[PATCH] lib/tests: add KUnit tests for xxHash

[PATCH] lib/tests: add KUnit tests for xxHash

[Amit Patole]

lib/xxhash.c provides xxh32() and xxh64(), used by zstd (frame
checksums and long-distance matching), btrfs and erofs, where the
values end up on disk. The crypto self-tests cover xxh64() through the
"xxhash64" shash, but nothing tests xxh32() or the library interface
directly.

Add a KUnit suite with known answers from the reference xxHash
implementation. The input is generated the same way as in xxHash's own
sanity check, so the lengths 1, 14 and 222 reproduce the values
published there. It covers:

- xxh32() with two seeds and xxh64() with three, for lengths around
  the 4, 8, 16 and 32 byte boundaries of the algorithms;
- the xxh64 streaming interface, split into two updates at every
  possible point and fed one byte at a time, and repeated
  xxh64_digest() calls;
- xxh64_update() rejecting a NULL input with -EINVAL;
- input at every offset from 1 to 7 bytes, which must not change
  the result.

An AI coding assistant (Claude Opus 5.5) was used to draft the tests,
and the expected values were generated with the reference
implementation (python-xxhash 3.7.0) after checking it against the
published sanity values. The tests were run with
"tools/testing/kunit/kunit.py run" on UML (146/146 pass), built with
W=1 without warnings, and checked against off-by-one changes to the
length checks in xxh32(), xxh64() and xxh64_update(), which the suite
catches.

Signed-off-by: Amit Patole <amit.patole@gmail.com>
---
Tested on UML with a kunitconfig of CONFIG_KUNIT=y and

CONFIG_XXHASH_KUNIT_TEST=y: 146/146 pass.
---
 lib/Kconfig.debug        |  14 +++
 lib/tests/Makefile       |   1 +
 lib/tests/xxhash_kunit.c | 260 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 275 insertions(+)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2d22638ec13a..d88fab338d4b 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -3461,6 +3461,20 @@ config RATELIMIT_KUNIT_TEST
 
 	  If unsure, say N.
 
+config XXHASH_KUNIT_TEST
+	tristate "KUnit test for xxHash" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	select XXHASH
+	default KUNIT_ALL_TESTS
+	help
+	  This option enables the KUnit test suite for lib/xxhash.c, the
+	  xxh32() and xxh64() hashes used by zstd, btrfs and erofs. The
+	  tests check known answers from the reference xxHash
+	  implementation, the xxh64 streaming interface and unaligned
+	  input.
+
+	  If unsure, say N.
+
 config UUID_KUNIT_TEST
 	tristate "KUnit test for UUID" if !KUNIT_ALL_TESTS
 	depends on KUNIT
diff --git a/lib/tests/Makefile b/lib/tests/Makefile
index df0537e1b91f..8828efce4412 100644
--- a/lib/tests/Makefile
+++ b/lib/tests/Makefile
@@ -58,5 +58,6 @@ obj-$(CONFIG_USERCOPY_KUNIT_TEST) += usercopy_kunit.o
 obj-$(CONFIG_UTIL_MACROS_KUNIT) += util_macros_kunit.o
 obj-$(CONFIG_RATELIMIT_KUNIT_TEST) += test_ratelimit.o
 obj-$(CONFIG_UUID_KUNIT_TEST) += uuid_kunit.o
+obj-$(CONFIG_XXHASH_KUNIT_TEST) += xxhash_kunit.o
 
 obj-$(CONFIG_TEST_RUNTIME_MODULE)		+= module/
diff --git a/lib/tests/xxhash_kunit.c b/lib/tests/xxhash_kunit.c
new file mode 100644
index 000000000000..5575c3ec9662
--- /dev/null
+++ b/lib/tests/xxhash_kunit.c
@@ -0,0 +1,260 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for the xxHash implementation in lib/xxhash.c
+ *
+ * The expected values come from the reference xxHash implementation. The
+ * input is generated the same way as in xxHash's own sanity check, so the
+ * entries for lengths 1, 14 and 222 match the values published there.
+ */
+
+#include <kunit/test.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/xxhash.h>
+
+#define XXH_TEST_LEN	222
+
+static const u32 xxh_prime32 = 2654435761U;
+static const u64 xxh_prime64 = 11400714785074694797ULL;
+
+struct xxh32_case {
+	unsigned int len;
+	u32 seed;
+	u32 hash;
+};
+
+struct xxh64_case {
+	unsigned int len;
+	u64 seed;
+	u64 hash;
+};
+
+static const struct xxh32_case xxh32_cases[] = {
+	{   0, 0x00000000, 0x02cc5d05 },
+	{   1, 0x00000000, 0xcf65b03e },
+	{   3, 0x00000000, 0xc23884f5 },
+	{   4, 0x00000000, 0xa9de7ce9 },
+	{   5, 0x00000000, 0xeb1734bb },
+	{   8, 0x00000000, 0xa3f6f44b },
+	{  14, 0x00000000, 0x1208e7e2 },
+	{  15, 0x00000000, 0x6b859e14 },
+	{  16, 0x00000000, 0x93ba3759 },
+	{  17, 0x00000000, 0x89fdc23e },
+	{  31, 0x00000000, 0x5f40e562 },
+	{  32, 0x00000000, 0xd89829ec },
+	{  33, 0x00000000, 0x31a427e5 },
+	{  63, 0x00000000, 0xf1d48fdb },
+	{  64, 0x00000000, 0x02e95dbb },
+	{  65, 0x00000000, 0x16992b3d },
+	{ 100, 0x00000000, 0x96ad8143 },
+	{ 222, 0x00000000, 0x5bd11dbd },
+	{   0, 0x9e3779b1, 0x36b78ae7 },
+	{   1, 0x9e3779b1, 0xb4545aa4 },
+	{   3, 0x9e3779b1, 0x1a269947 },
+	{   4, 0x9e3779b1, 0x2baafe83 },
+	{   5, 0x9e3779b1, 0x5874dab0 },
+	{   8, 0x9e3779b1, 0xc2a8e239 },
+	{  14, 0x9e3779b1, 0x6af1d1fe },
+	{  15, 0x9e3779b1, 0xad53090d },
+	{  16, 0x9e3779b1, 0xa94fc1e1 },
+	{  17, 0x9e3779b1, 0xc9910739 },
+	{  31, 0x9e3779b1, 0x5c0c3350 },
+	{  32, 0x9e3779b1, 0xa5c44467 },
+	{  33, 0x9e3779b1, 0x0de5b1f9 },
+	{  63, 0x9e3779b1, 0x956b3d77 },
+	{  64, 0x9e3779b1, 0xcf82f830 },
+	{  65, 0x9e3779b1, 0x428eec5f },
+	{ 100, 0x9e3779b1, 0x83d48124 },
+	{ 222, 0x9e3779b1, 0x58803c5f },
+};
+
+static const struct xxh64_case xxh64_cases[] = {
+	{   0, 0x0000000000000000ULL, 0xef46db3751d8e999ULL },
+	{   1, 0x0000000000000000ULL, 0xe934a84adb052768ULL },
+	{   3, 0x0000000000000000ULL, 0xff7e1959cb50794aULL },
+	{   4, 0x0000000000000000ULL, 0x9136a0dca57457eeULL },
+	{   5, 0x0000000000000000ULL, 0x9b046fb1397f09a5ULL },
+	{   8, 0x0000000000000000ULL, 0xcdbcf538e71d1348ULL },
+	{  14, 0x0000000000000000ULL, 0x8282dcc4994e35c8ULL },
+	{  15, 0x0000000000000000ULL, 0x180719316d622d84ULL },
+	{  16, 0x0000000000000000ULL, 0x98c90b57fdfcb55cULL },
+	{  17, 0x0000000000000000ULL, 0x0d39a2d051a30c2cULL },
+	{  31, 0x0000000000000000ULL, 0x299b39a290e6d783ULL },
+	{  32, 0x0000000000000000ULL, 0x18b216492bb44b70ULL },
+	{  33, 0x0000000000000000ULL, 0x55c8dc3e578f5b59ULL },
+	{  63, 0x0000000000000000ULL, 0xa9efbe0fa0f3f4e7ULL },
+	{  64, 0x0000000000000000ULL, 0xef558f8acac2b5cdULL },
+	{  65, 0x0000000000000000ULL, 0xde0f20dc2631af7aULL },
+	{ 100, 0x0000000000000000ULL, 0x4bfe019cd91d9ea4ULL },
+	{ 222, 0x0000000000000000ULL, 0xb641ae8cb691c174ULL },
+	{   0, 0x000000009e3779b1ULL, 0xac75fda2929b17efULL },
+	{   1, 0x000000009e3779b1ULL, 0x5014607643a9b4c3ULL },
+	{   3, 0x000000009e3779b1ULL, 0xaa8584e83660f7d1ULL },
+	{   4, 0x000000009e3779b1ULL, 0xcaab286bd8e9fdb5ULL },
+	{   5, 0x000000009e3779b1ULL, 0x2af5249930f984ecULL },
+	{   8, 0x000000009e3779b1ULL, 0xfe0c047a5353cdacULL },
+	{  14, 0x000000009e3779b1ULL, 0xc3bd6bf63deb6df0ULL },
+	{  15, 0x000000009e3779b1ULL, 0xd61105c20e91f99fULL },
+	{  16, 0x000000009e3779b1ULL, 0xc900ad2d536b607eULL },
+	{  17, 0x000000009e3779b1ULL, 0x495cd68a647c7a22ULL },
+	{  31, 0x000000009e3779b1ULL, 0xda673d5feb5c1d79ULL },
+	{  32, 0x000000009e3779b1ULL, 0xb3f33bdf93ade409ULL },
+	{  33, 0x000000009e3779b1ULL, 0xe92c292f64bc3071ULL },
+	{  63, 0x000000009e3779b1ULL, 0x6c911fadb05b6fc2ULL },
+	{  64, 0x000000009e3779b1ULL, 0xb5eeba99264cc44fULL },
+	{  65, 0x000000009e3779b1ULL, 0xd3f6ff3941e310caULL },
+	{ 100, 0x000000009e3779b1ULL, 0x4853706dc9625caeULL },
+	{ 222, 0x000000009e3779b1ULL, 0x20cb8ab7ae10c14aULL },
+	{   0, 0x9e3779b97f4a7c15ULL, 0xc4349fc93c010000ULL },
+	{   1, 0x9e3779b97f4a7c15ULL, 0x126bb57a12364aa5ULL },
+	{   3, 0x9e3779b97f4a7c15ULL, 0xe23f055f9113033dULL },
+	{   4, 0x9e3779b97f4a7c15ULL, 0xf6337e5fb526b92eULL },
+	{   5, 0x9e3779b97f4a7c15ULL, 0x3fe27fb9d0eb8e4cULL },
+	{   8, 0x9e3779b97f4a7c15ULL, 0x4fe88e05b3a5bfd8ULL },
+	{  14, 0x9e3779b97f4a7c15ULL, 0xbdd0f167d252e0bbULL },
+	{  15, 0x9e3779b97f4a7c15ULL, 0xb0298e00622d8613ULL },
+	{  16, 0x9e3779b97f4a7c15ULL, 0xb37a43269a32566aULL },
+	{  17, 0x9e3779b97f4a7c15ULL, 0xfd7e04ed256c9413ULL },
+	{  31, 0x9e3779b97f4a7c15ULL, 0xb9fa34ecbf9b57ffULL },
+	{  32, 0x9e3779b97f4a7c15ULL, 0xe65ea5f4eff5d5deULL },
+	{  33, 0x9e3779b97f4a7c15ULL, 0xf166a3272cadc4abULL },
+	{  63, 0x9e3779b97f4a7c15ULL, 0x0a36d884436efe01ULL },
+	{  64, 0x9e3779b97f4a7c15ULL, 0xe7bd5052c0d2145eULL },
+	{  65, 0x9e3779b97f4a7c15ULL, 0xfea9a8f0561339ddULL },
+	{ 100, 0x9e3779b97f4a7c15ULL, 0x8dd80a6ef6296bf7ULL },
+	{ 222, 0x9e3779b97f4a7c15ULL, 0x8cdf13ba7f241d67ULL },
+};
+
+static u8 *xxh_test_buf(struct kunit *test)
+{
+	u64 gen = xxh_prime32;
+	u8 *buf;
+	int i;
+
+	buf = kunit_kmalloc(test, XXH_TEST_LEN, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, buf);
+
+	for (i = 0; i < XXH_TEST_LEN; i++) {
+		buf[i] = gen >> 56;
+		gen *= xxh_prime64;
+	}
+	return buf;
+}
+
+static void xxh32_case_desc(const struct xxh32_case *t, char *desc)
+{
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE, "len %u seed %#x",
+		 t->len, t->seed);
+}
+
+static void xxh64_case_desc(const struct xxh64_case *t, char *desc)
+{
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE, "len %u seed %#llx",
+		 t->len, t->seed);
+}
+
+KUNIT_ARRAY_PARAM(xxh32, xxh32_cases, xxh32_case_desc);
+KUNIT_ARRAY_PARAM(xxh64, xxh64_cases, xxh64_case_desc);
+
+static void xxh32_test(struct kunit *test)
+{
+	const struct xxh32_case *t = test->param_value;
+	u8 *buf = xxh_test_buf(test);
+
+	KUNIT_EXPECT_EQ(test, xxh32(buf, t->len, t->seed), t->hash);
+}
+
+static void xxh64_test(struct kunit *test)
+{
+	const struct xxh64_case *t = test->param_value;
+	u8 *buf = xxh_test_buf(test);
+
+	KUNIT_EXPECT_EQ(test, xxh64(buf, t->len, t->seed), t->hash);
+}
+
+/*
+ * The streaming interface must give the same result as xxh64() however the
+ * input is split. Try every split into two updates, and one byte at a time.
+ */
+static void xxh64_streaming_test(struct kunit *test)
+{
+	const struct xxh64_case *t = test->param_value;
+	u8 *buf = xxh_test_buf(test);
+	struct xxh64_state state;
+	unsigned int split, i;
+
+	for (split = 0; split <= t->len; split++) {
+		xxh64_reset(&state, t->seed);
+		KUNIT_ASSERT_EQ(test, xxh64_update(&state, buf, split), 0);
+		KUNIT_ASSERT_EQ(test, xxh64_update(&state, buf + split,
+						   t->len - split), 0);
+		KUNIT_EXPECT_EQ_MSG(test, xxh64_digest(&state), t->hash,
+				    "split at %u", split);
+	}
+
+	xxh64_reset(&state, t->seed);
+	for (i = 0; i < t->len; i++)
+		KUNIT_ASSERT_EQ(test, xxh64_update(&state, buf + i, 1), 0);
+	KUNIT_EXPECT_EQ(test, xxh64_digest(&state), t->hash);
+
+	/* xxh64_digest() does not change the state, so it can be repeated. */
+	KUNIT_EXPECT_EQ(test, xxh64_digest(&state), t->hash);
+}
+
+static void xxh64_update_null_test(struct kunit *test)
+{
+	struct xxh64_state state;
+
+	xxh64_reset(&state, 0);
+	KUNIT_EXPECT_EQ(test, xxh64_update(&state, NULL, 0), -EINVAL);
+	/* A rejected update leaves the state as it was. */
+	KUNIT_EXPECT_EQ(test, xxh64_digest(&state), xxh64(NULL, 0, 0));
+}
+
+/* The result does not depend on the alignment of the input. */
+static void xxh_unaligned_test(struct kunit *test)
+{
+	u8 *buf = xxh_test_buf(test);
+	u32 h32 = xxh32(buf, XXH_TEST_LEN, 0);
+	u64 h64 = xxh64(buf, XXH_TEST_LEN, 0);
+	u8 *copy;
+	int off;
+
+	copy = kunit_kmalloc(test, XXH_TEST_LEN + 8, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_NULL(test, copy);
+
+	for (off = 1; off < 8; off++) {
+		struct xxh64_state state;
+
+		memcpy(copy + off, buf, XXH_TEST_LEN);
+		KUNIT_EXPECT_EQ_MSG(test, xxh32(copy + off, XXH_TEST_LEN, 0),
+				    h32, "offset %d", off);
+		KUNIT_EXPECT_EQ_MSG(test, xxh64(copy + off, XXH_TEST_LEN, 0),
+				    h64, "offset %d", off);
+
+		xxh64_reset(&state, 0);
+		xxh64_update(&state, copy + off, 5);
+		xxh64_update(&state, copy + off + 5, XXH_TEST_LEN - 5);
+		KUNIT_EXPECT_EQ_MSG(test, xxh64_digest(&state), h64,
+				    "offset %d", off);
+	}
+}
+
+static struct kunit_case xxhash_test_cases[] = {
+	KUNIT_CASE_PARAM(xxh32_test, xxh32_gen_params),
+	KUNIT_CASE_PARAM(xxh64_test, xxh64_gen_params),
+	KUNIT_CASE_PARAM(xxh64_streaming_test, xxh64_gen_params),
+	KUNIT_CASE(xxh64_update_null_test),
+	KUNIT_CASE(xxh_unaligned_test),
+	{}
+};
+
+static struct kunit_suite xxhash_test_suite = {
+	.name = "xxhash",
+	.test_cases = xxhash_test_cases,
+};
+
+kunit_test_suite(xxhash_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for xxHash");
+MODULE_LICENSE("GPL");

---
base-commit: 05441d697f7f9a927264f4058cbbc6a03dfcac9d
change-id: 20261106-kunit-xxhash-25a4cca743ac

Best regards,
--  
Amit Patole <amit.patole@gmail.com>