lib/test_strscpy.c

   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  */
  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
 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");