lib/test_hash.c

   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 #include <linux/compiler.h>
  18 #include <linux/types.h>
  19 #include <linux/module.h>
  20 #include <linux/hash.h>
  21 #include <linux/stringhash.h>
  22 #include <kunit/test.h>
  23
  24 /* 32-bit XORSHIFT generator.  Seed must not be zero. */
  25 static u32 __attribute_const__
  26 xorshift(u32 seed)
  27 {
  28         seed ^= seed << 13;
  29         seed ^= seed >> 17;
  30         seed ^= seed << 5;
  31         return seed;
  32 }
  33
  34 /* Given a non-zero x, returns a non-zero byte. */
  35 static u8 __attribute_const__
  36 mod255(u32 x)
  37 {
  38         x = (x & 0xffff) + (x >> 16);   /* 1 <= x <= 0x1fffe */
  39         x = (x & 0xff) + (x >> 8);      /* 1 <= x <= 0x2fd */
  40         x = (x & 0xff) + (x >> 8);      /* 1 <= x <= 0x100 */
  41         x = (x & 0xff) + (x >> 8);      /* 1 <= x <= 0xff */
  42         return x;
  43 }
  44
  45 /* Fill the buffer with non-zero bytes. */
  46 static void fill_buf(char *buf, size_t len, u32 seed)
  47 {
  48         size_t i;
  49
  50         for (i = 0; i < len; i++) {
  51                 seed = xorshift(seed);
  52                 buf[i] = mod255(seed);
  53         }
  54 }
  55
  56 /* Holds most testing variables for the int test. */
  57 struct test_hash_params {
  58         /* Pointer to integer to be hashed. */
  59         unsigned long long *h64;
  60         /* Low 32-bits of integer to be hashed. */
  61         u32 h0;
  62         /* Arch-specific hash result. */
  63         u32 h1;
  64         /* Generic hash result. */
  65         u32 h2;
  66         /* ORed hashes of given size (in bits). */
  67         u32 (*hash_or)[33];
  68 };
  69
  70 #ifdef HAVE_ARCH__HASH_32
  71 static void
  72 test_int__hash_32(struct kunit *test, struct test_hash_params *params)
  73 {
  74         params->hash_or[1][0] |= params->h2 = __hash_32_generic(params->h0);
  75 #if HAVE_ARCH__HASH_32 == 1
  76         KUNIT_EXPECT_EQ_MSG(test, params->h1, params->h2,
  77                             "__hash_32(%#x) = %#x != __hash_32_generic() = %#x",
  78                             params->h0, params->h1, params->h2);
  79 #endif
  80 }
  81 #endif
  82
  83 #ifdef HAVE_ARCH_HASH_64
  84 static void
  85 test_int_hash_64(struct kunit *test, struct test_hash_params *params, u32 const *m, int *k)
  86 {
  87         params->h2 = hash_64_generic(*params->h64, *k);
  88 #if HAVE_ARCH_HASH_64 == 1
  89         KUNIT_EXPECT_EQ_MSG(test, params->h1, params->h2,
  90                             "hash_64(%#llx, %d) = %#x != hash_64_generic() = %#x",
  91                             *params->h64, *k, params->h1, params->h2);
  92 #else
  93         KUNIT_EXPECT_LE_MSG(test, params->h1, params->h2,
  94                             "hash_64_generic(%#llx, %d) = %#x > %#x",
  95                             *params->h64, *k, params->h1, *m);
  96 #endif
  97 }
  98 #endif
  99
 100 /*
 101  * Test the various integer hash functions.  h64 (or its low-order bits)
 102  * is the integer to hash.  hash_or accumulates the OR of the hash values,
 103  * which are later checked to see that they cover all the requested bits.
 104  *
 105  * Because these functions (as opposed to the string hashes) are all
 106  * inline, the code being tested is actually in the module, and you can
 107  * recompile and re-test the module without rebooting.
 108  */
 109 static void
 110 test_int_hash(struct kunit *test, unsigned long long h64, u32 hash_or[2][33])
 111 {
 112         int k;
 113         struct test_hash_params params = { &h64, (u32)h64, 0, 0, hash_or };
 114
 115         /* Test __hash32 */
 116         hash_or[0][0] |= params.h1 = __hash_32(params.h0);
 117 #ifdef HAVE_ARCH__HASH_32
 118         test_int__hash_32(test, &params);
 119 #endif
 120
 121         /* Test k = 1..32 bits */
 122         for (k = 1; k <= 32; k++) {
 123                 u32 const m = ((u32)2 << (k-1)) - 1;    /* Low k bits set */
 124
 125                 /* Test hash_32 */
 126                 hash_or[0][k] |= params.h1 = hash_32(params.h0, k);
 127                 KUNIT_EXPECT_LE_MSG(test, params.h1, m,
 128                                     "hash_32(%#x, %d) = %#x > %#x",
 129                                     params.h0, k, params.h1, m);
 130
 131                 /* Test hash_64 */
 132                 hash_or[1][k] |= params.h1 = hash_64(h64, k);
 133                 KUNIT_EXPECT_LE_MSG(test, params.h1, m,
 134                                     "hash_64(%#llx, %d) = %#x > %#x",
 135                                     h64, k, params.h1, m);
 136 #ifdef HAVE_ARCH_HASH_64
 137                 test_int_hash_64(test, &params, &m, &k);
 138 #endif
 139         }
 140 }
 141
 142 #define SIZE 256        /* Run time is cubic in SIZE */
 143
 144 static void test_string_or(struct kunit *test)
 145 {
 146         char buf[SIZE+1];
 147         u32 string_or = 0;
 148         int i, j;
 149
 150         fill_buf(buf, SIZE, 1);
 151
 152         /* Test every possible non-empty substring in the buffer. */
 153         for (j = SIZE; j > 0; --j) {
 154                 buf[j] = '\0';
 155
 156                 for (i = 0; i <= j; i++) {
 157                         u32 h0 = full_name_hash(buf+i, buf+i, j-i);
 158
 159                         string_or |= h0;
 160                 } /* i */
 161         } /* j */
 162
 163         /* The OR of all the hash values should cover all the bits */
 164         KUNIT_EXPECT_EQ_MSG(test, string_or, -1u,
 165                             "OR of all string hash results = %#x != %#x",
 166                             string_or, -1u);
 167 }
 168
 169 static void test_hash_or(struct kunit *test)
 170 {
 171         char buf[SIZE+1];
 172         u32 hash_or[2][33] = { { 0, } };
 173         unsigned long long h64 = 0;
 174         int i, j;
 175
 176         fill_buf(buf, SIZE, 1);
 177
 178         /* Test every possible non-empty substring in the buffer. */
 179         for (j = SIZE; j > 0; --j) {
 180                 buf[j] = '\0';
 181
 182                 for (i = 0; i <= j; i++) {
 183                         u64 hashlen = hashlen_string(buf+i, buf+i);
 184                         u32 h0 = full_name_hash(buf+i, buf+i, j-i);
 185
 186                         /* Check that hashlen_string gets the length right */
 187                         KUNIT_EXPECT_EQ_MSG(test, hashlen_len(hashlen), j-i,
 188                                             "hashlen_string(%d..%d) returned length %u, expected %d",
 189                                             i, j, hashlen_len(hashlen), j-i);
 190                         /* Check that the hashes match */
 191                         KUNIT_EXPECT_EQ_MSG(test, hashlen_hash(hashlen), h0,
 192                                             "hashlen_string(%d..%d) = %08x != full_name_hash() = %08x",
 193                                             i, j, hashlen_hash(hashlen), h0);
 194
 195                         h64 = h64 << 32 | h0;   /* For use with hash_64 */
 196                         test_int_hash(test, h64, hash_or);
 197                 } /* i */
 198         } /* j */
 199
 200         KUNIT_EXPECT_EQ_MSG(test, hash_or[0][0], -1u,
 201                             "OR of all __hash_32 results = %#x != %#x",
 202                             hash_or[0][0], -1u);
 203 #ifdef HAVE_ARCH__HASH_32
 204 #if HAVE_ARCH__HASH_32 != 1     /* Test is pointless if results match */
 205         KUNIT_EXPECT_EQ_MSG(test, hash_or[1][0], -1u,
 206                             "OR of all __hash_32_generic results = %#x != %#x",
 207                             hash_or[1][0], -1u);
 208 #endif
 209 #endif
 210
 211         /* Likewise for all the i-bit hash values */
 212         for (i = 1; i <= 32; i++) {
 213                 u32 const m = ((u32)2 << (i-1)) - 1;    /* Low i bits set */
 214
 215                 KUNIT_EXPECT_EQ_MSG(test, hash_or[0][i], m,
 216                                     "OR of all hash_32(%d) results = %#x (%#x expected)",
 217                                     i, hash_or[0][i], m);
 218                 KUNIT_EXPECT_EQ_MSG(test, hash_or[1][i], m,
 219                                     "OR of all hash_64(%d) results = %#x (%#x expected)",
 220                                     i, hash_or[1][i], m);
 221         }
 222 }
 223
 224 static struct kunit_case hash_test_cases[] __refdata = {
 225         KUNIT_CASE(test_string_or),
 226         KUNIT_CASE(test_hash_or),
 227         {}
 228 };
 229
 230 static struct kunit_suite hash_test_suite = {
 231         .name = "hash",
 232         .test_cases = hash_test_cases,
 233 };
 234
 235
 236 kunit_test_suite(hash_test_suite);
 237
 238 MODULE_DESCRIPTION("Test cases for <linux/hash.h> and <linux/stringhash.h>");
 239 MODULE_LICENSE("GPL");