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Date:   Thu, 11 May 2023 22:22:09 +0800
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Subject: Re: [PATCH bpf-next v2] arm64,bpf: Support struct arguments in the
 BPF trampoline
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To:     Florent Revest <revest@chromium.org>, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Cc:     ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
        kpsingh@kernel.org, mark.rutland@arm.com, zlim.lnx@gmail.com,
        yhs@meta.com, Yonghong Song <yhs@fb.com>
References: <20230511140507.514888-1-revest@chromium.org>
From:   Xu Kuohai <xukuohai@huaweicloud.com>
In-Reply-To: <20230511140507.514888-1-revest@chromium.org>
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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@chromium.org>
> Acked-by: Yonghong Song <yhs@fb.com>
> ---
> 
> Diff since v1: The stack layout comment now says "arg reg" instead of "arg".
>

LGTM. Thanks for updating the description.