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);
 159                         u32 h0 = full_name_hash(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 #ifndef HAVE_ARCH__HASH_32
 223         pr_info("__hash_32() has no arch implementation to test.");
 224 #elif HAVE_ARCH__HASH_32 != 1
 225         pr_info("__hash_32() is arch-specific; not compared to generic.");
 226 #endif
 227 #ifndef HAVE_ARCH_HASH_32
 228         pr_info("hash_32() has no arch implementation to test.");
 229 #elif HAVE_ARCH_HASH_32 != 1
 230         pr_info("hash_32() is arch-specific; not compared to generic.");
 231 #endif
 232 #ifndef HAVE_ARCH_HASH_64
 233         pr_info("hash_64() has no arch implementation to test.");
 234 #elif HAVE_ARCH_HASH_64 != 1
 235         pr_info("hash_64() is arch-specific; not compared to generic.");
 236 #endif
 237
 238         pr_notice("%u tests passed.", tests);
 239
 240         return 0;
 241 }
 242
 243 static void __exit test_hash_exit(void)
 244 {
 245 }
 246
 247 module_init(test_hash_init);    /* Does everything */
 248 module_exit(test_hash_exit);    /* Does nothing */
 249
 250 MODULE_LICENSE("GPL");