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 DEFINE_STATIC_KEY_TRUE(crct10dif_fallback);
21 static DEFINE_MUTEX(crc_t10dif_mutex);
22 static struct work_struct crct10dif_rehash_work;
23
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 strcmp(alg->cra_name, CRC_T10DIF_STRING))
30 return NOTIFY_DONE;
31
32 schedule_work(&crct10dif_rehash_work);
33 return NOTIFY_OK;
34 }
35
36 static void crc_t10dif_rehash(struct work_struct *work)
37 {
38 struct crypto_shash *new, *old;
39
40 mutex_lock(&crc_t10dif_mutex);
41 old = rcu_dereference_protected(crct10dif_tfm,
42 lockdep_is_held(&crc_t10dif_mutex));
43 new = crypto_alloc_shash(CRC_T10DIF_STRING, 0, 0);
44 if (IS_ERR(new)) {
45 mutex_unlock(&crc_t10dif_mutex);
46 return;
47 }
48 rcu_assign_pointer(crct10dif_tfm, new);
49 mutex_unlock(&crc_t10dif_mutex);
50
51 if (old) {
52 synchronize_rcu();
53 crypto_free_shash(old);
54 } else {
55 static_branch_disable(&crct10dif_fallback);
56 }
57 }
58
59 static struct notifier_block crc_t10dif_nb = {
60 .notifier_call = crc_t10dif_notify,
61 };
62
63 __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
64 {
65 struct {
66 struct shash_desc shash;
67 __u16 crc;
68 } desc;
69 int err;
70
71 if (static_branch_unlikely(&crct10dif_fallback))
72 return crc_t10dif_generic(crc, buffer, len);
73
74 rcu_read_lock();
75 desc.shash.tfm = rcu_dereference(crct10dif_tfm);
76 desc.crc = crc;
77 err = crypto_shash_update(&desc.shash, buffer, len);
78 rcu_read_unlock();
79
80 BUG_ON(err);
81
82 return desc.crc;
83 }
84 EXPORT_SYMBOL(crc_t10dif_update);
85
86 __u16 crc_t10dif(const unsigned char *buffer, size_t len)
87 {
88 return crc_t10dif_update(0, buffer, len);
89 }
90 EXPORT_SYMBOL(crc_t10dif);
91
92 static int __init crc_t10dif_mod_init(void)
93 {
94 INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);
95 crypto_register_notifier(&crc_t10dif_nb);
96 crc_t10dif_rehash(&crct10dif_rehash_work);
97 return 0;
98 }
99
100 static void __exit crc_t10dif_mod_fini(void)
101 {
102 crypto_unregister_notifier(&crc_t10dif_nb);
103 cancel_work_sync(&crct10dif_rehash_work);
104 crypto_free_shash(rcu_dereference_protected(crct10dif_tfm, 1));
105 }
106
107 module_init(crc_t10dif_mod_init);
108 module_exit(crc_t10dif_mod_fini);
109
110 static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
111 {
112 struct crypto_shash *tfm;
113 int len;
114
115 if (static_branch_unlikely(&crct10dif_fallback))
116 return sprintf(buffer, "fallback\n");
117
118 rcu_read_lock();
119 tfm = rcu_dereference(crct10dif_tfm);
120 len = snprintf(buffer, PAGE_SIZE, "%s\n",
121 crypto_shash_driver_name(tfm));
122 rcu_read_unlock();
123
124 return len;
125 }
126
127 module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0444);
128
129 MODULE_DESCRIPTION("T10 DIF CRC calculation (library API)");
130 MODULE_LICENSE("GPL");
131 MODULE_SOFTDEP("pre: crct10dif");
132
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