rust/kernel/kunit.rs

// SPDX-License-Identifier: GPL-2.0

//! KUnit-based macros for Rust unit tests.
//!
//! C header: [`include/kunit/test.h`](srctree/include/kunit/test.h)
//!
//! Reference: <https://docs.kernel.org/dev-tools/kunit/index.html>

use core::{ffi::c_void, fmt};

/// Prints a KUnit error-level message.
///
/// Public but hidden since it should only be used from KUnit generated code.
#[doc(hidden)]
pub fn err(args: fmt::Arguments<'_>) {
    // SAFETY: The format string is null-terminated and the `%pA` specifier matches the argument we
    // are passing.
    #[cfg(CONFIG_PRINTK)]
    unsafe {
        bindings::_printk(
            b"\x013%pA\0".as_ptr() as _,
            &args as *const _ as *const c_void,
        );
    }
}

/// Prints a KUnit info-level message.
///
/// Public but hidden since it should only be used from KUnit generated code.
#[doc(hidden)]
pub fn info(args: fmt::Arguments<'_>) {
    // SAFETY: The format string is null-terminated and the `%pA` specifier matches the argument we
    // are passing.
    #[cfg(CONFIG_PRINTK)]
    unsafe {
        bindings::_printk(
            b"\x016%pA\0".as_ptr() as _,
            &args as *const _ as *const c_void,
        );
    }
}

/// Asserts that a boolean expression is `true` at runtime.
///
/// Public but hidden since it should only be used from generated tests.
///
/// Unlike the one in `core`, this one does not panic; instead, it is mapped to the KUnit
/// facilities. See [`assert!`] for more details.
#[doc(hidden)]
#[macro_export]
macro_rules! kunit_assert {
    ($name:literal, $file:literal, $diff:expr, $condition:expr $(,)?) => {
        'out: {
            // Do nothing if the condition is `true`.
            if $condition {
                break 'out;
            }

            static FILE: &'static $crate::str::CStr = $crate::c_str!($file);
            static LINE: i32 = core::line!() as i32 - $diff;
            static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));

            // SAFETY: FFI call without safety requirements.
            let kunit_test = unsafe { $crate::bindings::kunit_get_current_test() };
            if kunit_test.is_null() {
                // The assertion failed but this task is not running a KUnit test, so we cannot call
                // KUnit, but at least print an error to the kernel log. This may happen if this
                // macro is called from an spawned thread in a test (see
                // `scripts/rustdoc_test_gen.rs`) or if some non-test code calls this macro by
                // mistake (it is hidden to prevent that).
                //
                // This mimics KUnit's failed assertion format.
                $crate::kunit::err(format_args!(
                    "    # {}: ASSERTION FAILED at {FILE}:{LINE}\n",
                    $name
                ));
                $crate::kunit::err(format_args!(
                    "    Expected {CONDITION} to be true, but is false\n"
                ));
                $crate::kunit::err(format_args!(
                    "    Failure not reported to KUnit since this is a non-KUnit task\n"
                ));
                break 'out;
            }

            #[repr(transparent)]
            struct Location($crate::bindings::kunit_loc);

            #[repr(transparent)]
            struct UnaryAssert($crate::bindings::kunit_unary_assert);

            // SAFETY: There is only a static instance and in that one the pointer field points to
            // an immutable C string.
            unsafe impl Sync for Location {}

            // SAFETY: There is only a static instance and in that one the pointer field points to
            // an immutable C string.
            unsafe impl Sync for UnaryAssert {}

            static LOCATION: Location = Location($crate::bindings::kunit_loc {
                file: FILE.as_char_ptr(),
                line: LINE,
            });
            static ASSERTION: UnaryAssert = UnaryAssert($crate::bindings::kunit_unary_assert {
                assert: $crate::bindings::kunit_assert {},
                condition: CONDITION.as_char_ptr(),
                expected_true: true,
            });

            // SAFETY:
            //   - FFI call.
            //   - The `kunit_test` pointer is valid because we got it from
            //     `kunit_get_current_test()` and it was not null. This means we are in a KUnit
            //     test, and that the pointer can be passed to KUnit functions and assertions.
            //   - The string pointers (`file` and `condition` above) point to null-terminated
            //     strings since they are `CStr`s.
            //   - The function pointer (`format`) points to the proper function.
            //   - The pointers passed will remain valid since they point to `static`s.
            //   - The format string is allowed to be null.
            //   - There are, however, problems with this: first of all, this will end up stopping
            //     the thread, without running destructors. While that is problematic in itself,
            //     it is considered UB to have what is effectively a forced foreign unwind
            //     with `extern "C"` ABI. One could observe the stack that is now gone from
            //     another thread. We should avoid pinning stack variables to prevent library UB,
            //     too. For the moment, given that test failures are reported immediately before the
            //     next test runs, that test failures should be fixed and that KUnit is explicitly
            //     documented as not suitable for production environments, we feel it is reasonable.
            unsafe {
                $crate::bindings::__kunit_do_failed_assertion(
                    kunit_test,
                    core::ptr::addr_of!(LOCATION.0),
                    $crate::bindings::kunit_assert_type_KUNIT_ASSERTION,
                    core::ptr::addr_of!(ASSERTION.0.assert),
                    Some($crate::bindings::kunit_unary_assert_format),
                    core::ptr::null(),
                );
            }

            // SAFETY: FFI call; the `test` pointer is valid because this hidden macro should only
            // be called by the generated documentation tests which forward the test pointer given
            // by KUnit.
            unsafe {
                $crate::bindings::__kunit_abort(kunit_test);
            }
        }
    };
}

/// Asserts that two expressions are equal to each other (using [`PartialEq`]).
///
/// Public but hidden since it should only be used from generated tests.
///
/// Unlike the one in `core`, this one does not panic; instead, it is mapped to the KUnit
/// facilities. See [`assert!`] for more details.
#[doc(hidden)]
#[macro_export]
macro_rules! kunit_assert_eq {
    ($name:literal, $file:literal, $diff:expr, $left:expr, $right:expr $(,)?) => {{
        // For the moment, we just forward to the expression assert because, for binary asserts,
        // KUnit supports only a few types (e.g. integers).
        $crate::kunit_assert!($name, $file, $diff, $left == $right);
    }};
}