linux-kernel - [PATCH 2/2] rust/drm: Add gem::impl_aref_for_gem

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250908220657.165715-3-lyude@redhat.com>
Date: Mon,  8 Sep 2025 18:04:45 -0400
From: Lyude Paul <lyude@...hat.com>
To: dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Cc: David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Asahi Lina <lina+kernel@...hilina.net>
Subject: [PATCH 2/2] rust/drm: Add gem::impl_aref_for_gem_obj!

In the future we're going to be introducing more GEM object types in rust
then just gem::Object<T>. Since all types of GEM objects have refcounting,
let's introduce a macro that we can use in the gem crate in order to copy
this boilerplate implementation for each type: impl_aref_for_gem_obj!().

Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 rust/kernel/drm/gem/mod.rs | 53 +++++++++++++++++++++++++++-----------
 1 file changed, 38 insertions(+), 15 deletions(-)

diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index af92f2d46d8d8..317edd455cc1c 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -14,6 +14,43 @@
 };
 use core::{ops::Deref, ptr::NonNull};
 
+/// A macro for implementing [`AlwaysRefCounted`] for any GEM object type.
+///
+/// Since all GEM objects use the same refcounting scheme.
+macro_rules! impl_aref_for_gem_obj {
+    (
+        impl $( <$( $tparam_id:ident ),+> )? for $type:ty
+        $(
+            where
+                $( $bind_param:path : $bind_trait:path ),+
+        )?
+    ) => {
+        // SAFETY: All gem objects are refcounted
+        unsafe impl $( <$( $tparam_id ),+> )? crate::types::AlwaysRefCounted for $type
+        $(
+            where
+                $( $bind_param : $bind_trait ),+
+        )?
+        {
+            fn inc_ref(&self) {
+                // SAFETY: The existence of a shared reference guarantees that the refcount is
+                // non-zero.
+                unsafe { bindings::drm_gem_object_get(self.as_raw()) };
+            }
+
+            unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
+                // SAFETY: `obj` is a valid pointer to an `Object<T>`.
+                let obj = unsafe { obj.as_ref() };
+
+                // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+                unsafe { bindings::drm_gem_object_put(obj.as_raw()) };
+            }
+        }
+    };
+}
+
+pub(crate) use impl_aref_for_gem_obj;
+
 /// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its
 /// [`DriverObject`] implementation.
 ///
@@ -252,21 +289,7 @@ extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
     }
 }
 
-// SAFETY: Instances of `Object<T>` are always reference-counted.
-unsafe impl<T: DriverObject> crate::types::AlwaysRefCounted for Object<T> {
-    fn inc_ref(&self) {
-        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
-        unsafe { bindings::drm_gem_object_get(self.as_raw()) };
-    }
-
-    unsafe fn dec_ref(obj: NonNull<Self>) {
-        // SAFETY: `obj` is a valid pointer to an `Object<T>`.
-        let obj = unsafe { obj.as_ref() };
-
-        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
-        unsafe { bindings::drm_gem_object_put(obj.as_raw()) }
-    }
-}
+impl_aref_for_gem_obj!(impl<T> for Object<T> where T: DriverObject);
 
 impl<T: DriverObject> super::private::Sealed for Object<T> {}
 
-- 
2.51.0