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. */
27 static u32 __init __attribute_const__
xorshift(u32 seed)28 xorshift(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. */
37 static u8 __init __attribute_const__
mod255(u32 x)38 mod255(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. */
48 static void __init
fill_buf(char * buf,size_t len,u32 seed)49 fill_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  */
68 static bool __init
test_int_hash(unsigned long long h64,u32 hash_or[2][33])69 test_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 
143 static int __init
test_hash_init(void)144 test_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 
test_hash_exit(void)250 static void __exit test_hash_exit(void)
251 {
252 }
253 
254 module_init(test_hash_init);	/* Does everything */
255 module_exit(test_hash_exit);	/* Does nothing */
256 
257 MODULE_LICENSE("GPL");
258