linux-kernel - Re: [PATCH v2 2/6] kunit: kunit-test: Add test cases for extending log buffer

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Message-ID: <f26650d3-9a9f-3f1b-02c4-2feb1ddfa4a9@opensource.cirrus.com>
Date:   Wed, 9 Aug 2023 13:14:06 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     David Gow <davidgow@...gle.com>
CC:     Rae Moar <rmoar@...gle.com>, <brendan.higgins@...ux.dev>,
        <linux-kselftest@...r.kernel.org>, <kunit-dev@...glegroups.com>,
        <linux-kernel@...r.kernel.org>, <patches@...nsource.cirrus.com>
Subject: Re: [PATCH v2 2/6] kunit: kunit-test: Add test cases for extending
 log buffer

On 9/8/23 13:11, David Gow wrote:
> On Wed, 9 Aug 2023 at 17:39, Richard Fitzgerald
> <rf@...nsource.cirrus.com> wrote:
>>
>> On 8/8/23 22:16, Rae Moar wrote:
>>> On Tue, Aug 8, 2023 at 8:35 AM Richard Fitzgerald
>>> <rf@...nsource.cirrus.com> wrote:
>>>>
>>>> Add test cases for the dynamically-extending log buffer.
>>>>
>>>> kunit_log_extend_test_1() logs a series of numbered lines then tests
>>>> that the resulting log contains all the lines.
>>>>
>>>> kunit_log_extend_test_2() logs a large number of lines of varying length
>>>> to create many fragments, then tests that all lines are present.
>>>>
>>>> kunit_log_frag_sized_line_test() logs a line that exactly fills a
>>>> fragment. This should not cause an extension of the log or truncation
>>>> of the line.
>>>>
>>>> kunit_log_newline_test() has a new test to append a line that is exactly
>>>> the length of the available space in the current fragment and check that
>>>> the resulting log has a trailing '\n'.
>>>>
>>>> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
>>>
>>> Hello!
>>>
>>> I am happy to see so many tests in this patch series. I've been
>>> working with these patches and the debugfs logs seem to be working
>>> well.
>>>
>>> However, when I ran the new kunit-log-test tests three of the tests
>>> failed: kunit_log_extend_test_1(), kunit_log_extend_test_2(), and
>>> kunit_log_newline_test().
>>>
>>> The diagnostic info for kunit_log_extend_test_1() reports:
>>>
>>> [20:55:27] # kunit_log_extend_test_1: EXPECTATION FAILED at
>>> lib/kunit/kunit-test.c:705
>>> [20:55:27] Expected p == line, but
>>> [20:55:27]     p == "xxxxxx…xxxx12345678"
>>> [20:55:27]     line == "The quick brown fox jumps over the lazy penguin 0"
>>> …
>>> [20:55:27] # kunit_log_extend_test_1: EXPECTATION FAILED at
>>> lib/kunit/kunit-test.c:705
>>> [20:55:27] Expected p == line, but
>>> [20:55:27]     p == "The quick brown fox jumps over the lazy penguin 1"
>>> [20:55:27]     line == "The quick brown fox jumps over the lazy penguin 4"
>>> [20:55:27] # kunit_log_extend_test_1: EXPECTATION FAILED at
>>> lib/kunit/kunit-test.c:705
>>> [20:55:27] Expected p == line, but
>>> [20:55:27]     p == "The quick brown fox jumps over the lazy penguin 2"
>>> [20:55:27]     line == "The quick brown fox jumps over the lazy penguin 5"
>>> …
>>> [20:55:27] # kunit_log_extend_test_1: EXPECTATION FAILED at
>>> lib/kunit/kunit-test.c:709
>>> [20:55:27] Expected i == num_lines, but
>>> [20:55:27]     i == 64 (0x40)
>>> [20:55:27]     num_lines == 141 (0x8d)
>>>
>>> So it looks like the log contains a different number of lines than
>>> expected which is causing the difference of 3 between expected and
>>> what was obtained. Potentially the log is not getting cleared/freed
>>> properly in between test cases?
>>>
>>> The diagnostic info for kunit_log_extend_test_2() reports:
>>>
>>> [20:55:27]     # kunit_log_extend_test_2: EXPECTATION FAILED at
>>> lib/kunit/kunit-test.c:776
>>> [20:55:27]     Expected p == &line[i], but
>>> [20:55:27]         p ==
>>> "xxxxx...xxxxx123456780123456789abcdef101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f30313233343536373839"
>>> [20:55:27]         &line[i] ==
>>> "0123456789abcdef101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f30313233343536373839"
>>> [20:55:27]     # kunit_log_extend_test_2: EXPECTATION FAILED at
>>> lib/kunit/kunit-test.c:781
>>> [20:55:27]     Expected n == num_lines, but
>>> [20:55:27]         n == 147 (0x93)
>>> [20:55:27]         num_lines == 155 (0x9b)
>>> [20:55:27] Not enough lines.
>>>
>>> Similar difference in the number of lines here.
>>>
>>> The diagnostic info for kunit_log_newline_test() reports that the test
>>> fails on this line:
>>>
>>> KUNIT_EXPECT_EQ(test, p[strlen(p) - 1], '\n');
>>>
>>> Let me know if you are seeing similar errors. I can post the full log
>>> if that would be helpful.
>>>
>>> -Rae
>>>
>>
>> Ah, I see a bug in get_concatenated_log().
>> Does this change fix it for you?
>>
>>          len++; /* for terminating '\0' */
>> -       p = kunit_kmalloc(test, len, GFP_KERNEL);
>> +       p = kunit_kzalloc(test, len, GFP_KERNEL);
> 
> This fixes what seems to be the same issue for me, under x86_64/qemu.
> 
> Thanks,
> -- David

Good. It seems that the various memory security options have the
side-effect of covering up this bug. I don't know which one exactly
(I've just turned them all off). I had been testing with them on.

I'll send a V3.