Re: [PATCH bpf-next v2 0/4] Add ftrace direct call for arm64

From: Catalin Marinas <catalin.marinas@arm.com>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Xu Kuohai <xukuohai@huaweicloud.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	Mark Rutland <mark.rutland@arm.com>,
	Florent Revest <revest@chromium.org>,
	Will Deacon <will@kernel.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>, Oleg Nesterov <oleg@redhat.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <martin.lau@linux.dev>,
	Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
	Jiri Olsa <jolsa@kernel.org>, Zi Shen Lim <zlim.lnx@gmail.com>,
	Pasha Tatashin <pasha.tatashin@soleen.com>,
	Ard Biesheuvel <ardb@kernel.org>, Marc Zyngier <maz@kernel.org>,
	Guo Ren <guoren@kernel.org>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: Re: [PATCH bpf-next v2 0/4] Add ftrace direct call for arm64
Date: Mon, 26 Sep 2022 15:40:20 +0100	[thread overview]
Message-ID: <YzG51Jyd5zhvygtK@arm.com> (raw)
In-Reply-To: <f1e14934-dc54-9bf7-501a-89affdb7371e@iogearbox.net>

On Thu, Sep 22, 2022 at 08:01:16PM +0200, Daniel Borkmann wrote:
> On 9/13/22 6:27 PM, Xu Kuohai wrote:
> > This series adds ftrace direct call for arm64, which is required to attach
> > bpf trampoline to fentry.
> > 
> > Although there is no agreement on how to support ftrace direct call on arm64,
> > no patch has been posted except the one I posted in [1], so this series
> > continues the work of [1] with the addition of long jump support. Now ftrace
> > direct call works regardless of the distance between the callsite and custom
> > trampoline.
> > 
> > [1] https://lore.kernel.org/bpf/20220518131638.3401509-2-xukuohai@huawei.com/
> > 
> > v2:
> > - Fix compile and runtime errors caused by ftrace_rec_arch_init
> > 
> > v1: https://lore.kernel.org/bpf/20220913063146.74750-1-xukuohai@huaweicloud.com/
> > 
> > Xu Kuohai (4):
> >    ftrace: Allow users to disable ftrace direct call
> >    arm64: ftrace: Support long jump for ftrace direct call
> >    arm64: ftrace: Add ftrace direct call support
> >    ftrace: Fix dead loop caused by direct call in ftrace selftest
> 
> Given there's just a tiny fraction touching BPF JIT and most are around core arm64,
> it probably makes sense that this series goes via Catalin/Will through arm64 tree
> instead of bpf-next if it looks good to them. Catalin/Will, thoughts (Ack + bpf-next
> could work too, but I'd presume this just results in merge conflicts)?

I think it makes sense for the series to go via the arm64 tree but I'd
like Mark to have a look at the ftrace changes first.

Thanks.

-- 
Catalin

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