kernel/linux.git/rust/macros/lib.rs, branch v7.2-rc1

rust: types: add `ForLt` trait for higher-ranked lifetime support

2026-05-27T14:24:59+00:00

There are a few cases, e.g. when dealing with data referencing each other, one might want to write code that is generic over lifetimes. For example, if you want to take a function that takes `&'a Foo` and gives `Bar<'a>`, you can write: f: impl for<'a> FnOnce(&'a Foo) -> Bar<'a>, However, it becomes tricky when you want that function to not have a fixed `Bar`, but have it be generic again. In this case, one needs something that is generic over types that are themselves generic over lifetimes. `ForLt` provides such support. It provides a trait `ForLt` which describes a type generic over a lifetime. One may use `ForLt::Of<'a>` to get an instance of a type for a specific lifetime. For the case of cross referencing, one would almost always want the lifetime to be covariant. Therefore this is also made a requirement for the `ForLt` trait, so functions with `ForLt` trait bound can assume covariance. A macro `ForLt!()` is provided to be able to obtain a type that implements `ForLt`. For example, `ForLt!(for<'a> Bar<'a>)` would yield a type that `::Of<'a>` is `Bar<'a>`. This also works with lifetime elision, e.g. `ForLt!(Bar<'_>)` or for types without lifetime at all, e.g. `ForLt!(u32)`. The API design draws inspiration from the higher-kinded-types [1] crate, however a different design decision has been taken (e.g. covariance requirement) and the implementation is independent. License headers use "Apache-2.0 OR MIT" because I anticipate this to be used in pin-init crate too which is licensed as such. Link: https://docs.rs/higher-kinded-types/ [1] Reviewed-by: Greg Kroah-Hartman Reviewed-by: Eliot Courtney Signed-off-by: Gary Guo Acked-by: Miguel Ojeda Reviewed-by: Alexandre Courbot Link: https://patch.msgid.link/20260525202921.124698-23-dakr@kernel.org [ Handle macro_rules! invocations in the ForLt! proc macro's covariance and WF checks. Since proc macros cannot expand macro_rules!, add a visit_macro() implementation to conservatively assume macro invocations may contain lifetimes, forcing them through the compiler-assisted covariance proof. Fix a few typos in the documentation and in the commit message, add empty lines before samples, add missing periods and consistently use markdown. - Danilo ] Signed-off-by: Danilo Krummrich

rust: macros: simplify code using `feature(extract_if)`

2026-04-07T08:00:24+00:00

`feature(extract_if)` [1] was stabilized in Rust 1.87.0 [2], and the last significant change happened in Rust 1.85.0 [3] when the range parameter was added. That is, with our new minimum version, we can start using the feature. Thus simplify the code using the feature and remove the TODO comment. Suggested-by: Gary Guo Link: https://lore.kernel.org/rust-for-linux/DHHVSX66206Y.3E7I9QUNTCJ8I@garyguo.net/ Link: https://github.com/rust-lang/rust/issues/43244 [1] Link: https://github.com/rust-lang/rust/pull/137109 [2] Link: https://github.com/rust-lang/rust/pull/133265 [3] Link: https://patch.msgid.link/20260405235309.418950-16-ojeda@kernel.org Reviewed-by: Tamir Duberstein Signed-off-by: Miguel Ojeda

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

2026-02-10T19:53:01+00:00

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'. 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()]' 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 ...

rust: macros: convert `#[kunit_tests]` macro to use `syn`

2026-01-28T12:43:36+00:00

Make use of `syn` to parse the module structurally and thus improve the robustness of parsing. String interpolation is avoided by generating tokens directly using `quote!`. Reviewed-by: Tamir Duberstein Signed-off-by: Gary Guo Reviewed-by: Benno Lossin Reviewed-by: David Gow Link: https://patch.msgid.link/20260112170919.1888584-9-gary@kernel.org [ Pass C string to match commit 6c37b6841a92 ("rust: kunit: replace `kernel::c_str!` with C-Strings"). - Miguel ] Signed-off-by: Miguel Ojeda

rust: macros: convert `concat_idents!` to use `syn`

2026-01-27T23:55:25+00:00

This eliminates the need for `expect_punct` helper. Reviewed-by: Tamir Duberstein Reviewed-by: Benno Lossin Signed-off-by: Gary Guo Link: https://patch.msgid.link/20260112170919.1888584-8-gary@kernel.org Signed-off-by: Miguel Ojeda

rust: macros: convert `#[export]` to use `syn`

2026-01-27T23:55:25+00:00

This eliminates the custom `function_name` helper. Reviewed-by: Tamir Duberstein Reviewed-by: Benno Lossin Signed-off-by: Gary Guo Link: https://patch.msgid.link/20260112170919.1888584-7-gary@kernel.org Signed-off-by: Miguel Ojeda

rust: macros: use `syn` to parse `module!` macro

2026-01-27T23:55:24+00:00

With `syn` being available in the kernel, use it to parse the complex custom `module!` macro to replace existing helpers. Only parsing is changed in this commit, the code generation is untouched. This has the benefit of better error message when the macro is used incorrectly, as it can point to a concrete span on what's going wrong. For example, if a field is specified twice, previously it reads: error: proc macro panicked --> samples/rust/rust_minimal.rs:7:1 | 7 | / module! { 8 | | type: RustMinimal, 9 | | name: "rust_minimal", 10 | | author: "Rust for Linux Contributors", 11 | | description: "Rust minimal sample", 12 | | license: "GPL", 13 | | license: "GPL", 14 | | } | |_^ | = help: message: Duplicated key "license". Keys can only be specified once. now it reads: error: duplicated key "license". Keys can only be specified once. --> samples/rust/rust_minimal.rs:13:5 | 13 | license: "GPL", | ^^^^^^^ Reviewed-by: Tamir Duberstein Signed-off-by: Gary Guo Reviewed-by: Benno Lossin Link: https://patch.msgid.link/20260112170919.1888584-5-gary@kernel.org Signed-off-by: Miguel Ojeda

rust: macros: convert `#[vtable]` macro to use `syn`

2026-01-27T23:55:24+00:00

`#[vtable]` is converted to use syn. This is more robust than the previous heuristic-based searching of defined methods and functions. When doing so, the trait and impl are split into two code paths as the types are distinct when parsed by `syn`. Reviewed-by: Tamir Duberstein Signed-off-by: Gary Guo Reviewed-by: Benno Lossin Link: https://patch.msgid.link/20260112170919.1888584-4-gary@kernel.org Signed-off-by: Miguel Ojeda

rust: macros: use `quote!` from vendored crate

2026-01-27T23:55:24+00:00

With `quote` crate now vendored in the kernel, we can remove our custom `quote!` macro implementation and just rely on that crate instead. The `quote` crate uses types from the `proc-macro2` library so we also update to use that, and perform conversion in the top-level lib.rs. Clippy complains about unnecessary `.to_string()` as `proc-macro2` provides additional `PartialEq` impl, so they are removed. Reviewed-by: Tamir Duberstein Reviewed-by: Benno Lossin Signed-off-by: Gary Guo Acked-by: David Gow # for kunit Link: https://patch.msgid.link/20260112170919.1888584-3-gary@kernel.org Signed-off-by: Miguel Ojeda

rust: use consistent backtick formatting for NULL in docs

2026-01-26T02:13:27+00:00

Some doc comments use `NULL` while others use plain NULL. Make it consistent by adding backticks everywhere, matching the majority of existing usage. Signed-off-by: Peter Novak Acked-by: Stephen Boyd Acked-by: David Gow Reviewed-by: Alexandre Courbot Acked-by: Danilo Krummrich Link: https://patch.msgid.link/20251130211233.367946-1-seimun018r@gmail.com [ Reworded slightly. - Miguel ] Signed-off-by: Miguel Ojeda