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Tue, 15 Sep 2026 12:36:42 -0700 (PDT) From: =?UTF-8?q?Nicol=C3=A1s=20Antinori?= To: Alice Ryhl , Burak Emir , Brendan Higgins , David Gow , Miguel Ojeda Cc: =?UTF-8?q?Nicol=C3=A1s=20Antinori?= , Alexandre Courbot , Andreas Hindborg , Benno Lossin , =?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?= , Boqun Feng , Brigham Campbell , Daniel Almeida , Danilo Krummrich , Gary Guo , Jori Koolstra , =?UTF-8?q?Onur=20=C3=96zkan?= , Rae Moar , Shuah Khan , Tamir Duberstein , Trevor Gross , Yury Norov , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel-mentees@lists.linux.dev Subject: [PATCH RFC 0/3] rust: kunit: #[should_panic] and same test name with different #[cfg(...)] support Date: Tue, 15 Sep 2026 16:33:51 -0300 Message-ID: X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This patch series intends to implement two features for KUnit tests written in Rust. The work is based on a TODO comment made in the `bitmap.rs` module [1]. 1. Supporting `#[should_panic]` [2]: KUnit tests in Rust follow the user-space syntax, but at the moment `#[should_panic]` is not supported. The first patch of this series adds support for the attribute (only in its basic form, `#[should_panic = "message"]` is not supported, and I don't know if it makes sense to support it) The way it is supported is by having a separate `#[panic_handler]` when `CONFIG_KUNIT` is enabled. When a test is marked with `#[should_panic]`, a static value (KUNIT_SHOULD_PANIC = 0xDEAD7357) is assigned to the kunit's `priv` field, since it is meant for saving arbitrary user data [3]. At the moment, I did not find any place where Rust tests use that field, so it should be safe to write it. When the test panics, the `#[panic_handler]` function is called, obtains the kunit current test and checks if the `priv` field is not null and contains the value `KUNIT_SHOULD_PANIC`. If those conditions are true, it marks the test as successful (since it panicked as expected) and calls `__kunit_abort_expecting_error`, a new function that exits the testing thread but fills `try_catch->try_result` with a 0 so the test runner does not mistake it as a failed test. If those conditions are not true: - If `priv` is null, the test panics as it would have before having this feature, priv = null means that the test was not expected to panic. - If `priv` is not null but its value is not `KUNIT_SHOULD_PANIC`, the test panics with an error message informing that the code found in `priv` was invalid. If the test does not panic, the `#[panic_handler]` is not triggered. The test is marked as failed (since it was expected to panic). Regarding this feature: - Do this approach make sense? - Is it ok to mark the `#[should_panic]` tests with a static constant? Is another mechanism better to check in the `#[panic_handler]` that the test was supposed to panic? 2. Allow same test name with different #[cfg(...)]: When testing `#[should_panic]` in `bitmap.rs` (check the last patch of the series) I found that the test that was supposed to panic had the same name as another one, but they were run on different configurations. This caused the following compilation error: ERROR:root:error[E0428]: the name `kunit_rust_wrapper_owned_bitmap_out_of_bounds` is defined multiple times --> ../rust/kernel/bitmap.rs:503:1 | 503 | #[macros::kunit_tests(rust_kernel_bitmap)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `kunit_rust_wrapper_owned_bitmap_out_of_bounds` redefined here | = note: `kunit_rust_wrapper_owned_bitmap_out_of_bounds` must be defined only once in the value namespace of this module = note: this error originates in the attribute macro `macros::kunit_tests` (in Nightly builds, run with -Z macro-backtrace for more info) To fix this problem, I appended to the `kunit_rust_wrapper_*` identifiers an 'stringified' version of the test's #[cfg(...)] arguments. The purpose of this is that, if we have a test with the same name and configuration, it would fail. The configuration string was also appended to the tests names. This was done to have a better test run report: ... [SKIPPED] owned_bitmap_out_of_bounds_cfg_not_config_rust_bitmap_hardened [PASSED] owned_bitmap_out_of_bounds_cfg_config_rust_bitmap_hardened ... Otherwise we would have something like the following: ... [SKIPPED] owned_bitmap_out_of_bounds [PASSED] owned_bitmap_out_of_bounds ... Regarding this: - Does it makes sense to allow same test names with different cfgs? - Is it ok to 'stringify' the configuration so it can be distinguished in the report? Would you prefer something like `_case_1` `_case_2` .. instead? This is the first RFC patch I send to the LKML, if there's something not right with it please let me know. Kind Regards, Nicolás [1] https://github.com/Rust-for-Linux/linux/blob/fd73f4a6659897191fa0d40695fe370925dd3780/rust/kernel/bitmap.rs#L592-L600 [2] https://doc.rust-lang.org/rust-by-example/testing/unit_testing.html#testing-panics [3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/kunit/test.h?id=f6e7b42bf05b2427fb8a7a1d1c387a86638bb413#n314 Nicolás Antinori (3): rust: kunit: add #[should_panic] support rust: kunit: allow same test name with different #[cfg(...)] rust: bitmap: kunit: uncomment owned_bitmap_out_of_bounds panic case include/kunit/test.h | 1 + include/kunit/try-catch.h | 1 + lib/kunit/test.c | 14 +++++++ lib/kunit/try-catch.c | 7 ++++ rust/kernel/bitmap.rs | 40 +++++++++----------- rust/kernel/kunit.rs | 24 ++++++++++++ rust/kernel/lib.rs | 46 +++++++++++++++++++++-- rust/macros/kunit.rs | 78 ++++++++++++++++++++++++++++++++++++--- 8 files changed, 181 insertions(+), 30 deletions(-) -- 2.47.3