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b=e7WeBX4A/kNZjxVb02GhHV+Bv0Ut2qMnId5b7oOQUfLrVezRyqhhu3NVf8bQf91CG7 aaOMitYc7EWWBQr4u8+yILT4xCAxogoheAWFAisjyuxC7GZcQygxOSl7i4YoMqe3M1jc 9urY5+kw4NFsQn1e+yj57KcaL2Vf6tavA86XcmDU4CntuszWyQUuxUBRrHvnozqRk+OE O4pWYzX5Z5iDX+z76rTV8IfSCjiUgWED1jDbK0Q3z78eZGrOmBgH8dHfJp1GWXsaov3q uj0j+W/neOHqcTE2xQCOwsBCzm86y/GI2yY+81edgi9X5+Kr4qaJftgTW9+dV9N1iw0n EJLg== X-Forwarded-Encrypted: i=1; AJvYcCWi7pnEI8gYWk9N5UVkHDF3uFo4iqJc9UI/EVpKc1wAk1wNFmbPllX5OAP9P3yk8I7AU2TW4eBRr34O6MSHMCY=@vger.kernel.org X-Gm-Message-State: AOJu0YxLdPZOSp8IJNHGOzj/BcdeoTpJr68LL/hoLA5s4TgXEKxBJ8r2 q59D2wOssl5Ajwr4inZKZWnxqDGkMHjui4B9hkdmwdca/6EDwA21zmOlIZ7tCoJlUo80fAyrMs7 TKzWvOh2Hmw== X-Google-Smtp-Source: AGHT+IEIXo3M6l3NU9Qv2uOCk9CnzdlHFgd4U1XPtBHdD4Ek09zM+pvRo5MbMvTvDW7Nu3Tut9Zu4gtndT2qHg== X-Received: from slicestar.c.googlers.com ([fda3:e722:ac3:cc00:b1:7045:ac11:6237]) (user=davidgow job=sendgmr) by 2002:a25:aa83:0:b0:e30:c235:d79f with SMTP id 3f1490d57ef6-e30e5b282d1mr2857276.8.1730443523956; Thu, 31 Oct 2024 23:45:23 -0700 (PDT) Date: Fri, 1 Nov 2024 14:45:02 +0800 In-Reply-To: <20241101064505.3820737-1-davidgow@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241101064505.3820737-1-davidgow@google.com> X-Mailer: git-send-email 2.47.0.199.ga7371fff76-goog Message-ID: <20241101064505.3820737-4-davidgow@google.com> Subject: [PATCH v4 3/3] rust: kunit: allow to know if we are in a test From: David Gow To: Miguel Ojeda , " =?utf-8?b?Sm9zw6kgRXhww7NzaXRv?= " , Brendan Higgins , Rae Moar , Boqun Feng , Alex Gaynor , Gary Guo , Benno Lossin , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Alice Ryhl , Matt Gilbride Cc: kunit-dev@googlegroups.com, linux-kselftest@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, David Gow From: José Expósito 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: David Gow Signed-off-by: David Gow --- Changes since v3: https://lore.kernel.org/linux-kselftest/20241030045719.3085147-8-davidgow@google.com/ - The example test has been updated to no longer use assert_eq!() with a constant bool argument (fixes a clippy warning). No changes since v2: https://lore.kernel.org/linux-kselftest/20241029092422.2884505-4-davidgow@google.com/ Changes since v1: https://lore.kernel.org/lkml/20230720-rustbind-v1-3-c80db349e3b5@google.com/ - Rebased on top of rust-next. - Use the `kunit_get_current_test()` C function, which wasn't previously available, instead of rolling our own. - (Thanks also to Boqun for suggesting a nicer way of implementing this, which I tried, but the `kunit_get_current_test()` version obsoleted.) --- rust/kernel/kunit.rs | 72 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs index 71ce1d145be8..ad38d6d62446 100644 --- a/rust/kernel/kunit.rs +++ b/rust/kernel/kunit.rs @@ -276,10 +276,82 @@ macro_rules! kunit_unsafe_test_suite { }; } +/// In some cases, you need to call test-only code from outside the test case, for example, to +/// create a function mock. This function can be invoked to know whether we are currently running a +/// KUnit test or not. +/// +/// # Examples +/// +/// This example shows how a function can be mocked to return a well-known value while testing: +/// +/// ``` +/// # use kernel::kunit::in_kunit_test; +/// # +/// fn fn_mock_example(n: i32) -> i32 { +/// if in_kunit_test() { +/// 100 +/// } else { +/// n + 1 +/// } +/// } +/// +/// let mock_res = fn_mock_example(5); +/// assert_eq!(mock_res, 100); +/// ``` +/// +/// Sometimes, you don't control the code that needs to be mocked. This example shows how the +/// `bindings` module can be mocked: +/// +/// ``` +/// // Import our mock naming it as the real module. +/// #[cfg(CONFIG_KUNIT)] +/// use bindings_mock_example as bindings; +/// +/// // This module mocks `bindings`. +/// mod bindings_mock_example { +/// use kernel::kunit::in_kunit_test; +/// use kernel::bindings::u64_; +/// +/// // Make the other binding functions available. +/// pub(crate) use kernel::bindings::*; +/// +/// // Mock `ktime_get_boot_fast_ns` to return a well-known value when running a KUnit test. +/// pub(crate) unsafe fn ktime_get_boot_fast_ns() -> u64_ { +/// if in_kunit_test() { +/// 1234 +/// } else { +/// unsafe { kernel::bindings::ktime_get_boot_fast_ns() } +/// } +/// } +/// } +/// +/// // This is the function we want to test. Since `bindings` has been mocked, we can use its +/// // functions seamlessly. +/// fn get_boot_ns() -> u64 { +/// unsafe { bindings::ktime_get_boot_fast_ns() } +/// } +/// +/// let time = get_boot_ns(); +/// assert_eq!(time, 1234); +/// ``` +pub fn in_kunit_test() -> bool { + // SAFETY: kunit_get_current_test() is always safe to call from C (it has fallbacks for + // when KUnit is not enabled), and we're only comparing the result to NULL. + unsafe { !bindings::kunit_get_current_test().is_null() } +} + #[kunit_tests(rust_kernel_kunit)] mod tests { + use super::*; + #[test] fn rust_test_kunit_example_test() { assert_eq!(1 + 1, 2); } + + #[test] + fn rust_test_kunit_in_kunit_test() { + let in_kunit = in_kunit_test(); + assert!(in_kunit); + } }