projects/linux·blob v4.13 · refs

256 lines · 6.3 KiB

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