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crc-t10dif: use fallback in initial state
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40b0b3f8 1// SPDX-License-Identifier: GPL-2.0-only
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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>
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7 */
8
9#include <linux/types.h>
10#include <linux/module.h>
11#include <linux/crc-t10dif.h>
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12#include <linux/err.h>
13#include <linux/init.h>
14#include <crypto/hash.h>
b7637754 15#include <crypto/algapi.h>
26052f9b 16#include <linux/static_key.h>
b7637754 17#include <linux/notifier.h>
f11f594e 18
b7637754 19static struct crypto_shash __rcu *crct10dif_tfm;
be924e0a 20static DEFINE_STATIC_KEY_TRUE(crct10dif_fallback);
a7e7edfe 21static DEFINE_MUTEX(crc_t10dif_mutex);
3906f640 22static struct work_struct crct10dif_rehash_work;
b7637754 23
3906f640 24static int crc_t10dif_notify(struct notifier_block *self, unsigned long val, void *data)
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25{
26 struct crypto_alg *alg = data;
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27
28 if (val != CRYPTO_MSG_ALG_LOADED ||
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29 strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
30 return 0;
31
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32 schedule_work(&crct10dif_rehash_work);
33 return 0;
34}
35
36static void crc_t10dif_rehash(struct work_struct *work)
37{
38 struct crypto_shash *new, *old;
39
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40 mutex_lock(&crc_t10dif_mutex);
41 old = rcu_dereference_protected(crct10dif_tfm,
42 lockdep_is_held(&crc_t10dif_mutex));
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43 new = crypto_alloc_shash("crct10dif", 0, 0);
44 if (IS_ERR(new)) {
45 mutex_unlock(&crc_t10dif_mutex);
3906f640 46 return;
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47 }
48 rcu_assign_pointer(crct10dif_tfm, new);
49 mutex_unlock(&crc_t10dif_mutex);
50
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51 if (old) {
52 synchronize_rcu();
53 crypto_free_shash(old);
54 } else {
55 static_branch_disable(&crct10dif_fallback);
56 }
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57}
58
59static struct notifier_block crc_t10dif_nb = {
3906f640 60 .notifier_call = crc_t10dif_notify,
b7637754 61};
f11f594e 62
10081fb5 63__u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
f11f594e 64{
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65 struct {
66 struct shash_desc shash;
67 char ctx[2];
68 } desc;
69 int err;
70
be924e0a 71 if (static_branch_unlikely(&crct10dif_fallback))
10081fb5 72 return crc_t10dif_generic(crc, buffer, len);
26052f9b 73
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74 rcu_read_lock();
75 desc.shash.tfm = rcu_dereference(crct10dif_tfm);
10081fb5 76 *(__u16 *)desc.ctx = crc;
f11f594e 77
68411521 78 err = crypto_shash_update(&desc.shash, buffer, len);
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79 rcu_read_unlock();
80
68411521 81 BUG_ON(err);
f11f594e 82
68411521 83 return *(__u16 *)desc.ctx;
f11f594e 84}
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85EXPORT_SYMBOL(crc_t10dif_update);
86
87__u16 crc_t10dif(const unsigned char *buffer, size_t len)
88{
89 return crc_t10dif_update(0, buffer, len);
90}
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91EXPORT_SYMBOL(crc_t10dif);
92
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93static int __init crc_t10dif_mod_init(void)
94{
3906f640 95 INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);
b7637754 96 crypto_register_notifier(&crc_t10dif_nb);
be924e0a 97 crc_t10dif_rehash(&crct10dif_rehash_work);
26052f9b 98 return 0;
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99}
100
101static void __exit crc_t10dif_mod_fini(void)
102{
b7637754 103 crypto_unregister_notifier(&crc_t10dif_nb);
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104 cancel_work_sync(&crct10dif_rehash_work);
105 crypto_free_shash(rcu_dereference_protected(crct10dif_tfm, 1));
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106}
107
108module_init(crc_t10dif_mod_init);
109module_exit(crc_t10dif_mod_fini);
110
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111static int crc_t10dif_transform_show(char *buffer, const struct kernel_param *kp)
112{
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113 struct crypto_shash *tfm;
114 const char *name;
115 int len;
116
be924e0a 117 if (static_branch_unlikely(&crct10dif_fallback))
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118 return sprintf(buffer, "fallback\n");
119
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120 rcu_read_lock();
121 tfm = rcu_dereference(crct10dif_tfm);
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122 name = crypto_tfm_alg_driver_name(crypto_shash_tfm(tfm));
123 len = sprintf(buffer, "%s\n", name);
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124 rcu_read_unlock();
125
126 return len;
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127}
128
129module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
130
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131MODULE_DESCRIPTION("T10 DIF CRC calculation");
132MODULE_LICENSE("GPL");
68411521 133MODULE_SOFTDEP("pre: crct10dif");