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Linux/lib/test_hash.c

  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. */
 26 static u32 __init __attribute_const__
 27 xorshift(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. */
 36 static u8 __init __attribute_const__
 37 mod255(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. */
 47 static void __init
 48 fill_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  */
 67 static bool __init
 68 test_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 
142 static int __init
143 test_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 
249 static void __exit test_hash_exit(void)
250 {
251 }
252 
253 module_init(test_hash_init);    /* Does everything */
254 module_exit(test_hash_exit);    /* Does nothing */
255 
256 MODULE_LICENSE("GPL");
257 

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