1 /* 2 * CRC32C 3 *@Article{castagnoli-crc, 4 * author = { Guy Castagnoli and Stefan Braeuer and Martin Herrman}, 5 * title = {{Optimization of Cyclic Redundancy-Check Codes with 24 6 * and 32 Parity Bits}}, 7 * journal = IEEE Transactions on Communication, 8 * year = {1993}, 9 * volume = {41}, 10 * number = {6}, 11 * pages = {}, 12 * month = {June}, 13 *} 14 * Used by the iSCSI driver, possibly others, and derived from the 15 * the iscsi-crc.c module of the linux-iscsi driver at 16 * http://linux-iscsi.sourceforge.net. 17 * 18 * Following the example of lib/crc32, this function is intended to be 19 * flexible and useful for all users. Modules that currently have their 20 * own crc32c, but hopefully may be able to use this one are: 21 * net/sctp (please add all your doco to here if you change to 22 * use this one!) 23 * <endoflist> 24 * 25 * Copyright (c) 2004 Cisco Systems, Inc. 26 * 27 * This program is free software; you can redistribute it and/or modify it 28 * under the terms of the GNU General Public License as published by the Free 29 * Software Foundation; either version 2 of the License, or (at your option) 30 * any later version. 31 * 32 */ 33 34 #include <crypto/hash.h> 35 #include <linux/err.h> 36 #include <linux/init.h> 37 #include <linux/kernel.h> 38 #include <linux/module.h> 39 40 static struct crypto_shash *tfm; 41 42 u32 crc32c(u32 crc, const void *address, unsigned int length) 43 { 44 struct { 45 struct shash_desc shash; 46 char ctx[crypto_shash_descsize(tfm)]; 47 } desc; 48 int err; 49 50 desc.shash.tfm = tfm; 51 desc.shash.flags = 0; 52 *(u32 *)desc.ctx = crc; 53 54 err = crypto_shash_update(&desc.shash, address, length); 55 BUG_ON(err); 56 57 return *(u32 *)desc.ctx; 58 } 59 60 EXPORT_SYMBOL(crc32c); 61 62 static int __init libcrc32c_mod_init(void) 63 { 64 tfm = crypto_alloc_shash("crc32c", 0, 0); 65 if (IS_ERR(tfm)) 66 return PTR_ERR(tfm); 67 68 return 0; 69 } 70 71 static void __exit libcrc32c_mod_fini(void) 72 { 73 crypto_free_shash(tfm); 74 } 75 76 module_init(libcrc32c_mod_init); 77 module_exit(libcrc32c_mod_fini); 78 79 MODULE_AUTHOR("Clay Haapala <chaapala@cisco.com>"); 80 MODULE_DESCRIPTION("CRC32c (Castagnoli) calculations"); 81 MODULE_LICENSE("GPL"); 82