fs/f2fs/hash.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * fs/f2fs/hash.c
   4  *
   5  * Copyright (c) 2012 Samsung Electronics Co., Ltd.
   6  *             http://www.samsung.com/
   7  *
   8  * Portions of this code from linux/fs/ext3/hash.c
   9  *
  10  * Copyright (C) 2002 by Theodore Ts'o
  11  */
  12 #include <linux/types.h>
  13 #include <linux/fs.h>
  14 #include <linux/f2fs_fs.h>
  15 #include <linux/cryptohash.h>
  16 #include <linux/pagemap.h>
  17
  18 #include "f2fs.h"
  19
  20 /*
  21  * Hashing code copied from ext3
  22  */
  23 #define DELTA 0x9E3779B9
  24
  25 static void TEA_transform(unsigned int buf[4], unsigned int const in[])
  26 {
  27         __u32 sum = 0;
  28         __u32 b0 = buf[0], b1 = buf[1];
  29         __u32 a = in[0], b = in[1], c = in[2], d = in[3];
  30         int n = 16;
  31
  32         do {
  33                 sum += DELTA;
  34                 b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
  35                 b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
  36         } while (--n);
  37
  38         buf[0] += b0;
  39         buf[1] += b1;
  40 }
  41
  42 static void str2hashbuf(const unsigned char *msg, size_t len,
  43                                 unsigned int *buf, int num)
  44 {
  45         unsigned pad, val;
  46         int i;
  47
  48         pad = (__u32)len | ((__u32)len << 8);
  49         pad |= pad << 16;
  50
  51         val = pad;
  52         if (len > num * 4)
  53                 len = num * 4;
  54         for (i = 0; i < len; i++) {
  55                 if ((i % 4) == 0)
  56                         val = pad;
  57                 val = msg[i] + (val << 8);
  58                 if ((i % 4) == 3) {
  59                         *buf++ = val;
  60                         val = pad;
  61                         num--;
  62                 }
  63         }
  64         if (--num >= 0)
  65                 *buf++ = val;
  66         while (--num >= 0)
  67                 *buf++ = pad;
  68 }
  69
  70 f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
  71                                 struct fscrypt_name *fname)
  72 {
  73         __u32 hash;
  74         f2fs_hash_t f2fs_hash;
  75         const unsigned char *p;
  76         __u32 in[8], buf[4];
  77         const unsigned char *name = name_info->name;
  78         size_t len = name_info->len;
  79
  80         /* encrypted bigname case */
  81         if (fname && !fname->disk_name.name)
  82                 return cpu_to_le32(fname->hash);
  83
  84         if (is_dot_dotdot(name_info))
  85                 return 0;
  86
  87         /* Initialize the default seed for the hash checksum functions */
  88         buf[0] = 0x67452301;
  89         buf[1] = 0xefcdab89;
  90         buf[2] = 0x98badcfe;
  91         buf[3] = 0x10325476;
  92
  93         p = name;
  94         while (1) {
  95                 str2hashbuf(p, len, in, 4);
  96                 TEA_transform(buf, in);
  97                 p += 16;
  98                 if (len <= 16)
  99                         break;
 100                 len -= 16;
 101         }
 102         hash = buf[0];
 103         f2fs_hash = cpu_to_le32(hash & ~F2FS_HASH_COL_BIT);
 104         return f2fs_hash;
 105 }