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 static struct work_struct crct10dif_rehash_work;
23
crc_t10dif_notify(struct notifier_block * self,unsigned long val,void * data)24 static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, void *data)
25 {
26 struct crypto_alg *alg = data;
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 schedule_work(&crct10dif_rehash_work);
34 return 0;
35 }
36
crc_t10dif_rehash(struct work_struct * work)37 static void crc_t10dif_rehash(struct work_struct *work)
38 {
39 struct crypto_shash *new, *old;
40
41 mutex_lock(&crc_t10dif_mutex);
42 old = rcu_dereference_protected(crct10dif_tfm,
43 lockdep_is_held(&crc_t10dif_mutex));
44 if (!old) {
45 mutex_unlock(&crc_t10dif_mutex);
46 return;
47 }
48 new = crypto_alloc_shash("crct10dif", 0, 0);
49 if (IS_ERR(new)) {
50 mutex_unlock(&crc_t10dif_mutex);
51 return;
52 }
53 rcu_assign_pointer(crct10dif_tfm, new);
54 mutex_unlock(&crc_t10dif_mutex);
55
56 synchronize_rcu();
57 crypto_free_shash(old);
58 }
59
60 static struct notifier_block crc_t10dif_nb = {
61 .notifier_call = crc_t10dif_notify,
62 };
63
crc_t10dif_update(__u16 crc,const unsigned char * buffer,size_t len)64 __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
65 {
66 struct {
67 struct shash_desc shash;
68 char ctx[2];
69 } desc;
70 int err;
71
72 if (static_key_false(&crct10dif_fallback))
73 return crc_t10dif_generic(crc, buffer, len);
74
75 rcu_read_lock();
76 desc.shash.tfm = rcu_dereference(crct10dif_tfm);
77 *(__u16 *)desc.ctx = crc;
78
79 err = crypto_shash_update(&desc.shash, buffer, len);
80 rcu_read_unlock();
81
82 BUG_ON(err);
83
84 return *(__u16 *)desc.ctx;
85 }
86 EXPORT_SYMBOL(crc_t10dif_update);
87
crc_t10dif(const unsigned char * buffer,size_t len)88 __u16 crc_t10dif(const unsigned char *buffer, size_t len)
89 {
90 return crc_t10dif_update(0, buffer, len);
91 }
92 EXPORT_SYMBOL(crc_t10dif);
93
crc_t10dif_mod_init(void)94 static int __init crc_t10dif_mod_init(void)
95 {
96 struct crypto_shash *tfm;
97
98 INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);
99 crypto_register_notifier(&crc_t10dif_nb);
100 mutex_lock(&crc_t10dif_mutex);
101 tfm = crypto_alloc_shash("crct10dif", 0, 0);
102 if (IS_ERR(tfm)) {
103 static_key_slow_inc(&crct10dif_fallback);
104 tfm = NULL;
105 }
106 RCU_INIT_POINTER(crct10dif_tfm, tfm);
107 mutex_unlock(&crc_t10dif_mutex);
108 return 0;
109 }
110
crc_t10dif_mod_fini(void)111 static void __exit crc_t10dif_mod_fini(void)
112 {
113 crypto_unregister_notifier(&crc_t10dif_nb);
114 cancel_work_sync(&crct10dif_rehash_work);
115 crypto_free_shash(rcu_dereference_protected(crct10dif_tfm, 1));
116 }
117
118 module_init(crc_t10dif_mod_init);
119 module_exit(crc_t10dif_mod_fini);
120
crc_t10dif_transform_show(char * buffer,const struct kernel_param * kp)121 static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
122 {
123 struct crypto_shash *tfm;
124 const char *name;
125 int len;
126
127 if (static_key_false(&crct10dif_fallback))
128 return sprintf(buffer, "fallback\n");
129
130 rcu_read_lock();
131 tfm = rcu_dereference(crct10dif_tfm);
132 if (!tfm) {
133 len = sprintf(buffer, "init\n");
134 goto unlock;
135 }
136
137 name = crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm));
138 len = sprintf(buffer, "%s\n", name);
139
140 unlock:
141 rcu_read_unlock();
142
143 return len;
144 }
145
146 module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
147
148 MODULE_DESCRIPTION("T10 DIF CRC calculation");
149 MODULE_LICENSE("GPL");
150 MODULE_SOFTDEP("pre: crct10dif");
151