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
13 KSTM_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 */
tc(char * src,int count,int expected,int chars,int terminator,int pad)29 static 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;
109 fail:
110 failed_tests++;
111 return -1;
112 }
113
selftest(void)114 static 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
148 KSTM_MODULE_LOADERS(test_strscpy);
149 MODULE_AUTHOR("Tobin C. Harding <tobin@kernel.org>");
150 MODULE_LICENSE("GPL");
151
