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Date:   Mon, 15 Aug 2022 12:18:38 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Jiri Olsa <jolsa@kernel.org>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>, bpf@vger.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@chromium.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>,
        "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Subject: Re: [PATCHv2 bpf-next 3/6] bpf: Use given function address for
 trampoline ip arg
Message-ID: <Yvodfh6OJhSIq8X9@worktop.programming.kicks-ass.net>
References: <20220811091526.172610-1-jolsa@kernel.org>
 <20220811091526.172610-4-jolsa@kernel.org>
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On Thu, Aug 11, 2022 at 11:15:23AM +0200, Jiri Olsa wrote:
> Using function address given at the generation time as the trampoline
> ip argument. This way we get directly the function address that we
> need, so we don't need to:
>   - read the ip from the stack
>   - subtract X86_PATCH_SIZE
>   - subtract ENDBR_INSN_SIZE if CONFIG_X86_KERNEL_IBT is enabled
>     which is not even implemented yet ;-)

Can you please tell me what all this does and why?