LXR linux/lib/test

   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");
 257