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
crc32c(u32 crc,const void * address,unsigned int length)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
libcrc32c_mod_init(void)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
libcrc32c_mod_fini(void)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