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b=pLWvzXrG5uc7gzHZ0NriyBDtRDSG1IH8hS6WhERtIF4zJvT23DzIPfrV6GtZdb+2Oc 4YC9slMIN0pD3OemzZcxF3IZ/S/37VwuP99YML2DTR84IuxGnsNrbMUwZniyTua1Q/G7 2SkRDPupVB1mMiHv3Md+WTw9nVAgIF1xau3NgDvrw66eD8gz2G8QhdAoCclMeJcR99Po apD0RAN/ooogMVGo16EMOGfdBSSCW8suTOUGR8msC+vYy5bLJeLNlN+hLCtALiJTHYqA AImi9He3jomHAIGrX5h+N/H71iFUvsKnL7meNGkb83COkVI/yoM4p5XUq8uOPCUtGvS8 j4KA== X-Forwarded-Encrypted: i=1; AJvYcCWSaV3V94h46bQ32SL8gwVZ83q4PX9kGdxKXjKkpTrB/WWvXN7aIyCBmRnrklifNNPGu7+pOioIjIJCUGj0vWY=@vger.kernel.org X-Gm-Message-State: AOJu0Yxt4D6lXsahG1Y7NKYuBBaqsJwBT7HklLzxbcISqVNFz4t4drZR 6m5PBIIpgAVe568TkYcZpdyKckfg5GOVmaGNUHDIIDSL/WJ3UxY2J7aiDMe4w0Q6MG9/40s/wkS HOLcjOuDdqQ== X-Google-Smtp-Source: AGHT+IEqlyW4/tadreX6bN11wpCmzXQCZWMdmwaTsthqhgrxW9b3cNSTo/5NH/qdY8Gte5je22w3U1+J/ieEyw== X-Received: from slicestar.c.googlers.com ([fda3:e722:ac3:cc00:b1:7045:ac11:6237]) (user=davidgow job=sendgmr) by 2002:a5b:2ca:0:b0:e30:bf92:7a64 with SMTP id 3f1490d57ef6-e30bf927b96mr1319276.2.1730193884736; Tue, 29 Oct 2024 02:24:44 -0700 (PDT) Date: Tue, 29 Oct 2024 17:24:19 +0800 In-Reply-To: <20241029092422.2884505-1-davidgow@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241029092422.2884505-1-davidgow@google.com> X-Mailer: git-send-email 2.47.0.163.g1226f6d8fa-goog Message-ID: <20241029092422.2884505-4-davidgow@google.com> Subject: [PATCH v2 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 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 abcf0229ffee..bfc80394546a 100644 --- a/rust/kernel/kunit.rs +++ b/rust/kernel/kunit.rs @@ -272,11 +272,83 @@ 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_kunit_tests() { let running = true; assert_eq!(running, true); } + + #[test] + fn rust_test_kunit_in_kunit_test() { + let in_kunit = in_kunit_test(); + assert_eq!(in_kunit, true); + } }