lib/strscpy_kunit.c

   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  */
  25 static 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
  82 static 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
 129 static struct kunit_case strscpy_test_cases[] = {
 130         KUNIT_CASE(strscpy_test),
 131         {}
 132 };
 133
 134 static struct kunit_suite strscpy_test_suite = {
 135         .name = "strscpy",
 136         .test_cases = strscpy_test_cases,
 137 };
 138
 139 kunit_test_suite(strscpy_test_suite);
 140
 141 MODULE_AUTHOR("Tobin C. Harding <tobin@kernel.org>");
 142 MODULE_LICENSE("GPL");