linux-kernel - [PATCH v2 1/3] rust: revocable: implement Revocable::access()

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Message-ID: <20250428140137.468709-2-dakr@kernel.org>
Date: Mon, 28 Apr 2025 16:00:27 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: gregkh@...uxfoundation.org,
	rafael@...nel.org,
	bhelgaas@...gle.com,
	kwilczynski@...nel.org,
	zhiw@...dia.com,
	cjia@...dia.com,
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	ttabi@...dia.com,
	acourbot@...dia.com,
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	alex.gaynor@...il.com,
	boqun.feng@...il.com,
	gary@...yguo.net,
	bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me,
	a.hindborg@...nel.org,
	aliceryhl@...gle.com,
	tmgross@...ch.edu
Cc: linux-pci@...r.kernel.org,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Danilo Krummrich <dakr@...nel.org>,
	Christian Schrefl <chrisi.schrefl@...il.com>
Subject: [PATCH v2 1/3] rust: revocable: implement Revocable::access()

Implement an unsafe direct accessor for the data stored within the
Revocable.

This is useful for cases where we can prove that the data stored within
the Revocable is not and cannot be revoked for the duration of the
lifetime of the returned reference.

Reviewed-by: Christian Schrefl <chrisi.schrefl@...il.com>
Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
Signed-off-by: Danilo Krummrich <dakr@...nel.org>
---
 rust/kernel/revocable.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/rust/kernel/revocable.rs b/rust/kernel/revocable.rs
index 971d0dc38d83..db4aa46bb121 100644
--- a/rust/kernel/revocable.rs
+++ b/rust/kernel/revocable.rs
@@ -139,6 +139,18 @@ pub fn try_access_with<R, F: FnOnce(&T) -> R>(&self, f: F) -> Option<R> {
         self.try_access().map(|t| f(&*t))
     }
 
+    /// Directly access the revocable wrapped object.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure this [`Revocable`] instance hasn't been revoked and won't be revoked
+    /// as long as the returned `&T` lives.
+    pub unsafe fn access(&self) -> &T {
+        // SAFETY: By the safety requirement of this function it is guaranteed that
+        // `self.data.get()` is a valid pointer to an instance of `T`.
+        unsafe { &*self.data.get() }
+    }
+
     /// # Safety
     ///
     /// Callers must ensure that there are no more concurrent users of the revocable object.
-- 
2.49.0