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Subject[PATCH v8 22/31] scripts: add `rustdoc_test_{builder,gen}.py` scripts
Date
Rust documentation tests are typically examples of usage of any
item (e.g. function, struct, module...). They are very convenient
because they are just written alongside the documentation, e.g.:

/// Sums two numbers.
///
/// # Examples
///
/// ```
/// assert_eq!(mymod::f(10, 20), 30);
/// ```
pub fn f(a: i32, b: i32) -> i32 {
a + b
}

These scripts are used to transform Rust documentation tests into
KUnit tests, so that they can be run in-kernel. In turn, this allows
us to run tests that use kernel APIs.

In particular, the test builder receives `rustdoc`-generated tests,
parses them and stores the result. Then, the test generator takes
the saved results and generates a KUnit suite where each original
documentation test is a test case.

For the moment, this is only done for the `kernel` crate, but
the plan is to generalize it for other crates and modules.

Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
scripts/rustdoc_test_builder.py | 59 ++++++++++++
scripts/rustdoc_test_gen.py | 164 ++++++++++++++++++++++++++++++++
2 files changed, 223 insertions(+)
create mode 100755 scripts/rustdoc_test_builder.py
create mode 100755 scripts/rustdoc_test_gen.py

diff --git a/scripts/rustdoc_test_builder.py b/scripts/rustdoc_test_builder.py
new file mode 100755
index 000000000000..d9b47a5c54fc
--- /dev/null
+++ b/scripts/rustdoc_test_builder.py
@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+"""rustdoc_test_builder - Test builder for `rustdoc`-generated tests.
+"""
+
+import json
+import pathlib
+import re
+import sys
+
+RUST_DIR = pathlib.Path("rust")
+TESTS_DIR = RUST_DIR / "test" / "doctests" / "kernel"
+
+# `[^\s]*` removes the prefix (e.g. `_doctest_main_`) plus any
+# leading path (for `O=` builds).
+MAIN_RE = re.compile(
+ r"^"
+ r"fn main\(\) { "
+ r"#\[allow\(non_snake_case\)\] "
+ r"fn ([^\s]*rust_kernel_([a-zA-Z0-9_]+))\(\) {"
+ r"$"
+)
+
+def main():
+ found_main = False
+ test_header = ""
+ test_body = ""
+ for line in sys.stdin.readlines():
+ main_match = MAIN_RE.match(line)
+ if main_match:
+ if found_main:
+ raise Exception("More than one `main` line found.")
+ found_main = True
+ function_name = main_match.group(1)
+ test_name = f"rust_kernel_doctest_{main_match.group(2)}"
+ continue
+
+ if found_main:
+ test_body += line
+ else:
+ test_header += line
+
+ if not found_main:
+ raise Exception("No `main` line found.")
+
+ call_line = f"}} {function_name}() }}"
+ if not test_body.endswith(call_line):
+ raise Exception("Unexpected end of test body.")
+ test_body = test_body[:-len(call_line)]
+
+ with open(TESTS_DIR / f"{test_name}.json", "w") as fd:
+ json.dump({
+ "name": test_name,
+ "header": test_header,
+ "body": test_body,
+ }, fd, sort_keys=True, indent=4)
+
+if __name__ == "__main__":
+ main()
diff --git a/scripts/rustdoc_test_gen.py b/scripts/rustdoc_test_gen.py
new file mode 100755
index 000000000000..ad9a94293ab5
--- /dev/null
+++ b/scripts/rustdoc_test_gen.py
@@ -0,0 +1,164 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+"""rustdoc_test_gen - Generates KUnit tests from saved `rustdoc`-generated tests.
+"""
+
+import json
+import os
+import pathlib
+
+RUST_DIR = pathlib.Path("rust")
+TESTS_DIR = RUST_DIR / "test" / "doctests" / "kernel"
+
+RUST_FILE = RUST_DIR / "doctests_kernel_generated.rs"
+C_FILE = RUST_DIR / "doctests_kernel_generated_kunit.c"
+
+RUST_TEMPLATE_TEST = """
+/// Generated `{test_name}` KUnit test case from a Rust documentation test.
+#[no_mangle]
+pub fn {test_name}(__kunit_test: *mut kernel::bindings::kunit) {{
+ /// Provides mutual exclusion (see `# Implementation` notes).
+ static __KUNIT_TEST_MUTEX: kernel::sync::smutex::Mutex<()> =
+ kernel::sync::smutex::Mutex::new(());
+
+ /// Saved argument (see `# Implementation` notes).
+ static __KUNIT_TEST: core::sync::atomic::AtomicPtr<kernel::bindings::kunit> =
+ core::sync::atomic::AtomicPtr::new(core::ptr::null_mut());
+
+ let __kunit_test_mutex_guard = __KUNIT_TEST_MUTEX.lock();
+ __KUNIT_TEST.store(__kunit_test, core::sync::atomic::Ordering::SeqCst);
+
+ /// Overrides the usual [`assert!`] macro with one that calls KUnit instead.
+ macro_rules! assert {{
+ ($cond:expr $(,)?) => {{{{
+ kernel::kunit_assert!(
+ __KUNIT_TEST.load(core::sync::atomic::Ordering::SeqCst),
+ $cond
+ );
+ }}}}
+ }}
+
+ /// Overrides the usual [`assert_eq!`] macro with one that calls KUnit instead.
+ macro_rules! assert_eq {{
+ ($left:expr, $right:expr $(,)?) => {{{{
+ kernel::kunit_assert_eq!(
+ __KUNIT_TEST.load(core::sync::atomic::Ordering::SeqCst),
+ $left,
+ $right
+ );
+ }}}}
+ }}
+
+ // Many tests need the prelude, so provide it by default.
+ use kernel::prelude::*;
+
+ {test_body}
+}}
+"""
+RUST_TEMPLATE = """// SPDX-License-Identifier: GPL-2.0
+
+//! `kernel` crate documentation tests.
+
+// # Implementation
+//
+// KUnit gives us a context in the form of the `kunit_test` parameter that one
+// needs to pass back to other KUnit functions and macros.
+//
+// However, we want to keep this as an implementation detail because:
+//
+// - Test code should not care about the implementation.
+//
+// - Documentation looks worse if it needs to carry extra details unrelated
+// to the piece being described.
+//
+// - Test code should be able to define functions and call them, without
+// having to carry the context (since functions cannot capture dynamic
+// environment).
+//
+// - Later on, we may want to be able to test non-kernel code (e.g. `core`,
+// `alloc` or external crates) which likely use the standard library
+// `assert*!` macros.
+//
+// For this reason, `static`s are used in the generated code to save the
+// argument which then gets read by the asserting macros. These macros then
+// call back into KUnit, instead of panicking.
+//
+// To avoid depending on whether KUnit allows to run tests concurrently and/or
+// reentrantly, we ensure mutual exclusion on our end. To ensure a single test
+// being killed does not trigger failure of every other test (timing out),
+// we provide different `static`s per test (which also allow for concurrent
+// execution, though KUnit runs them sequentially).
+//
+// Furthermore, since test code may create threads and assert from them, we use
+// an `AtomicPtr` to hold the context (though each test only writes once before
+// threads may be created).
+
+{rust_header}
+
+const __LOG_PREFIX: &[u8] = b"rust_kernel_doctests\\0";
+
+{rust_tests}
+"""
+
+C_TEMPLATE_TEST_DECLARATION = "void {test_name}(struct kunit *);\n"
+C_TEMPLATE_TEST_CASE = " KUNIT_CASE({test_name}),\n"
+C_TEMPLATE = """// SPDX-License-Identifier: GPL-2.0
+/*
+ * `kernel` crate documentation tests.
+ */
+
+#include <kunit/test.h>
+
+{c_test_declarations}
+
+static struct kunit_case test_cases[] = {{
+ {c_test_cases}
+ {{ }}
+}};
+
+static struct kunit_suite test_suite = {{
+ .name = "rust_kernel_doctests",
+ .test_cases = test_cases,
+}};
+
+kunit_test_suite(test_suite);
+
+MODULE_LICENSE("GPL");
+"""
+
+def main():
+ rust_header = set()
+ rust_tests = ""
+ c_test_declarations = ""
+ c_test_cases = ""
+ for filename in sorted(os.listdir(TESTS_DIR)):
+ with open(TESTS_DIR / filename, "r") as fd:
+ test = json.load(fd)
+ for line in test["header"].strip().split("\n"):
+ rust_header.add(line)
+ rust_tests += RUST_TEMPLATE_TEST.format(
+ test_name = test["name"],
+ test_body = test["body"]
+ )
+ c_test_declarations += C_TEMPLATE_TEST_DECLARATION.format(
+ test_name = test["name"]
+ )
+ c_test_cases += C_TEMPLATE_TEST_CASE.format(
+ test_name = test["name"]
+ )
+ rust_header = sorted(rust_header)
+
+ with open(RUST_FILE, "w") as fd:
+ fd.write(RUST_TEMPLATE.format(
+ rust_header = "\n".join(rust_header).strip(),
+ rust_tests = rust_tests.strip(),
+ ))
+
+ with open(C_FILE, "w") as fd:
+ fd.write(C_TEMPLATE.format(
+ c_test_declarations=c_test_declarations.strip(),
+ c_test_cases=c_test_cases.strip(),
+ ))
+
+if __name__ == "__main__":
+ main()
--
2.37.1
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