Re: [PATCH] ubifs: use crypto_shash_tfm_digest() in ubifs_hmac_wkm()

[Zhihao Cheng <chengzhihao1@huawei.com>]

在 2023/10/29 13:03, Eric Biggers 写道:
> From: Eric Biggers <ebiggers@google.com>
>
> Simplify ubifs_hmac_wkm() by using crypto_shash_tfm_digest() instead of
> an alloc+init+update+final sequence.  This should also improve
> performance.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>   fs/ubifs/auth.c | 19 ++-----------------
>   1 file changed, 2 insertions(+), 17 deletions(-)

Tested-by: Zhihao Cheng <chengzhihao1@huawei.com>

Time cost of ubifs_hmac_wkm(unit: us):

Before: 381~1634

After:278~1539

>
> diff --git a/fs/ubifs/auth.c b/fs/ubifs/auth.c
> index e564d5ff8781..4add4a4f0720 100644
> --- a/fs/ubifs/auth.c
> +++ b/fs/ubifs/auth.c
> @@ -501,42 +501,27 @@ int __ubifs_shash_copy_state(const struct ubifs_info *c, struct shash_desc *src,
>    *
>    * This function creates a HMAC of a well known message. This is used
>    * to check if the provided key is suitable to authenticate a UBIFS
>    * image. This is only a convenience to the user to provide a better
>    * error message when the wrong key is provided.
>    *
>    * This function returns 0 for success or a negative error code otherwise.
>    */
>   int ubifs_hmac_wkm(struct ubifs_info *c, u8 *hmac)
>   {
> -	SHASH_DESC_ON_STACK(shash, c->hmac_tfm);
> -	int err;
>   	const char well_known_message[] = "UBIFS";
>   
>   	if (!ubifs_authenticated(c))
>   		return 0;
>   
> -	shash->tfm = c->hmac_tfm;
> -
> -	err = crypto_shash_init(shash);
> -	if (err)
> -		return err;
> -
> -	err = crypto_shash_update(shash, well_known_message,
> -				  sizeof(well_known_message) - 1);
> -	if (err < 0)
> -		return err;
> -
> -	err = crypto_shash_final(shash, hmac);
> -	if (err)
> -		return err;
> -	return 0;
> +	return crypto_shash_tfm_digest(c->hmac_tfm, well_known_message,
> +				       sizeof(well_known_message) - 1, hmac);
>   }
>   
>   /*
>    * ubifs_hmac_zero - test if a HMAC is zero
>    * @c: UBIFS file-system description object
>    * @hmac: the HMAC to test
>    *
>    * This function tests if a HMAC is zero and returns true if it is
>    * and false otherwise.
>    */
>
> base-commit: 2af9b20dbb39f6ebf9b9b6c090271594627d818e