xref: /kernel/linux/linux-5.10/lib/test_hash.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Test cases for <linux/hash.h> and <linux/stringhash.h>
4 * This just verifies that various ways of computing a hash
5 * produce the same thing and, for cases where a k-bit hash
6 * value is requested, is of the requested size.
7 *
8 * We fill a buffer with a 255-byte null-terminated string,
9 * and use both full_name_hash() and hashlen_string() to hash the
10 * substrings from i to j, where 0 <= i < j < 256.
11 *
12 * The returned values are used to check that __hash_32() and
13 * __hash_32_generic() compute the same thing.  Likewise hash_32()
14 * and hash_64().
15 */
16
17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt "\n"
18
19#include <linux/compiler.h>
20#include <linux/types.h>
21#include <linux/module.h>
22#include <linux/hash.h>
23#include <linux/stringhash.h>
24#include <linux/printk.h>
25
26/* 32-bit XORSHIFT generator.  Seed must not be zero. */
27static u32 __init __attribute_const__
28xorshift(u32 seed)
29{
30	seed ^= seed << 13;
31	seed ^= seed >> 17;
32	seed ^= seed << 5;
33	return seed;
34}
35
36/* Given a non-zero x, returns a non-zero byte. */
37static u8 __init __attribute_const__
38mod255(u32 x)
39{
40	x = (x & 0xffff) + (x >> 16);	/* 1 <= x <= 0x1fffe */
41	x = (x & 0xff) + (x >> 8);	/* 1 <= x <= 0x2fd */
42	x = (x & 0xff) + (x >> 8);	/* 1 <= x <= 0x100 */
43	x = (x & 0xff) + (x >> 8);	/* 1 <= x <= 0xff */
44	return x;
45}
46
47/* Fill the buffer with non-zero bytes. */
48static void __init
49fill_buf(char *buf, size_t len, u32 seed)
50{
51	size_t i;
52
53	for (i = 0; i < len; i++) {
54		seed = xorshift(seed);
55		buf[i] = mod255(seed);
56	}
57}
58
59/*
60 * Test the various integer hash functions.  h64 (or its low-order bits)
61 * is the integer to hash.  hash_or accumulates the OR of the hash values,
62 * which are later checked to see that they cover all the requested bits.
63 *
64 * Because these functions (as opposed to the string hashes) are all
65 * inline, the code being tested is actually in the module, and you can
66 * recompile and re-test the module without rebooting.
67 */
68static bool __init
69test_int_hash(unsigned long long h64, u32 hash_or[2][33])
70{
71	int k;
72	u32 h0 = (u32)h64, h1, h2;
73
74	/* Test __hash32 */
75	hash_or[0][0] |= h1 = __hash_32(h0);
76#ifdef HAVE_ARCH__HASH_32
77	hash_or[1][0] |= h2 = __hash_32_generic(h0);
78#if HAVE_ARCH__HASH_32 == 1
79	if (h1 != h2) {
80		pr_err("__hash_32(%#x) = %#x != __hash_32_generic() = %#x",
81			h0, h1, h2);
82		return false;
83	}
84#endif
85#endif
86
87	/* Test k = 1..32 bits */
88	for (k = 1; k <= 32; k++) {
89		u32 const m = ((u32)2 << (k-1)) - 1;	/* Low k bits set */
90
91		/* Test hash_32 */
92		hash_or[0][k] |= h1 = hash_32(h0, k);
93		if (h1 > m) {
94			pr_err("hash_32(%#x, %d) = %#x > %#x", h0, k, h1, m);
95			return false;
96		}
97#ifdef HAVE_ARCH_HASH_32
98		h2 = hash_32_generic(h0, k);
99#if HAVE_ARCH_HASH_32 == 1
100		if (h1 != h2) {
101			pr_err("hash_32(%#x, %d) = %#x != hash_32_generic() "
102				" = %#x", h0, k, h1, h2);
103			return false;
104		}
105#else
106		if (h2 > m) {
107			pr_err("hash_32_generic(%#x, %d) = %#x > %#x",
108				h0, k, h1, m);
109			return false;
110		}
111#endif
112#endif
113		/* Test hash_64 */
114		hash_or[1][k] |= h1 = hash_64(h64, k);
115		if (h1 > m) {
116			pr_err("hash_64(%#llx, %d) = %#x > %#x", h64, k, h1, m);
117			return false;
118		}
119#ifdef HAVE_ARCH_HASH_64
120		h2 = hash_64_generic(h64, k);
121#if HAVE_ARCH_HASH_64 == 1
122		if (h1 != h2) {
123			pr_err("hash_64(%#llx, %d) = %#x != hash_64_generic() "
124				"= %#x", h64, k, h1, h2);
125			return false;
126		}
127#else
128		if (h2 > m) {
129			pr_err("hash_64_generic(%#llx, %d) = %#x > %#x",
130				h64, k, h1, m);
131			return false;
132		}
133#endif
134#endif
135	}
136
137	(void)h2;	/* Suppress unused variable warning */
138	return true;
139}
140
141#define SIZE 256	/* Run time is cubic in SIZE */
142
143static int __init
144test_hash_init(void)
145{
146	char buf[SIZE+1];
147	u32 string_or = 0, hash_or[2][33] = { { 0, } };
148	unsigned tests = 0;
149	unsigned long long h64 = 0;
150	int i, j;
151
152	fill_buf(buf, SIZE, 1);
153
154	/* Test every possible non-empty substring in the buffer. */
155	for (j = SIZE; j > 0; --j) {
156		buf[j] = '\0';
157
158		for (i = 0; i <= j; i++) {
159			u64 hashlen = hashlen_string(buf+i, buf+i);
160			u32 h0 = full_name_hash(buf+i, buf+i, j-i);
161
162			/* Check that hashlen_string gets the length right */
163			if (hashlen_len(hashlen) != j-i) {
164				pr_err("hashlen_string(%d..%d) returned length"
165					" %u, expected %d",
166					i, j, hashlen_len(hashlen), j-i);
167				return -EINVAL;
168			}
169			/* Check that the hashes match */
170			if (hashlen_hash(hashlen) != h0) {
171				pr_err("hashlen_string(%d..%d) = %08x != "
172					"full_name_hash() = %08x",
173					i, j, hashlen_hash(hashlen), h0);
174				return -EINVAL;
175			}
176
177			string_or |= h0;
178			h64 = h64 << 32 | h0;	/* For use with hash_64 */
179			if (!test_int_hash(h64, hash_or))
180				return -EINVAL;
181			tests++;
182		} /* i */
183	} /* j */
184
185	/* The OR of all the hash values should cover all the bits */
186	if (~string_or) {
187		pr_err("OR of all string hash results = %#x != %#x",
188			string_or, -1u);
189		return -EINVAL;
190	}
191	if (~hash_or[0][0]) {
192		pr_err("OR of all __hash_32 results = %#x != %#x",
193			hash_or[0][0], -1u);
194		return -EINVAL;
195	}
196#ifdef HAVE_ARCH__HASH_32
197#if HAVE_ARCH__HASH_32 != 1	/* Test is pointless if results match */
198	if (~hash_or[1][0]) {
199		pr_err("OR of all __hash_32_generic results = %#x != %#x",
200			hash_or[1][0], -1u);
201		return -EINVAL;
202	}
203#endif
204#endif
205
206	/* Likewise for all the i-bit hash values */
207	for (i = 1; i <= 32; i++) {
208		u32 const m = ((u32)2 << (i-1)) - 1;	/* Low i bits set */
209
210		if (hash_or[0][i] != m) {
211			pr_err("OR of all hash_32(%d) results = %#x "
212				"(%#x expected)", i, hash_or[0][i], m);
213			return -EINVAL;
214		}
215		if (hash_or[1][i] != m) {
216			pr_err("OR of all hash_64(%d) results = %#x "
217				"(%#x expected)", i, hash_or[1][i], m);
218			return -EINVAL;
219		}
220	}
221
222	/* Issue notices about skipped tests. */
223#ifdef HAVE_ARCH__HASH_32
224#if HAVE_ARCH__HASH_32 != 1
225	pr_info("__hash_32() is arch-specific; not compared to generic.");
226#endif
227#else
228	pr_info("__hash_32() has no arch implementation to test.");
229#endif
230#ifdef HAVE_ARCH_HASH_32
231#if HAVE_ARCH_HASH_32 != 1
232	pr_info("hash_32() is arch-specific; not compared to generic.");
233#endif
234#else
235	pr_info("hash_32() has no arch implementation to test.");
236#endif
237#ifdef HAVE_ARCH_HASH_64
238#if HAVE_ARCH_HASH_64 != 1
239	pr_info("hash_64() is arch-specific; not compared to generic.");
240#endif
241#else
242	pr_info("hash_64() has no arch implementation to test.");
243#endif
244
245	pr_notice("%u tests passed.", tests);
246
247	return 0;
248}
249
250static void __exit test_hash_exit(void)
251{
252}
253
254module_init(test_hash_init);	/* Does everything */
255module_exit(test_hash_exit);	/* Does nothing */
256
257MODULE_LICENSE("GPL");
258