From nobody Mon Nov 25 02:23:35 2024 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EE848155301 for ; Fri, 1 Nov 2024 06:45:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730443527; cv=none; b=B1pCLIqFfsHKcksEYOe1L1x0n9PlhWCDY9Oroxh7CQjYySjTHemdO9jglpNyX/oORKF/JO1s5Qtn9DWZfOvp27fKAI+qXPfungoZT27Q9Ywv4bZ8SImoR1Msh7BMvn7z1hOSczMbRu9+HZ/HNgd4MhER95UPzaSYhDbZlcpkHEY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730443527; c=relaxed/simple; bh=f3EQWER6RRuCLdLa6B3j/75NplNWzvD63Oagrzez9Kg=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=oviGDYZdaCf4TOLFtTm6UqX34KadZcqVHF7IVAgGXPvRM8qcfoSZeUY19O9/cPz9jNYQWnUpXsnOGBmwi5uviDzTgstF1+7j1EmlJx2/+NmI05Tb8foP67i6/9+peSfAaR4ZHQz9PQdIkBeTMeSqAdddAdX6qah6g/KugU1zIFE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--davidgow.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=H0FBm8o7; arc=none smtp.client-ip=209.85.219.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--davidgow.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="H0FBm8o7" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-e2e3321aae0so2862897276.1 for ; Thu, 31 Oct 2024 23:45:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1730443524; x=1731048324; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=lHPJiykftORb/g35WFmCs+9SKBvzp/KNUqXI3sEF0e8=; b=H0FBm8o75WDSOJooUUCigqPjMN3jae5MqpmZunAzEgBkm6gJ5vbwxfhq+yKMVTvleH 6Wgc5bsj7iVTFbtCt+xBIQLohnIL68AQJlj1qtD2tuOWBWCEoM+xXulN5cF4PDavEGjT BY3iD0BkUqTXzoI9v4K8gHp+Qp4x4AjYPCahqf/m5gHnOqyBhEp/CkzW1oEVfjNisAqz wfUiU2PkB8X1C7hvzk/t8mLIIkNJF7zclY3M81JI/p5sFJGBYJkXON/ktQbhrN9B7y7M 2WnqMp/HzSgCZd6JAaye4Pstz2ghkF63RktuA11RM+OwsWsIO85tgTCTNX70ivF+CbYD o8uw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730443524; x=1731048324; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=lHPJiykftORb/g35WFmCs+9SKBvzp/KNUqXI3sEF0e8=; b=Y61vpzZf07Zns+hEay3xfSu5Y4hdbrqRch/lAcwyf/J1FEu7/z3f+QbuA1X66tMxmb cV1+HEqQnuJyHvawVbXONQK1fr8Zp1pCUgtCJZn0Mz//9MXaHMU0+ElXStsHAmA1/KE1 4m4JLyoIlpt1VlLnIDUO500y0R2IaHi3qaLu5S5QqivmE+rSUsb3oNzOsF2Z8iLuJ5A2 pMD14zUuZpY6IxwTpT37R+//3iwIhsY2PO5TYIqOrTA5FM2jgY0ykiZEOaEy36pbETuz Mxg+Oxj4/KRMyxwd7hUDE7SGRgogjNsGeW6QBpT6ezrZ9+F26VDdpzZhDvR25YQjP2h/ 9qiQ== X-Forwarded-Encrypted: i=1; AJvYcCUJ7jy//xLkAGn/oAVm1F3LTeyzc4dBfl0fNNq6PuEiu7F37pKusLkxA2GNXc5A8cMcXXaIX/A9ke24KYQ=@vger.kernel.org X-Gm-Message-State: AOJu0YyUibsCmfIJZSpTP5wfZP2gilRzSGwAJIWYwuXng6o6aJxm3LcT 3GrDM+4jl8Nw5RMWM0N/tNGQhuLA6lADX4a+QHQtB8c9Ov7C8axQzlxNFt1I6v41jHyv8cNCwbS AUQVXO8GztQ== 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-kernel@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?q?Jos=C3=A9=20Exp=C3=B3sito?=" , Brendan Higgins , Rae Moar , Boqun Feng , Alex Gaynor , Gary Guo , Benno Lossin , "=?UTF-8?q?Bj=C3=B6rn=20Roy=20Baron?=" , 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 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Jos=C3=A9 Exp=C3=B3sito 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 !=3D 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: Jos=C3=A9 Exp=C3=B3sito Co-developed-by: David Gow Signed-off-by: David Gow --- Changes since v3: https://lore.kernel.org/linux-kselftest/20241030045719.3085147-8-davidgow@g= oogle.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@g= oogle.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 { }; } =20 +/// In some cases, you need to call test-only code from outside the test c= ase, for example, to +/// create a function mock. This function can be invoked to know whether w= e 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 =3D fn_mock_example(5); +/// assert_eq!(mock_res, 100); +/// ``` +/// +/// Sometimes, you don't control the code that needs to be mocked. This ex= ample 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 moc= ked, we can use its +/// // functions seamlessly. +/// fn get_boot_ns() -> u64 { +/// unsafe { bindings::ktime_get_boot_fast_ns() } +/// } +/// +/// let time =3D 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 =3D in_kunit_test(); + assert!(in_kunit); + } } --=20 2.47.0.199.ga7371fff76-goog