Re: [PATCH 1/3] rust: kunit: add KUnit case and suite macros

[Boqun Feng <boqun.feng@gmail.com>]

On Thu, Jul 20, 2023 at 02:38:52PM +0800, David Gow wrote:
> From: José Expósito <jose.exposito89@gmail.com>
> 
> Add a couple of Rust 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.
>  - The `kunit_case!` Rust macro is similar to the `KUNIT_CASE` C macro.
>    It can be used with parameters to generate a test case or without
>    parameters to be used as delimiter in `kunit_test_suite!`.
> 
> While these macros can be used on their own, a future patch will
> introduce another macro to create KUnit tests using a user-space like
> syntax.
> 
> Co-developed-by: David Gow <davidgow@google.com>
> Signed-off-by: David Gow <davidgow@google.com>
> Signed-off-by: José Expósito <jose.exposito89@gmail.com>
> ---
>  rust/kernel/kunit.rs | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  rust/kernel/lib.rs   |  1 +
>  2 files changed, 93 insertions(+)
> 
> diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> index 722655b2d62d..4cffc71e463b 100644
> --- a/rust/kernel/kunit.rs
> +++ b/rust/kernel/kunit.rs
> @@ -161,3 +161,95 @@ macro_rules! kunit_assert_eq {
>          $crate::kunit_assert!($name, $file, $diff, $left == $right);
>      }};
>  }
> +
> +/// Represents an individual test case.
> +///
> +/// The test case should have the signature
> +/// `unsafe extern "C" fn test_case(test: *mut crate::bindings::kunit)`.
> +///
> +/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases. This macro
> +/// can be invoked without parameters to generate the delimiter.
> +#[macro_export]
> +macro_rules! kunit_case {

kunit_case doesn't need to be a macro, right? We can define it as a
const fn. Maybe one `kunit_case_null` and one `kunit_case`. Macros
should be avoided whenever possible.

Thoughts?

Regards,
Boqun

> +    () => {
> +        $crate::bindings::kunit_case {
> +            run_case: None,
> +            name: core::ptr::null_mut(),
> +            generate_params: None,
> +            status: $crate::bindings::kunit_status_KUNIT_SUCCESS,
> +            log: core::ptr::null_mut(),
> +        }
> +    };
> +    ($name:ident, $run_case:ident) => {
> +        $crate::bindings::kunit_case {
> +            run_case: Some($run_case),
> +            name: $crate::c_str!(core::stringify!($name)).as_char_ptr(),
> +            generate_params: None,
> +            status: $crate::bindings::kunit_status_KUNIT_SUCCESS,
> +            log: core::ptr::null_mut(),
> +        }
> +    };
> +}
> +
> +/// Registers a KUnit test suite.
> +///
> +/// # Safety
> +///
> +/// `test_cases` must be a NULL terminated array of test cases.
> +///
> +/// # Examples
> +///
> +/// ```ignore
> +/// unsafe extern "C" fn test_fn(_test: *mut crate::bindings::kunit) {
> +///     let actual = 1 + 1;
> +///     let expected = 2;
> +///     assert_eq!(actual, expected);
> +/// }
> +///
> +/// static mut KUNIT_TEST_CASE: crate::bindings::kunit_case = crate::kunit_case!(name, test_fn);
> +/// static mut KUNIT_NULL_CASE: crate::bindings::kunit_case = crate::kunit_case!();
> +/// static mut KUNIT_TEST_CASES: &mut[crate::bindings::kunit_case] = unsafe {
> +///     &mut[KUNIT_TEST_CASE, KUNIT_NULL_CASE]
> +/// };
> +/// crate::kunit_unsafe_test_suite!(suite_name, KUNIT_TEST_CASES);
> +/// ```
> +#[macro_export]
> +macro_rules! kunit_unsafe_test_suite {
> +    ($name:ident, $test_cases:ident) => {
> +        const _: () = {
> +            static KUNIT_TEST_SUITE_NAME: [i8; 256] = {
> +                let name_u8 = core::stringify!($name).as_bytes();
> +                let mut ret = [0; 256];
> +
> +                let mut i = 0;
> +                while i < name_u8.len() {
> +                    ret[i] = name_u8[i] as i8;
> +                    i += 1;
> +                }
> +
> +                ret
> +            };
> +
> +            // SAFETY: `test_cases` is valid as it should be static.
> +            static mut KUNIT_TEST_SUITE: core::cell::UnsafeCell<$crate::bindings::kunit_suite> =
> +                core::cell::UnsafeCell::new($crate::bindings::kunit_suite {
> +                    name: KUNIT_TEST_SUITE_NAME,
> +                    test_cases: unsafe { $test_cases.as_mut_ptr() },
> +                    suite_init: None,
> +                    suite_exit: None,
> +                    init: None,
> +                    exit: None,
> +                    status_comment: [0; 256usize],
> +                    debugfs: core::ptr::null_mut(),
> +                    log: core::ptr::null_mut(),
> +                    suite_init_err: 0,
> +                });
> +
> +            // SAFETY: `KUNIT_TEST_SUITE` is static.
> +            #[used]
> +            #[link_section = ".kunit_test_suites"]
> +            static mut KUNIT_TEST_SUITE_ENTRY: *const $crate::bindings::kunit_suite =
> +                unsafe { KUNIT_TEST_SUITE.get() };
> +        };
> +    };
> +}
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 3642cadc34b1..ec81fd28d71a 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -18,6 +18,7 @@
>  #![feature(new_uninit)]
>  #![feature(receiver_trait)]
>  #![feature(unsize)]
> +#![feature(const_mut_refs)]
>  
>  // Ensure conditional compilation based on the kernel configuration works;
>  // otherwise we may silently break things like initcall handling.
> 
> -- 
> 2.41.0.255.g8b1d071c50-goog
>