linux/rust/kernel/kunit.rs, branch v6.16

rust: use `#[used(compiler)]` to fix build and `modpost` with Rust >= 1.89.0

2025-07-14T21:30:44Z

Starting with Rust 1.89.0 (expected 2025-08-07), the Rust compiler fails to build the `rusttest` target due to undefined references such as: kernel...-cgu.0:(.text....+0x116): undefined reference to `rust_helper_kunit_get_current_test' Moreover, tooling like `modpost` gets confused: WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/gpu/drm/nova/nova.o ERROR: modpost: missing MODULE_LICENSE() in drivers/gpu/nova-core/nova_core.o The reason behind both issues is that the Rust compiler will now [1] treat `#[used]` as `#[used(linker)]` instead of `#[used(compiler)]` for our targets. This means that the retain section flag (`R`, `SHF_GNU_RETAIN`) will be used and that they will be marked as `unique` too, with different IDs. In turn, that means we end up with undefined references that did not get discarded in `rusttest` and that multiple `.modinfo` sections are generated, which confuse tooling like `modpost` because they only expect one. Thus start using `#[used(compiler)]` to keep the previous behavior and to be explicit about what we want. Sadly, it is an unstable feature (`used_with_arg`) [2] -- we will talk to upstream Rust about it. The good news is that it has been available for a long time (Rust >= 1.60) [3]. The changes should also be fine for previous Rust versions, since they behave the same way as before [4]. Alternatively, we could use `#[no_mangle]` or `#[export_name = ...]` since those still behave like `#[used(compiler)]`, but of course it is not really what we want to express, and it requires other changes to avoid symbol conflicts. Cc: David Wood Cc: Wesley Wiser Cc: stable@vger.kernel.org # Needed in 6.12.y and later (Rust is pinned in older LTSs). Link: https://github.com/rust-lang/rust/pull/140872 [1] Link: https://github.com/rust-lang/rust/issues/93798 [2] Link: https://github.com/rust-lang/rust/pull/91504 [3] Link: https://godbolt.org/z/sxzWTMfzW [4] Reviewed-by: Alice Ryhl Acked-by: Björn Roy Baron Link: https://lore.kernel.org/r/20250712160103.1244945-3-ojeda@kernel.org Signed-off-by: Miguel Ojeda

rust: add `kunit_tests` to the prelude

2025-05-27T18:09:59Z

It is convenient to have certain things in the `kernel` prelude, and means kernel developers will find it even easier to start writing tests. And, anyway, nobody should need to use this identifier for anything else. Thus add it to the prelude. Reviewed-by: David Gow Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20250502215133.1923676-4-ojeda@kernel.org Signed-off-by: Miguel Ojeda

rust: kunit: support checked `-> Result`s in KUnit `#[test]`s

2025-05-27T18:09:59Z

Currently, return values of KUnit `#[test]` functions are ignored. Thus introduce support for `-> Result` functions by checking their returned values. At the same time, require that test functions return `()` or `Result`, which should avoid mistakes, especially with non-`#[must_use]` types. Other types can be supported in the future if needed. With this, a failing test like: #[test] fn my_test() -> Result { f()?; Ok(()) } will output: [ 3.744214] KTAP version 1 [ 3.744287] # Subtest: my_test_suite [ 3.744378] # speed: normal [ 3.744399] 1..1 [ 3.745817] # my_test: ASSERTION FAILED at rust/kernel/lib.rs:321 [ 3.745817] Expected is_test_result_ok(my_test()) to be true, but is false [ 3.747152] # my_test.speed: normal [ 3.747199] not ok 1 my_test [ 3.747345] not ok 4 my_test_suite Reviewed-by: David Gow Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20250502215133.1923676-3-ojeda@kernel.org [ Used `::kernel` for paths. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kunit: support KUnit-mapped `assert!` macros in `#[test]`s

2025-05-27T18:07:09Z

The KUnit `#[test]` support that landed recently is very basic and does not map the `assert*!` macros into KUnit like the doctests do, so they panic at the moment. Thus implement the custom mapping in a similar way to doctests, reusing the infrastructure there. In Rust 1.88.0, the `file()` method in `Span` may be stable [1]. However, it was changed recently (from `SourceFile`), so we need to do something different in previous versions. Thus create a helper for it and use it to get the path. With this, a failing test suite like: #[kunit_tests(my_test_suite)] mod tests { use super::*; #[test] fn my_first_test() { assert_eq!(42, 43); } #[test] fn my_second_test() { assert!(42 >= 43); } } will properly map back to KUnit, printing something like: [ 1.924325] KTAP version 1 [ 1.924421] # Subtest: my_test_suite [ 1.924506] # speed: normal [ 1.924525] 1..2 [ 1.926385] # my_first_test: ASSERTION FAILED at rust/kernel/lib.rs:251 [ 1.926385] Expected 42 == 43 to be true, but is false [ 1.928026] # my_first_test.speed: normal [ 1.928075] not ok 1 my_first_test [ 1.928723] # my_second_test: ASSERTION FAILED at rust/kernel/lib.rs:256 [ 1.928723] Expected 42 >= 43 to be true, but is false [ 1.929834] # my_second_test.speed: normal [ 1.929868] not ok 2 my_second_test [ 1.930032] # my_test_suite: pass:0 fail:2 skip:0 total:2 [ 1.930153] # Totals: pass:0 fail:2 skip:0 total Link: https://github.com/rust-lang/rust/pull/140514 [1] Reviewed-by: David Gow Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20250502215133.1923676-2-ojeda@kernel.org [ Required `KUNIT=y` like for doctests. Used the `cfg_attr` from the TODO comment and clarified its comment now that the stabilization is in beta and thus quite likely stable in Rust 1.88.0. Simplified the `new_body` code by introducing a new variable. Added `#[allow(clippy::incompatible_msrv)]`. - Miguel ] Signed-off-by: Miguel Ojeda

rust: use absolute paths in macros referencing core and kernel

2025-05-22T22:12:14Z

Macros and auto-generated code should use absolute paths, `::core::...` and `::kernel::...`, for core and kernel references. This prevents issues where user-defined modules named `core` or `kernel` could be picked up instead of the `core` or `kernel` crates. Thus clean some references up. Suggested-by: Benno Lossin Closes: https://github.com/Rust-for-Linux/linux/issues/1150 Signed-off-by: Igor Korotin Reviewed-by: Benno Lossin Acked-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20250519164615.3310844-1-igor.korotin.linux@gmail.com [ Applied `rustfmt`. Reworded slightly. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kunit: allow to know if we are in a test

2025-03-20T11:27:05Z

In some cases, we need to call test-only code from outside the test case, for example, to mock a function or a module. In order to check whether we are in a test or not, we need to test if `CONFIG_KUNIT` is set. Unfortunately, we cannot rely only on this condition because: - a test could be running in another thread, - some distros compile KUnit in production kernels, so checking at runtime that `current->kunit_test != NULL` is required. Forturately, KUnit provides an optimised check in `kunit_get_current_test()`, which checks CONFIG_KUNIT, a global static key, and then the current thread's running KUnit test. Add a safe wrapper function around this to know whether or not we are in a KUnit test and examples showing how to mock a function and a module. Signed-off-by: José Expósito Co-developed-by: Miguel Ojeda Signed-off-by: Miguel Ojeda Co-developed-by: David Gow Signed-off-by: David Gow Link: https://lore.kernel.org/r/20250307090103.918788-4-davidgow@google.com Signed-off-by: Miguel Ojeda

rust: macros: add macro to easily run KUnit tests

2025-03-20T11:26:54Z

Add a new procedural macro (`#[kunit_tests(kunit_test_suit_name)]`) to run KUnit tests using a user-space like syntax. The macro, that should be used on modules, transforms every `#[test]` in a `kunit_case!` and adds a `kunit_unsafe_test_suite!` registering all of them. The only difference with user-space tests is that instead of using `#[cfg(test)]`, `#[kunit_tests(kunit_test_suit_name)]` is used. Note that `#[cfg(CONFIG_KUNIT)]` is added so the test module is not compiled when `CONFIG_KUNIT` is set to `n`. Reviewed-by: David Gow Signed-off-by: José Expósito Co-developed-by: Boqun Feng Signed-off-by: Boqun Feng Co-developed-by: Miguel Ojeda Signed-off-by: Miguel Ojeda Reviewed-by: Tamir Duberstein Signed-off-by: David Gow Link: https://lore.kernel.org/r/20250307090103.918788-3-davidgow@google.com [ Removed spurious (in rendered form) newline in docs. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kunit: add KUnit case and suite macros

2025-03-20T11:26:42Z

Add a couple of Rust const functions and macros to allow to develop KUnit tests without relying on generated C code: - The `kunit_unsafe_test_suite!` Rust macro is similar to the `kunit_test_suite` C macro. It requires a NULL-terminated array of test cases (see below). - The `kunit_case` Rust function is similar to the `KUNIT_CASE` C macro. It generates as case from the name and function. - The `kunit_case_null` Rust function generates a NULL test case, which is to be used as delimiter in `kunit_test_suite!`. While these functions and macros can be used on their own, a future patch will introduce another macro to create KUnit tests using a user-space like syntax. Signed-off-by: José Expósito Co-developed-by: Matt Gilbride Signed-off-by: Matt Gilbride Co-developed-by: Miguel Ojeda Signed-off-by: Miguel Ojeda Co-developed-by: David Gow Signed-off-by: David Gow Link: https://lore.kernel.org/r/20250307090103.918788-2-davidgow@google.com [ Applied Markdown in comment. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kunit: use C-string literals to clean warning

2024-10-01T21:46:42Z

Starting with upstream Rust commit a5e3a3f9b6bd ("move `manual_c_str_literals` to complexity"), to be released in Rust 1.83.0 [1], Clippy now warns on `manual_c_str_literals` by default, e.g.: error: manually constructing a nul-terminated string --> rust/kernel/kunit.rs:21:13 | 21 | b"\x013%pA\0".as_ptr() as _, | ^^^^^^^^^^^^^ help: use a `c""` literal: `c"\x013%pA"` | = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_c_str_literals = note: `-D clippy::manual-c-str-literals` implied by `-D warnings` = help: to override `-D warnings` add `#[allow(clippy::manual_c_str_literals)]` Apply the suggestion to clean up the warnings. Link: https://github.com/rust-lang/rust-clippy/pull/13263 [1] Reviewed-by: Trevor Gross Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20240927164414.560906-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda

rust: support `srctree`-relative links

2023-12-21T19:54:17Z

Some of our links use relative paths in order to point to files in the source tree, e.g.: //! C header: [`include/linux/printk.h`](../../../../include/linux/printk.h) /// [`struct mutex`]: ../../../../include/linux/mutex.h These are problematic because they are hard to maintain and do not support `O=` builds. Instead, provide support for `srctree`-relative links, e.g.: //! C header: [`include/linux/printk.h`](srctree/include/linux/printk.h) /// [`struct mutex`]: srctree/include/linux/mutex.h The links are fixed after `rustdoc` generation to be based on the absolute path to the source tree. Essentially, this is the automatic version of Tomonori's fix [1], suggested by Gary [2]. Suggested-by: Gary Guo Reported-by: FUJITA Tomonori Closes: https://lore.kernel.org/r/20231026.204058.2167744626131849993.fujita.tomonori@gmail.com [1] Fixes: 48fadf440075 ("docs: Move rustdoc output, cross-reference it") Link: https://lore.kernel.org/rust-for-linux/20231026154525.6d14b495@eugeo/ [2] Reviewed-by: Martin Rodriguez Reboredo Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20231215235428.243211-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda