xref: /linux/lib/crc-t10dif.c (revision 4b4193256c8d3bc3a5397b5cd9494c2ad386317d)
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 
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 	    strcmp(alg->cra_name, CRC_T10DIF_STRING))
30 		return NOTIFY_DONE;
31 
32 	schedule_work(&crct10dif_rehash_work);
33 	return NOTIFY_OK;
34 }
35 
crc_t10dif_rehash(struct work_struct * work)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 
crc_t10dif_update(__u16 crc,const unsigned char * buffer,size_t len)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 
crc_t10dif(const unsigned char * buffer,size_t len)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 
crc_t10dif_mod_init(void)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 
crc_t10dif_mod_fini(void)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 
crc_t10dif_transform_show(char * buffer,const struct kernel_param * kp)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