// SPDX-License-Identifier: GPL-2.0-only

  /*
   * T10 Data Integrity Field CRC16 calculation
   *
   * Copyright (c) 2007 Oracle Corporation.  All rights reserved.
   * Written by Martin K. Petersen <martin.petersen@oracle.com>

   */
  
  #include <linux/types.h>
  #include <linux/module.h>
  #include <linux/crc-t10dif.h>

  #include <linux/err.h>
  #include <linux/init.h>
  #include <crypto/hash.h>

  #include <crypto/algapi.h>

  #include <linux/static_key.h>

  #include <linux/notifier.h>

  static struct crypto_shash __rcu *crct10dif_tfm;

  static struct static_key crct10dif_fallback __read_mostly;

  static DEFINE_MUTEX(crc_t10dif_mutex);

  static struct work_struct crct10dif_rehash_work;

  static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, void *data)

  {
  	struct crypto_alg *alg = data;

  
  	if (val != CRYPTO_MSG_ALG_LOADED ||
  	    static_key_false(&crct10dif_fallback) ||
  	    strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
  		return 0;

  	schedule_work(&crct10dif_rehash_work);
  	return 0;
  }
  
  static void crc_t10dif_rehash(struct work_struct *work)
  {
  	struct crypto_shash *new, *old;

  	mutex_lock(&crc_t10dif_mutex);
  	old = rcu_dereference_protected(crct10dif_tfm,
  					lockdep_is_held(&crc_t10dif_mutex));
  	if (!old) {
  		mutex_unlock(&crc_t10dif_mutex);

  		return;

  	}
  	new = crypto_alloc_shash("crct10dif", 0, 0);
  	if (IS_ERR(new)) {
  		mutex_unlock(&crc_t10dif_mutex);

  		return;

  	}
  	rcu_assign_pointer(crct10dif_tfm, new);
  	mutex_unlock(&crc_t10dif_mutex);
  
  	synchronize_rcu();
  	crypto_free_shash(old);

  }
  
  static struct notifier_block crc_t10dif_nb = {

  	.notifier_call = crc_t10dif_notify,

  };

  __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)

  {

  	struct {
  		struct shash_desc shash;
  		char ctx[2];
  	} desc;
  	int err;

  	if (static_key_false(&crct10dif_fallback))

  		return crc_t10dif_generic(crc, buffer, len);

  	rcu_read_lock();
  	desc.shash.tfm = rcu_dereference(crct10dif_tfm);

  	*(__u16 *)desc.ctx = crc;

  	err = crypto_shash_update(&desc.shash, buffer, len);

  	rcu_read_unlock();

  	BUG_ON(err);

  	return *(__u16 *)desc.ctx;

  }

  EXPORT_SYMBOL(crc_t10dif_update);
  
  __u16 crc_t10dif(const unsigned char *buffer, size_t len)
  {
  	return crc_t10dif_update(0, buffer, len);
  }

  EXPORT_SYMBOL(crc_t10dif);

  static int __init crc_t10dif_mod_init(void)
  {

  	struct crypto_shash *tfm;
  
  	INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);

  	crypto_register_notifier(&crc_t10dif_nb);

  	mutex_lock(&crc_t10dif_mutex);
  	tfm = crypto_alloc_shash("crct10dif", 0, 0);
  	if (IS_ERR(tfm)) {

  		static_key_slow_inc(&crct10dif_fallback);

  		tfm = NULL;

  	}

  	RCU_INIT_POINTER(crct10dif_tfm, tfm);
  	mutex_unlock(&crc_t10dif_mutex);

  	return 0;

  }
  
  static void __exit crc_t10dif_mod_fini(void)
  {

  	crypto_unregister_notifier(&crc_t10dif_nb);

  	cancel_work_sync(&crct10dif_rehash_work);
  	crypto_free_shash(rcu_dereference_protected(crct10dif_tfm, 1));

  }
  
  module_init(crc_t10dif_mod_init);
  module_exit(crc_t10dif_mod_fini);

  static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
  {

  	struct crypto_shash *tfm;
  	const char *name;
  	int len;

  	if (static_key_false(&crct10dif_fallback))
  		return sprintf(buffer, "fallback
  ");

  	rcu_read_lock();
  	tfm = rcu_dereference(crct10dif_tfm);
  	if (!tfm) {
  		len = sprintf(buffer, "init
  ");
  		goto unlock;
  	}
  
  	name = crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm));
  	len = sprintf(buffer, "%s
  ", name);
  
  unlock:
  	rcu_read_unlock();
  
  	return len;

  }
  
  module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);

  MODULE_DESCRIPTION("T10 DIF CRC calculation");
  MODULE_LICENSE("GPL");

  MODULE_SOFTDEP("pre: crct10dif");