fs/ext3/hash.c

   1 /*
   2  *  linux/fs/ext3/hash.c
   3  *
   4  * Copyright (C) 2002 by Theodore Ts'o
   5  *
   6  * This file is released under the GPL v2.
   7  *
   8  * This file may be redistributed under the terms of the GNU Public
   9  * License.
  10  */
  11
  12 #include <linux/fs.h>
  13 #include <linux/jbd.h>
  14 #include <linux/sched.h>
  15 #include <linux/ext3_fs.h>
  16
  17 #define DELTA 0x9E3779B9
  18
  19 static void TEA_transform(__u32 buf[4], __u32 const in[])
  20 {
  21         __u32   sum = 0;
  22         __u32   b0 = buf[0], b1 = buf[1];
  23         __u32   a = in[0], b = in[1], c = in[2], d = in[3];
  24         int     n = 16;
  25
  26         do {
  27                 sum += DELTA;
  28                 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
  29                 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
  30         } while(--n);
  31
  32         buf[0] += b0;
  33         buf[1] += b1;
  34 }
  35
  36 /* F, G and H are basic MD4 functions: selection, majority, parity */
  37 #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z))))
  38 #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z)))
  39 #define H(x, y, z) ((x) ^ (y) ^ (z))
  40
  41 /*
  42  * The generic round function.  The application is so specific that
  43  * we don't bother protecting all the arguments with parens, as is generally
  44  * good macro practice, in favor of extra legibility.
  45  * Rotation is separate from addition to prevent recomputation
  46  */
  47 #define ROUND(f, a, b, c, d, x, s)      \
  48         (a += f(b, c, d) + x, a = (a << s) | (a >> (32-s)))
  49 #define K1 0
  50 #define K2 013240474631UL
  51 #define K3 015666365641UL
  52
  53 /*
  54  * Basic cut-down MD4 transform.  Returns only 32 bits of result.
  55  */
  56 static void halfMD4Transform (__u32 buf[4], __u32 const in[])
  57 {
  58         __u32   a = buf[0], b = buf[1], c = buf[2], d = buf[3];
  59
  60         /* Round 1 */
  61         ROUND(F, a, b, c, d, in[0] + K1,  3);
  62         ROUND(F, d, a, b, c, in[1] + K1,  7);
  63         ROUND(F, c, d, a, b, in[2] + K1, 11);
  64         ROUND(F, b, c, d, a, in[3] + K1, 19);
  65         ROUND(F, a, b, c, d, in[4] + K1,  3);
  66         ROUND(F, d, a, b, c, in[5] + K1,  7);
  67         ROUND(F, c, d, a, b, in[6] + K1, 11);
  68         ROUND(F, b, c, d, a, in[7] + K1, 19);
  69
  70         /* Round 2 */
  71         ROUND(G, a, b, c, d, in[1] + K2,  3);
  72         ROUND(G, d, a, b, c, in[3] + K2,  5);
  73         ROUND(G, c, d, a, b, in[5] + K2,  9);
  74         ROUND(G, b, c, d, a, in[7] + K2, 13);
  75         ROUND(G, a, b, c, d, in[0] + K2,  3);
  76         ROUND(G, d, a, b, c, in[2] + K2,  5);
  77         ROUND(G, c, d, a, b, in[4] + K2,  9);
  78         ROUND(G, b, c, d, a, in[6] + K2, 13);
  79
  80         /* Round 3 */
  81         ROUND(H, a, b, c, d, in[3] + K3,  3);
  82         ROUND(H, d, a, b, c, in[7] + K3,  9);
  83         ROUND(H, c, d, a, b, in[2] + K3, 11);
  84         ROUND(H, b, c, d, a, in[6] + K3, 15);
  85         ROUND(H, a, b, c, d, in[1] + K3,  3);
  86         ROUND(H, d, a, b, c, in[5] + K3,  9);
  87         ROUND(H, c, d, a, b, in[0] + K3, 11);
  88         ROUND(H, b, c, d, a, in[4] + K3, 15);
  89
  90         buf[0] += a;
  91         buf[1] += b;
  92         buf[2] += c;
  93         buf[3] += d;
  94 }
  95
  96 #undef ROUND
  97 #undef F
  98 #undef G
  99 #undef H
 100 #undef K1
 101 #undef K2
 102 #undef K3
 103
 104 /* The old legacy hash */
 105 static __u32 dx_hack_hash (const char *name, int len)
 106 {
 107         __u32 hash0 = 0x12a3fe2d, hash1 = 0x37abe8f9;
 108         while (len--) {
 109                 __u32 hash = hash1 + (hash0 ^ (*name++ * 7152373));
 110
 111                 if (hash & 0x80000000) hash -= 0x7fffffff;
 112                 hash1 = hash0;
 113                 hash0 = hash;
 114         }
 115         return (hash0 << 1);
 116 }
 117
 118 static void str2hashbuf(const char *msg, int len, __u32 *buf, int num)
 119 {
 120         __u32   pad, val;
 121         int     i;
 122
 123         pad = (__u32)len | ((__u32)len << 8);
 124         pad |= pad << 16;
 125
 126         val = pad;
 127         if (len > num*4)
 128                 len = num * 4;
 129         for (i=0; i < len; i++) {
 130                 if ((i % 4) == 0)
 131                         val = pad;
 132                 val = msg[i] + (val << 8);
 133                 if ((i % 4) == 3) {
 134                         *buf++ = val;
 135                         val = pad;
 136                         num--;
 137                 }
 138         }
 139         if (--num >= 0)
 140                 *buf++ = val;
 141         while (--num >= 0)
 142                 *buf++ = pad;
 143 }
 144
 145 /*
 146  * Returns the hash of a filename.  If len is 0 and name is NULL, then
 147  * this function can be used to test whether or not a hash version is
 148  * supported.
 149  *
 150  * The seed is an 4 longword (32 bits) "secret" which can be used to
 151  * uniquify a hash.  If the seed is all zero's, then some default seed
 152  * may be used.
 153  *
 154  * A particular hash version specifies whether or not the seed is
 155  * represented, and whether or not the returned hash is 32 bits or 64
 156  * bits.  32 bit hashes will return 0 for the minor hash.
 157  */
 158 int ext3fs_dirhash(const char *name, int len, struct dx_hash_info *hinfo)
 159 {
 160         __u32   hash;
 161         __u32   minor_hash = 0;
 162         const char      *p;
 163         int             i;
 164         __u32           in[8], buf[4];
 165
 166         /* Initialize the default seed for the hash checksum functions */
 167         buf[0] = 0x67452301;
 168         buf[1] = 0xefcdab89;
 169         buf[2] = 0x98badcfe;
 170         buf[3] = 0x10325476;
 171
 172         /* Check to see if the seed is all zero's */
 173         if (hinfo->seed) {
 174                 for (i=0; i < 4; i++) {
 175                         if (hinfo->seed[i])
 176                                 break;
 177                 }
 178                 if (i < 4)
 179                         memcpy(buf, hinfo->seed, sizeof(buf));
 180         }
 181
 182         switch (hinfo->hash_version) {
 183         case DX_HASH_LEGACY:
 184                 hash = dx_hack_hash(name, len);
 185                 break;
 186         case DX_HASH_HALF_MD4:
 187                 p = name;
 188                 while (len > 0) {
 189                         str2hashbuf(p, len, in, 8);
 190                         halfMD4Transform(buf, in);
 191                         len -= 32;
 192                         p += 32;
 193                 }
 194                 minor_hash = buf[2];
 195                 hash = buf[1];
 196                 break;
 197         case DX_HASH_TEA:
 198                 p = name;
 199                 while (len > 0) {
 200                         str2hashbuf(p, len, in, 4);
 201                         TEA_transform(buf, in);
 202                         len -= 16;
 203                         p += 16;
 204                 }
 205                 hash = buf[0];
 206                 minor_hash = buf[1];
 207                 break;
 208         default:
 209                 hinfo->hash = 0;
 210                 return -1;
 211         }
 212         hash = hash & ~1;
 213         if (hash == (EXT3_HTREE_EOF << 1))
 214                 hash = (EXT3_HTREE_EOF-1) << 1;
 215         hinfo->hash = hash;
 216         hinfo->minor_hash = minor_hash;
 217         return 0;
 218 }