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checkstack.pl

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  • crc-t10dif.c 3.16 KiB
    // 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 DEFINE_STATIC_KEY_TRUE(crct10dif_fallback);
    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 ||
    	    strcmp(alg->cra_name, CRC_T10DIF_STRING))
    		return NOTIFY_DONE;
    
    	schedule_work(&crct10dif_rehash_work);
    	return NOTIFY_OK;
    }
    
    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));
    	new = crypto_alloc_shash(CRC_T10DIF_STRING, 0, 0);
    	if (IS_ERR(new)) {
    		mutex_unlock(&crc_t10dif_mutex);
    		return;
    	}
    	rcu_assign_pointer(crct10dif_tfm, new);
    	mutex_unlock(&crc_t10dif_mutex);
    
    	if (old) {
    		synchronize_rcu();
    		crypto_free_shash(old);
    	} else {
    		static_branch_disable(&crct10dif_fallback);
    	}
    }
    
    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;
    		__u16 crc;
    	} desc;
    	int err;
    
    	if (static_branch_unlikely(&crct10dif_fallback))
    		return crc_t10dif_generic(crc, buffer, len);
    
    	rcu_read_lock();
    	desc.shash.tfm = rcu_dereference(crct10dif_tfm);
    	desc.crc = crc;
    	err = crypto_shash_update(&desc.shash, buffer, len);
    	rcu_read_unlock();
    
    	BUG_ON(err);
    
    	return desc.crc;
    }
    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)
    {
    	INIT_WORK(&crct10dif_rehash_work, crc_t10dif_rehash);
    	crypto_register_notifier(&crc_t10dif_nb);
    	crc_t10dif_rehash(&crct10dif_rehash_work);
    	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;
    	int len;
    
    	if (static_branch_unlikely(&crct10dif_fallback))
    		return sprintf(buffer, "fallback\n");
    
    	rcu_read_lock();
    	tfm = rcu_dereference(crct10dif_tfm);
    	len = snprintf(buffer, PAGE_SIZE, "%s\n",
    		       crypto_shash_driver_name(tfm));
    	rcu_read_unlock();
    
    	return len;
    }
    
    module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0444);
    
    MODULE_DESCRIPTION("T10 DIF CRC calculation (library API)");
    MODULE_LICENSE("GPL");
    MODULE_SOFTDEP("pre: crct10dif");