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Linux/lib/crc-t10dif.c

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  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 DEFINE_STATIC_KEY_TRUE(crct10dif_fallback);
 21 static DEFINE_MUTEX(crc_t10dif_mutex);
 22 static struct work_struct crct10dif_rehash_work;
 23 
 24 static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, void *data)
 25 {
 26         struct crypto_alg *alg = data;
 27 
 28         if (val != CRYPTO_MSG_ALG_LOADED ||
 29             strcmp(alg->cra_name, CRC_T10DIF_STRING))
 30                 return NOTIFY_DONE;
 31 
 32         schedule_work(&crct10dif_rehash_work);
 33         return NOTIFY_OK;
 34 }
 35 
 36 static void crc_t10dif_rehash(struct work_struct *work)
 37 {
 38         struct crypto_shash *new, *old;
 39 
 40         mutex_lock(&crc_t10dif_mutex);
 41         old = rcu_dereference_protected(crct10dif_tfm,
 42                                         lockdep_is_held(&crc_t10dif_mutex));
 43         new = crypto_alloc_shash(CRC_T10DIF_STRING, 0, 0);
 44         if (IS_ERR(new)) {
 45                 mutex_unlock(&crc_t10dif_mutex);
 46                 return;
 47         }
 48         rcu_assign_pointer(crct10dif_tfm, new);
 49         mutex_unlock(&crc_t10dif_mutex);
 50 
 51         if (old) {
 52                 synchronize_rcu();
 53                 crypto_free_shash(old);
 54         } else {
 55                 static_branch_disable(&crct10dif_fallback);
 56         }
 57 }
 58 
 59 static struct notifier_block crc_t10dif_nb = {
 60         .notifier_call = crc_t10dif_notify,
 61 };
 62 
 63 __u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
 64 {
 65         struct {
 66                 struct shash_desc shash;
 67                 __u16 crc;
 68         } desc;
 69         int err;
 70 
 71         if (static_branch_unlikely(&crct10dif_fallback))
 72                 return crc_t10dif_generic(crc, buffer, len);
 73 
 74         rcu_read_lock();
 75         desc.shash.tfm = rcu_dereference(crct10dif_tfm);
 76         desc.crc = crc;
 77         err = crypto_shash_update(&desc.shash, buffer, len);
 78         rcu_read_unlock();
 79 
 80         BUG_ON(err);
 81 
 82         return desc.crc;
 83 }
 84 EXPORT_SYMBOL(crc_t10dif_update);
 85 
 86 __u16 crc_t10dif(const unsigned char *buffer, size_t len)
 87 {
 88         return crc_t10dif_update(0, buffer, len);
 89 }
 90 EXPORT_SYMBOL(crc_t10dif);
 91 
 92 static int __init crc_t10dif_mod_init(void)
 93 {
 94         INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);
 95         crypto_register_notifier(&crc_t10dif_nb);
 96         crc_t10dif_rehash(&crct10dif_rehash_work);
 97         return 0;
 98 }
 99 
100 static void __exit crc_t10dif_mod_fini(void)
101 {
102         crypto_unregister_notifier(&crc_t10dif_nb);
103         cancel_work_sync(&crct10dif_rehash_work);
104         crypto_free_shash(rcu_dereference_protected(crct10dif_tfm, 1));
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         struct crypto_shash *tfm;
113         int len;
114 
115         if (static_branch_unlikely(&crct10dif_fallback))
116                 return sprintf(buffer, "fallback\n");
117 
118         rcu_read_lock();
119         tfm = rcu_dereference(crct10dif_tfm);
120         len = snprintf(buffer, PAGE_SIZE, "%s\n",
121                        crypto_shash_driver_name(tfm));
122         rcu_read_unlock();
123 
124         return len;
125 }
126 
127 module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0444);
128 
129 MODULE_DESCRIPTION("T10 DIF CRC calculation (library API)");
130 MODULE_LICENSE("GPL");
131 MODULE_SOFTDEP("pre: crct10dif");
132 

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