LXR linux/lib/test

   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. */
  27static u32 __init __attribute_const__
  28xorshift(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. */
  37static u8 __init __attribute_const__
  38mod255(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. */
  48static void __init
  49fill_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 */
  68static bool __init
  69test_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
 143static int __init
 144test_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
 250static void __exit test_hash_exit(void)
 251{
 252}
 253
 254module_init(test_hash_init);    /* Does everything */
 255module_exit(test_hash_exit);    /* Does nothing */
 256
 257MODULE_LICENSE("GPL");
 258