xref: /kernel/linux/linux-5.10/lib/test_strscpy.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0+
2
3#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
4
5#include <linux/string.h>
6
7#include "../tools/testing/selftests/kselftest_module.h"
8
9/*
10 * Kernel module for testing 'strscpy' family of functions.
11 */
12
13KSTM_MODULE_GLOBALS();
14
15/*
16 * tc() - Run a specific test case.
17 * @src: Source string, argument to strscpy_pad()
18 * @count: Size of destination buffer, argument to strscpy_pad()
19 * @expected: Expected return value from call to strscpy_pad()
20 * @terminator: 1 if there should be a terminating null byte 0 otherwise.
21 * @chars: Number of characters from the src string expected to be
22 *         written to the dst buffer.
23 * @pad: Number of pad characters expected (in the tail of dst buffer).
24 *       (@pad does not include the null terminator byte.)
25 *
26 * Calls strscpy_pad() and verifies the return value and state of the
27 * destination buffer after the call returns.
28 */
29static int __init tc(char *src, int count, int expected,
30		     int chars, int terminator, int pad)
31{
32	int nr_bytes_poison;
33	int max_expected;
34	int max_count;
35	int written;
36	char buf[6];
37	int index, i;
38	const char POISON = 'z';
39
40	total_tests++;
41
42	if (!src) {
43		pr_err("null source string not supported\n");
44		return -1;
45	}
46
47	memset(buf, POISON, sizeof(buf));
48	/* Future proofing test suite, validate args */
49	max_count = sizeof(buf) - 2; /* Space for null and to verify overflow */
50	max_expected = count - 1;    /* Space for the null */
51	if (count > max_count) {
52		pr_err("count (%d) is too big (%d) ... aborting", count, max_count);
53		return -1;
54	}
55	if (expected > max_expected) {
56		pr_warn("expected (%d) is bigger than can possibly be returned (%d)",
57			expected, max_expected);
58	}
59
60	written = strscpy_pad(buf, src, count);
61	if ((written) != (expected)) {
62		pr_err("%d != %d (written, expected)\n", written, expected);
63		goto fail;
64	}
65
66	if (count && written == -E2BIG) {
67		if (strncmp(buf, src, count - 1) != 0) {
68			pr_err("buffer state invalid for -E2BIG\n");
69			goto fail;
70		}
71		if (buf[count - 1] != '\0') {
72			pr_err("too big string is not null terminated correctly\n");
73			goto fail;
74		}
75	}
76
77	for (i = 0; i < chars; i++) {
78		if (buf[i] != src[i]) {
79			pr_err("buf[i]==%c != src[i]==%c\n", buf[i], src[i]);
80			goto fail;
81		}
82	}
83
84	if (terminator) {
85		if (buf[count - 1] != '\0') {
86			pr_err("string is not null terminated correctly\n");
87			goto fail;
88		}
89	}
90
91	for (i = 0; i < pad; i++) {
92		index = chars + terminator + i;
93		if (buf[index] != '\0') {
94			pr_err("padding missing at index: %d\n", i);
95			goto fail;
96		}
97	}
98
99	nr_bytes_poison = sizeof(buf) - chars - terminator - pad;
100	for (i = 0; i < nr_bytes_poison; i++) {
101		index = sizeof(buf) - 1 - i; /* Check from the end back */
102		if (buf[index] != POISON) {
103			pr_err("poison value missing at index: %d\n", i);
104			goto fail;
105		}
106	}
107
108	return 0;
109fail:
110	failed_tests++;
111	return -1;
112}
113
114static void __init selftest(void)
115{
116	/*
117	 * tc() uses a destination buffer of size 6 and needs at
118	 * least 2 characters spare (one for null and one to check for
119	 * overflow).  This means we should only call tc() with
120	 * strings up to a maximum of 4 characters long and 'count'
121	 * should not exceed 4.  To test with longer strings increase
122	 * the buffer size in tc().
123	 */
124
125	/* tc(src, count, expected, chars, terminator, pad) */
126	KSTM_CHECK_ZERO(tc("a", 0, -E2BIG, 0, 0, 0));
127	KSTM_CHECK_ZERO(tc("", 0, -E2BIG, 0, 0, 0));
128
129	KSTM_CHECK_ZERO(tc("a", 1, -E2BIG, 0, 1, 0));
130	KSTM_CHECK_ZERO(tc("", 1, 0, 0, 1, 0));
131
132	KSTM_CHECK_ZERO(tc("ab", 2, -E2BIG, 1, 1, 0));
133	KSTM_CHECK_ZERO(tc("a", 2, 1, 1, 1, 0));
134	KSTM_CHECK_ZERO(tc("", 2, 0, 0, 1, 1));
135
136	KSTM_CHECK_ZERO(tc("abc", 3, -E2BIG, 2, 1, 0));
137	KSTM_CHECK_ZERO(tc("ab", 3, 2, 2, 1, 0));
138	KSTM_CHECK_ZERO(tc("a", 3, 1, 1, 1, 1));
139	KSTM_CHECK_ZERO(tc("", 3, 0, 0, 1, 2));
140
141	KSTM_CHECK_ZERO(tc("abcd", 4, -E2BIG, 3, 1, 0));
142	KSTM_CHECK_ZERO(tc("abc", 4, 3, 3, 1, 0));
143	KSTM_CHECK_ZERO(tc("ab", 4, 2, 2, 1, 1));
144	KSTM_CHECK_ZERO(tc("a", 4, 1, 1, 1, 2));
145	KSTM_CHECK_ZERO(tc("", 4, 0, 0, 1, 3));
146}
147
148KSTM_MODULE_LOADERS(test_strscpy);
149MODULE_AUTHOR("Tobin C. Harding <tobin@kernel.org>");
150MODULE_LICENSE("GPL");
151