linux-kernel - Re: [PATCH] crypto: arm/sha1 - Fix clang function cast warnings

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Message-ID: <Y5jWUytRsZatKmCk@sol.localdomain>
Date:   Tue, 13 Dec 2022 11:45:23 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        kernel test robot <lkp@...el.com>,
        Robert Elliott <elliott@....com>, llvm@...ts.linux.dev,
        oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>
Subject: Re: [PATCH] crypto: arm/sha1 - Fix clang function cast warnings

On Tue, Dec 13, 2022 at 06:43:30PM +0800, Herbert Xu wrote:
> -asmlinkage void sha1_block_data_order(u32 *digest,
> -		const unsigned char *data, unsigned int rounds);
> +asmlinkage void sha1_block_data_order(struct sha1_state *digest,
> +		const u8 *data, int rounds);

The last parameter should be called 'blocks', not 'rounds'.

>  int sha1_update_arm(struct shash_desc *desc, const u8 *data,
>  		    unsigned int len)
>  {
> -	/* make sure casting to sha1_block_fn() is safe */
> +	/* make sure signature matches sha1_block_fn() */
>  	BUILD_BUG_ON(offsetof(struct sha1_state, state) != 0);

The above comment doesn't really make sense, since making sure function
signatures match is the responsibility of the compiler.

A better comment would be:

	/* sha1_block_data_order() expects the actual state at the beginning. */

It would also be helpful to add a comment to the definition of struct
sha1_state, analogous to the comment in struct blake2s_state:

struct sha1_state {
	/* 'state' is used by assembly code, so keep it as-is. */
	u32 state[SHA1_DIGEST_SIZE / 4];

- Eric