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Message-Id: <20250325-ptr-as-ptr-v7-7-87ab452147b9@gmail.com>
Date: Tue, 25 Mar 2025 16:07:47 -0400
From: Tamir Duberstein <tamird@...il.com>
To: Masahiro Yamada <masahiroy@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, 
 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 <benno.lossin@...ton.me>, 
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, 
 Brendan Higgins <brendan.higgins@...ux.dev>, 
 David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>, 
 Bjorn Helgaas <bhelgaas@...gle.com>, Luis Chamberlain <mcgrof@...nel.org>, 
 Russ Weight <russ.weight@...ux.dev>, Rob Herring <robh@...nel.org>, 
 Saravana Kannan <saravanak@...gle.com>, 
 Abdiel Janulgue <abdiel.janulgue@...il.com>, 
 Daniel Almeida <daniel.almeida@...labora.com>, 
 Robin Murphy <robin.murphy@....com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, 
 rust-for-linux@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 kunit-dev@...glegroups.com, linux-pci@...r.kernel.org, 
 linux-block@...r.kernel.org, devicetree@...r.kernel.org, 
 dri-devel@...ts.freedesktop.org, netdev@...r.kernel.org, 
 Tamir Duberstein <tamird@...il.com>
Subject: [PATCH v7 7/7] rust: enable `clippy::ref_as_ptr` lint

In Rust 1.78.0, Clippy introduced the `ref_as_ptr` lint [1]:

> Using `as` casts may result in silently changing mutability or type.

While this doesn't eliminate unchecked `as` conversions, it makes such
conversions easier to scrutinize.  It also has the slight benefit of
removing a degree of freedom on which to bikeshed. Thus apply the
changes and enable the lint -- no functional change intended.

Link: https://rust-lang.github.io/rust-clippy/master/index.html#ref_as_ptr [1]
Suggested-by: Benno Lossin <benno.lossin@...ton.me>
Link: https://lore.kernel.org/all/D8PGG7NTWB6U.3SS3A5LN4XWMN@proton.me/
Signed-off-by: Tamir Duberstein <tamird@...il.com>
---
 Makefile                 | 1 +
 rust/bindings/lib.rs     | 1 +
 rust/kernel/device_id.rs | 3 ++-
 rust/kernel/fs/file.rs   | 3 ++-
 rust/kernel/str.rs       | 4 ++--
 rust/kernel/uaccess.rs   | 5 +++--
 rust/uapi/lib.rs         | 1 +
 7 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/Makefile b/Makefile
index 2e9eca8b7671..081b5fa2aa81 100644
--- a/Makefile
+++ b/Makefile
@@ -488,6 +488,7 @@ export rust_common_flags := --edition=2021 \
 			    -Wclippy::no_mangle_with_rust_abi \
 			    -Wclippy::ptr_as_ptr \
 			    -Wclippy::ptr_cast_constness \
+			    -Wclippy::ref_as_ptr \
 			    -Wclippy::undocumented_unsafe_blocks \
 			    -Wclippy::unnecessary_safety_comment \
 			    -Wclippy::unnecessary_safety_doc \
diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs
index b105a0d899cc..2b69016070c6 100644
--- a/rust/bindings/lib.rs
+++ b/rust/bindings/lib.rs
@@ -27,6 +27,7 @@
 #[allow(dead_code)]
 #[allow(clippy::cast_lossless)]
 #[allow(clippy::ptr_as_ptr)]
+#[allow(clippy::ref_as_ptr)]
 #[allow(clippy::undocumented_unsafe_blocks)]
 mod bindings_raw {
     // Manual definition for blocklisted types.
diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs
index 4063f09d76d9..37cc03d1df4c 100644
--- a/rust/kernel/device_id.rs
+++ b/rust/kernel/device_id.rs
@@ -136,7 +136,8 @@ impl<T: RawDeviceId, U, const N: usize> IdTable<T, U> for IdArray<T, U, N> {
     fn as_ptr(&self) -> *const T::RawType {
         // This cannot be `self.ids.as_ptr()`, as the return pointer must have correct provenance
         // to access the sentinel.
-        (self as *const Self).cast()
+        let this: *const Self = self;
+        this.cast()
     }
 
     fn id(&self, index: usize) -> &T::RawType {
diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 9e2639aee61a..366e23dc0803 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -359,12 +359,13 @@ impl core::ops::Deref for File {
     type Target = LocalFile;
     #[inline]
     fn deref(&self) -> &LocalFile {
+        let this: *const Self = self;
         // SAFETY: The caller provides a `&File`, and since it is a reference, it must point at a
         // valid file for the desired duration.
         //
         // By the type invariants, there are no `fdget_pos` calls that did not take the
         // `f_pos_lock` mutex.
-        unsafe { LocalFile::from_raw_file((self as *const Self).cast()) }
+        unsafe { LocalFile::from_raw_file(this.cast()) }
     }
 }
 
diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 40034f77fc2f..6233af50bab7 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -29,7 +29,7 @@ pub const fn is_empty(&self) -> bool {
     #[inline]
     pub const fn from_bytes(bytes: &[u8]) -> &Self {
         // SAFETY: `BStr` is transparent to `[u8]`.
-        unsafe { &*(bytes as *const [u8] as *const BStr) }
+        unsafe { &*(core::mem::transmute::<*const [u8], *const Self>(bytes)) }
     }
 
     /// Strip a prefix from `self`. Delegates to [`slice::strip_prefix`].
@@ -290,7 +290,7 @@ pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError
     #[inline]
     pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
         // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
-        unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
+        unsafe { &mut *(core::mem::transmute::<*mut [u8], *mut Self>(bytes)) }
     }
 
     /// Returns a C pointer to the string.
diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs
index 80a9782b1c6e..c042b1fe499e 100644
--- a/rust/kernel/uaccess.rs
+++ b/rust/kernel/uaccess.rs
@@ -242,7 +242,7 @@ pub fn read_raw(&mut self, out: &mut [MaybeUninit<u8>]) -> Result {
     pub fn read_slice(&mut self, out: &mut [u8]) -> Result {
         // SAFETY: The types are compatible and `read_raw` doesn't write uninitialized bytes to
         // `out`.
-        let out = unsafe { &mut *(out as *mut [u8] as *mut [MaybeUninit<u8>]) };
+        let out = unsafe { &mut *(core::mem::transmute::<*mut [u8], *mut [MaybeUninit<u8>]>(out)) };
         self.read_raw(out)
     }
 
@@ -348,6 +348,7 @@ pub fn write<T: AsBytes>(&mut self, value: &T) -> Result {
         if len > self.length {
             return Err(EFAULT);
         }
+        let value: *const T = value;
         // SAFETY: The reference points to a value of type `T`, so it is valid for reading
         // `size_of::<T>()` bytes.
         //
@@ -357,7 +358,7 @@ pub fn write<T: AsBytes>(&mut self, value: &T) -> Result {
         let res = unsafe {
             bindings::_copy_to_user(
                 self.ptr as *mut c_void,
-                (value as *const T).cast::<c_void>(),
+                value.cast::<c_void>(),
                 len,
             )
         };
diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs
index d5dab4dfabec..6230ba48201d 100644
--- a/rust/uapi/lib.rs
+++ b/rust/uapi/lib.rs
@@ -16,6 +16,7 @@
     clippy::all,
     clippy::cast_lossless,
     clippy::ptr_as_ptr,
+    clippy::ref_as_ptr,
     clippy::undocumented_unsafe_blocks,
     dead_code,
     missing_docs,

-- 
2.49.0


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