Re: [PATCH 01/15] crypto: lib/sha256 - Move partial block handling out

[Eric Biggers <ebiggers@kernel.org>]

On Thu, Apr 24, 2025 at 06:46:58PM +0800, Herbert Xu wrote:
> Extract the common partial block handling into a helper macro
> that can be reused by other library code.
> 
> Also delete the unused sha256_base_do_finalize function.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> ---
>  include/crypto/internal/blockhash.h | 52 +++++++++++++++++++++++++++++
>  include/crypto/sha2.h               |  9 +++--
>  include/crypto/sha256_base.h        | 38 ++-------------------
>  3 files changed, 62 insertions(+), 37 deletions(-)
>  create mode 100644 include/crypto/internal/blockhash.h
> 
> diff --git a/include/crypto/internal/blockhash.h b/include/crypto/internal/blockhash.h
> new file mode 100644
> index 000000000000..4184e2337d68
> --- /dev/null
> +++ b/include/crypto/internal/blockhash.h
> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Handle partial blocks for block hash.
> + *
> + * Copyright (c) 2015 Linaro Ltd <ard.biesheuvel@linaro.org>
> + * Copyright (c) 2025 Herbert Xu <herbert@gondor.apana.org.au>
> + */
> +
> +#ifndef _CRYPTO_INTERNAL_BLOCKHASH_H
> +#define _CRYPTO_INTERNAL_BLOCKHASH_H
> +
> +#include <linux/string.h>
> +#include <linux/types.h>
> +
> +#define BLOCK_HASH_UPDATE_BASE(block, state, src, nbytes, bs, dv, buf,	\
> +			       buflen)					\
> +	({								\
> +		unsigned int _nbytes = (nbytes);			\
> +		unsigned int _buflen = (buflen);			\
> +		typeof(block) _block = (block);				\
> +		typeof(state) _state = (state); 			\
> +		unsigned int _bs = (bs);				\
> +		unsigned int _dv = (dv);				\
> +		const u8 *_src = (src);					\
> +		u8 *_buf = (buf);					\
> +		while ((_buflen + _nbytes) >= _bs) {			\
> +			unsigned int len = _nbytes;			\
> +			const u8 *data = _src;				\
> +			int blocks, remain;				\
> +			if (_buflen) {					\
> +				remain = _bs - _buflen;			\
> +				memcpy(_buf + _buflen, _src, remain);	\
> +				data = _buf;				\
> +				len = _bs;				\
> +			}						\
> +			remain = len % bs;				\
> +			blocks = (len - remain) / _dv;			\
> +			_block(_state, data, blocks);			\
> +			_src += len - remain - _buflen;			\
> +			_nbytes -= len - remain - _buflen;		\
> +			_buflen = 0;					\
> +		}							\
> +		memcpy(_buf + _buflen, _src, _nbytes);			\
> +		_buflen += _nbytes;					\
> +	})

Do we really have to have this random macro that obfuscates what is going on?

- Eric