LXR linux/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
  21static struct crypto_shash __rcu *crct10dif_tfm;
  22static struct static_key crct10dif_fallback __read_mostly;
  23static DEFINE_MUTEX(crc_t10dif_mutex);
  24
  25static 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
  55static 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}
  82EXPORT_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}
  88EXPORT_SYMBOL(crc_t10dif);
  89
  90static 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
 101static void __exit crc_t10dif_mod_fini(void)
 102{
 103        crypto_unregister_notifier(&crc_t10dif_nb);
 104        crypto_free_shash(crct10dif_tfm);
 105}
 106
 107module_init(crc_t10dif_mod_init);
 108module_exit(crc_t10dif_mod_fini);
 109
 110static 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
 119module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
 120
 121MODULE_DESCRIPTION("T10 DIF CRC calculation");
 122MODULE_LICENSE("GPL");
 123MODULE_SOFTDEP("pre: crct10dif");
 124