY: The invariants of `Interface` guarantee that `self.as_raw()` // returns a valid `struct usb_interface` pointer, for which we will @@ -406,6 +409,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Interface`. +unsafe impl AlwaysRefCounted for Interface {} + // SAFETY: A `Interface` is always reference-counted and can be released from any thread. unsafe impl Send for Interface {} @@ -443,7 +450,7 @@ fn as_raw(&self) -> *mut bindings::usb_device { kernel::impl_device_context_into_aref!(Device); // SAFETY: Instances of `Device` are always reference-counted. -unsafe impl AlwaysRefCounted for Device { +unsafe impl RefCounted for Device { fn inc_ref(&self) { // SAFETY: The invariants of `Device` guarantee that `self.as_raw()` // returns a valid `struct usb_device` pointer, for which we will @@ -457,6 +464,10 @@ unsafe fn dec_ref(obj: NonNull) { } } +// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef` from a +// `&Device`. +unsafe impl AlwaysRefCounted for Device {} + impl AsRef> for Device { fn as_ref(&self) -> &device::Device { // SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid -- 2.51.2