xref: /openbmc/linux/fs/f2fs/hash.c (revision 0be1511f)
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/pagemap.h>
16  #include <linux/unicode.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  static u32 TEA_hash_name(const u8 *p, size_t len)
71  {
72  	__u32 in[8], buf[4];
73  
74  	/* Initialize the default seed for the hash checksum functions */
75  	buf[0] = 0x67452301;
76  	buf[1] = 0xefcdab89;
77  	buf[2] = 0x98badcfe;
78  	buf[3] = 0x10325476;
79  
80  	while (1) {
81  		str2hashbuf(p, len, in, 4);
82  		TEA_transform(buf, in);
83  		p += 16;
84  		if (len <= 16)
85  			break;
86  		len -= 16;
87  	}
88  	return buf[0] & ~F2FS_HASH_COL_BIT;
89  }
90  
91  /*
92   * Compute @fname->hash.  For all directories, @fname->disk_name must be set.
93   * For casefolded directories, @fname->usr_fname must be set, and also
94   * @fname->cf_name if the filename is valid Unicode.
95   */
96  void f2fs_hash_filename(const struct inode *dir, struct f2fs_filename *fname)
97  {
98  	const u8 *name = fname->disk_name.name;
99  	size_t len = fname->disk_name.len;
100  
101  	WARN_ON_ONCE(!name);
102  
103  	if (is_dot_dotdot(name, len)) {
104  		fname->hash = 0;
105  		return;
106  	}
107  
108  #ifdef CONFIG_UNICODE
109  	if (IS_CASEFOLDED(dir)) {
110  		/*
111  		 * If the casefolded name is provided, hash it instead of the
112  		 * on-disk name.  If the casefolded name is *not* provided, that
113  		 * should only be because the name wasn't valid Unicode, so fall
114  		 * back to treating the name as an opaque byte sequence.  Note
115  		 * that to handle encrypted directories, the fallback must use
116  		 * usr_fname (plaintext) rather than disk_name (ciphertext).
117  		 */
118  		WARN_ON_ONCE(!fname->usr_fname->name);
119  		if (fname->cf_name.name) {
120  			name = fname->cf_name.name;
121  			len = fname->cf_name.len;
122  		} else {
123  			name = fname->usr_fname->name;
124  			len = fname->usr_fname->len;
125  		}
126  		if (IS_ENCRYPTED(dir)) {
127  			struct qstr tmp = QSTR_INIT(name, len);
128  
129  			fname->hash =
130  				cpu_to_le32(fscrypt_fname_siphash(dir, &tmp));
131  			return;
132  		}
133  	}
134  #endif
135  	fname->hash = cpu_to_le32(TEA_hash_name(name, len));
136  }
137