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T10 CRC library is linked into the kernel thanks to block and SCSI. The crypto accelerators are typically loaded later as modules and are therefore not available when the T10 CRC library is initialized. Use the crypto notifier facility to trigger a switch to a better algorithm if one becomes available after the initial hash has been registered. Use RCU to protect the original transform while the new one is being set up. Suggested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org Suggested-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
113 lines
2.7 KiB
C
113 lines
2.7 KiB
C
/*
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* T10 Data Integrity Field CRC16 calculation
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*
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* Copyright (c) 2007 Oracle Corporation. All rights reserved.
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* Written by Martin K. Petersen <martin.petersen@oracle.com>
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*
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* This source code is licensed under the GNU General Public License,
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* Version 2. See the file COPYING for more details.
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*/
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#include <linux/types.h>
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#include <linux/module.h>
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#include <linux/crc-t10dif.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <crypto/hash.h>
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#include <crypto/algapi.h>
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#include <linux/static_key.h>
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#include <linux/notifier.h>
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static struct crypto_shash __rcu *crct10dif_tfm;
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static struct static_key crct10dif_fallback __read_mostly;
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DEFINE_MUTEX(crc_t10dif_mutex);
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static int crc_t10dif_rehash(struct notifier_block *self, unsigned long val, void *data)
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{
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struct crypto_alg *alg = data;
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struct crypto_shash *new, *old;
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if (val != CRYPTO_MSG_ALG_LOADED ||
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static_key_false(&crct10dif_fallback) ||
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strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
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return 0;
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mutex_lock(&crc_t10dif_mutex);
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old = rcu_dereference_protected(crct10dif_tfm,
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lockdep_is_held(&crc_t10dif_mutex));
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if (!old) {
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mutex_unlock(&crc_t10dif_mutex);
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return 0;
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}
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new = crypto_alloc_shash("crct10dif", 0, 0);
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if (IS_ERR(new)) {
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mutex_unlock(&crc_t10dif_mutex);
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return 0;
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}
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rcu_assign_pointer(crct10dif_tfm, new);
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mutex_unlock(&crc_t10dif_mutex);
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synchronize_rcu();
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crypto_free_shash(old);
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return 0;
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}
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static struct notifier_block crc_t10dif_nb = {
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.notifier_call = crc_t10dif_rehash,
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};
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__u16 crc_t10dif_update(__u16 crc, const unsigned char *buffer, size_t len)
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{
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struct {
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struct shash_desc shash;
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char ctx[2];
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} desc;
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int err;
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if (static_key_false(&crct10dif_fallback))
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return crc_t10dif_generic(crc, buffer, len);
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rcu_read_lock();
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desc.shash.tfm = rcu_dereference(crct10dif_tfm);
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desc.shash.flags = 0;
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*(__u16 *)desc.ctx = crc;
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err = crypto_shash_update(&desc.shash, buffer, len);
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rcu_read_unlock();
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BUG_ON(err);
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return *(__u16 *)desc.ctx;
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}
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EXPORT_SYMBOL(crc_t10dif_update);
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__u16 crc_t10dif(const unsigned char *buffer, size_t len)
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{
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return crc_t10dif_update(0, buffer, len);
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}
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EXPORT_SYMBOL(crc_t10dif);
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static int __init crc_t10dif_mod_init(void)
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{
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crypto_register_notifier(&crc_t10dif_nb);
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crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);
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if (IS_ERR(crct10dif_tfm)) {
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static_key_slow_inc(&crct10dif_fallback);
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crct10dif_tfm = NULL;
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}
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return 0;
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}
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static void __exit crc_t10dif_mod_fini(void)
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{
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crypto_unregister_notifier(&crc_t10dif_nb);
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crypto_free_shash(crct10dif_tfm);
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}
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module_init(crc_t10dif_mod_init);
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module_exit(crc_t10dif_mod_fini);
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MODULE_DESCRIPTION("T10 DIF CRC calculation");
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MODULE_LICENSE("GPL");
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MODULE_SOFTDEP("pre: crct10dif");
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