1 files changed, 150 insertions, 0 deletions

diff --git a/lib/test_strscpy.c b/lib/test_strscpy.c
new file mode 100644
index 000000000000..a827f94601f5
--- /dev/null
+++ b/lib/test_strscpy.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/string.h>
+
+#include "../tools/testing/selftests/kselftest_module.h"
+
+/*
+ * Kernel module for testing 'strscpy' family of functions.
+ */
+
+KSTM_MODULE_GLOBALS();
+
+/*
+ * tc() - Run a specific test case.
+ * @src: Source string, argument to strscpy_pad()
+ * @count: Size of destination buffer, argument to strscpy_pad()
+ * @expected: Expected return value from call to strscpy_pad()
+ * @terminator: 1 if there should be a terminating null byte 0 otherwise.
+ * @chars: Number of characters from the src string expected to be
+ *         written to the dst buffer.
+ * @pad: Number of pad characters expected (in the tail of dst buffer).
+ *       (@pad does not include the null terminator byte.)
+ *
+ * Calls strscpy_pad() and verifies the return value and state of the
+ * destination buffer after the call returns.
+ */
+static int __init tc(char *src, int count, int expected,
+                     int chars, int terminator, int pad)
+{
+        int nr_bytes_poison;
+        int max_expected;
+        int max_count;
+        int written;
+        char buf[6];
+        int index, i;
+        const char POISON = 'z';
+
+        total_tests++;
+
+        if (!src) {
+                pr_err("null source string not supported\n");
+                return -1;
+        }
+
+        memset(buf, POISON, sizeof(buf));
+        /* Future proofing test suite, validate args */
+        max_count = sizeof(buf) - 2; /* Space for null and to verify overflow */
+        max_expected = count - 1;    /* Space for the null */
+        if (count > max_count) {
+                pr_err("count (%d) is too big (%d) ... aborting", count, max_count);
+                return -1;
+        }
+        if (expected > max_expected) {
+                pr_warn("expected (%d) is bigger than can possibly be returned (%d)",
+                        expected, max_expected);
+        }
+
+        written = strscpy_pad(buf, src, count);
+        if ((written) != (expected)) {
+                pr_err("%d != %d (written, expected)\n", written, expected);
+                goto fail;
+        }
+
+        if (count && written == -E2BIG) {
+                if (strncmp(buf, src, count - 1) != 0) {
+                        pr_err("buffer state invalid for -E2BIG\n");
+                        goto fail;
+                }
+                if (buf[count - 1] != '\0') {
+                        pr_err("too big string is not null terminated correctly\n");
+                        goto fail;
+                }
+        }
+
+        for (i = 0; i < chars; i++) {
+                if (buf[i] != src[i]) {
+                        pr_err("buf[i]==%c != src[i]==%c\n", buf[i], src[i]);
+                        goto fail;
+                }
+        }
+
+        if (terminator) {
+                if (buf[count - 1] != '\0') {
+                        pr_err("string is not null terminated correctly\n");
+                        goto fail;
+                }
+        }
+
+        for (i = 0; i < pad; i++) {
+                index = chars + terminator + i;
+                if (buf[index] != '\0') {
+                        pr_err("padding missing at index: %d\n", i);
+                        goto fail;
+                }
+        }
+
+        nr_bytes_poison = sizeof(buf) - chars - terminator - pad;
+        for (i = 0; i < nr_bytes_poison; i++) {
+                index = sizeof(buf) - 1 - i; /* Check from the end back */
+                if (buf[index] != POISON) {
+                        pr_err("poison value missing at index: %d\n", i);
+                        goto fail;
+                }
+        }
+
+        return 0;
+fail:
+        failed_tests++;
+        return -1;
+}
+
+static void __init selftest(void)
+{
+        /*
+         * tc() uses a destination buffer of size 6 and needs at
+         * least 2 characters spare (one for null and one to check for
+         * overflow).  This means we should only call tc() with
+         * strings up to a maximum of 4 characters long and 'count'
+         * should not exceed 4.  To test with longer strings increase
+         * the buffer size in tc().
+         */
+
+        /* tc(src, count, expected, chars, terminator, pad) */
+        KSTM_CHECK_ZERO(tc("a", 0, -E2BIG, 0, 0, 0));
+        KSTM_CHECK_ZERO(tc("", 0, -E2BIG, 0, 0, 0));
+
+        KSTM_CHECK_ZERO(tc("a", 1, -E2BIG, 0, 1, 0));
+        KSTM_CHECK_ZERO(tc("", 1, 0, 0, 1, 0));
+
+        KSTM_CHECK_ZERO(tc("ab", 2, -E2BIG, 1, 1, 0));
+        KSTM_CHECK_ZERO(tc("a", 2, 1, 1, 1, 0));
+        KSTM_CHECK_ZERO(tc("", 2, 0, 0, 1, 1));
+
+        KSTM_CHECK_ZERO(tc("abc", 3, -E2BIG, 2, 1, 0));
+        KSTM_CHECK_ZERO(tc("ab", 3, 2, 2, 1, 0));
+        KSTM_CHECK_ZERO(tc("a", 3, 1, 1, 1, 1));
+        KSTM_CHECK_ZERO(tc("", 3, 0, 0, 1, 2));
+
+        KSTM_CHECK_ZERO(tc("abcd", 4, -E2BIG, 3, 1, 0));
+        KSTM_CHECK_ZERO(tc("abc", 4, 3, 3, 1, 0));
+        KSTM_CHECK_ZERO(tc("ab", 4, 2, 2, 1, 1));
+        KSTM_CHECK_ZERO(tc("a", 4, 1, 1, 1, 2));
+        KSTM_CHECK_ZERO(tc("", 4, 0, 0, 1, 3));
+}
+
+KSTM_MODULE_LOADERS(test_strscpy);
+MODULE_AUTHOR("Tobin C. Harding <tobin@kernel.org>");
+MODULE_LICENSE("GPL");