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Subject: Re: [PATCH bpf-next] bpf, arm64: sign return address for jited code
To:     Xu Kuohai <xukuohai@huawei.com>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Zi Shen Lim <zlim.lnx@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>
References: <20220318102936.838459-1-xukuohai@huawei.com>
From:   Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <da82d26e-8269-5b95-2cbb-1c147e55fcd4@iogearbox.net>
Date:   Fri, 1 Apr 2022 22:22:51 +0200
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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@huawei.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