linux-kernel - Re: [PATCH bpf-next v2] arm64,bpf: Support struct arguments in the BPF trampoline

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Message-ID: <7d5cc151-e6c3-73a9-59c0-c4e5821cec1c@huaweicloud.com>
Date:   Thu, 11 May 2023 22:22:09 +0800
From:   Xu Kuohai <xukuohai@...weicloud.com>
To:     Florent Revest <revest@...omium.org>, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kpsingh@...nel.org, mark.rutland@....com, zlim.lnx@...il.com,
        yhs@...a.com, Yonghong Song <yhs@...com>
Subject: Re: [PATCH bpf-next v2] arm64,bpf: Support struct arguments in the
 BPF trampoline

On 5/11/2023 10:05 PM, Florent Revest wrote:
> This extends the BPF trampoline JIT to support attachment to functions
> that take small structures (up to 128bit) as argument. This is trivially
> achieved by saving/restoring a number of "argument registers" rather
> than a number of arguments.
> 
> The AAPCS64 section 6.8.2 describes the parameter passing ABI.
> "Composite types" (like C structs) below 16 bytes (as enforced by the
> BPF verifier) are provided as part of the 8 argument registers as
> explained in the section C.12.
> 
> Signed-off-by: Florent Revest <revest@...omium.org>
> Acked-by: Yonghong Song <yhs@...com>
> ---
> 
> Diff since v1: The stack layout comment now says "arg reg" instead of "arg".
>

LGTM. Thanks for updating the description.