Re: [PATCH v6 2/3] rust: macros: add macro to easily run KUnit tests

On Fri, Feb 14, 2025 at 2:41 AM David Gow davidgow@google.com wrote:

From: José Expósito jose.exposito89@gmail.com

Add a new procedural macro (`#[kunit_tests(kunit_test_suit_name)]`) to run KUnit tests using a user-space like syntax.

The macro, that should be used on modules, transforms every `#[test]` in a `kunit_case!` and adds a `kunit_unsafe_test_suite!` registering all of them.

The only difference with user-space tests is that instead of using `#[cfg(test)]`, `#[kunit_tests(kunit_test_suit_name)]` is used.

Note that `#[cfg(CONFIG_KUNIT)]` is added so the test module is not compiled when `CONFIG_KUNIT` is set to `n`.

Reviewed-by: David Gow davidgow@google.com Signed-off-by: José Expósito jose.exposito89@gmail.com Co-developed-by: Boqun Feng boqun.feng@gmail.com Signed-off-by: Boqun Feng boqun.feng@gmail.com Co-developed-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: David Gow davidgow@google.com

---

Changes since v5: https://lore.kernel.org/all/20241213081035.2069066-3-davidgow@google.com/

• Fix some rustfmt-related formatting shenanigans. (Thanks, Miguel)
• Fix some documentation comment formatting as well. (Thanks, Miguel)
• Tidy up the generated code to avoid unneeded &mut[] everywhere. (Thanks, Miguel)
• Fix a new clippy warning for using .as_bytes().len() instead of .len() directly.

Changes since v4: https://lore.kernel.org/linux-kselftest/20241101064505.3820737-3-davidgow@go...

• Rebased against 6.13-rc1
• "Expect" that the sample assert_eq!(1+1, 2) produces a clippy warning due to a redundant assertion. (Thanks Boqun, Miguel)

Changes since v3: https://lore.kernel.org/linux-kselftest/20241030045719.3085147-6-davidgow@go...

• The #[kunit_tests()] macro now preserves span information, so errors can be better reported. (Thanks, Boqun!)
• The example test has been replaced to no longer use assert_eq!() with a constant bool argument (which triggered a clippy warning now we have the span info). It now checks 1 + 1 == 2, to match the C example.
  • (The in_kunit_test() test in the next patch uses assert!() to check a bool, so having something different here seemed to make a better example.)

Changes since v2: https://lore.kernel.org/linux-kselftest/20241029092422.2884505-3-davidgow@go...

• Include missing rust/macros/kunit.rs file from v2. (Thanks Boqun!)
• The proc macro now emits an error if the suite name is too long.

Changes since v1: https://lore.kernel.org/lkml/20230720-rustbind-v1-2-c80db349e3b5@google.com/

• Rebased on top of rust-next
• Make use of the new const functions, rather than the kunit_case!() macro.

---

MAINTAINERS | 1 + rust/kernel/kunit.rs | 12 ++++ rust/macros/kunit.rs | 161 +++++++++++++++++++++++++++++++++++++++++++ rust/macros/lib.rs | 29 ++++++++ 4 files changed, 203 insertions(+) create mode 100644 rust/macros/kunit.rs

diff --git a/MAINTAINERS b/MAINTAINERS index c8d9e8187eb0..4e7a6d2f2c49 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -12677,6 +12677,7 @@ F: Documentation/dev-tools/kunit/ F: include/kunit/ F: lib/kunit/ F: rust/kernel/kunit.rs +F: rust/macros/kunit.rs F: scripts/rustdoc_test_* F: tools/testing/kunit/

diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs index d34a92075174..9e27b74a605b 100644 --- a/rust/kernel/kunit.rs +++ b/rust/kernel/kunit.rs @@ -40,6 +40,8 @@ pub fn info(args: fmt::Arguments<'_>) { } }

+use macros::kunit_tests;

/// Asserts that a boolean expression is `true` at runtime. /// /// Public but hidden since it should only be used from generated tests. @@ -275,6 +277,7 @@ macro_rules! kunit_unsafe_test_suite { };

         #[used]

•        #[allow(unused_unsafe)]
         #[link_section = ".kunit_test_suites"]
         static mut KUNIT_TEST_SUITE_ENTRY: *const ::kernel::bindings::kunit_suite =
             // SAFETY: `KUNIT_TEST_SUITE` is static.
  

@@ -282,3 +285,12 @@ macro_rules! kunit_unsafe_test_suite { }; }; }

+#[kunit_tests(rust_kernel_kunit)] +mod tests {

• #[test]
• fn rust_test_kunit_example_test() {

•    #![expect(clippy::eq_op)]
  

•    assert_eq!(1 + 1, 2);
  

• }

+} diff --git a/rust/macros/kunit.rs b/rust/macros/kunit.rs new file mode 100644 index 000000000000..4f553ecf40c0 --- /dev/null +++ b/rust/macros/kunit.rs @@ -0,0 +1,161 @@ +// SPDX-License-Identifier: GPL-2.0

+//! Procedural macro to run KUnit tests using a user-space like syntax. +//! +//! Copyright (c) 2023 José Expósito jose.exposito89@gmail.com

+use proc_macro::{Delimiter, Group, TokenStream, TokenTree}; +use std::fmt::Write;

+pub(crate) fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {

• let attr = attr.to_string();
• if attr.is_empty() {

•    panic!("Missing test name in `#[kunit_tests(test_name)]` macro")
  

• }
• if attr.len() > 255 {

•    panic!(
  

•        "The test suite name `{}` exceeds the maximum length of 255 bytes",
  

•        attr
  

•    )
  

• }
• let mut tokens: Vec<_> = ts.into_iter().collect();
• // Scan for the `mod` keyword.
• tokens

•    .iter()
  

•    .find_map(|token| match token {
  

•        TokenTree::Ident(ident) => match ident.to_string().as_str() {
  

•            "mod" => Some(true),
  

•            _ => None,
  

•        },
  

•        _ => None,
  

•    })
  

•    .expect("`#[kunit_tests(test_name)]` attribute should only be applied to modules");
  

• // Retrieve the main body. The main body should be the last token tree.
• let body = match tokens.pop() {

•    Some(TokenTree::Group(group)) if group.delimiter() == Delimiter::Brace => group,
  

•    _ => panic!("Cannot locate main body of module"),
  

• };
• // Get the functions set as tests. Search for `[test]` -> `fn`.
• let mut body_it = body.stream().into_iter();
• let mut tests = Vec::new();
• while let Some(token) = body_it.next() {

•    match token {
  

•        TokenTree::Group(ident) if ident.to_string() == "[test]" => match body_it.next() {
  

•            Some(TokenTree::Ident(ident)) if ident.to_string() == "fn" => {
  

•                let test_name = match body_it.next() {
  

•                    Some(TokenTree::Ident(ident)) => ident.to_string(),
  

•                    _ => continue,
  

•                };
  

•                tests.push(test_name);
  

•            }
  

•            _ => continue,
  

•        },
  

•        _ => (),
  

•    }
  

• }
• // Add `#[cfg(CONFIG_KUNIT)]` before the module declaration.
• let config_kunit = "#[cfg(CONFIG_KUNIT)]".to_owned().parse().unwrap();
• tokens.insert(

•    0,
  

•    TokenTree::Group(Group::new(Delimiter::None, config_kunit)),
  

• );
• // Generate the test KUnit test suite and a test case for each `#[test]`.
• // The code generated for the following test module:
• //
• // ```
• // #[kunit_tests(kunit_test_suit_name)]
• // mod tests {
• // #[test]
• // fn foo() {
• // assert_eq!(1, 1);
• // }
• //
• // #[test]
• // fn bar() {
• // assert_eq!(2, 2);
• // }
• // }
• // ```
• //
• // Looks like:
• //
• // ```
• // unsafe extern "C" fn kunit_rust_wrapper_foo(_test: *mut kernel::bindings::kunit) { foo(); }
• // unsafe extern "C" fn kunit_rust_wrapper_bar(_test: *mut kernel::bindings::kunit) { bar(); }
• //
• // static mut TEST_CASES: [kernel::bindings::kunit_case; 3] = [
• // kernel::kunit::kunit_case(kernel::c_str!("foo"), kunit_rust_wrapper_foo),
• // kernel::kunit::kunit_case(kernel::c_str!("bar"), kunit_rust_wrapper_bar),
• // kernel::kunit::kunit_case_null(),
• // ];
• //
• // kernel::kunit_unsafe_test_suite!(kunit_test_suit_name, TEST_CASES);
• // ```

This is a really helpful comment. It got me wondering: can we have host-side unit tests for our proc macros? Code is better than comments, of course.

• let mut kunit_macros = "".to_owned();
• let mut test_cases = "".to_owned();
• for test in &tests {

•    let kunit_wrapper_fn_name = format!("kunit_rust_wrapper_{}", test);
  

•    let kunit_wrapper = format!(
  

•        "unsafe extern \"C\" fn {}(_test: *mut kernel::bindings::kunit) {{ {}(); }}",
  

•        kunit_wrapper_fn_name, test
  

•    );
  

•    writeln!(kunit_macros, "{kunit_wrapper}").unwrap();
  

•    writeln!(
  

•        test_cases,
  

•        "    kernel::kunit::kunit_case(kernel::c_str!(\"{}\"), {}),",
  

•        test, kunit_wrapper_fn_name
  

•    )
  

•    .unwrap();
  

• }
• writeln!(kunit_macros).unwrap();
• writeln!(

•    kunit_macros,
  

•    "static mut TEST_CASES: [kernel::bindings::kunit_case; {}] = [\n{test_cases}    kernel::kunit::kunit_case_null(),\n];",
  

•    tests.len() + 1
  

• )
• .unwrap();
• writeln!(

•    kunit_macros,
  

•    "kernel::kunit_unsafe_test_suite!({attr}, TEST_CASES);"
  

• )
• .unwrap();
• // Remove the `#[test]` macros.

This makes sense. I wonder if we should think about being able to declare a test that runs both on host and in KUnit.

• // We do this at a token level, in order to preserve span information.
• let mut new_body = vec![];
• let mut body_it = body.stream().into_iter();
• while let Some(token) = body_it.next() {

•    match token {
  

•        TokenTree::Punct(ref c) if c.as_char() == '#' => match body_it.next() {
  

•            Some(TokenTree::Group(group)) if group.to_string() == "[test]" => (),
  

•            Some(next) => {
  

•                new_body.extend([token, next]);
  

•            }
  

•            _ => {
  

•                new_body.push(token);
  

•            }
  

•        },
  

•        _ => {
  

•            new_body.push(token);
  

•        }
  

•    }
  

• }
• let mut new_body = TokenStream::from_iter(new_body);
• new_body.extend::<TokenStream>(kunit_macros.parse().unwrap());
• tokens.push(TokenTree::Group(Group::new(Delimiter::Brace, new_body)));
• tokens.into_iter().collect()

+} diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs index d61bc6a56425..50b58259c577 100644 --- a/rust/macros/lib.rs +++ b/rust/macros/lib.rs @@ -10,6 +10,7 @@ mod quote; mod concat_idents; mod helpers; +mod kunit; mod module; mod paste; mod pin_data; @@ -492,3 +493,31 @@ pub fn paste(input: TokenStream) -> TokenStream { pub fn derive_zeroable(input: TokenStream) -> TokenStream { zeroable::derive(input) }

+/// Registers a KUnit test suite and its test cases using a user-space like syntax. +/// +/// This macro should be used on modules. If `CONFIG_KUNIT` (in `.config`) is `n`, the target module +/// is ignored. +/// +/// # Examples +/// +/// ```ignore +/// # use macros::kunit_tests; +/// +/// #[kunit_tests(kunit_test_suit_name)] +/// mod tests { +/// #[test] +/// fn foo() { +/// assert_eq!(1, 1); +/// } +/// +/// #[test] +/// fn bar() { +/// assert_eq!(2, 2); +/// } +/// } +/// ``` +#[proc_macro_attribute] +pub fn kunit_tests(attr: TokenStream, ts: TokenStream) -> TokenStream {

• kunit::kunit_tests(attr, ts)

+}

2.48.1.601.g30ceb7b040-goog