1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * KUnits tests for CRC16.
  4 *
  5 * Copyright (C) 2024, LKCAMP
  6 * Author: Vinicius Peixoto <vpeixoto@lkcamp.dev>
  7 * Author: Fabricio Gasperin <fgasperin@lkcamp.dev>
  8 * Author: Enzo Bertoloti <ebertoloti@lkcamp.dev>
  9 */
 10#include <kunit/test.h>
 11#include <linux/crc16.h>
 12#include <linux/prandom.h>
 13
 14#define CRC16_KUNIT_DATA_SIZE 4096
 15#define CRC16_KUNIT_TEST_SIZE 100
 16#define CRC16_KUNIT_SEED 0x12345678
 17
 18/**
 19 * struct crc16_test - CRC16 test data
 20 * @crc: initial input value to CRC16
 21 * @start: Start index within the data buffer
 22 * @length: Length of the data
 23 */
 24static struct crc16_test {
 25	u16 crc;
 26	u16 start;
 27	u16 length;
 28} tests[CRC16_KUNIT_TEST_SIZE];
 29
 30u8 data[CRC16_KUNIT_DATA_SIZE];
 31
 32
 33/* Naive implementation of CRC16 for validation purposes */
 34static inline u16 _crc16_naive_byte(u16 crc, u8 data)
 35{
 36	u8 i = 0;
 37
 38	crc ^= (u16) data;
 39	for (i = 0; i < 8; i++) {
 40		if (crc & 0x01)
 41			crc = (crc >> 1) ^ 0xa001;
 42		else
 43			crc = crc >> 1;
 44	}
 45
 46	return crc;
 47}
 48
 49
 50static inline u16 _crc16_naive(u16 crc, u8 *buffer, size_t len)
 51{
 52	while (len--)
 53		crc = _crc16_naive_byte(crc, *buffer++);
 54	return crc;
 55}
 56
 57
 58/* Small helper for generating pseudorandom 16-bit data */
 59static inline u16 _rand16(void)
 60{
 61	static u32 rand = CRC16_KUNIT_SEED;
 62
 63	rand = next_pseudo_random32(rand);
 64	return rand & 0xFFFF;
 65}
 66
 67
 68static int crc16_init_test_data(struct kunit_suite *suite)
 69{
 70	size_t i;
 71
 72	/* Fill the data buffer with random bytes */
 73	for (i = 0; i < CRC16_KUNIT_DATA_SIZE; i++)
 74		data[i] = _rand16() & 0xFF;
 75
 76	/* Generate random test data while ensuring the random
 77	 * start + length values won't overflow the 4096-byte
 78	 * buffer (0x7FF * 2 = 0xFFE < 0x1000)
 79	 */
 80	for (size_t i = 0; i < CRC16_KUNIT_TEST_SIZE; i++) {
 81		tests[i].crc = _rand16();
 82		tests[i].start = _rand16() & 0x7FF;
 83		tests[i].length = _rand16() & 0x7FF;
 84	}
 85
 86	return 0;
 87}
 88
 89static void crc16_test_empty(struct kunit *test)
 90{
 91	u16 crc;
 92
 93	/* The result for empty data should be the same as the
 94	 * initial crc
 95	 */
 96	crc = crc16(0x00, data, 0);
 97	KUNIT_EXPECT_EQ(test, crc, 0);
 98	crc = crc16(0xFF, data, 0);
 99	KUNIT_EXPECT_EQ(test, crc, 0xFF);
100}
101
102static void crc16_test_correctness(struct kunit *test)
103{
104	size_t i;
105	u16 crc, crc_naive;
106
107	for (i = 0; i < CRC16_KUNIT_TEST_SIZE; i++) {
108		/* Compare results with the naive crc16 implementation */
109		crc = crc16(tests[i].crc, data + tests[i].start,
110			    tests[i].length);
111		crc_naive = _crc16_naive(tests[i].crc, data + tests[i].start,
112					 tests[i].length);
113		KUNIT_EXPECT_EQ(test, crc, crc_naive);
114	}
115}
116
117
118static void crc16_test_combine(struct kunit *test)
119{
120	size_t i, j;
121	u16 crc, crc_naive;
122
123	/* Make sure that combining two consecutive crc16 calculations
124	 * yields the same result as calculating the crc16 for the whole thing
125	 */
126	for (i = 0; i < CRC16_KUNIT_TEST_SIZE; i++) {
127		crc_naive = crc16(tests[i].crc, data + tests[i].start, tests[i].length);
128		for (j = 0; j < tests[i].length; j++) {
129			crc = crc16(tests[i].crc, data + tests[i].start, j);
130			crc = crc16(crc, data + tests[i].start + j, tests[i].length - j);
131			KUNIT_EXPECT_EQ(test, crc, crc_naive);
132		}
133	}
134}
135
136
137static struct kunit_case crc16_test_cases[] = {
138	KUNIT_CASE(crc16_test_empty),
139	KUNIT_CASE(crc16_test_combine),
140	KUNIT_CASE(crc16_test_correctness),
141	{},
142};
143
144static struct kunit_suite crc16_test_suite = {
145	.name = "crc16",
146	.test_cases = crc16_test_cases,
147	.suite_init = crc16_init_test_data,
148};
149kunit_test_suite(crc16_test_suite);
150
151MODULE_AUTHOR("Fabricio Gasperin <fgasperin@lkcamp.dev>");
152MODULE_AUTHOR("Vinicius Peixoto <vpeixoto@lkcamp.dev>");
153MODULE_AUTHOR("Enzo Bertoloti <ebertoloti@lkcamp.dev>");
154MODULE_DESCRIPTION("Unit tests for crc16");
155MODULE_LICENSE("GPL");