linux-kernel - [PATCH v4 4/4] KASAN: Testing Documentation

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Message-Id: <20200402204639.161637-3-trishalfonso@google.com>
Date:   Thu,  2 Apr 2020 13:46:37 -0700
From:   Patricia Alfonso <trishalfonso@...gle.com>
To:     davidgow@...gle.com, brendanhiggins@...gle.com,
        aryabinin@...tuozzo.com, dvyukov@...gle.com, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org
Cc:     linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org,
        Patricia Alfonso <trishalfonso@...gle.com>
Subject: [PATCH v4 4/4] KASAN: Testing Documentation

Include documentation on how to test KASAN using CONFIG_TEST_KASAN and
CONFIG_TEST_KASAN_USER.

Signed-off-by: Patricia Alfonso <trishalfonso@...gle.com>
Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
---
 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 c652d740735d..287ba063d9f6 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_TEST_KASAN & CONFIG_TEST_KASAN_USER
+-------------------------------------------
+
+``CONFIG_TEST_KASAN`` 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:
+
+pass::
+
+        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_kunit_test
+
+or::
+
+        not ok 1 - kasan_kunit_test
+
+(1) Loadable Module
+~~~~~~~~~~~~~~~~~~~~
+
+With ``CONFIG_KUNIT`` built-in, ``CONFIG_TEST_KASAN`` can be built as
+a loadable module and run on any architecture that supports KASAN
+using something like insmod or modprobe.
+
+(2) Built-In
+~~~~~~~~~~~~~
+
+With ``CONFIG_KUNIT`` built-in, ``CONFIG_TEST_KASAN`` 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
+call.
+
+(3) Using kunit_tool
+~~~~~~~~~~~~~~~~~~~~~
+
+With ``CONFIG_KUNIT`` and ``CONFIG_TEST_KASAN`` 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_USER`` 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_USER`` 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.
-- 
2.26.0.292.g33ef6b2f38-goog