linux/lib/test_hash.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Test cases for <linux/hash.h> and <linux/stringhash.h>
 * This just verifies that various ways of computing a hash
 * produce the same thing and, for cases where a k-bit hash
 * value is requested, is of the requested size.
 *
 * We fill a buffer with a 255-byte null-terminated string,
 * and use both full_name_hash() and hashlen_string() to hash the
 * substrings from i to j, where 0 <= i < j < 256.
 *
 * The returned values are used to check that __hash_32() and
 * __hash_32_generic() compute the same thing.  Likewise hash_32()
 * and hash_64().
 */

#include <linux/compiler.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/hash.h>
#include <linux/stringhash.h>
#include <kunit/test.h>

/* 32-bit XORSHIFT generator.  Seed must not be zero. */
static u32 __attribute_const__
xorshift(u32 seed)
{
	seed ^= seed << 13;
	seed ^= seed >> 17;
	seed ^= seed << 5;
	return seed;
}

/* Given a non-zero x, returns a non-zero byte. */
static u8 __attribute_const__
mod255(u32 x)
{
	x = (x & 0xffff) + (x >> 16);	/* 1 <= x <= 0x1fffe */
	x = (x & 0xff) + (x >> 8);	/* 1 <= x <= 0x2fd */
	x = (x & 0xff) + (x >> 8);	/* 1 <= x <= 0x100 */
	x = (x & 0xff) + (x >> 8);	/* 1 <= x <= 0xff */
	return x;
}

/* Fill the buffer with non-zero bytes. */
static void fill_buf(char *buf, size_t len, u32 seed)
{
	size_t i;

	for (i = 0; i < len; i++) {
		seed = xorshift(seed);
		buf[i] = mod255(seed);
	}
}

/* Holds most testing variables for the int test. */
struct test_hash_params {
        /* Pointer to integer to be hashed. */
	unsigned long long *h64;
        /* Low 32-bits of integer to be hashed. */
	u32 h0;
        /* Arch-specific hash result. */
	u32 h1;
        /* Generic hash result. */
	u32 h2;
        /* ORed hashes of given size (in bits). */
	u32 (*hash_or)[33];
};

#ifdef HAVE_ARCH__HASH_32
static void
test_int__hash_32(struct kunit *test, struct test_hash_params *params)
{
	params->hash_or[1][0] |= params->h2 = __hash_32_generic(params->h0);
#if HAVE_ARCH__HASH_32 == 1
	KUNIT_EXPECT_EQ_MSG(test, params->h1, params->h2,
			    "__hash_32(%#x) = %#x != __hash_32_generic() = %#x",
			    params->h0, params->h1, params->h2);
#endif
}
#endif

#ifdef HAVE_ARCH_HASH_64
static void
test_int_hash_64(struct kunit *test, struct test_hash_params *params, u32 const *m, int *k)
{
	params->h2 = hash_64_generic(*params->h64, *k);
#if HAVE_ARCH_HASH_64 == 1
	KUNIT_EXPECT_EQ_MSG(test, params->h1, params->h2,
			    "hash_64(%#llx, %d) = %#x != hash_64_generic() = %#x",
			    *params->h64, *k, params->h1, params->h2);
#else
	KUNIT_EXPECT_LE_MSG(test, params->h1, params->h2,
			    "hash_64_generic(%#llx, %d) = %#x > %#x",
			    *params->h64, *k, params->h1, *m);
#endif
}
#endif

/*
 * Test the various integer hash functions.  h64 (or its low-order bits)
 * is the integer to hash.  hash_or accumulates the OR of the hash values,
 * which are later checked to see that they cover all the requested bits.
 *
 * Because these functions (as opposed to the string hashes) are all
 * inline, the code being tested is actually in the module, and you can
 * recompile and re-test the module without rebooting.
 */
static void
test_int_hash(struct kunit *test, unsigned long long h64, u32 hash_or[2][33])
{
	int k;
	struct test_hash_params params = { &h64, (u32)h64, 0, 0, hash_or };

	/* Test __hash32 */
	hash_or[0][0] |= params.h1 = __hash_32(params.h0);
#ifdef HAVE_ARCH__HASH_32
	test_int__hash_32(test, &params);
#endif

	/* Test k = 1..32 bits */
	for (k = 1; k <= 32; k++) {
		u32 const m = ((u32)2 << (k-1)) - 1;	/* Low k bits set */

		/* Test hash_32 */
		hash_or[0][k] |= params.h1 = hash_32(params.h0, k);
		KUNIT_EXPECT_LE_MSG(test, params.h1, m,
				    "hash_32(%#x, %d) = %#x > %#x",
				    params.h0, k, params.h1, m);

		/* Test hash_64 */
		hash_or[1][k] |= params.h1 = hash_64(h64, k);
		KUNIT_EXPECT_LE_MSG(test, params.h1, m,
				    "hash_64(%#llx, %d) = %#x > %#x",
				    h64, k, params.h1, m);
#ifdef HAVE_ARCH_HASH_64
		test_int_hash_64(test, &params, &m, &k);
#endif
	}
}

#define SIZE 256	/* Run time is cubic in SIZE */

static void test_string_or(struct kunit *test)
{
	char buf[SIZE+1];
	u32 string_or = 0;
	int i, j;

	fill_buf(buf, SIZE, 1);

	/* Test every possible non-empty substring in the buffer. */
	for (j = SIZE; j > 0; --j) {
		buf[j] = '\0';

		for (i = 0; i <= j; i++) {
			u32 h0 = full_name_hash(buf+i, buf+i, j-i);

			string_or |= h0;
		} /* i */
	} /* j */

	/* The OR of all the hash values should cover all the bits */
	KUNIT_EXPECT_EQ_MSG(test, string_or, -1u,
			    "OR of all string hash results = %#x != %#x",
			    string_or, -1u);
}

static void test_hash_or(struct kunit *test)
{
	char buf[SIZE+1];
	u32 hash_or[2][33] = { { 0, } };
	unsigned long long h64 = 0;
	int i, j;

	fill_buf(buf, SIZE, 1);

	/* Test every possible non-empty substring in the buffer. */
	for (j = SIZE; j > 0; --j) {
		buf[j] = '\0';

		for (i = 0; i <= j; i++) {
			u64 hashlen = hashlen_string(buf+i, buf+i);
			u32 h0 = full_name_hash(buf+i, buf+i, j-i);

			/* Check that hashlen_string gets the length right */
			KUNIT_EXPECT_EQ_MSG(test, hashlen_len(hashlen), j-i,
					    "hashlen_string(%d..%d) returned length %u, expected %d",
					    i, j, hashlen_len(hashlen), j-i);
			/* Check that the hashes match */
			KUNIT_EXPECT_EQ_MSG(test, hashlen_hash(hashlen), h0,
					    "hashlen_string(%d..%d) = %08x != full_name_hash() = %08x",
					    i, j, hashlen_hash(hashlen), h0);

			h64 = h64 << 32 | h0;	/* For use with hash_64 */
			test_int_hash(test, h64, hash_or);
		} /* i */
	} /* j */

	KUNIT_EXPECT_EQ_MSG(test, hash_or[0][0], -1u,
			    "OR of all __hash_32 results = %#x != %#x",
			    hash_or[0][0], -1u);
#ifdef HAVE_ARCH__HASH_32
#if HAVE_ARCH__HASH_32 != 1	/* Test is pointless if results match */
	KUNIT_EXPECT_EQ_MSG(test, hash_or[1][0], -1u,
			    "OR of all __hash_32_generic results = %#x != %#x",
			    hash_or[1][0], -1u);
#endif
#endif

	/* Likewise for all the i-bit hash values */
	for (i = 1; i <= 32; i++) {
		u32 const m = ((u32)2 << (i-1)) - 1;	/* Low i bits set */

		KUNIT_EXPECT_EQ_MSG(test, hash_or[0][i], m,
				    "OR of all hash_32(%d) results = %#x (%#x expected)",
				    i, hash_or[0][i], m);
		KUNIT_EXPECT_EQ_MSG(test, hash_or[1][i], m,
				    "OR of all hash_64(%d) results = %#x (%#x expected)",
				    i, hash_or[1][i], m);
	}
}

static struct kunit_case hash_test_cases[] __refdata = {
	KUNIT_CASE(test_string_or),
	KUNIT_CASE(test_hash_or),
	{}
};

static struct kunit_suite hash_test_suite = {
	.name = "hash",
	.test_cases = hash_test_cases,
};


kunit_test_suite(hash_test_suite);

MODULE_DESCRIPTION("Test cases for <linux/hash.h> and <linux/stringhash.h>");
MODULE_LICENSE("GPL");