1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Kernel module for testing 'strscpy' family of functions.
4 */
5
6#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
7
8#include <kunit/test.h>
9#include <linux/string.h>
10
11/*
12 * tc() - Run a specific test case.
13 * @src: Source string, argument to strscpy_pad()
14 * @count: Size of destination buffer, argument to strscpy_pad()
15 * @expected: Expected return value from call to strscpy_pad()
16 * @terminator: 1 if there should be a terminating null byte 0 otherwise.
17 * @chars: Number of characters from the src string expected to be
18 *         written to the dst buffer.
19 * @pad: Number of pad characters expected (in the tail of dst buffer).
20 *       (@pad does not include the null terminator byte.)
21 *
22 * Calls strscpy_pad() and verifies the return value and state of the
23 * destination buffer after the call returns.
24 */
25static void tc(struct kunit *test, char *src, int count, int expected,
26	       int chars, int terminator, int pad)
27{
28	int nr_bytes_poison;
29	int max_expected;
30	int max_count;
31	int written;
32	char buf[6];
33	int index, i;
34	const char POISON = 'z';
35
36	KUNIT_ASSERT_TRUE_MSG(test, src != NULL,
37			      "null source string not supported");
38
39	memset(buf, POISON, sizeof(buf));
40	/* Future proofing test suite, validate args */
41	max_count = sizeof(buf) - 2; /* Space for null and to verify overflow */
42	max_expected = count - 1;    /* Space for the null */
43
44	KUNIT_ASSERT_LE_MSG(test, count, max_count,
45		"count (%d) is too big (%d) ... aborting", count, max_count);
46	KUNIT_EXPECT_LE_MSG(test, expected, max_expected,
47		"expected (%d) is bigger than can possibly be returned (%d)",
48		expected, max_expected);
49
50	written = strscpy_pad(buf, src, count);
51	KUNIT_ASSERT_EQ(test, written, expected);
52
53	if (count && written == -E2BIG) {
54		KUNIT_ASSERT_EQ_MSG(test, 0, strncmp(buf, src, count - 1),
55			"buffer state invalid for -E2BIG");
56		KUNIT_ASSERT_EQ_MSG(test, buf[count - 1], '\0',
57			"too big string is not null terminated correctly");
58	}
59
60	for (i = 0; i < chars; i++)
61		KUNIT_ASSERT_EQ_MSG(test, buf[i], src[i],
62			"buf[i]==%c != src[i]==%c", buf[i], src[i]);
63
64	if (terminator)
65		KUNIT_ASSERT_EQ_MSG(test, buf[count - 1], '\0',
66			"string is not null terminated correctly");
67
68	for (i = 0; i < pad; i++) {
69		index = chars + terminator + i;
70		KUNIT_ASSERT_EQ_MSG(test, buf[index], '\0',
71			"padding missing at index: %d", i);
72	}
73
74	nr_bytes_poison = sizeof(buf) - chars - terminator - pad;
75	for (i = 0; i < nr_bytes_poison; i++) {
76		index = sizeof(buf) - 1 - i; /* Check from the end back */
77		KUNIT_ASSERT_EQ_MSG(test, buf[index], POISON,
78			"poison value missing at index: %d", i);
79	}
80}
81
82static void strscpy_test(struct kunit *test)
83{
84	char dest[8];
85
86	/*
87	 * tc() uses a destination buffer of size 6 and needs at
88	 * least 2 characters spare (one for null and one to check for
89	 * overflow).  This means we should only call tc() with
90	 * strings up to a maximum of 4 characters long and 'count'
91	 * should not exceed 4.  To test with longer strings increase
92	 * the buffer size in tc().
93	 */
94
95	/* tc(test, src, count, expected, chars, terminator, pad) */
96	tc(test, "a", 0, -E2BIG, 0, 0, 0);
97	tc(test, "",  0, -E2BIG, 0, 0, 0);
98
99	tc(test, "a", 1, -E2BIG, 0, 1, 0);
100	tc(test, "",  1, 0,	 0, 1, 0);
101
102	tc(test, "ab", 2, -E2BIG, 1, 1, 0);
103	tc(test, "a",  2, 1,	  1, 1, 0);
104	tc(test, "",   2, 0,	  0, 1, 1);
105
106	tc(test, "abc", 3, -E2BIG, 2, 1, 0);
107	tc(test, "ab",  3, 2,	   2, 1, 0);
108	tc(test, "a",   3, 1,	   1, 1, 1);
109	tc(test, "",    3, 0,	   0, 1, 2);
110
111	tc(test, "abcd", 4, -E2BIG, 3, 1, 0);
112	tc(test, "abc",  4, 3,	    3, 1, 0);
113	tc(test, "ab",   4, 2,	    2, 1, 1);
114	tc(test, "a",    4, 1,	    1, 1, 2);
115	tc(test, "",     4, 0,	    0, 1, 3);
116
117	/* Compile-time-known source strings. */
118	KUNIT_EXPECT_EQ(test, strscpy(dest, "", ARRAY_SIZE(dest)), 0);
119	KUNIT_EXPECT_EQ(test, strscpy(dest, "", 3), 0);
120	KUNIT_EXPECT_EQ(test, strscpy(dest, "", 1), 0);
121	KUNIT_EXPECT_EQ(test, strscpy(dest, "", 0), -E2BIG);
122	KUNIT_EXPECT_EQ(test, strscpy(dest, "Fixed", ARRAY_SIZE(dest)), 5);
123	KUNIT_EXPECT_EQ(test, strscpy(dest, "Fixed", 3), -E2BIG);
124	KUNIT_EXPECT_EQ(test, strscpy(dest, "Fixed", 1), -E2BIG);
125	KUNIT_EXPECT_EQ(test, strscpy(dest, "Fixed", 0), -E2BIG);
126	KUNIT_EXPECT_EQ(test, strscpy(dest, "This is too long", ARRAY_SIZE(dest)), -E2BIG);
127}
128
129static struct kunit_case strscpy_test_cases[] = {
130	KUNIT_CASE(strscpy_test),
131	{}
132};
133
134static struct kunit_suite strscpy_test_suite = {
135	.name = "strscpy",
136	.test_cases = strscpy_test_cases,
137};
138
139kunit_test_suite(strscpy_test_suite);
140
141MODULE_AUTHOR("Tobin C. Harding <tobin@kernel.org>");
142MODULE_LICENSE("GPL");
143