Merge tag 'rust-6.20-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux

Pull rust updates from Miguel Ojeda:
 "Toolchain and infrastructure:

   - Add '__rust_helper' annotation to the C helpers

     This is needed to inline these helpers into Rust code

   - Remove imports available via the prelude, treewide

     This was possible thanks to a new lint in Klint that Gary has
     implemented -- more Klint-related changes, including initial
     upstream support, are coming

   - Deduplicate pin-init flags

  'kernel' crate:

   - Add support for calling a function exactly once with the new
     'do_once_lite!' macro (and 'OnceLite' type)

     Based on this, add 'pr_*_once!' macros to print only once

   - Add 'impl_flags!' macro for defining common bitflags operations:

         impl_flags!(
             /// Represents multiple permissions.
             #[derive(Debug, Clone, Default, Copy, PartialEq, Eq)]
             pub struct Permissions(u32);

             /// Represents a single permission.
             #[derive(Debug, Clone, Copy, PartialEq, Eq)]
             pub enum Permission {
                 /// Read permission.
                 Read = 1 << 0,

                 /// Write permission.
                 Write = 1 << 1,

                 /// Execute permission.
                 Execute = 1 << 2,
             }
         );

         let mut f: Permissions = Permission::Read | Permission::Write;
         assert!(f.contains(Permission::Read));
         assert!(!f.contains(Permission::Execute));

         f |= Permission::Execute;
         assert!(f.contains(Permission::Execute));

         let f2: Permissions = Permission::Write | Permission::Execute;
         assert!((f ^ f2).contains(Permission::Read));
         assert!(!(f ^ f2).contains(Permission::Write));

   - 'bug' module: support 'CONFIG_DEBUG_BUGVERBOSE_DETAILED' in the
     'warn_on!' macro in order to show the evaluated condition alongside
     the file path:

          ------------[ cut here ]------------
          WARNING: [val == 1] linux/samples/rust/rust_minimal.rs:27 at ...
          Modules linked in: rust_minimal(+)

   - Add safety module with 'unsafe_precondition_assert!' macro,
     currently a wrapper for 'debug_assert!', intended to mark the
     validation of safety preconditions where possible:

         /// # Safety
         ///
         /// The caller must ensure that `index` is less than `N`.
         unsafe fn set_unchecked(&mut self, index: usize, value: T) {
             unsafe_precondition_assert!(
                 index < N,
                 "set_unchecked() requires index ({index}) < N ({N})"
             );

             ...
         }

   - Add instructions to 'build_assert!' documentation requesting to
     always inline functions when used with function arguments

   - 'ptr' module: replace 'build_assert!' with a 'const' one

   - 'rbtree' module: reduce unsafe blocks on pointer derefs

   - 'transmute' module: implement 'FromBytes' and 'AsBytes' for
     inhabited ZSTs, and use it in Nova

   - More treewide replacements of 'c_str!' with C string literals

  'macros' crate:

   - Rewrite most procedural macros ('module!', 'concat_idents!',
     '#[export]', '#[vtable]', '#[kunit_tests]') to use the 'syn'
     parsing library which we introduced last cycle, with better
     diagnostics

     This also allows to support '#[cfg]' properly in the '#[vtable]'
     macro, to support arbitrary types in 'module!' macro (not just an
     identifier) and to remove several custom parsing helpers we had

   - Use 'quote!' from the recently vendored 'quote' library and remove
     our custom one

     The vendored one also allows us to avoid quoting '"' and '{}'
     inside the template anymore and editors can now highlight it. In
     addition, it improves robustness as it eliminates the need for
     string quoting and escaping

   - Use 'pin_init::zeroed()' to simplify KUnit code

  'pin-init' crate:

   - Rewrite all procedural macros ('[pin_]init!', '#[pin_data]',
     '#[pinned_drop]', 'derive([Maybe]Zeroable)') to use the 'syn'
     parsing library which we introduced last cycle, with better
     diagnostics

   - Implement 'InPlaceWrite' for '&'static mut MaybeUninit<T>'. This
     enables users to use external allocation mechanisms such as
     'static_cell'

   - Support tuple structs in 'derive([Maybe]Zeroable)'

   - Support attributes on fields in '[pin_]init!' (such as
     '#[cfg(...)]')

   - Add a '#[default_error(<type>)]' attribute to '[pin_]init!' to
     override the default error (when no '? Error' is specified)

   - Support packed structs in '[pin_]init!' with
     '#[disable_initialized_field_access]'

   - Remove 'try_[pin_]init!' in favor of merging their feature with
     '[pin_]init!'. Update the kernel's own 'try_[pin_]init!' macros to
     use the 'default_error' attribute

   - Correct 'T: Sized' bounds to 'T: ?Sized' in the generated
     'PinnedDrop' check by '#[pin_data]'

  Documentation:

   - Conclude the Rust experiment

  MAINTAINERS:

   - Add "RUST [RUST-ANALYZER]" entry for the rust-analyzer support.
     Tamir and Jesung will take care of it. They have both been active
     around it for a while. The new tree will flow through the Rust one

   - Add Gary as maintainer for "RUST [PIN-INIT]"

   - Update Boqun and Tamir emails to their kernel.org accounts

  And a few other cleanups and improvements"

* tag 'rust-6.20-7.0' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (59 commits)
  rust: safety: introduce `unsafe_precondition_assert!` macro
  rust: add `impl_flags!` macro for defining common bitflag operations
  rust: print: Add pr_*_once macros
  rust: bug: Support DEBUG_BUGVERBOSE_DETAILED option
  rust: print: Add support for calling a function exactly once
  rust: kbuild: deduplicate pin-init flags
  gpu: nova-core: remove imports available via prelude
  rust: clk: replace `kernel::c_str!` with C-Strings
  MAINTAINERS: Update my email address to @kernel.org
  rust: macros: support `#[cfg]` properly in `#[vtable]` macro.
  rust: kunit: use `pin_init::zeroed` instead of custom null value
  rust: macros: rearrange `#[doc(hidden)]` in `module!` macro
  rust: macros: allow arbitrary types to be used in `module!` macro
  rust: macros: convert `#[kunit_tests]` macro to use `syn`
  rust: macros: convert `concat_idents!` to use `syn`
  rust: macros: convert `#[export]` to use `syn`
  rust: macros: use `quote!` for `module!` macro
  rust: macros: use `syn` to parse `module!` macro
  rust: macros: convert `#[vtable]` macro to use `syn`
  rust: macros: use `quote!` from vendored crate
  ...

14 files changed, 555 insertions, 97 deletions

diff --git a/rust/kernel/bug.rs b/rust/kernel/bug.rs
index 36aef43e5ebe..ed943960f851 100644
--- a/rust/kernel/bug.rs
+++ b/rust/kernel/bug.rs
@@ -11,9 +11,9 @@
 #[cfg(all(CONFIG_BUG, not(CONFIG_UML), not(CONFIG_LOONGARCH), not(CONFIG_ARM)))]
 #[cfg(CONFIG_DEBUG_BUGVERBOSE)]
 macro_rules! warn_flags {
-    ($flags:expr) => {
+    ($file:expr, $flags:expr) => {
         const FLAGS: u32 = $crate::bindings::BUGFLAG_WARNING | $flags;
-        const _FILE: &[u8] = file!().as_bytes();
+        const _FILE: &[u8] = $file.as_bytes();
         // Plus one for null-terminator.
         static FILE: [u8; _FILE.len() + 1] = {
             let mut bytes = [0; _FILE.len() + 1];
@@ -50,7 +50,7 @@ macro_rules! warn_flags {
 #[cfg(all(CONFIG_BUG, not(CONFIG_UML), not(CONFIG_LOONGARCH), not(CONFIG_ARM)))]
 #[cfg(not(CONFIG_DEBUG_BUGVERBOSE))]
 macro_rules! warn_flags {
-    ($flags:expr) => {
+    ($file:expr, $flags:expr) => {
         const FLAGS: u32 = $crate::bindings::BUGFLAG_WARNING | $flags;
 
         // SAFETY:
@@ -75,7 +75,7 @@ macro_rules! warn_flags {
 #[doc(hidden)]
 #[cfg(all(CONFIG_BUG, CONFIG_UML))]
 macro_rules! warn_flags {
-    ($flags:expr) => {
+    ($file:expr, $flags:expr) => {
         // SAFETY: It is always safe to call `warn_slowpath_fmt()`
         // with a valid null-terminated string.
         unsafe {
@@ -93,7 +93,7 @@ macro_rules! warn_flags {
 #[doc(hidden)]
 #[cfg(all(CONFIG_BUG, any(CONFIG_LOONGARCH, CONFIG_ARM)))]
 macro_rules! warn_flags {
-    ($flags:expr) => {
+    ($file:expr, $flags:expr) => {
         // SAFETY: It is always safe to call `WARN_ON()`.
         unsafe { $crate::bindings::WARN_ON(true) }
     };
@@ -103,7 +103,7 @@ macro_rules! warn_flags {
 #[doc(hidden)]
 #[cfg(not(CONFIG_BUG))]
 macro_rules! warn_flags {
-    ($flags:expr) => {};
+    ($file:expr, $flags:expr) => {};
 }
 
 #[doc(hidden)]
@@ -116,10 +116,16 @@ pub const fn bugflag_taint(value: u32) -> u32 {
 macro_rules! warn_on {
     ($cond:expr) => {{
         let cond = $cond;
+
+        #[cfg(CONFIG_DEBUG_BUGVERBOSE_DETAILED)]
+        const _COND_STR: &str = concat!("[", stringify!($cond), "] ", file!());
+        #[cfg(not(CONFIG_DEBUG_BUGVERBOSE_DETAILED))]
+        const _COND_STR: &str = file!();
+
         if cond {
             const WARN_ON_FLAGS: u32 = $crate::bug::bugflag_taint($crate::bindings::TAINT_WARN);
 
-            $crate::warn_flags!(WARN_ON_FLAGS);
+            $crate::warn_flags!(_COND_STR, WARN_ON_FLAGS);
         }
         cond
     }};
diff --git a/rust/kernel/build_assert.rs b/rust/kernel/build_assert.rs
index 6331b15d7c4d..f8124dbc663f 100644
--- a/rust/kernel/build_assert.rs
+++ b/rust/kernel/build_assert.rs
@@ -61,8 +61,13 @@ macro_rules! build_error {
 ///     build_assert!(N > 1); // Build-time check
 ///     assert!(N > 1); // Run-time check
 /// }
+/// ```
 ///
-/// #[inline]
+/// When a condition depends on a function argument, the function must be annotated with
+/// `#[inline(always)]`. Without this attribute, the compiler may choose to not inline the
+/// function, preventing it from optimizing out the error path.
+/// ```
+/// #[inline(always)]
 /// fn bar(n: usize) {
 ///     // `static_assert!(n > 1);` is not allowed
 ///     build_assert!(n > 1); // Build-time check
diff --git a/rust/kernel/clk.rs b/rust/kernel/clk.rs
index c1cfaeaa36a2..4059aff34d09 100644
--- a/rust/kernel/clk.rs
+++ b/rust/kernel/clk.rs
@@ -94,7 +94,7 @@ mod common_clk {
     /// # Invariants
     ///
     /// A [`Clk`] instance holds either a pointer to a valid [`struct clk`] created by the C
-    /// portion of the kernel or a NULL pointer.
+    /// portion of the kernel or a `NULL` pointer.
     ///
     /// Instances of this type are reference-counted. Calling [`Clk::get`] ensures that the
     /// allocation remains valid for the lifetime of the [`Clk`].
@@ -104,13 +104,12 @@ mod common_clk {
     /// The following example demonstrates how to obtain and configure a clock for a device.
     ///
     /// ```
-    /// use kernel::c_str;
     /// use kernel::clk::{Clk, Hertz};
     /// use kernel::device::Device;
     /// use kernel::error::Result;
     ///
     /// fn configure_clk(dev: &Device) -> Result {
-    ///     let clk = Clk::get(dev, Some(c_str!("apb_clk")))?;
+    ///     let clk = Clk::get(dev, Some(c"apb_clk"))?;
     ///
     ///     clk.prepare_enable()?;
     ///
@@ -272,13 +271,12 @@ mod common_clk {
     /// device. The code functions correctly whether or not the clock is available.
     ///
     /// ```
-    /// use kernel::c_str;
     /// use kernel::clk::{OptionalClk, Hertz};
     /// use kernel::device::Device;
     /// use kernel::error::Result;
     ///
     /// fn configure_clk(dev: &Device) -> Result {
-    ///     let clk = OptionalClk::get(dev, Some(c_str!("apb_clk")))?;
+    ///     let clk = OptionalClk::get(dev, Some(c"apb_clk"))?;
     ///
     ///     clk.prepare_enable()?;
     ///
diff --git a/rust/kernel/debugfs/entry.rs b/rust/kernel/debugfs/entry.rs
index 706cb7f73d6c..a30bf8f29679 100644
--- a/rust/kernel/debugfs/entry.rs
+++ b/rust/kernel/debugfs/entry.rs
@@ -148,7 +148,7 @@ impl Entry<'_> {
     /// # Guarantees
     ///
     /// Due to the type invariant, the value returned from this function will always be an error
-    /// code, NULL, or a live DebugFS directory. If it is live, it will remain live at least as
+    /// code, `NULL`, or a live DebugFS directory. If it is live, it will remain live at least as
     /// long as this entry lives.
     pub(crate) fn as_ptr(&self) -> *mut bindings::dentry {
         self.entry
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 39b0a9a207fd..bb5b830f48c3 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -262,7 +262,7 @@ macro_rules! module_i2c_driver {
 /// # Example
 ///
 ///```
-/// # use kernel::{acpi, bindings, c_str, device::Core, i2c, of};
+/// # use kernel::{acpi, bindings, device::Core, i2c, of};
 ///
 /// struct MyDriver;
 ///
@@ -271,7 +271,7 @@ macro_rules! module_i2c_driver {
 ///     MODULE_ACPI_TABLE,
 ///     <MyDriver as i2c::Driver>::IdInfo,
 ///     [
-///         (acpi::DeviceId::new(c_str!("LNUXBEEF")), ())
+///         (acpi::DeviceId::new(c"LNUXBEEF"), ())
 ///     ]
 /// );
 ///
@@ -280,7 +280,7 @@ macro_rules! module_i2c_driver {
 ///     MODULE_I2C_TABLE,
 ///     <MyDriver as i2c::Driver>::IdInfo,
 ///     [
-///          (i2c::DeviceId::new(c_str!("rust_driver_i2c")), ())
+///          (i2c::DeviceId::new(c"rust_driver_i2c"), ())
 ///     ]
 /// );
 ///
@@ -289,7 +289,7 @@ macro_rules! module_i2c_driver {
 ///     MODULE_OF_TABLE,
 ///     <MyDriver as i2c::Driver>::IdInfo,
 ///     [
-///         (of::DeviceId::new(c_str!("test,device")), ())
+///         (of::DeviceId::new(c"test,device"), ())
 ///     ]
 /// );
 ///
diff --git a/rust/kernel/impl_flags.rs b/rust/kernel/impl_flags.rs
new file mode 100644
index 000000000000..e2bd7639da12
--- /dev/null
+++ b/rust/kernel/impl_flags.rs
@@ -0,0 +1,272 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Bitflag type generator.
+
+/// Common helper for declaring bitflag and bitmask types.
+///
+/// This macro takes as input:
+/// - A struct declaration representing a bitmask type
+///   (e.g., `pub struct Permissions(u32)`).
+/// - An enumeration declaration representing individual bit flags
+///   (e.g., `pub enum Permission { ... }`).
+///
+/// And generates:
+/// - The struct and enum types with appropriate `#[repr]` attributes.
+/// - Implementations of common bitflag operators
+///   ([`::core::ops::BitOr`], [`::core::ops::BitAnd`], etc.).
+/// - Utility methods such as `.contains()` to check flags.
+///
+/// # Examples
+///
+/// ```
+/// use kernel::impl_flags;
+///
+/// impl_flags!(
+///     /// Represents multiple permissions.
+///     #[derive(Debug, Clone, Default, Copy, PartialEq, Eq)]
+///     pub struct Permissions(u32);
+///
+///     /// Represents a single permission.
+///     #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+///     pub enum Permission {
+///         /// Read permission.
+///         Read = 1 << 0,
+///
+///         /// Write permission.
+///         Write = 1 << 1,
+///
+///         /// Execute permission.
+///         Execute = 1 << 2,
+///     }
+/// );
+///
+/// // Combine multiple permissions using the bitwise OR (`|`) operator.
+/// let mut read_write: Permissions = Permission::Read | Permission::Write;
+/// assert!(read_write.contains(Permission::Read));
+/// assert!(read_write.contains(Permission::Write));
+/// assert!(!read_write.contains(Permission::Execute));
+/// assert!(read_write.contains_any(Permission::Read | Permission::Execute));
+/// assert!(read_write.contains_all(Permission::Read | Permission::Write));
+///
+/// // Using the bitwise OR assignment (`|=`) operator.
+/// read_write |= Permission::Execute;
+/// assert!(read_write.contains(Permission::Execute));
+///
+/// // Masking a permission with the bitwise AND (`&`) operator.
+/// let read_only: Permissions = read_write & Permission::Read;
+/// assert!(read_only.contains(Permission::Read));
+/// assert!(!read_only.contains(Permission::Write));
+///
+/// // Toggling permissions with the bitwise XOR (`^`) operator.
+/// let toggled: Permissions = read_only ^ Permission::Read;
+/// assert!(!toggled.contains(Permission::Read));
+///
+/// // Inverting permissions with the bitwise NOT (`!`) operator.
+/// let negated = !read_only;
+/// assert!(negated.contains(Permission::Write));
+/// assert!(!negated.contains(Permission::Read));
+/// ```
+#[macro_export]
+macro_rules! impl_flags {
+    (
+        $(#[$outer_flags:meta])*
+        $vis_flags:vis struct $flags:ident($ty:ty);
+
+        $(#[$outer_flag:meta])*
+        $vis_flag:vis enum $flag:ident {
+            $(
+                $(#[$inner_flag:meta])*
+                $name:ident = $value:expr
+            ),+ $( , )?
+        }
+    ) => {
+        $(#[$outer_flags])*
+        #[repr(transparent)]
+        $vis_flags struct $flags($ty);
+
+        $(#[$outer_flag])*
+        #[repr($ty)]
+        $vis_flag enum $flag {
+            $(
+                $(#[$inner_flag])*
+                $name = $value
+            ),+
+        }
+
+        impl ::core::convert::From<$flag> for $flags {
+            #[inline]
+            fn from(value: $flag) -> Self {
+                Self(value as $ty)
+            }
+        }
+
+        impl ::core::convert::From<$flags> for $ty {
+            #[inline]
+            fn from(value: $flags) -> Self {
+                value.0
+            }
+        }
+
+        impl ::core::ops::BitOr for $flags {
+            type Output = Self;
+            #[inline]
+            fn bitor(self, rhs: Self) -> Self::Output {
+                Self(self.0 | rhs.0)
+            }
+        }
+
+        impl ::core::ops::BitOrAssign for $flags {
+            #[inline]
+            fn bitor_assign(&mut self, rhs: Self) {
+                *self = *self | rhs;
+            }
+        }
+
+        impl ::core::ops::BitOr<$flag> for $flags {
+            type Output = Self;
+            #[inline]
+            fn bitor(self, rhs: $flag) -> Self::Output {
+                self | Self::from(rhs)
+            }
+        }
+
+        impl ::core::ops::BitOrAssign<$flag> for $flags {
+            #[inline]
+            fn bitor_assign(&mut self, rhs: $flag) {
+                *self = *self | rhs;
+            }
+        }
+
+        impl ::core::ops::BitAnd for $flags {
+            type Output = Self;
+            #[inline]
+            fn bitand(self, rhs: Self) -> Self::Output {
+                Self(self.0 & rhs.0)
+            }
+        }
+
+        impl ::core::ops::BitAndAssign for $flags {
+            #[inline]
+            fn bitand_assign(&mut self, rhs: Self) {
+                *self = *self & rhs;
+            }
+        }
+
+        impl ::core::ops::BitAnd<$flag> for $flags {
+            type Output = Self;
+            #[inline]
+            fn bitand(self, rhs: $flag) -> Self::Output {
+                self & Self::from(rhs)
+            }
+        }
+
+        impl ::core::ops::BitAndAssign<$flag> for $flags {
+            #[inline]
+            fn bitand_assign(&mut self, rhs: $flag) {
+                *self = *self & rhs;
+            }
+        }
+
+        impl ::core::ops::BitXor for $flags {
+            type Output = Self;
+            #[inline]
+            fn bitxor(self, rhs: Self) -> Self::Output {
+                Self((self.0 ^ rhs.0) & Self::all_bits())
+            }
+        }
+
+        impl ::core::ops::BitXorAssign for $flags {
+            #[inline]
+            fn bitxor_assign(&mut self, rhs: Self) {
+                *self = *self ^ rhs;
+            }
+        }
+
+        impl ::core::ops::BitXor<$flag> for $flags {
+            type Output = Self;
+            #[inline]
+            fn bitxor(self, rhs: $flag) -> Self::Output {
+                self ^ Self::from(rhs)
+            }
+        }
+
+        impl ::core::ops::BitXorAssign<$flag> for $flags {
+            #[inline]
+            fn bitxor_assign(&mut self, rhs: $flag) {
+                *self = *self ^ rhs;
+            }
+        }
+
+        impl ::core::ops::Not for $flags {
+            type Output = Self;
+            #[inline]
+            fn not(self) -> Self::Output {
+                Self((!self.0) & Self::all_bits())
+            }
+        }
+
+        impl ::core::ops::BitOr for $flag {
+            type Output = $flags;
+            #[inline]
+            fn bitor(self, rhs: Self) -> Self::Output {
+                $flags(self as $ty | rhs as $ty)
+            }
+        }
+
+        impl ::core::ops::BitAnd for $flag {
+            type Output = $flags;
+            #[inline]
+            fn bitand(self, rhs: Self) -> Self::Output {
+                $flags(self as $ty & rhs as $ty)
+            }
+        }
+
+        impl ::core::ops::BitXor for $flag {
+            type Output = $flags;
+            #[inline]
+            fn bitxor(self, rhs: Self) -> Self::Output {
+                $flags((self as $ty ^ rhs as $ty) & $flags::all_bits())
+            }
+        }
+
+        impl ::core::ops::Not for $flag {
+            type Output = $flags;
+            #[inline]
+            fn not(self) -> Self::Output {
+                $flags((!(self as $ty)) & $flags::all_bits())
+            }
+        }
+
+        impl $flags {
+            /// Returns an empty instance where no flags are set.
+            #[inline]
+            pub const fn empty() -> Self {
+                Self(0)
+            }
+
+            /// Returns a mask containing all valid flag bits.
+            #[inline]
+            pub const fn all_bits() -> $ty {
+                0 $( | $value )+
+            }
+
+            /// Checks if a specific flag is set.
+            #[inline]
+            pub fn contains(self, flag: $flag) -> bool {
+                (self.0 & flag as $ty) == flag as $ty
+            }
+
+            /// Checks if at least one of the provided flags is set.
+            #[inline]
+            pub fn contains_any(self, flags: $flags) -> bool {
+                (self.0 & flags.0) != 0
+            }
+
+            /// Checks if all of the provided flags are set.
+            #[inline]
+            pub fn contains_all(self, flags: $flags) -> bool {
+                (self.0 & flags.0) == flags.0
+            }
+        }
+    };
+}
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 899b9a962762..7a0d4559d7b5 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -219,20 +219,12 @@ pub trait InPlaceInit<T>: Sized {
 /// [`Error`]: crate::error::Error
 #[macro_export]
 macro_rules! try_init {
-    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
-        $($fields:tt)*
-    }) => {
-        ::pin_init::try_init!($(&$this in)? $t $(::<$($generics),*>)? {
-            $($fields)*
-        }? $crate::error::Error)
-    };
-    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
-        $($fields:tt)*
-    }? $err:ty) => {
-        ::pin_init::try_init!($(&$this in)? $t $(::<$($generics),*>)? {
-            $($fields)*
-        }? $err)
-    };
+    ($($args:tt)*) => {
+        ::pin_init::init!(
+            #[default_error($crate::error::Error)]
+            $($args)*
+        )
+    }
 }
 
 /// Construct an in-place, fallible pinned initializer for `struct`s.
@@ -279,18 +271,10 @@ macro_rules! try_init {
 /// [`Error`]: crate::error::Error
 #[macro_export]
 macro_rules! try_pin_init {
-    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
-        $($fields:tt)*
-    }) => {
-        ::pin_init::try_pin_init!($(&$this in)? $t $(::<$($generics),*>)? {
-            $($fields)*
-        }? $crate::error::Error)
-    };
-    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
-        $($fields:tt)*
-    }? $err:ty) => {
-        ::pin_init::try_pin_init!($(&$this in)? $t $(::<$($generics),*>)? {
-            $($fields)*
-        }? $err)
-    };
+    ($($args:tt)*) => {
+        ::pin_init::pin_init!(
+            #[default_error($crate::error::Error)]
+            $($args)*
+        )
+    }
 }
diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 79436509dd73..f93f24a60bdd 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -9,9 +9,6 @@
 use crate::fmt;
 use crate::prelude::*;
 
-#[cfg(CONFIG_PRINTK)]
-use crate::c_str;
-
 /// Prints a KUnit error-level message.
 ///
 /// Public but hidden since it should only be used from KUnit generated code.
@@ -22,7 +19,7 @@ pub fn err(args: fmt::Arguments<'_>) {
     #[cfg(CONFIG_PRINTK)]
     unsafe {
         bindings::_printk(
-            c_str!("\x013%pA").as_char_ptr(),
+            c"\x013%pA".as_char_ptr(),
             core::ptr::from_ref(&args).cast::<c_void>(),
         );
     }
@@ -38,7 +35,7 @@ pub fn info(args: fmt::Arguments<'_>) {
     #[cfg(CONFIG_PRINTK)]
     unsafe {
         bindings::_printk(
-            c_str!("\x016%pA").as_char_ptr(),
+            c"\x016%pA".as_char_ptr(),
             core::ptr::from_ref(&args).cast::<c_void>(),
         );
     }
@@ -60,7 +57,7 @@ macro_rules! kunit_assert {
                 break 'out;
             }
 
-            static FILE: &'static $crate::str::CStr = $crate::c_str!($file);
+            static FILE: &'static $crate::str::CStr = $file;
             static LINE: i32 = ::core::line!() as i32 - $diff;
             static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));
 
@@ -192,9 +189,6 @@ pub fn is_test_result_ok(t: impl TestResult) -> bool {
 }
 
 /// Represents an individual test case.
-///
-/// The [`kunit_unsafe_test_suite!`] macro expects a NULL-terminated list of valid test cases.
-/// Use [`kunit_case_null`] to generate such a delimiter.
 #[doc(hidden)]
 pub const fn kunit_case(
     name: &'static kernel::str::CStr,
@@ -215,32 +209,11 @@ pub const fn kunit_case(
     }
 }
 
-/// Represents the NULL test case delimiter.
-///
-/// The [`kunit_unsafe_test_suite!`] macro expects a NULL-terminated list of test cases. This
-/// function returns such a delimiter.
-#[doc(hidden)]
-pub const fn kunit_case_null() -> kernel::bindings::kunit_case {
-    kernel::bindings::kunit_case {
-        run_case: None,
-        name: core::ptr::null_mut(),
-        generate_params: None,
-        attr: kernel::bindings::kunit_attributes {
-            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
-        },
-        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
-        module_name: core::ptr::null_mut(),
-        log: core::ptr::null_mut(),
-        param_init: None,
-        param_exit: None,
-    }
-}
-
 /// Registers a KUnit test suite.
 ///
 /// # Safety
 ///
-/// `test_cases` must be a NULL terminated array of valid test cases,
+/// `test_cases` must be a `NULL` terminated array of valid test cases,
 /// whose lifetime is at least that of the test suite (i.e., static).
 ///
 /// # Examples
@@ -253,8 +226,8 @@ pub const fn kunit_case_null() -> kernel::bindings::kunit_case {
 /// }
 ///
 /// static mut KUNIT_TEST_CASES: [kernel::bindings::kunit_case; 2] = [
-///     kernel::kunit::kunit_case(kernel::c_str!("name"), test_fn),
-///     kernel::kunit::kunit_case_null(),
+///     kernel::kunit::kunit_case(c"name", test_fn),
+///     pin_init::zeroed(),
 /// ];
 /// kernel::kunit_unsafe_test_suite!(suite_name, KUNIT_TEST_CASES);
 /// ```
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index f812cf120042..696f62f85eb5 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -100,6 +100,8 @@ pub mod fs;
 #[cfg(CONFIG_I2C = "y")]
 pub mod i2c;
 pub mod id_pool;
+#[doc(hidden)]
+pub mod impl_flags;
 pub mod init;
 pub mod io;
 pub mod ioctl;
@@ -133,6 +135,7 @@ pub mod pwm;
 pub mod rbtree;
 pub mod regulator;
 pub mod revocable;
+pub mod safety;
 pub mod scatterlist;
 pub mod security;
 pub mod seq_file;
diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
index 2d743d78d220..6fd84389a858 100644
--- a/rust/kernel/print.rs
+++ b/rust/kernel/print.rs
@@ -11,6 +11,11 @@ use crate::{
     fmt,
     prelude::*,
     str::RawFormatter,
+    sync::atomic::{
+        Atomic,
+        AtomicType,
+        Relaxed, //
+    },
 };
 
 // Called from `vsprintf` with format specifier `%pA`.
@@ -423,3 +428,151 @@ macro_rules! pr_cont (
         $crate::print_macro!($crate::print::format_strings::CONT, true, $($arg)*)
     )
 );
+
+/// A lightweight `call_once` primitive.
+///
+/// This structure provides the Rust equivalent of the kernel's `DO_ONCE_LITE` macro.
+/// While it would be possible to implement the feature entirely as a Rust macro,
+/// the functionality that can be implemented as regular functions has been
+/// extracted and implemented as the `OnceLite` struct for better code maintainability.
+pub struct OnceLite(Atomic<State>);
+
+#[derive(Clone, Copy, PartialEq, Eq)]
+#[repr(i32)]
+enum State {
+    Incomplete = 0,
+    Complete = 1,
+}
+
+// SAFETY: `State` and `i32` has the same size and alignment, and it's round-trip
+// transmutable to `i32`.
+unsafe impl AtomicType for State {
+    type Repr = i32;
+}
+
+impl OnceLite {
+    /// Creates a new [`OnceLite`] in the incomplete state.
+    #[inline(always)]
+    #[allow(clippy::new_without_default)]
+    pub const fn new() -> Self {
+        OnceLite(Atomic::new(State::Incomplete))
+    }
+
+    /// Calls the provided function exactly once.
+    ///
+    /// There is no other synchronization between two `call_once()`s
+    /// except that only one will execute `f`, in other words, callers
+    /// should not use a failed `call_once()` as a proof that another
+    /// `call_once()` has already finished and the effect is observable
+    /// to this thread.
+    pub fn call_once<F>(&self, f: F) -> bool
+    where
+        F: FnOnce(),
+    {
+        // Avoid expensive cmpxchg if already completed.
+        // ORDERING: `Relaxed` is used here since no synchronization is required.
+        let old = self.0.load(Relaxed);
+        if old == State::Complete {
+            return false;
+        }
+
+        // ORDERING: `Relaxed` is used here since no synchronization is required.
+        let old = self.0.xchg(State::Complete, Relaxed);
+        if old == State::Complete {
+            return false;
+        }
+
+        f();
+        true
+    }
+}
+
+/// Run the given function exactly once.
+///
+/// This is equivalent to the kernel's `DO_ONCE_LITE` macro.
+///
+/// # Examples
+///
+/// ```
+/// kernel::do_once_lite! {
+///     kernel::pr_info!("This will be printed only once\n");
+/// };
+/// ```
+#[macro_export]
+macro_rules! do_once_lite {
+    { $($e:tt)* } => {{
+        #[link_section = ".data..once"]
+        static ONCE: $crate::print::OnceLite = $crate::print::OnceLite::new();
+        ONCE.call_once(|| { $($e)* });
+    }};
+}
+
+/// Prints an emergency-level message (level 0) only once.
+///
+/// Equivalent to the kernel's `pr_emerg_once` macro.
+#[macro_export]
+macro_rules! pr_emerg_once (
+    ($($arg:tt)*) => (
+        $crate::do_once_lite! { $crate::pr_emerg!($($arg)*) }
+    )
+);
+
+/// Prints an alert-level message (level 1) only once.
+///
+/// Equivalent to the kernel's `pr_alert_once` macro.
+#[macro_export]
+macro_rules! pr_alert_once (
+    ($($arg:tt)*) => (
+        $crate::do_once_lite! { $crate::pr_alert!($($arg)*) }
+    )
+);
+
+/// Prints a critical-level message (level 2) only once.
+///
+/// Equivalent to the kernel's `pr_crit_once` macro.
+#[macro_export]
+macro_rules! pr_crit_once (
+    ($($arg:tt)*) => (
+        $crate::do_once_lite! { $crate::pr_crit!($($arg)*) }
+    )
+);
+
+/// Prints an error-level message (level 3) only once.
+///
+/// Equivalent to the kernel's `pr_err_once` macro.
+#[macro_export]
+macro_rules! pr_err_once (
+    ($($arg:tt)*) => (
+        $crate::do_once_lite! { $crate::pr_err!($($arg)*) }
+    )
+);
+
+/// Prints a warning-level message (level 4) only once.
+///
+/// Equivalent to the kernel's `pr_warn_once` macro.
+#[macro_export]
+macro_rules! pr_warn_once (
+    ($($arg:tt)*) => (
+        $crate::do_once_lite! { $crate::pr_warn!($($arg)*) }
+    )
+);
+
+/// Prints a notice-level message (level 5) only once.
+///
+/// Equivalent to the kernel's `pr_notice_once` macro.
+#[macro_export]
+macro_rules! pr_notice_once (
+    ($($arg:tt)*) => (
+        $crate::do_once_lite! { $crate::pr_notice!($($arg)*) }
+    )
+);
+
+/// Prints an info-level message (level 6) only once.
+///
+/// Equivalent to the kernel's `pr_info_once` macro.
+#[macro_export]
+macro_rules! pr_info_once (
+    ($($arg:tt)*) => (
+        $crate::do_once_lite! { $crate::pr_info!($($arg)*) }
+    )
+);
diff --git a/rust/kernel/ptr.rs b/rust/kernel/ptr.rs
index e3893ed04049..5b6a382637fe 100644
--- a/rust/kernel/ptr.rs
+++ b/rust/kernel/ptr.rs
@@ -5,8 +5,6 @@
 use core::mem::align_of;
 use core::num::NonZero;
 
-use crate::build_assert;
-
 /// Type representing an alignment, which is always a power of two.
 ///
 /// It is used to validate that a given value is a valid alignment, and to perform masking and
@@ -40,10 +38,12 @@ impl Alignment {
     /// ```
     #[inline(always)]
     pub const fn new<const ALIGN: usize>() -> Self {
-        build_assert!(
-            ALIGN.is_power_of_two(),
-            "Provided alignment is not a power of two."
-        );
+        const {
+            assert!(
+                ALIGN.is_power_of_two(),
+                "Provided alignment is not a power of two."
+            );
+        }
 
         // INVARIANT: `align` is a power of two.
         // SAFETY: `align` is a power of two, and thus non-zero.
diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs
index 312cecab72e7..6fbd579d4a43 100644
--- a/rust/kernel/rbtree.rs
+++ b/rust/kernel/rbtree.rs
@@ -414,14 +414,17 @@ where
             // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self`
             // point to the links field of `Node<K, V>` objects.
             let this = unsafe { container_of!(node, Node<K, V>, links) };
+
             // SAFETY: `this` is a non-null node so it is valid by the type invariants.
-            node = match key.cmp(unsafe { &(*this).key }) {
-                // SAFETY: `node` is a non-null node so it is valid by the type invariants.
-                Ordering::Less => unsafe { (*node).rb_left },
-                // SAFETY: `node` is a non-null node so it is valid by the type invariants.
-                Ordering::Greater => unsafe { (*node).rb_right },
-                // SAFETY: `node` is a non-null node so it is valid by the type invariants.
-                Ordering::Equal => return Some(unsafe { &(*this).value }),
+            let this_ref = unsafe { &*this };
+
+            // SAFETY: `node` is a non-null node so it is valid by the type invariants.
+            let node_ref = unsafe { &*node };
+
+            node = match key.cmp(&this_ref.key) {
+                Ordering::Less => node_ref.rb_left,
+                Ordering::Greater => node_ref.rb_right,
+                Ordering::Equal => return Some(&this_ref.value),
             }
         }
         None
@@ -498,10 +501,10 @@ where
             let this = unsafe { container_of!(node, Node<K, V>, links) };
             // SAFETY: `this` is a non-null node so it is valid by the type invariants.
             let this_key = unsafe { &(*this).key };
+
             // SAFETY: `node` is a non-null node so it is valid by the type invariants.
-            let left_child = unsafe { (*node).rb_left };
-            // SAFETY: `node` is a non-null node so it is valid by the type invariants.
-            let right_child = unsafe { (*node).rb_right };
+            let node_ref = unsafe { &*node };
+
             match key.cmp(this_key) {
                 Ordering::Equal => {
                     // SAFETY: `this` is a non-null node so it is valid by the type invariants.
@@ -509,7 +512,7 @@ where
                     break;
                 }
                 Ordering::Greater => {
-                    node = right_child;
+                    node = node_ref.rb_right;
                 }
                 Ordering::Less => {
                     let is_better_match = match best_key {
@@ -521,7 +524,7 @@ where
                         // SAFETY: `this` is a non-null node so it is valid by the type invariants.
                         best_links = Some(unsafe { NonNull::new_unchecked(&mut (*this).links) });
                     }
-                    node = left_child;
+                    node = node_ref.rb_left;
                 }
             };
         }
diff --git a/rust/kernel/safety.rs b/rust/kernel/safety.rs
new file mode 100644
index 000000000000..c1c6bd0fa2cc
--- /dev/null
+++ b/rust/kernel/safety.rs
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Safety related APIs.
+
+/// Checks that a precondition of an unsafe function is followed.
+///
+/// The check is enabled at runtime if debug assertions (`CONFIG_RUST_DEBUG_ASSERTIONS`)
+/// are enabled. Otherwise, this macro is a no-op.
+///
+/// # Examples
+///
+/// ```no_run
+/// use kernel::unsafe_precondition_assert;
+///
+/// struct RawBuffer<T: Copy, const N: usize> {
+///     data: [T; N],
+/// }
+///
+/// impl<T: Copy, const N: usize> RawBuffer<T, N> {
+///     /// # Safety
+///     ///
+///     /// The caller must ensure that `index` is less than `N`.
+///     unsafe fn set_unchecked(&mut self, index: usize, value: T) {
+///         unsafe_precondition_assert!(
+///             index < N,
+///             "RawBuffer::set_unchecked() requires index ({index}) < N ({N})"
+///         );
+///
+///         // SAFETY: By the safety requirements of this function, `index` is valid.
+///         unsafe {
+///             *self.data.get_unchecked_mut(index) = value;
+///         }
+///     }
+/// }
+/// ```
+///
+/// # Panics
+///
+/// Panics if the expression is evaluated to [`false`] at runtime.
+#[macro_export]
+macro_rules! unsafe_precondition_assert {
+    ($cond:expr $(,)?) => {
+        $crate::unsafe_precondition_assert!(@inner $cond, ::core::stringify!($cond))
+    };
+
+    ($cond:expr, $($arg:tt)+) => {
+        $crate::unsafe_precondition_assert!(@inner $cond, $crate::prelude::fmt!($($arg)+))
+    };
+
+    (@inner $cond:expr, $msg:expr) => {
+        ::core::debug_assert!($cond, "unsafe precondition violated: {}", $msg)
+    };
+}
diff --git a/rust/kernel/transmute.rs b/rust/kernel/transmute.rs
index be5dbf3829e2..5711580c9f9b 100644
--- a/rust/kernel/transmute.rs
+++ b/rust/kernel/transmute.rs
@@ -170,6 +170,10 @@ macro_rules! impl_frombytes {
 }
 
 impl_frombytes! {
+    // SAFETY: Inhabited ZSTs only have one possible bit pattern, and these two have no invariant.
+    (),
+    {<T>} core::marker::PhantomData<T>,
+
     // SAFETY: All bit patterns are acceptable values of the types below.
     u8, u16, u32, u64, usize,
     i8, i16, i32, i64, isize,
@@ -230,6 +234,10 @@ macro_rules! impl_asbytes {
 }
 
 impl_asbytes! {
+    // SAFETY: Inhabited ZSTs only have one possible bit pattern, and these two have no invariant.
+    (),
+    {<T>} core::marker::PhantomData<T>,
+
     // SAFETY: Instances of the following types have no uninitialized portions.
     u8, u16, u32, u64, usize,
     i8, i16, i32, i64, isize,