linux-kernel - Re: [PATCH bpf-next] bpf, arm64: sign return address for jited code

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Message-ID: <da82d26e-8269-5b95-2cbb-1c147e55fcd4@iogearbox.net>
Date:   Fri, 1 Apr 2022 22:22:51 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Xu Kuohai <xukuohai@...wei.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Zi Shen Lim <zlim.lnx@...il.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>
Subject: Re: [PATCH bpf-next] bpf, arm64: sign return address for jited code

On 3/18/22 11:29 AM, Xu Kuohai wrote:
> Sign return address for jited code when the kernel is built with pointer
> authentication enabled.
> 
> 1. Sign lr with paciasp instruction before lr is pushed to stack. Since
>     paciasp acts like landing pads for function entry, no need to insert
>     bti instruction before paciasp.
> 
> 2. Authenticate lr with autiasp instruction after lr is poped from stack.
> 
> Signed-off-by: Xu Kuohai <xukuohai@...wei.com>

This would need a rebase, but please also use the commit description to provide
some more details how this inter-operates wrt BPF infra such as tail calls and
BPF-2-BPF calls when we look back into this in few months from now.

Thanks,
Daniel