Merging upstream version 6.9.2.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 138 insertions, 25 deletions

diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst
index 73203ba1e..c91377106 100644
--- a/Documentation/rust/arch-support.rst
+++ b/Documentation/rust/arch-support.rst
@@ -15,7 +15,8 @@ support corresponds to ``S`` values in the ``MAINTAINERS`` file.
 =============  ================  ==============================================
 Architecture   Level of support  Constraints
 =============  ================  ==============================================
-``loongarch``  Maintained        -
+``arm64``      Maintained        Little Endian only.
+``loongarch``  Maintained        \-
 ``um``         Maintained        ``x86_64`` only.
 ``x86``        Maintained        ``x86_64`` only.
 =============  ================  ==============================================
diff --git a/Documentation/rust/general-information.rst b/Documentation/rust/general-information.rst
index 236c6dd3c..081397827 100644
--- a/Documentation/rust/general-information.rst
+++ b/Documentation/rust/general-information.rst
@@ -77,27 +77,3 @@ configuration:
 	#[cfg(CONFIG_X="y")]   // Enabled as a built-in (`y`)
 	#[cfg(CONFIG_X="m")]   // Enabled as a module   (`m`)
 	#[cfg(not(CONFIG_X))]  // Disabled
-
-
-Testing
--------
-
-There are the tests that come from the examples in the Rust documentation
-and get transformed into KUnit tests. These can be run via KUnit. For example
-via ``kunit_tool`` (``kunit.py``) on the command line::
-
-	./tools/testing/kunit/kunit.py run --make_options LLVM=1 --arch x86_64 --kconfig_add CONFIG_RUST=y
-
-Alternatively, KUnit can run them as kernel built-in at boot. Refer to
-Documentation/dev-tools/kunit/index.rst for the general KUnit documentation
-and Documentation/dev-tools/kunit/architecture.rst for the details of kernel
-built-in vs. command line testing.
-
-Additionally, there are the ``#[test]`` tests. These can be run using
-the ``rusttest`` Make target::
-
-	make LLVM=1 rusttest
-
-This requires the kernel ``.config`` and downloads external repositories.
-It runs the ``#[test]`` tests on the host (currently) and thus is fairly
-limited in what these tests can test.
diff --git a/Documentation/rust/index.rst b/Documentation/rust/index.rst
index 965f2db52..46d35bd39 100644
--- a/Documentation/rust/index.rst
+++ b/Documentation/rust/index.rst
@@ -40,6 +40,7 @@ configurations.
     general-information
     coding-guidelines
     arch-support
+    testing
 
 .. only::  subproject and html
 
diff --git a/Documentation/rust/testing.rst b/Documentation/rust/testing.rst
new file mode 100644
index 000000000..6658998d1
--- /dev/null
+++ b/Documentation/rust/testing.rst
@@ -0,0 +1,135 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Testing
+=======
+
+This document contains useful information how to test the Rust code in the
+kernel.
+
+There are two sorts of tests:
+
+- The KUnit tests.
+- The ``#[test]`` tests.
+
+The KUnit tests
+---------------
+
+These are the tests that come from the examples in the Rust documentation. They
+get transformed into KUnit tests.
+
+Usage
+*****
+
+These tests can be run via KUnit. For example via ``kunit_tool`` (``kunit.py``)
+on the command line::
+
+	./tools/testing/kunit/kunit.py run --make_options LLVM=1 --arch x86_64 --kconfig_add CONFIG_RUST=y
+
+Alternatively, KUnit can run them as kernel built-in at boot. Refer to
+Documentation/dev-tools/kunit/index.rst for the general KUnit documentation
+and Documentation/dev-tools/kunit/architecture.rst for the details of kernel
+built-in vs. command line testing.
+
+To use these KUnit doctests, the following must be enabled::
+
+	CONFIG_KUNIT
+	   Kernel hacking -> Kernel Testing and Coverage -> KUnit - Enable support for unit tests
+	CONFIG_RUST_KERNEL_DOCTESTS
+	   Kernel hacking -> Rust hacking -> Doctests for the `kernel` crate
+
+in the kernel config system.
+
+KUnit tests are documentation tests
+***********************************
+
+These 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. For instance:
+
+.. code-block:: rust
+
+	/// Sums two numbers.
+	///
+	/// ```
+	/// assert_eq!(mymod::f(10, 20), 30);
+	/// ```
+	pub fn f(a: i32, b: i32) -> i32 {
+	    a + b
+	}
+
+In userspace, the tests are collected and run via ``rustdoc``. Using the tool
+as-is would be useful already, since it allows verifying that examples compile
+(thus enforcing they are kept in sync with the code they document) and as well
+as running those that do not depend on in-kernel APIs.
+
+For the kernel, however, these tests get transformed into KUnit test suites.
+This means that doctests get compiled as Rust kernel objects, allowing them to
+run against a built kernel.
+
+A benefit of this KUnit integration is that Rust doctests get to reuse existing
+testing facilities. For instance, the kernel log would look like::
+
+	KTAP version 1
+	1..1
+	    KTAP version 1
+	    # Subtest: rust_doctests_kernel
+	    1..59
+	    # rust_doctest_kernel_build_assert_rs_0.location: rust/kernel/build_assert.rs:13
+	    ok 1 rust_doctest_kernel_build_assert_rs_0
+	    # rust_doctest_kernel_build_assert_rs_1.location: rust/kernel/build_assert.rs:56
+	    ok 2 rust_doctest_kernel_build_assert_rs_1
+	    # rust_doctest_kernel_init_rs_0.location: rust/kernel/init.rs:122
+	    ok 3 rust_doctest_kernel_init_rs_0
+	    ...
+	    # rust_doctest_kernel_types_rs_2.location: rust/kernel/types.rs:150
+	    ok 59 rust_doctest_kernel_types_rs_2
+	# rust_doctests_kernel: pass:59 fail:0 skip:0 total:59
+	# Totals: pass:59 fail:0 skip:0 total:59
+	ok 1 rust_doctests_kernel
+
+Tests using the `? <https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator>`_
+operator are also supported as usual, e.g.:
+
+.. code-block:: rust
+
+	/// ```
+	/// # use kernel::{spawn_work_item, workqueue};
+	/// spawn_work_item!(workqueue::system(), || pr_info!("x"))?;
+	/// # Ok::<(), Error>(())
+	/// ```
+
+The tests are also compiled with Clippy under ``CLIPPY=1``, just like normal
+code, thus also benefitting from extra linting.
+
+In order for developers to easily see which line of doctest code caused a
+failure, a KTAP diagnostic line is printed to the log. This contains the
+location (file and line) of the original test (i.e. instead of the location in
+the generated Rust file)::
+
+	# rust_doctest_kernel_types_rs_2.location: rust/kernel/types.rs:150
+
+Rust tests appear to assert using the usual ``assert!`` and ``assert_eq!``
+macros from the Rust standard library (``core``). We provide a custom version
+that forwards the call to KUnit instead. Importantly, these macros do not
+require passing context, unlike those for KUnit testing (i.e.
+``struct kunit *``). This makes them easier to use, and readers of the
+documentation do not need to care about which testing framework is used. In
+addition, it may allow us to test third-party code more easily in the future.
+
+A current limitation is that KUnit does not support assertions in other tasks.
+Thus, we presently simply print an error to the kernel log if an assertion
+actually failed. Additionally, doctests are not run for nonpublic functions.
+
+The ``#[test]`` tests
+---------------------
+
+Additionally, there are the ``#[test]`` tests. These can be run using the
+``rusttest`` Make target::
+
+	make LLVM=1 rusttest
+
+This requires the kernel ``.config`` and downloads external repositories. It
+runs the ``#[test]`` tests on the host (currently) and thus is fairly limited in
+what these tests can test.