Re: [PATCH v4 3/3] lib/test_crc: Add test cases for crc calculation

[Coly Li]

On 2018/7/24 12:44 PM, Eric Biggers wrote:
> On Thu, Jul 19, 2018 at 12:55:45AM +0800, Coly Li wrote:
>> This patch adds a kernel module to test the consistency of multiple crc
>> calculation in Linux kernel. It is enabled with CONFIG_TEST_CRC enabled.
>>
>> The test results are printed into kernel message, which look like,
>>
>> test_crc: crc64_be: FAILED (0x03d4d0d85685d9a1, expected 0x3d4d0d85685d9a1f)
>>
>> kernel 0day system has framework to check kernel message, then the above
>> result can be handled by 0day system. If crc calculation inconsistency
>> happens, it can be detected quite soon.
>>
>> lib/test_crc.c is a testing frame work for many crc consistency
>> testings. For now, there is only one test caes for crc64_be().
> 
> Are you aware there's already a CRC-32 test module: CONFIG_CRC32_SELFTEST and
> lib/crc32test.c?  Confusingly, your patch uses a different naming convention for
> the new CRC-64 one, and puts the Kconfig option in a different place, and makes
> it sound like it's a generic test for all CRC implementations rather than just
> the CRC-64 one.  Please use the existing convention (i.e. add
> CONFIG_CRC64_SELFTEST and lib/crc64test.c) unless you have a strong argument for
> why it should be done differently.
> 
> (And I don't think it makes sense to combine all CRC tests into one module,
> since you should be able to e.g. enable just CRC32 and CRC32_SELFTEST without
> also pulling in a dependency on all the other CRC variants.)
> 

Hi Eric,

The purpose of test_crc is to provide a unified crc calculation
consistency testing for 0day. So far it is only crc64, and I will add
more test cases later. I see there is crc-32 test module, which does
more testing then consistency check, and no unified format for 0day
system to detect. This is why people suggested me to add this test
framework.

>> +/* Add your crc test cases here */
>> +static void test_crc64_be(struct crc_test_record *rec)
>> +{
>> +	u64 crc;
>> +
>> +	crc = crc64_be(rec->initval, rec->data, sizeof(rec->data));
>> +	chk_and_msg(rec->name, crc, rec->expval);
>> +}
>> +
>> +/*
>> + * Set up your crc test initial data here.
>> + * Do not change the existing items, they are hard coded with
>> + * pre-calculated values.
>> + */
>> +static struct crc_test_record test_data[] = {
>> +	{ .name		= "crc64_be",
>> +	  .data		= { 0x42F0E1EBA9EA3693, 0x85E1C3D753D46D26,
>> +			    0xC711223CFA3E5BB5, 0x493366450E42ECDF },
>> +	  .initval	= 0x61C8864680B583EB,
>> +	  .expval	= 0xb2c863673f4292bf,
>> +	  .handler	= test_crc64_be,
>> +	},
>> +	{}
>> +};
> 
> This is incorrect; the test is checksumming data that has a CPU-specific
> endianness.  So, it will fail on big-endian systems.  The data needs to be
> declared as a byte or char array instead.  See e.g. what crypto/testmgr.h does
> for crypto API algorithms.
> 
> Also please mark the test data structures 'const'.

Sure, I will send fix patches (not rebase the posted patches because
they are in linux-next for now) soon.

Thanks for your comments.

Coly Li