1/*
2 * T10 Data Integrity Field CRC16 calculation
3 *
4 * Copyright (c) 2007 Oracle Corporation. All rights reserved.
5 * Written by Martin K. Petersen <martin.petersen@oracle.com>
6 *
7 * This source code is licensed under the GNU General Public License,
8 * Version 2. See the file COPYING for more details.
9 */
10
11#include <linux/types.h>
12#include <linux/module.h>
13#include <linux/crc-t10dif.h>
14#include <linux/err.h>
15#include <linux/init.h>
16#include <crypto/hash.h>
17#include <crypto/algapi.h>
18#include <linux/static_key.h>
19#include <linux/notifier.h>
20
21static struct crypto_shash __rcu *crct10dif_tfm;
22static struct static_key crct10dif_fallback __read_mostly;
23static DEFINE_MUTEX(crc_t10dif_mutex);
24
25static int crc_t10dif_rehash(struct notifier_block *self, unsigned long val, void *data)
26{
27 struct crypto_alg *alg = data;
28 struct crypto_shash *new, *old;
29
30 if (val != CRYPTO_MSG_ALG_LOADED ||
31 static_key_false(&crct10dif_fallback) ||
32 strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
33 return 0;
34
35 mutex_lock(&crc_t10dif_mutex);
36 old = rcu_dereference_protected(crct10dif_tfm,
37 lockdep_is_held(&crc_t10dif_mutex));
38 if (!old) {
39 mutex_unlock(&crc_t10dif_mutex);
40 return 0;
41 }
42 new = crypto_alloc_shash("crct10dif", 0, 0);
43 if (IS_ERR(new)) {
44 mutex_unlock(&crc_t10dif_mutex);
45 return 0;
46 }
47 rcu_assign_pointer(crct10dif_tfm, new);
48 mutex_unlock(&crc_t10dif_mutex);
49
50 synchronize_rcu();
51 crypto_free_shash(old);
52 return 0;
53}
54
55static struct notifier_block crc_t10dif_nb = {
56 .notifier_call = crc_t10dif_rehash,
57};
58
59__u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
60{
61 struct {
62 struct shash_desc shash;
63 char ctx[2];
64 } desc;
65 int err;
66
67 if (static_key_false(&crct10dif_fallback))
68 return crc_t10dif_generic(crc, buffer, len);
69
70 rcu_read_lock();
71 desc.shash.tfm = rcu_dereference(crct10dif_tfm);
72 desc.shash.flags = 0;
73 *(__u16 *)desc.ctx = crc;
74
75 err = crypto_shash_update(&desc.shash, buffer, len);
76 rcu_read_unlock();
77
78 BUG_ON(err);
79
80 return *(__u16 *)desc.ctx;
81}
82EXPORT_SYMBOL(crc_t10dif_update);
83
84__u16 crc_t10dif(const unsigned char *buffer, size_t len)
85{
86 return crc_t10dif_update(0, buffer, len);
87}
88EXPORT_SYMBOL(crc_t10dif);
89
90static int __init crc_t10dif_mod_init(void)
91{
92 crypto_register_notifier(&crc_t10dif_nb);
93 crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);
94 if (IS_ERR(crct10dif_tfm)) {
95 static_key_slow_inc(&crct10dif_fallback);
96 crct10dif_tfm = NULL;
97 }
98 return 0;
99}
100
101static void __exit crc_t10dif_mod_fini(void)
102{
103 crypto_unregister_notifier(&crc_t10dif_nb);
104 crypto_free_shash(crct10dif_tfm);
105}
106
107module_init(crc_t10dif_mod_init);
108module_exit(crc_t10dif_mod_fini);
109
110static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
111{
112 if (static_key_false(&crct10dif_fallback))
113 return sprintf(buffer, "fallback\n");
114
115 return sprintf(buffer, "%s\n",
116 crypto_tfm_alg_driver_name(crypto_shash_tfm(crct10dif_tfm)));
117}
118
119module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
120
121MODULE_DESCRIPTION("T10 DIF CRC calculation");
122MODULE_LICENSE("GPL");
123MODULE_SOFTDEP("pre: crct10dif");
124