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 21 static struct crypto_shash __rcu *crct10dif_tfm; 22 static struct static_key crct10dif_fallback __read_mostly; 23 static DEFINE_MUTEX(crc_t10dif_mutex); 24 25 static 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 55 static 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 } 82 EXPORT_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 } 88 EXPORT_SYMBOL(crc_t10dif); 89 90 static 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 } 100 101 static void __exit crc_t10dif_mod_fini(void) 102 { 103 crypto_unregister_notifier(&crc_t10dif_nb); 104 crypto_free_shash(crct10dif_tfm); 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 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 } 118 119 module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644); 120 121 MODULE_DESCRIPTION("T10 DIF CRC calculation"); 122 MODULE_LICENSE("GPL"); 123 MODULE_SOFTDEP("pre: crct10dif"); 124