linux-kernel - Re: [PATCH v3] kasan: test: Improve failure message in KUNIT_EXPECT_KASAN

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Date:   Mon, 7 Jun 2021 13:02:38 -0700
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     David Gow <davidgow@...gle.com>
Cc:     Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Daniel Axtens <dja@...ens.net>,
        kasan-dev <kasan-dev@...glegroups.com>,
        KUnit Development <kunit-dev@...glegroups.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v3] kasan: test: Improve failure message in KUNIT_EXPECT_KASAN_FAIL()

On Sat, Jun 5, 2021 at 5:55 PM David Gow <davidgow@...gle.com> wrote:
>
> The KUNIT_EXPECT_KASAN_FAIL() macro currently uses KUNIT_EXPECT_EQ() to
> compare fail_data.report_expected and fail_data.report_found. This
> always gave a somewhat useless error message on failure, but the
> addition of extra compile-time checking with READ_ONCE() has caused it
> to get much longer, and be truncated before anything useful is displayed.
>
> Instead, just check fail_data.report_found by hand (we've just set
> report_expected to 'true'), and print a better failure message with
> KUNIT_FAIL(). Because of this, report_expected is no longer used
> anywhere, and can be removed.
>
> Beforehand, a failure in:
> KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)area)[3100]);
> would have looked like:
> [22:00:34] [FAILED] vmalloc_oob
> [22:00:34]     # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:991
> [22:00:34]     Expected ({ do { extern void __compiletime_assert_705(void) __attribute__((__error__("Unsupported access size for {READ,WRITE}_ONCE()."))); if (!((sizeof(fail_data.report_expected) == sizeof(char) || sizeof(fail_data.repp
> [22:00:34]     not ok 45 - vmalloc_oob
>
> With this change, it instead looks like:
> [22:04:04] [FAILED] vmalloc_oob
> [22:04:04]     # vmalloc_oob: EXPECTATION FAILED at lib/test_kasan.c:993
> [22:04:04]     KASAN failure expected in "((volatile char *)area)[3100]", but none occurred
> [22:04:04]     not ok 45 - vmalloc_oob
>
> Also update the example failure in the documentation to reflect this.
>
> Signed-off-by: David Gow <davidgow@...gle.com>

Nice work!

Acked-by: Brendan Higgins <brendanhiggins@...gle.com>