Re: [PATCH v4 1/3] rust: kunit: add KUnit case and suite macros

[David Gow <davidgow@google.com>]

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On Sat, 2 Nov 2024 at 01:47, Boqun Feng <boqun.feng@gmail.com> wrote:
>
> On Fri, Nov 01, 2024 at 02:45:00PM +0800, David Gow wrote:
> > From: José Expósito <jose.exposito89@gmail.com>
> >
> > 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 <jose.exposito89@gmail.com>
> > Co-developed-by: Matt Gilbride <mattgilbride@google.com>
> > Signed-off-by: Matt Gilbride <mattgilbride@google.com>
> > Co-developed-by: David Gow <davidgow@google.com>
> > Signed-off-by: David Gow <davidgow@google.com>
> > ---
> >
> > Changes since v3:
> > https://lore.kernel.org/linux-kselftest/20241030045719.3085147-4-davidgow@google.com/
> > - The kunit_unsafe_test_suite!() macro now panic!s if the suite name is
> >   too long, triggering a compile error. (Thanks, Alice!)
> >
> > Changes since v2:
> > https://lore.kernel.org/linux-kselftest/20241029092422.2884505-2-davidgow@google.com/
> > - The kunit_unsafe_test_suite!() macro will truncate the name of the
> >   suite if it is too long. (Thanks Alice!)
> > - We no longer needlessly use UnsafeCell<> in
> >   kunit_unsafe_test_suite!(). (Thanks Alice!)
> >
> > Changes since v1:
> > https://lore.kernel.org/lkml/20230720-rustbind-v1-1-c80db349e3b5@google.com/
> > - Rebase on top of rust-next
> > - As a result, KUnit attributes are new set. These are hardcoded to the
> >   defaults of "normal" speed and no module name.
> > - Split the kunit_case!() macro into two const functions, kunit_case()
> >   and kunit_case_null() (for the NULL terminator).
> >
> > ---
> >  rust/kernel/kunit.rs | 112 +++++++++++++++++++++++++++++++++++++++++++
> >  rust/kernel/lib.rs   |   1 +
> >  2 files changed, 113 insertions(+)
> >
> > diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
> > index 824da0e9738a..85bc1faff0d5 100644
> > --- a/rust/kernel/kunit.rs
> > +++ b/rust/kernel/kunit.rs
> > @@ -161,3 +161,115 @@ 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.
> > +/// Use `kunit_case_null` to generate such a delimeter.
> > +const fn kunit_case(name: &'static kernel::str::CStr, run_case: unsafe extern "C" fn(*mut kernel::bindings::kunit)) -> kernel::bindings::kunit_case {
> > +    kernel::bindings::kunit_case {
> > +        run_case: Some(run_case),
> > +        name: name.as_char_ptr(),
> > +        attr: kernel::bindings::kunit_attributes {
> > +            speed: kernel::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> > +        },
> > +        generate_params: None,
> > +        status: kernel::bindings::kunit_status_KUNIT_SUCCESS,
> > +        module_name: core::ptr::null_mut(),
> > +        log: core::ptr::null_mut(),
> > +    }
> > +}
> > +
> > +/// Represents the NULL test case delimiter.
> > +///
> > +/// The `kunit_unsafe_test_suite!` macro expects a NULL-terminated list of test cases. This
> > +/// function retuns such a delimiter.
> > +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(),
> > +    }
> > +}
> > +
> > +
> > +/// 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_null();
> > +/// 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];
> > +
> > +                if name_u8.len() > 255 {
> > +                    panic!(concat!("The test suite name `", core::stringify!($name), "` exceeds the maximum length of 255 bytes."));
> > +                }
> > +
> > +                let mut i = 0;
> > +                while i < name_u8.len() {
> > +                    ret[i] = name_u8[i] as i8;
> > +                    i += 1;
> > +                }
> > +
> > +                ret
> > +            };
> > +
> > +            static mut KUNIT_TEST_SUITE: $crate::bindings::kunit_suite =
> > +                $crate::bindings::kunit_suite {
> > +                    name: KUNIT_TEST_SUITE_NAME,
> > +                    // SAFETY: User is expected to pass a correct `test_cases`, hence this macro
> > +                    // named 'unsafe'.
> > +                    test_cases: unsafe { $test_cases.as_mut_ptr() },
> > +                    suite_init: None,
> > +                    suite_exit: None,
> > +                    init: None,
> > +                    exit: None,
> > +                    attr: $crate::bindings::kunit_attributes {
> > +                        speed: $crate::bindings::kunit_speed_KUNIT_SPEED_NORMAL,
> > +                    },
> > +                    status_comment: [0; 256usize],
> > +                    debugfs: core::ptr::null_mut(),
> > +                    log: core::ptr::null_mut(),
> > +                    suite_init_err: 0,
> > +                    is_init: false,
> > +                };
> > +
> > +            #[used]
> > +            #[link_section = ".kunit_test_suites"]
> > +            static mut KUNIT_TEST_SUITE_ENTRY: *const $crate::bindings::kunit_suite =
> > +                // SAFETY: `KUNIT_TEST_SUITE` is static.
> > +                unsafe { core::ptr::addr_of_mut!(KUNIT_TEST_SUITE) };
>
> FYI, `addr_of` and `addr_of_mut` is safe now on statics since 1.82:
>
>         https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html#safely-addressing-unsafe-statics
>
> We need a `#[allow(unused_unsafe)]` here to avoid the unused unsafe
> warning.
>

I've not been able to work out how to fix this: adding
"#![allow(unused_unsafe)]" to the unsafe block here triggers another
error:
ERROR:root:error[E0658]: attributes on expressions are experimental

Is there somewhere else we can put the attribute to support this
without having to either disable the warning, or use the experimental
feature globally?

-- David

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