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Date:   Mon, 24 May 2021 14:53:14 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Ard Biesheuvel <ardb@kernel.org>
Cc:     linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        herbert@gondor.apana.org.au, will@kernel.org,
        kernel-team@android.com
Subject: Re: [PATCH v5 5/5] crypto: arm64/aes-ccm - avoid by-ref argument for
 ce_aes_ccm_auth_data
Message-ID: <YKwgSnb4RJr40Ns2@gmail.com>
References: <20210521102053.66609-1-ardb@kernel.org>
 <20210521102053.66609-6-ardb@kernel.org>
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On Fri, May 21, 2021 at 12:20:53PM +0200, Ard Biesheuvel wrote:
> With the SIMD code path removed, we can clean up the CCM auth-only path
> a bit further, by passing the 'macp' input buffer pointer by value,
> rather than by reference, and taking the output value from the
> function's return value.
> 
> This way, the compiler is no longer forced to allocate macp on the
> stack. This is not expected to make any difference in practice, it just
> makes for slightly cleaner code.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  arch/arm64/crypto/aes-ce-ccm-core.S | 23 ++++++++++----------
>  arch/arm64/crypto/aes-ce-ccm-glue.c | 17 +++++----------
>  2 files changed, 17 insertions(+), 23 deletions(-)
> 
> diff --git a/arch/arm64/crypto/aes-ce-ccm-core.S b/arch/arm64/crypto/aes-ce-ccm-core.S
> index 8adff299fcd3..b03f7f71f893 100644
> --- a/arch/arm64/crypto/aes-ce-ccm-core.S
> +++ b/arch/arm64/crypto/aes-ce-ccm-core.S
> @@ -12,22 +12,21 @@
>  	.arch	armv8-a+crypto
>  
>  	/*
> -	 * void ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
> -	 *			     u32 *macp, u8 const rk[], u32 rounds);
> +	 * u32 ce_aes_ccm_auth_data(u8 mac[], u8 const in[], u32 abytes,
> +	 *			    u32 macp, u8 const rk[], u32 rounds);

How is this different from 'u8 mac[]' which is already one of the parameters?

- Eric