On Wed, Apr 09, 2025 at 10:47:23AM -0400, Tamir Duberstein wrote:
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@proton.me Link: https://lore.kernel.org/all/D8PGG7NTWB6U.3SS3A5LN4XWMN@proton.me/ Signed-off-by: Tamir Duberstein tamird@gmail.com
Makefile | 1 + rust/bindings/lib.rs | 1 + rust/kernel/device_id.rs | 3 ++- rust/kernel/fs/file.rs | 3 ++- rust/kernel/str.rs | 6 ++++-- rust/kernel/uaccess.rs | 10 ++++------ rust/uapi/lib.rs | 1 + 7 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/Makefile b/Makefile index eb5a942241a2..2a16e02f26db 100644 --- a/Makefile +++ b/Makefile @@ -485,6 +485,7 @@ 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;
Hmm.. so this lint usually just requires to use a let statement instead of as expression when casting a reference to a pointer? Not 100% convinced this results into better code TBH..
this.cast()fn id(&self, index: usize) -> &T::RawType { diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs index 791f493ada10..559a4bfa123f 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..75b4a18c67c4 100644 --- a/rust/kernel/str.rs +++ b/rust/kernel/str.rs @@ -28,8 +28,9 @@ pub const fn is_empty(&self) -> bool { /// Creates a [`BStr`] from a `[u8]`. #[inline] pub const fn from_bytes(bytes: &[u8]) -> &Self {
let bytes: *const [u8] = bytes; // SAFETY: `BStr` is transparent to `[u8]`.
unsafe { &*(bytes as *const [u8] as *const BStr) }
unsafe { &*(bytes as *const BStr) }
unsafe { &*(bytes.cast::<BStr>()) }
? I'm curious why this dodged the other lint (ptr_as_ptr).
}/// Strip a prefix from `self`. Delegates to [`slice::strip_prefix`]. @@ -289,8 +290,9 @@ pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError /// `NUL` byte (or the string will be truncated). #[inline] pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
let bytes: *mut [u8] = bytes; // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
unsafe { &mut *(bytes as *mut CStr) }
Ditto.
}/// Returns a C pointer to the string. diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs index 80a9782b1c6e..7a6fc78fc314 100644 --- a/rust/kernel/uaccess.rs +++ b/rust/kernel/uaccess.rs @@ -240,9 +240,10 @@ pub fn read_raw(&mut self, out: &mut [MaybeUninit<u8>]) -> Result { /// Fails with [`EFAULT`] if the read happens on a bad address, or if the read goes out of /// bounds of this [`UserSliceReader`]. This call may modify `out` even if it returns an error. pub fn read_slice(&mut self, out: &mut [u8]) -> Result {
let out: *mut [u8] = out; // 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 *(out as *mut [MaybeUninit<u8>]) };
Ditto.
Regards, Boqun
self.read_raw(out) }@@ -348,6 +349,7 @@ 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. //@@ -355,11 +357,7 @@ pub fn write<T: AsBytes>(&mut self, value: &T) -> Result { // kernel pointer. This mirrors the logic on the C side that skips the check when the length // is a compile-time constant. let res = unsafe {
bindings::_copy_to_user(self.ptr as *mut c_void,(value as *const T).cast::<c_void>(),len,)
bindings::_copy_to_user(self.ptr as *mut c_void, value.cast::<c_void>(), len) }; if res != 0 { return Err(EFAULT);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