Re: [PATCH v3 3/3] lib/test_crc: Add test cases for crc calculation

[Coly Li]

On 2018/7/18 2:51 AM, Noah Massey wrote:
> On Tue, Jul 17, 2018 at 10:56 AM Coly Li <colyli@xxxxxxx> 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: PASSED (0x4e6b1ff972fa8c55, expected 0x4e6b1ff972fa8c55)
>> test_crc: crc64_bch: PASSED (0x0e4f1391d7a4a62e, expected 0x0e4f1391d7a4a62e)
>> test_crc: crc64_update: 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 are only test caes for 3 crc routines,
>> - crc64()
>> - crc64_bch()
>> - crc64_update()
>>
>> Changelog:
>> v3: Add test cases passed/failed statistic
>>     More fixes for review comments of v2
>> v2: Fixes for review comments of v1
>> v1: Initial version.
>>
>> Signed-off-by: Coly Li <colyli@xxxxxxx>
>> Reviewed-by: Hannes Reinecke <hare@xxxxxxx>
>> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>> Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx>
>> ---
>>  lib/Kconfig.debug |  10 ++++
>>  lib/Makefile      |   1 +
>>  lib/test_crc.c    | 138 ++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 149 insertions(+)
>>  create mode 100644 lib/test_crc.c
>>
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index 8838d1158d19..a9c1de0c2a7d 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -1911,6 +1911,16 @@ config TEST_SYSCTL
>>
>>           If unsure, say N.
>>
>> +config TEST_CRC
>> +       tristate "CRC calculation test driver"
>> +       depends on CRC64
>> +       help
>> +         This builds the "test_crc" module. This driver enables to test the
>> +         CRC calculation consistency to make sure new modification does not
>> +         break existing checksum calculation.
>> +
>> +         if unsure, say N.
>> +
>>  config TEST_UDELAY
>>         tristate "udelay test driver"
>>         default n
>> diff --git a/lib/Makefile b/lib/Makefile
>> index 40c215181687..224d047d026a 100644
>> --- a/lib/Makefile
>> +++ b/lib/Makefile
>> @@ -49,6 +49,7 @@ obj-$(CONFIG_FIND_BIT_BENCHMARK) += find_bit_benchmark.o
>>  obj-$(CONFIG_TEST_BPF) += test_bpf.o
>>  obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o
>>  obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o
>> +obj-$(CONFIG_TEST_CRC) += test_crc.o
>>  obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o
>>  obj-$(CONFIG_TEST_KASAN) += test_kasan.o
>>  CFLAGS_test_kasan.o += -fno-builtin
>> diff --git a/lib/test_crc.c b/lib/test_crc.c
>> new file mode 100644
>> index 000000000000..441bf835fbd3
>> --- /dev/null
>> +++ b/lib/test_crc.c
>> @@ -0,0 +1,138 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * CRC test driver
>> + *
>> + * Copyright (C) 2018 Coly Li <colyli@xxxxxxx>
>> + *
>> + * This module provides an simple framework to check the consistency of
>> + * Linux kernel CRC calculation routines in lib/crc*.c. This driver
>> + * requires CONFIG_CRC* items to be enabled if the associated routines are
>> + * tested here. The test results will be printed to kernel message
>> + * when this test driver is loaded.
>> + *
>> + * Current test routines are,
>> + * - crc64()
>> + * - crc64_bch()
>> + * - crc64_update()
>> + *
>> + */
>> +
>> +#include <linux/async.h>
>> +#include <linux/delay.h>
>> +#include <linux/fs.h>
>> +#include <linux/list.h>
>> +#include <linux/module.h>
>> +#include <linux/printk.h>
>> +#include <linux/miscdevice.h>
>> +#include <linux/slab.h>
>> +#include <linux/uaccess.h>
>> +#include <linux/vmalloc.h>
>> +#include <linux/crc64.h>
>> +
>> +struct crc_test_record {
>> +       char    *name;
>> +       u64     data[4];
>> +       u64     initval;
>> +       u64     expval;
>> +       int     (*handler)(struct crc_test_record *rec);
>> +};
>> +
>> +static int chk_and_msg(const char *name, u64 crc, u64 expval)
>> +{
>> +       int ret = 0;
>> +
>> +       if (crc == expval) {
>> +               pr_info("test_crc: %s: PASSED:(0x%016llx, expected 0x%016llx)\n",
>> +                       name, crc, expval);
> 
> I don't think we should have specific kernel output for passed tests.
> If a new test is added which follows this pattern, the 0-day will fail
> because the kernel output would change. Along the lines of "silence is
> golden", if no test hit the error output, we're good.
> 
>> +       } else {
>> +               pr_err("test_crc: %s: FAILED:(0x%016llx, expected 0x%016llx)\n",
>> +                       name, crc, expval);
>> +               ret = -EINVAL;
>> +       }
>> +
>> +       return ret;
>> +}
>> +
>> +/* Add your crc test cases here */
>> +static int test_crc64(struct crc_test_record *rec)
>> +{
>> +       u64 crc;
>> +
>> +       crc = crc64(rec->data, sizeof(rec->data));
>> +       return chk_and_msg(rec->name, crc, rec->expval);
>> +}
>> +
>> +static int test_crc64_bch(struct crc_test_record *rec)
>> +{
>> +       u64 crc;
>> +
>> +       crc = crc64_bch(rec->data, sizeof(rec->data));
>> +       return chk_and_msg(rec->name, crc, rec->expval);
>> +}
>> +
>> +static int test_crc64_update(struct crc_test_record *rec)
>> +{
>> +       u64 crc = rec->initval;
>> +
>> +       crc = crc64_update(crc, rec->data, sizeof(rec->data));
>> +       return 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",
>> +         .data         = { 0x42F0E1EBA9EA3693, 0x85E1C3D753D46D26,
>> +                           0xC711223CFA3E5BB5, 0x493366450E42ECDF },
>> +         .initval      = 0,
>> +         .expval       = 0xe2b9911e7b997201,
>> +         .handler      = test_crc64,
>> +       },
>> +       { .name         = "crc64_bch",
>> +         .data         = { 0x42F0E1EBA9EA3693, 0x85E1C3D753D46D26,
>> +                           0xC711223CFA3E5BB5, 0x493366450E42ECDF },
>> +         .initval      = 0,
>> +         .expval       = 0xd2753a20fd862892,
>> +         .handler      = test_crc64_bch,
>> +       },
>> +       { .name         = "crc64_update",
>> +         .data         = { 0x42F0E1EBA9EA3693, 0x85E1C3D753D46D26,
>> +                           0xC711223CFA3E5BB5, 0x493366450E42ECDF },
>> +         .initval      = 0x61C8864680B583EB,
>> +         .expval       = 0xb2c863673f4292bf,
>> +         .handler      = test_crc64_update,
>> +       },
>> +       {}
>> +};
>> +
>> +static int __init test_crc_init(void)
>> +{
>> +       int i;
>> +       int v, err = 0;
>> +
>> +       pr_info("Kernel CRC consitency testing:\n");
>> +       for (i = 0; test_data[i].name; i++) {
>> +               v = test_data[i].handler(&test_data[i]);
>> +               if (v < 0)
>> +                       err++;
>> +       }
>> +
>> +       if (err == 0)
>> +               pr_info("test_crc: all %d tests passed\n", i);
> 
> Similar to previous comment: we should not report the number of passed
> tests, since adding a test would invalidate previous golden output.
> Also, consider the situation where some tests are conditionally
> executed depending on kconfig.

Sure, I fix this in v4 series. Thanks.

Coly Li

[snipped]