linux-kernel - [PATCH v2 07/14] lib/string_kunit: add correctness test for strrchr()

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Message-Id: <20260113082748.250916-8-jiangfeng@kylinos.cn>
Date: Tue, 13 Jan 2026 16:27:41 +0800
From: Feng Jiang <jiangfeng@...inos.cn>
To: pjw@...nel.org,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alex@...ti.fr,
	kees@...nel.org,
	andy@...nel.org,
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	jiangfeng@...inos.cn,
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	nathan@...nel.org
Cc: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH v2 07/14] lib/string_kunit: add correctness test for strrchr()

Introduce a KUnit test to verify strrchr() across various memory
alignments and character positions. This ensures the implementation
correctly identifies the last occurrence of a character.

Signed-off-by: Feng Jiang <jiangfeng@...inos.cn>
---
 lib/tests/string_kunit.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/lib/tests/string_kunit.c b/lib/tests/string_kunit.c
index 89fe52378442..8eb095404b95 100644
--- a/lib/tests/string_kunit.c
+++ b/lib/tests/string_kunit.c
@@ -181,6 +181,35 @@ static void string_test_strchr(struct kunit *test)
 	KUNIT_ASSERT_NULL(test, result);
 }
 
+static void string_test_strrchr(struct kunit *test)
+{
+	char *buf;
+	size_t offset, len;
+	const size_t buf_size = STRING_TEST_MAX_LEN + STRING_TEST_MAX_OFFSET + 1;
+
+	buf = kunit_kzalloc(test, buf_size, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf);
+
+	memset(buf, 'A', buf_size);
+	buf[buf_size - 1] = '\0';
+
+	for (offset = 0; offset < STRING_TEST_MAX_OFFSET; offset++) {
+		for (len = 0; len <= STRING_TEST_MAX_LEN; len++) {
+			buf[offset + len] = '\0';
+
+			KUNIT_EXPECT_PTR_EQ(test, strrchr(buf + offset, 'Z'), NULL);
+
+			if (len > 0)
+				KUNIT_EXPECT_PTR_EQ(test, strrchr(buf + offset, 'A'),
+						buf + offset + len - 1);
+			else
+				KUNIT_EXPECT_PTR_EQ(test, strrchr(buf + offset, 'A'), NULL);
+
+			buf[offset + len] = 'A';
+		}
+	}
+}
+
 static void string_test_strnchr(struct kunit *test)
 {
 	const char *test_string = "abcdefghijkl";
@@ -676,6 +705,7 @@ static struct kunit_case string_test_cases[] = {
 	KUNIT_CASE(string_test_strnlen),
 	KUNIT_CASE(string_test_strchr),
 	KUNIT_CASE(string_test_strnchr),
+	KUNIT_CASE(string_test_strrchr),
 	KUNIT_CASE(string_test_strspn),
 	KUNIT_CASE(string_test_strcmp),
 	KUNIT_CASE(string_test_strcmp_long_strings),
-- 
2.25.1