lib/crc-t10dif.c

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