1/*
  2 * fs/f2fs/hash.c
  3 *
  4 * Copyright (c) 2012 Samsung Electronics Co., Ltd.
  5 *             http://www.samsung.com/
  6 *
  7 * Portions of this code from linux/fs/ext3/hash.c
  8 *
  9 * Copyright (C) 2002 by Theodore Ts'o
 10 *
 11 * This program is free software; you can redistribute it and/or modify
 12 * it under the terms of the GNU General Public License version 2 as
 13 * published by the Free Software Foundation.
 14 */
 15#include <linux/types.h>
 16#include <linux/fs.h>
 17#include <linux/f2fs_fs.h>
 18#include <linux/cryptohash.h>
 19#include <linux/pagemap.h>
 20
 21#include "f2fs.h"
 22
 23/*
 24 * Hashing code copied from ext3
 25 */
 26#define DELTA 0x9E3779B9
 27
 28static void TEA_transform(unsigned int buf[4], unsigned int const in[])
 29{
 30	__u32 sum = 0;
 31	__u32 b0 = buf[0], b1 = buf[1];
 32	__u32 a = in[0], b = in[1], c = in[2], d = in[3];
 33	int n = 16;
 34
 35	do {
 36		sum += DELTA;
 37		b0 += ((b1 << 4)+a) ^ (b1+sum) ^ ((b1 >> 5)+b);
 38		b1 += ((b0 << 4)+c) ^ (b0+sum) ^ ((b0 >> 5)+d);
 39	} while (--n);
 40
 41	buf[0] += b0;
 42	buf[1] += b1;
 43}
 44
 45static void str2hashbuf(const unsigned char *msg, size_t len,
 46				unsigned int *buf, int num)
 47{
 48	unsigned pad, val;
 49	int i;
 50
 51	pad = (__u32)len | ((__u32)len << 8);
 52	pad |= pad << 16;
 53
 54	val = pad;
 55	if (len > num * 4)
 56		len = num * 4;
 57	for (i = 0; i < len; i++) {
 58		if ((i % 4) == 0)
 59			val = pad;
 60		val = msg[i] + (val << 8);
 61		if ((i % 4) == 3) {
 62			*buf++ = val;
 63			val = pad;
 64			num--;
 65		}
 66	}
 67	if (--num >= 0)
 68		*buf++ = val;
 69	while (--num >= 0)
 70		*buf++ = pad;
 71}
 72
 73f2fs_hash_t f2fs_dentry_hash(const struct qstr *name_info,
 74				struct fscrypt_name *fname)
 75{
 76	__u32 hash;
 77	f2fs_hash_t f2fs_hash;
 78	const unsigned char *p;
 79	__u32 in[8], buf[4];
 80	const unsigned char *name = name_info->name;
 81	size_t len = name_info->len;
 82
 83	/* encrypted bigname case */
 84	if (fname && !fname->disk_name.name)
 85		return cpu_to_le32(fname->hash);
 86
 87	if (is_dot_dotdot(name_info))
 88		return 0;
 89
 90	/* Initialize the default seed for the hash checksum functions */
 91	buf[0] = 0x67452301;
 92	buf[1] = 0xefcdab89;
 93	buf[2] = 0x98badcfe;
 94	buf[3] = 0x10325476;
 95
 96	p = name;
 97	while (1) {
 98		str2hashbuf(p, len, in, 4);
 99		TEA_transform(buf, in);
100		p += 16;
101		if (len <= 16)
102			break;
103		len -= 16;
104	}
105	hash = buf[0];
106	f2fs_hash = cpu_to_le32(hash & ~F2FS_HASH_COL_BIT);
107	return f2fs_hash;
108}