Merge tag 'pin-init-v7.1' of https://github.com/Rust-for-Linux/linux into rust-next

Pull pin-init updates from Benno Lossin:

 - Replace the 'Zeroable' impls for 'Option<NonZero*>' with impls of
   'ZeroableOption' for 'NonZero*'.

 - Improve feature gate handling for unstable features.

 - Declutter the documentation of implementations of 'Zeroable' for
   tuples.

 - Replace uses of 'addr_of[_mut]!' with '&raw [mut]'.

* tag 'pin-init-v7.1' of https://github.com/Rust-for-Linux/linux:
  rust: pin-init: replace `addr_of_mut!` with `&raw mut`
  rust: pin-init: implement ZeroableOption for NonZero* integer types
  rust: pin-init: doc: de-clutter documentation with fake-variadics
  rust: pin-init: properly document let binding workaround
  rust: pin-init: build: simplify use of nightly features

10 files changed, 75 insertions, 36 deletions

diff --git a/rust/Makefile b/rust/Makefile
index bfa1b77c9671..b361bfedfdf0 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -119,7 +119,7 @@ syn-flags := \
     $(call cfgs-to-flags,$(syn-cfgs))
 
 pin_init_internal-cfgs := \
-    kernel
+    kernel USE_RUSTC_FEATURES
 
 pin_init_internal-flags := \
     --extern proc_macro2 \
@@ -128,7 +128,7 @@ pin_init_internal-flags := \
     $(call cfgs-to-flags,$(pin_init_internal-cfgs))
 
 pin_init-cfgs := \
-    kernel
+    kernel USE_RUSTC_FEATURES
 
 pin_init-flags := \
     --extern pin_init_internal \
diff --git a/rust/pin-init/README.md b/rust/pin-init/README.md
index 6cee6ab1eb57..9095d6661ff6 100644
--- a/rust/pin-init/README.md
+++ b/rust/pin-init/README.md
@@ -160,7 +160,6 @@ actually does the initialization in the correct way. Here are the things to look
 ```rust
 use pin_init::{pin_data, pinned_drop, PinInit, PinnedDrop, pin_init_from_closure};
 use core::{
-    ptr::addr_of_mut,
     marker::PhantomPinned,
     cell::UnsafeCell,
     pin::Pin,
@@ -199,7 +198,7 @@ impl RawFoo {
         unsafe {
             pin_init_from_closure(move |slot: *mut Self| {
                 // `slot` contains uninit memory, avoid creating a reference.
-                let foo = addr_of_mut!((*slot).foo);
+                let foo = &raw mut (*slot).foo;
                 let foo = UnsafeCell::raw_get(foo).cast::<bindings::foo>();
 
                 // Initialize the `foo`
diff --git a/rust/pin-init/examples/big_struct_in_place.rs b/rust/pin-init/examples/big_struct_in_place.rs
index c05139927486..80f89b5f8fd6 100644
--- a/rust/pin-init/examples/big_struct_in_place.rs
+++ b/rust/pin-init/examples/big_struct_in_place.rs
@@ -1,5 +1,8 @@
 // SPDX-License-Identifier: Apache-2.0 OR MIT
 
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(raw_ref_op))]
+
 use pin_init::*;
 
 // Struct with size over 1GiB
diff --git a/rust/pin-init/examples/linked_list.rs b/rust/pin-init/examples/linked_list.rs
index 8445a5890cb7..119169e4dc41 100644
--- a/rust/pin-init/examples/linked_list.rs
+++ b/rust/pin-init/examples/linked_list.rs
@@ -2,7 +2,8 @@
 
 #![allow(clippy::undocumented_unsafe_blocks)]
 #![cfg_attr(feature = "alloc", feature(allocator_api))]
-#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(raw_ref_op))]
 
 use core::{
     cell::Cell,
diff --git a/rust/pin-init/examples/mutex.rs b/rust/pin-init/examples/mutex.rs
index 9f295226cd64..d53671f0edb8 100644
--- a/rust/pin-init/examples/mutex.rs
+++ b/rust/pin-init/examples/mutex.rs
@@ -2,7 +2,8 @@
 
 #![allow(clippy::undocumented_unsafe_blocks)]
 #![cfg_attr(feature = "alloc", feature(allocator_api))]
-#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(raw_ref_op))]
 #![allow(clippy::missing_safety_doc)]
 
 use core::{
diff --git a/rust/pin-init/examples/pthread_mutex.rs b/rust/pin-init/examples/pthread_mutex.rs
index 4e082ec7d5de..f3b5cc9b7134 100644
--- a/rust/pin-init/examples/pthread_mutex.rs
+++ b/rust/pin-init/examples/pthread_mutex.rs
@@ -3,7 +3,8 @@
 // inspired by <https://github.com/nbdd0121/pin-init/blob/trunk/examples/pthread_mutex.rs>
 #![allow(clippy::undocumented_unsafe_blocks)]
 #![cfg_attr(feature = "alloc", feature(allocator_api))]
-#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(raw_ref_op))]
 
 #[cfg(not(windows))]
 mod pthread_mtx {
diff --git a/rust/pin-init/examples/static_init.rs b/rust/pin-init/examples/static_init.rs
index 0e165daa9798..f7e53d1a5ae6 100644
--- a/rust/pin-init/examples/static_init.rs
+++ b/rust/pin-init/examples/static_init.rs
@@ -2,7 +2,8 @@
 
 #![allow(clippy::undocumented_unsafe_blocks)]
 #![cfg_attr(feature = "alloc", feature(allocator_api))]
-#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(raw_ref_op))]
 #![allow(unused_imports)]
 
 use core::{
diff --git a/rust/pin-init/internal/src/init.rs b/rust/pin-init/internal/src/init.rs
index 2fe918f4d82a..daa3f1c6466e 100644
--- a/rust/pin-init/internal/src/init.rs
+++ b/rust/pin-init/internal/src/init.rs
@@ -173,6 +173,12 @@ pub(crate) fn expand(
         };
         // SAFETY: TODO
         let init = unsafe { ::pin_init::#init_from_closure::<_, #error>(init) };
+        // FIXME: this let binding is required to avoid a compiler error (cycle when computing the
+        // opaque type returned by this function) before Rust 1.81. Remove after MSRV bump.
+        #[allow(
+            clippy::let_and_return,
+            reason = "some clippy versions warn about the let binding"
+        )]
         init
     }})
 }
@@ -264,7 +270,7 @@ fn init_fields(
                     {
                         #value_prep
                         // SAFETY: TODO
-                        unsafe { #write(::core::ptr::addr_of_mut!((*#slot).#ident), #value_ident) };
+                        unsafe { #write(&raw mut (*#slot).#ident, #value_ident) };
                     }
                     #(#cfgs)*
                     #[allow(unused_variables)]
@@ -287,7 +293,7 @@ fn init_fields(
                             //   return when an error/panic occurs.
                             // - We also use `#data` to require the correct trait (`Init` or `PinInit`)
                             //   for `#ident`.
-                            unsafe { #data.#ident(::core::ptr::addr_of_mut!((*#slot).#ident), #init)? };
+                            unsafe { #data.#ident(&raw mut (*#slot).#ident, #init)? };
                         },
                         quote! {
                             // SAFETY: TODO
@@ -302,7 +308,7 @@ fn init_fields(
                             unsafe {
                                 ::pin_init::Init::__init(
                                     #init,
-                                    ::core::ptr::addr_of_mut!((*#slot).#ident),
+                                    &raw mut (*#slot).#ident,
                                 )?
                             };
                         },
@@ -342,7 +348,7 @@ fn init_fields(
                 // SAFETY: We forget the guard later when initialization has succeeded.
                 let #guard = unsafe {
                     ::pin_init::__internal::DropGuard::new(
-                        ::core::ptr::addr_of_mut!((*slot).#ident)
+                        &raw mut (*slot).#ident
                     )
                 };
             });
diff --git a/rust/pin-init/internal/src/lib.rs b/rust/pin-init/internal/src/lib.rs
index 08372c8f65f0..b08dfe003031 100644
--- a/rust/pin-init/internal/src/lib.rs
+++ b/rust/pin-init/internal/src/lib.rs
@@ -6,7 +6,7 @@
 
 //! `pin-init` proc macros.
 
-#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
 // Documentation is done in the pin-init crate instead.
 #![allow(missing_docs)]
 
diff --git a/rust/pin-init/src/lib.rs b/rust/pin-init/src/lib.rs
index fe4c85ae3f02..64eec095c859 100644
--- a/rust/pin-init/src/lib.rs
+++ b/rust/pin-init/src/lib.rs
@@ -172,7 +172,6 @@
 //! # #![feature(extern_types)]
 //! use pin_init::{pin_data, pinned_drop, PinInit, PinnedDrop, pin_init_from_closure};
 //! use core::{
-//!     ptr::addr_of_mut,
 //!     marker::PhantomPinned,
 //!     cell::UnsafeCell,
 //!     pin::Pin,
@@ -211,7 +210,7 @@
 //!         unsafe {
 //!             pin_init_from_closure(move |slot: *mut Self| {
 //!                 // `slot` contains uninit memory, avoid creating a reference.
-//!                 let foo = addr_of_mut!((*slot).foo);
+//!                 let foo = &raw mut (*slot).foo;
 //!                 let foo = UnsafeCell::raw_get(foo).cast::<bindings::foo>();
 //!
 //!                 // Initialize the `foo`
@@ -264,12 +263,10 @@
 //! [`impl Init<T, E>`]: crate::Init
 //! [Rust-for-Linux]: https://rust-for-linux.com/
 
-#![cfg_attr(not(RUSTC_LINT_REASONS_IS_STABLE), feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(lint_reasons))]
+#![cfg_attr(USE_RUSTC_FEATURES, feature(raw_ref_op))]
 #![cfg_attr(
-    all(
-        any(feature = "alloc", feature = "std"),
-        not(RUSTC_NEW_UNINIT_IS_STABLE)
-    ),
+    all(any(feature = "alloc", feature = "std"), USE_RUSTC_FEATURES),
     feature(new_uninit)
 )]
 #![forbid(missing_docs, unsafe_op_in_unsafe_fn)]
@@ -279,6 +276,8 @@
     all(feature = "unsafe-pinned", CONFIG_RUSTC_HAS_UNSAFE_PINNED),
     feature(unsafe_pinned)
 )]
+#![cfg_attr(all(USE_RUSTC_FEATURES, doc), allow(internal_features))]
+#![cfg_attr(all(USE_RUSTC_FEATURES, doc), feature(rustdoc_internals))]
 
 use core::{
     cell::UnsafeCell,
@@ -755,7 +754,7 @@ macro_rules! stack_try_pin_init {
 ///
 /// ```rust
 /// # use pin_init::*;
-/// # use core::{ptr::addr_of_mut, marker::PhantomPinned};
+/// # use core::marker::PhantomPinned;
 /// #[pin_data]
 /// #[derive(Zeroable)]
 /// struct Buf {
@@ -769,7 +768,7 @@ macro_rules! stack_try_pin_init {
 /// let init = pin_init!(&this in Buf {
 ///     buf: [0; 64],
 ///     // SAFETY: TODO.
-///     ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() },
+///     ptr: unsafe { (&raw mut (*this.as_ptr()).buf).cast() },
 ///     pin: PhantomPinned,
 /// });
 /// let init = pin_init!(Buf {
@@ -1147,9 +1146,12 @@ pub const unsafe fn cast_pin_init<T, U, E>(init: impl PinInit<T, E>) -> impl Pin
     // SAFETY: initialization delegated to a valid initializer. Cast is valid by function safety
     // requirements.
     let res = unsafe { pin_init_from_closure(|ptr: *mut U| init.__pinned_init(ptr.cast::<T>())) };
-    // FIXME: remove the let statement once the nightly-MSRV allows it (1.78 otherwise encounters a
-    // cycle when computing the type returned by this function)
-    #[allow(clippy::let_and_return)]
+    // FIXME: this let binding is required to avoid a compiler error (cycle when computing the opaque
+    // type returned by this function) before Rust 1.81. Remove after MSRV bump.
+    #[allow(
+        clippy::let_and_return,
+        reason = "some clippy versions warn about the let binding"
+    )]
     res
 }
 
@@ -1163,9 +1165,12 @@ pub const unsafe fn cast_init<T, U, E>(init: impl Init<T, E>) -> impl Init<U, E>
     // SAFETY: initialization delegated to a valid initializer. Cast is valid by function safety
     // requirements.
     let res = unsafe { init_from_closure(|ptr: *mut U| init.__init(ptr.cast::<T>())) };
-    // FIXME: remove the let statement once the nightly-MSRV allows it (1.78 otherwise encounters a
-    // cycle when computing the type returned by this function)
-    #[allow(clippy::let_and_return)]
+    // FIXME: this let binding is required to avoid a compiler error (cycle when computing the opaque
+    // type returned by this function) before Rust 1.81. Remove after MSRV bump.
+    #[allow(
+        clippy::let_and_return,
+        reason = "some clippy versions warn about the let binding"
+    )]
     res
 }
 
@@ -1610,13 +1615,6 @@ impl_zeroable! {
     // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`.
     {<T: ?Sized + Zeroable>} UnsafeCell<T>,
 
-    // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee:
-    // <https://doc.rust-lang.org/stable/std/option/index.html#representation>).
-    Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>,
-    Option<NonZeroU128>, Option<NonZeroUsize>,
-    Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>,
-    Option<NonZeroI128>, Option<NonZeroIsize>,
-
     // SAFETY: `null` pointer is valid.
     //
     // We cannot use `T: ?Sized`, since the VTABLE pointer part of fat pointers is not allowed to be
@@ -1635,8 +1633,14 @@ impl_zeroable! {
 }
 
 macro_rules! impl_tuple_zeroable {
-    ($(,)?) => {};
+    ($first:ident, $(,)?) => {
+        #[cfg_attr(all(USE_RUSTC_FEATURES, doc), doc(fake_variadic))]
+        /// Implemented for tuples up to 10 items long.
+        // SAFETY: All elements are zeroable and padding can be zero.
+        unsafe impl<$first: Zeroable> Zeroable for ($first,) {}
+    };
     ($first:ident, $($t:ident),* $(,)?) => {
+        #[cfg_attr(doc, doc(hidden))]
         // SAFETY: All elements are zeroable and padding can be zero.
         unsafe impl<$first: Zeroable, $($t: Zeroable),*> Zeroable for ($first, $($t),*) {}
         impl_tuple_zeroable!($($t),* ,);
@@ -1651,7 +1655,16 @@ macro_rules! impl_fn_zeroable_option {
         $(impl_fn_zeroable_option!({unsafe extern $abi} $args);)*
     };
     ({$($prefix:tt)*} {$(,)?}) => {};
+    ({$($prefix:tt)*} {$ret:ident, $arg:ident $(,)?}) => {
+        #[cfg_attr(all(USE_RUSTC_FEATURES, doc), doc(fake_variadic))]
+        /// Implemented for function pointers with up to 20 arity.
+        // SAFETY: function pointers are part of the option layout optimization:
+        // <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
+        unsafe impl<$ret, $arg> ZeroableOption for $($prefix)* fn($arg) -> $ret {}
+        impl_fn_zeroable_option!({$($prefix)*} {$arg,});
+    };
     ({$($prefix:tt)*} {$ret:ident, $($rest:ident),* $(,)?}) => {
+        #[cfg_attr(doc, doc(hidden))]
         // SAFETY: function pointers are part of the option layout optimization:
         // <https://doc.rust-lang.org/stable/std/option/index.html#representation>.
         unsafe impl<$ret, $($rest),*> ZeroableOption for $($prefix)* fn($($rest),*) -> $ret {}
@@ -1661,6 +1674,20 @@ macro_rules! impl_fn_zeroable_option {
 
 impl_fn_zeroable_option!(["Rust", "C"] { A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U });
 
+macro_rules! impl_non_zero_int_zeroable_option {
+    ($($int:ty),* $(,)?) => {
+        // SAFETY: Safety comment written in the macro invocation.
+        $(unsafe impl ZeroableOption for $int {})*
+    };
+}
+
+impl_non_zero_int_zeroable_option! {
+    // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee:
+    // <https://doc.rust-lang.org/stable/std/option/index.html#representation>).
+    NonZeroU8, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU128, NonZeroUsize,
+    NonZeroI8, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI128, NonZeroIsize,
+}
+
 /// This trait allows creating an instance of `Self` which contains exactly one
 /// [structurally pinned value](https://doc.rust-lang.org/std/pin/index.html#projections-and-structural-pinning).
 ///