[PATCH v13 4/5] KASAN: Testing Documentation

From: David Gow
Date: Thu Sep 10 2020 - 03:06:52 EST

From: Patricia Alfonso <trishalfonso@xxxxxxxxxx>

Include documentation on how to test KASAN using CONFIG_TEST_KASAN_KUNIT

Signed-off-by: Patricia Alfonso <trishalfonso@xxxxxxxxxx>
Signed-off-by: David Gow <davidgow@xxxxxxxxxx>
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Acked-by: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
Tested-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Documentation/dev-tools/kasan.rst | 70 +++++++++++++++++++++++++++++++
1 file changed, 70 insertions(+)

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index 38fd5681fade..072ecdadba07 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -281,3 +281,73 @@ unmapped. This will require changes in arch-specific code.

This allows ``VMAP_STACK`` support on x86, and can simplify support of
architectures that do not have a fixed module region.
+``CONFIG_KASAN_KUNIT_TEST`` utilizes the KUnit Test Framework for testing.
+This means each test focuses on a small unit of functionality and
+there are a few ways these tests can be run.
+Each test will print the KASAN report if an error is detected and then
+print the number of the test and the status of the test:
+ ok 28 - kmalloc_double_kzfree
+or, if kmalloc failed::
+ # kmalloc_large_oob_right: ASSERTION FAILED at lib/test_kasan.c:163
+ Expected ptr is not null, but is
+ not ok 4 - kmalloc_large_oob_right
+or, if a KASAN report was expected, but not found::
+ # kmalloc_double_kzfree: EXPECTATION FAILED at lib/test_kasan.c:629
+ Expected kasan_data->report_expected == kasan_data->report_found, but
+ kasan_data->report_expected == 1
+ kasan_data->report_found == 0
+ not ok 28 - kmalloc_double_kzfree
+All test statuses are tracked as they run and an overall status will
+be printed at the end::
+ ok 1 - kasan
+ not ok 1 - kasan
+(1) Loadable Module
+With ``CONFIG_KUNIT`` enabled, ``CONFIG_KASAN_KUNIT_TEST`` can be built as
+a loadable module and run on any architecture that supports KASAN
+using something like insmod or modprobe. The module is called ``test_kasan``.
+(2) Built-In
+With ``CONFIG_KUNIT`` built-in, ``CONFIG_KASAN_KUNIT_TEST`` can be built-in
+on any architecure that supports KASAN. These and any other KUnit
+tests enabled will run and print the results at boot as a late-init
+(3) Using kunit_tool
+With ``CONFIG_KUNIT`` and ``CONFIG_KASAN_KUNIT_TEST`` built-in, we can also
+use kunit_tool to see the results of these along with other KUnit
+tests in a more readable way. This will not print the KASAN reports
+of tests that passed. Use `KUnit documentation <https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html>`_ for more up-to-date
+information on kunit_tool.
+.. _KUnit: https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html
+``CONFIG_TEST_KASAN_MODULE`` is a set of KASAN tests that could not be
+converted to KUnit. These tests can be run only as a module with
+``CONFIG_TEST_KASAN_MODULE`` built as a loadable module and
+``CONFIG_KASAN`` built-in. The type of error expected and the
+function being run is printed before the expression expected to give
+an error. Then the error is printed, if found, and that test
+should be interpretted to pass only if the error was the one expected
+by the test.