crc32c_generic.c 4.37 KB
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/*
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 * Cryptographic API.
 *
 * CRC32C chksum
 *
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 *@Article{castagnoli-crc,
 * author =       { Guy Castagnoli and Stefan Braeuer and Martin Herrman},
 * title =        {{Optimization of Cyclic Redundancy-Check Codes with 24
 *                 and 32 Parity Bits}},
 * journal =      IEEE Transactions on Communication,
 * year =         {1993},
 * volume =       {41},
 * number =       {6},
 * pages =        {},
 * month =        {June},
 *}
 * Used by the iSCSI driver, possibly others, and derived from the
 * the iscsi-crc.c module of the linux-iscsi driver at
 * http://linux-iscsi.sourceforge.net.
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 *
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 * Following the example of lib/crc32, this function is intended to be
 * flexible and useful for all users.  Modules that currently have their
 * own crc32c, but hopefully may be able to use this one are:
 *  net/sctp (please add all your doco to here if you change to
 *            use this one!)
 *  <endoflist>
 *
 * Copyright (c) 2004 Cisco Systems, Inc.
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 * Copyright (c) 2008 Herbert Xu <herbert@gondor.apana.org.au>
 *
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 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
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 * Software Foundation; either version 2 of the License, or (at your option)
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 * any later version.
 *
 */
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#include <asm/unaligned.h>
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#include <crypto/internal/hash.h>
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#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
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#include <linux/kernel.h>
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#include <linux/crc32.h>
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#define CHKSUM_BLOCK_SIZE	1
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#define CHKSUM_DIGEST_SIZE	4

struct chksum_ctx {
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	u32 key;
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};

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struct chksum_desc_ctx {
	u32 crc;
};

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/*
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 * Steps through buffer one byte at at time, calculates reflected
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 * crc using table.
 */

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static int chksum_init(struct shash_desc *desc)
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{
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	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);

	ctx->crc = mctx->key;
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	return 0;
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}

/*
 * 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.
 */
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static int chksum_setkey(struct crypto_shash *tfm, const u8 *key,
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			 unsigned int keylen)
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{
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	struct chksum_ctx *mctx = crypto_shash_ctx(tfm);
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	if (keylen != sizeof(mctx->key)) {
		crypto_shash_set_flags(tfm, CRYPTO_TFM_RES_BAD_KEY_LEN);
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		return -EINVAL;
	}
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	mctx->key = get_unaligned_le32(key);
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	return 0;
}

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static int chksum_update(struct shash_desc *desc, const u8 *data,
			 unsigned int length)
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{
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	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
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	ctx->crc = __crc32c_le(ctx->crc, data, length);
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	return 0;
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}

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static int chksum_final(struct shash_desc *desc, u8 *out)
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{
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	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
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	put_unaligned_le32(~ctx->crc, out);
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	return 0;
}

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static int __chksum_finup(u32 *crcp, const u8 *data, unsigned int len, u8 *out)
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{
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	put_unaligned_le32(~__crc32c_le(*crcp, data, len), out);
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	return 0;
}

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static int chksum_finup(struct shash_desc *desc, const u8 *data,
			unsigned int len, u8 *out)
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{
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	struct chksum_desc_ctx *ctx = shash_desc_ctx(desc);
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	return __chksum_finup(&ctx->crc, data, len, out);
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}

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static int chksum_digest(struct shash_desc *desc, const u8 *data,
			 unsigned int length, u8 *out)
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{
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	struct chksum_ctx *mctx = crypto_shash_ctx(desc->tfm);
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	return __chksum_finup(&mctx->key, data, length, out);
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}

static int crc32c_cra_init(struct crypto_tfm *tfm)
{
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	struct chksum_ctx *mctx = crypto_tfm_ctx(tfm);
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	mctx->key = ~0;
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	return 0;
}

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static struct shash_alg alg = {
	.digestsize		=	CHKSUM_DIGEST_SIZE,
	.setkey			=	chksum_setkey,
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	.init		=	chksum_init,
	.update		=	chksum_update,
	.final		=	chksum_final,
	.finup		=	chksum_finup,
	.digest		=	chksum_digest,
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	.descsize		=	sizeof(struct chksum_desc_ctx),
	.base			=	{
		.cra_name		=	"crc32c",
		.cra_driver_name	=	"crc32c-generic",
		.cra_priority		=	100,
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		.cra_flags		=	CRYPTO_ALG_OPTIONAL_KEY,
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		.cra_blocksize		=	CHKSUM_BLOCK_SIZE,
		.cra_ctxsize		=	sizeof(struct chksum_ctx),
		.cra_module		=	THIS_MODULE,
		.cra_init		=	crc32c_cra_init,
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	}
};

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static int __init crc32c_mod_init(void)
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{
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	return crypto_register_shash(&alg);
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}

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static void __exit crc32c_mod_fini(void)
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{
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	crypto_unregister_shash(&alg);
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}

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module_init(crc32c_mod_init);
module_exit(crc32c_mod_fini);
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MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>");
MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations wrapper for lib/crc32c");
MODULE_LICENSE("GPL");
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MODULE_ALIAS_CRYPTO("crc32c");
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MODULE_ALIAS_CRYPTO("crc32c-generic");