1. 根目录:
2. crypto
3. crc32.c

/* GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see http://www.gnu.org/licenses
 *
 * Please  visit http://www.xyratex.com/contact if you need additional
 * information or have any questions.
 *
 * GPL HEADER END
 */

/*
 * Copyright 2012 Xyratex Technology Limited
 */

/*
 * This is crypto api shash wrappers to crc32_le.
 */

#include <linux/crc32.h>
#include <crypto/internal/hash.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/kernel.h>

#define CHKSUM_BLOCK_SIZE	1
#define CHKSUM_DIGEST_SIZE	4

static u32 __crc32_le(u32 crc, unsigned char const *p, size_t len)
{
	return crc32_le(crc, p, len);
}

/** No default init with ~0 */
static int crc32_cra_init(struct crypto_tfm *tfm)
{
	u32 *key = crypto_tfm_ctx(tfm);

	*key = 0;

	return 0;
}


/*
 * Setting the seed allows arbitrary accumulators and flexible XOR policy
 * If your algorithm starts with ~0, then XOR with ~0 before you set
 * the seed.
 */
static int crc32_setkey(struct crypto_shash *hash, const u8 *key,
			unsigned int keylen)
{
	u32 *mctx = crypto_shash_ctx(hash);

	if (keylen != sizeof(u32)) {
		crypto_shash_set_flags(hash, CRYPTO_TFM_RES_BAD_KEY_LEN);
		return -EINVAL;
	}
	*mctx = le32_to_cpup((__le32 *)key);
	return 0;
}

static int crc32_init(struct shash_desc *desc)
{
	u32 *mctx = crypto_shash_ctx(desc->tfm);
	u32 *crcp = shash_desc_ctx(desc);

	*crcp = *mctx;

	return 0;
}

static int crc32_update(struct shash_desc *desc, const u8 *data,
			unsigned int len)
{
	u32 *crcp = shash_desc_ctx(desc);

	*crcp = __crc32_le(*crcp, data, len);
	return 0;
}

/* No final XOR 0xFFFFFFFF, like crc32_le */
static int __crc32_finup(u32 *crcp, const u8 *data, unsigned int len,
			 u8 *out)
{
	*(__le32 *)out = cpu_to_le32(__crc32_le(*crcp, data, len));
	return 0;
}

static int crc32_finup(struct shash_desc *desc, const u8 *data,
		       unsigned int len, u8 *out)
{
	return __crc32_finup(shash_desc_ctx(desc), data, len, out);
}

static int crc32_final(struct shash_desc *desc, u8 *out)
{
	u32 *crcp = shash_desc_ctx(desc);

	*(__le32 *)out = cpu_to_le32p(crcp);
	return 0;
}

static int crc32_digest(struct shash_desc *desc, const u8 *data,
			unsigned int len, u8 *out)
{
	return __crc32_finup(crypto_shash_ctx(desc->tfm), data, len,
			     out);
}
static struct shash_alg alg = {
	.setkey		= crc32_setkey,
	.init		= crc32_init,
	.update		= crc32_update,
	.final		= crc32_final,
	.finup		= crc32_finup,
	.digest		= crc32_digest,
	.descsize	= sizeof(u32),
	.digestsize	= CHKSUM_DIGEST_SIZE,
	.base		= {
		.cra_name		= "crc32",
		.cra_driver_name	= "crc32-table",
		.cra_priority		= 100,
		.cra_blocksize		= CHKSUM_BLOCK_SIZE,
		.cra_ctxsize		= sizeof(u32),
		.cra_module		= THIS_MODULE,
		.cra_init		= crc32_cra_init,
	}
};

static int __init crc32_mod_init(void)
{
	return crypto_register_shash(&alg);
}

static void __exit crc32_mod_fini(void)
{
	crypto_unregister_shash(&alg);
}

module_init(crc32_mod_init);
module_exit(crc32_mod_fini);

MODULE_AUTHOR("Alexander Boyko <alexander_boyko@xyratex.com>");
MODULE_DESCRIPTION("CRC32 calculations wrapper for lib/crc32");
MODULE_LICENSE("GPL");