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// SPDX-License-Identifier: GPL-2.0
//! Generates KUnit tests from saved `rustdoc`-generated tests.
//! KUnit passes a context (`struct kunit *`) to each test, which should be forwarded to the 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.
//! - Later on, we may want to be able to test non-kernel code (e.g. `core`, `alloc` or
//! third-party crates) which likely use the standard library `assert*!` macros.
//! For this reason, instead of the passed context, `kunit_get_current_test()` is used instead
//! (i.e. `current->kunit_test`).
//! Note that this means other threads/tasks potentially spawned by a given test, if failing, will
//! report the failure in the kernel log but will not fail the actual test. Saving the pointer in
//! e.g. a `static` per test does not fully solve the issue either, because currently KUnit does
//! not support assertions (only expectations) from other tasks. Thus leave that feature for
//! the future, which simplifies the code here too. We could also simply not allow `assert`s in
//! other tasks, but that seems overly constraining, and we do want to support them, eventually.
use std::{
io::{BufWriter, Read, Write},
path::{Path, PathBuf},
/// Find the real path to the original file based on the `file` portion of the test name.
/// `rustdoc` generated `file`s look like `sync_locked_by_rs`. Underscores (except the last one)
/// may represent an actual underscore in a directory/file, or a path separator. Thus the actual
/// file might be ``, `sync/`, `sync_locked/` or
/// `sync/locked/`. This function walks the file system to determine which is the real one.
/// This does require that ambiguities do not exist, but that seems fair, especially since this is
/// all supposed to be temporary until `rustdoc` gives us proper metadata to build this. If such
/// ambiguities are detected, they are diagnosed and the script panics.
fn find_real_path<'a>(srctree: &Path, valid_paths: &'a mut Vec<PathBuf>, file: &str) -> &'a str {
let potential_components: Vec<&str> = file.strip_suffix("_rs").unwrap().split('_').collect();
find_candidates(srctree, valid_paths, Path::new(""), &potential_components);
fn find_candidates(
srctree: &Path,
valid_paths: &mut Vec<PathBuf>,
prefix: &Path,
potential_components: &[&str],
) {
// The base case: check whether all the potential components left, joined by underscores,
// is a file.
let joined_potential_components = potential_components.join("_") + ".rs";
if srctree
// Avoid `srctree` here in order to keep paths relative to it in the KTAP output.
// In addition, check whether each component prefix, joined by underscores, is a directory.
// If not, there is no need to check for combinations with that prefix.
for i in 1..potential_components.len() {
let (components_prefix, components_rest) = potential_components.split_at(i);
let prefix = prefix.join(components_prefix.join("_"));
if srctree.join("rust/kernel").join(&prefix).is_dir() {
find_candidates(srctree, valid_paths, &prefix, components_rest);
valid_paths.len() > 0,
"No path candidates found. This is likely a bug in the build system, or some files went \
away while compiling."
if valid_paths.len() > 1 {
eprintln!("Several path candidates found:");
for path in valid_paths {
eprintln!(" {path:?}");
"Several path candidates found, please resolve the ambiguity by renaming a file or \
fn main() {
let srctree = std::env::var("srctree").unwrap();
let srctree = Path::new(&srctree);
let mut paths = fs::read_dir("rust/test/doctests/kernel")
.map(|entry| entry.unwrap().path())
// Sort paths.
let mut rust_tests = String::new();
let mut c_test_declarations = String::new();
let mut c_test_cases = String::new();
let mut body = String::new();
let mut last_file = String::new();
let mut number = 0;
let mut valid_paths: Vec<PathBuf> = Vec::new();
let mut real_path: &str = "";
for path in paths {
// The `name` follows the `{file}_{line}_{number}` pattern (see description in
// `scripts/`). Discard the `number`.
let name = path.file_name().unwrap().to_str().unwrap().to_string();
// Extract the `file` and the `line`, discarding the `number`.
let (file, line) = name.rsplit_once('_').unwrap().0.rsplit_once('_').unwrap();
// Generate an ID sequence ("test number") for each one in the file.
if file == last_file {
number += 1;
} else {
number = 0;
last_file = file.to_string();
// Figure out the real path, only once per file.
real_path = find_real_path(srctree, &mut valid_paths, file);
// Generate a KUnit name (i.e. test name and C symbol) for this test.
// We avoid the line number, like `rustdoc` does, to make things slightly more stable for
// bisection purposes. However, to aid developers in mapping back what test failed, we will
// print a diagnostics line in the KTAP report.
let kunit_name = format!("rust_doctest_kernel_{file}_{number}");
// Read the test's text contents to dump it below.
File::open(path).unwrap().read_to_string(&mut body).unwrap();
// Calculate how many lines before `main` function (including the `main` function line).
let body_offset = body
.take_while(|line| !line.contains("fn main() {"))
+ 1;
use std::fmt::Write;
r#"/// Generated `{name}` KUnit test case from a Rust documentation test.
pub extern "C" fn {kunit_name}(__kunit_test: *mut kernel::bindings::kunit) {{
/// Overrides the usual [`assert!`] macro with one that calls KUnit instead.
macro_rules! assert {{
($cond:expr $(,)?) => {{{{
kernel::kunit_assert!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $cond);
/// Overrides the usual [`assert_eq!`] macro with one that calls KUnit instead.
macro_rules! assert_eq {{
($left:expr, $right:expr $(,)?) => {{{{
kernel::kunit_assert_eq!("{kunit_name}", "{real_path}", __DOCTEST_ANCHOR - {line}, $left, $right);
// Many tests need the prelude, so provide it by default.
use kernel::prelude::*;
// Unconditionally print the location of the original doctest (i.e. rather than the location in
// the generated file) so that developers can easily map the test back to the source code.
// This information is also printed when assertions fail, but this helps in the successful cases
// when the user is running KUnit manually, or when passing `--raw_output` to ``.
// This follows the syntax for declaring test metadata in the proposed KTAP v2 spec, which may
// be used for the proposed KUnit test attributes API. Thus hopefully this will make migration
// easier later on.
kernel::kunit::info(format_args!(" # {kunit_name}.location: {real_path}:{line}\n"));
/// The anchor where the test code body starts.
static __DOCTEST_ANCHOR: i32 = core::line!() as i32 + {body_offset} + 1;
write!(c_test_declarations, "void {kunit_name}(struct kunit *);\n").unwrap();
write!(c_test_cases, " KUNIT_CASE({kunit_name}),\n").unwrap();
let rust_tests = rust_tests.trim();
let c_test_declarations = c_test_declarations.trim();
let c_test_cases = c_test_cases.trim();
r#"//! `kernel` crate documentation tests.
const __LOG_PREFIX: &[u8] = b"rust_doctests_kernel\0";
* `kernel` crate documentation tests.
#include <kunit/test.h>
static struct kunit_case test_cases[] = {{
{{ }}
static struct kunit_suite test_suite = {{
.name = "rust_doctests_kernel",
.test_cases = test_cases,