lib/crc-t10dif.c

   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");