1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * T10 Data Integrity Field CRC16 calculation
4 *
5 * Copyright (c) 2007 Oracle Corporation. All rights reserved.
6 * Written by Martin K. Petersen <martin.petersen@oracle.com>
7 */
8
9 #include <linux/types.h>
10 #include <linux/module.h>
11 #include <linux/crc-t10dif.h>
12 #include <linux/err.h>
13 #include <linux/init.h>
14 #include <crypto/hash.h>
15 #include <crypto/algapi.h>
16 #include <linux/static_key.h>
17 #include <linux/notifier.h>
18
19 static struct crypto_shash __rcu *crct10dif_tfm;
20 static struct static_key crct10dif_fallback __read_mostly;
21 static DEFINE_MUTEX(crc_t10dif_mutex);
22
crc_t10dif_rehash(struct notifier_block * self,unsigned long val,void * data)23 static int crc_t10dif_rehash(struct notifier_block *self, unsigned long val, void *data)
24 {
25 struct crypto_alg *alg = data;
26 struct crypto_shash *new, *old;
27
28 if (val != CRYPTO_MSG_ALG_LOADED ||
29 static_key_false(&crct10dif_fallback) ||
30 strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
31 return 0;
32
33 mutex_lock(&crc_t10dif_mutex);
34 old = rcu_dereference_protected(crct10dif_tfm,
35 lockdep_is_held(&crc_t10dif_mutex));
36 if (!old) {
37 mutex_unlock(&crc_t10dif_mutex);
38 return 0;
39 }
40 new = crypto_alloc_shash("crct10dif", 0, 0);
41 if (IS_ERR(new)) {
42 mutex_unlock(&crc_t10dif_mutex);
43 return 0;
44 }
45 rcu_assign_pointer(crct10dif_tfm, new);
46 mutex_unlock(&crc_t10dif_mutex);
47
48 synchronize_rcu();
49 crypto_free_shash(old);
50 return 0;
51 }
52
53 static struct notifier_block crc_t10dif_nb = {
54 .notifier_call = crc_t10dif_rehash,
55 };
56
crc_t10dif_update(__u16 crc,const unsigned char * buffer,size_t len)57 __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
58 {
59 struct {
60 struct shash_desc shash;
61 char ctx[2];
62 } desc;
63 int err;
64
65 if (static_key_false(&crct10dif_fallback))
66 return crc_t10dif_generic(crc, buffer, len);
67
68 rcu_read_lock();
69 desc.shash.tfm = rcu_dereference(crct10dif_tfm);
70 *(__u16 *)desc.ctx = crc;
71
72 err = crypto_shash_update(&desc.shash, buffer, len);
73 rcu_read_unlock();
74
75 BUG_ON(err);
76
77 return *(__u16 *)desc.ctx;
78 }
79 EXPORT_SYMBOL(crc_t10dif_update);
80
crc_t10dif(const unsigned char * buffer,size_t len)81 __u16 crc_t10dif(const unsigned char *buffer, size_t len)
82 {
83 return crc_t10dif_update(0, buffer, len);
84 }
85 EXPORT_SYMBOL(crc_t10dif);
86
crc_t10dif_mod_init(void)87 static int __init crc_t10dif_mod_init(void)
88 {
89 crypto_register_notifier(&crc_t10dif_nb);
90 crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);
91 if (IS_ERR(crct10dif_tfm)) {
92 static_key_slow_inc(&crct10dif_fallback);
93 crct10dif_tfm = NULL;
94 }
95 return 0;
96 }
97
crc_t10dif_mod_fini(void)98 static void __exit crc_t10dif_mod_fini(void)
99 {
100 crypto_unregister_notifier(&crc_t10dif_nb);
101 crypto_free_shash(crct10dif_tfm);
102 }
103
104 module_init(crc_t10dif_mod_init);
105 module_exit(crc_t10dif_mod_fini);
106
crc_t10dif_transform_show(char * buffer,const struct kernel_param * kp)107 static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
108 {
109 if (static_key_false(&crct10dif_fallback))
110 return sprintf(buffer, "fallback\n");
111
112 return sprintf(buffer, "%s\n",
113 crypto_tfm_alg_driver_name(crypto_shash_tfm(crct10dif_tfm)));
114 }
115
116 module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
117
118 MODULE_DESCRIPTION("T10 DIF CRC calculation");
119 MODULE_LICENSE("GPL");
120 MODULE_SOFTDEP("pre: crct10dif");
121