LXR linux/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
  19static struct crypto_shash __rcu *crct10dif_tfm;
  20static struct static_key crct10dif_fallback __read_mostly;
  21static DEFINE_MUTEX(crc_t10dif_mutex);
  22
  23static 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
  53static 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}
  79EXPORT_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}
  85EXPORT_SYMBOL(crc_t10dif);
  86
  87static 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
  98static void __exit crc_t10dif_mod_fini(void)
  99{
 100        crypto_unregister_notifier(&crc_t10dif_nb);
 101        crypto_free_shash(crct10dif_tfm);
 102}
 103
 104module_init(crc_t10dif_mod_init);
 105module_exit(crc_t10dif_mod_fini);
 106
 107static 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
 116module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
 117
 118MODULE_DESCRIPTION("T10 DIF CRC calculation");
 119MODULE_LICENSE("GPL");
 120MODULE_SOFTDEP("pre: crct10dif");
 121