linux/lib/crc-t10dif.c
Eric Biggers 877b5691f2 crypto: shash - remove shash_desc::flags
The flags field in 'struct shash_desc' never actually does anything.
The only ostensibly supported flag is CRYPTO_TFM_REQ_MAY_SLEEP.
However, no shash algorithm ever sleeps, making this flag a no-op.

With this being the case, inevitably some users who can't sleep wrongly
pass MAY_SLEEP.  These would all need to be fixed if any shash algorithm
actually started sleeping.  For example, the shash_ahash_*() functions,
which wrap a shash algorithm with the ahash API, pass through MAY_SLEEP
from the ahash API to the shash API.  However, the shash functions are
called under kmap_atomic(), so actually they're assumed to never sleep.

Even if it turns out that some users do need preemption points while
hashing large buffers, we could easily provide a helper function
crypto_shash_update_large() which divides the data into smaller chunks
and calls crypto_shash_update() and cond_resched() for each chunk.  It's
not necessary to have a flag in 'struct shash_desc', nor is it necessary
to make individual shash algorithms aware of this at all.

Therefore, remove shash_desc::flags, and document that the
crypto_shash_*() functions can be called from any context.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2019-04-25 15:38:12 +08:00

123 lines
3.0 KiB
C

/*
* T10 Data Integrity Field CRC16 calculation
*
* Copyright (c) 2007 Oracle Corporation. All rights reserved.
* Written by Martin K. Petersen <martin.petersen@oracle.com>
*
* This source code is licensed under the GNU General Public License,
* Version 2. See the file COPYING for more details.
*/
#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 int crc_t10dif_rehash(struct notifier_block *self, unsigned long val, void *data)
{
struct crypto_alg *alg = data;
struct crypto_shash *new, *old;
if (val != CRYPTO_MSG_ALG_LOADED ||
static_key_false(&crct10dif_fallback) ||
strncmp(alg->cra_name, CRC_T10DIF_STRING, strlen(CRC_T10DIF_STRING)))
return 0;
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 0;
}
new = crypto_alloc_shash("crct10dif", 0, 0);
if (IS_ERR(new)) {
mutex_unlock(&crc_t10dif_mutex);
return 0;
}
rcu_assign_pointer(crct10dif_tfm, new);
mutex_unlock(&crc_t10dif_mutex);
synchronize_rcu();
crypto_free_shash(old);
return 0;
}
static struct notifier_block crc_t10dif_nb = {
.notifier_call = crc_t10dif_rehash,
};
__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)
{
crypto_register_notifier(&crc_t10dif_nb);
crct10dif_tfm = crypto_alloc_shash("crct10dif", 0, 0);
if (IS_ERR(crct10dif_tfm)) {
static_key_slow_inc(&crct10dif_fallback);
crct10dif_tfm = NULL;
}
return 0;
}
static void __exit crc_t10dif_mod_fini(void)
{
crypto_unregister_notifier(&crc_t10dif_nb);
crypto_free_shash(crct10dif_tfm);
}
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)
{
if (static_key_false(&crct10dif_fallback))
return sprintf(buffer, "fallback\n");
return sprintf(buffer, "%s\n",
crypto_tfm_alg_driver_name(crypto_shash_tfm(crct10dif_tfm)));
}
module_param_call(transform, NULL, crc_t10dif_transform_show, NULL, 0644);
MODULE_DESCRIPTION("T10 DIF CRC calculation");
MODULE_LICENSE("GPL");
MODULE_SOFTDEP("pre: crct10dif");