Re: [PATCH v13 bpf-next 0/1] fprobe: Introduce fprobe function entry/exit probe

From: Mark Rutland <mark.rutland@arm.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
	Jiri Olsa <jolsa@kernel.org>, Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	netdev@vger.kernel.org, bpf@vger.kernel.org,
	lkml <linux-kernel@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>,
	Steven Rostedt <rostedt@goodmis.org>,
	"Naveen N . Rao" <naveen.n.rao@linux.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	"David S . Miller" <davem@davemloft.net>,
	catalin.marinas@arm.com, will@kernel.org
Subject: Re: [PATCH v13 bpf-next 0/1] fprobe: Introduce fprobe function entry/exit probe
Date: Wed, 23 Mar 2022 16:47:48 +0000	[thread overview]
Message-ID: <YjtPNAFQZ15NY0sp@lakrids> (raw)
In-Reply-To: <20220323235539.644ad8ace98347467de3e897@kernel.org>

On Wed, Mar 23, 2022 at 11:55:39PM +0900, Masami Hiramatsu wrote:
> On Wed, 23 Mar 2022 14:18:40 +0000
> Mark Rutland <mark.rutland@arm.com> wrote:
> 
> > On Wed, Mar 23, 2022 at 11:34:46AM +0900, Masami Hiramatsu wrote:
> > > Hi,
> > 
> > Hi Masami,
> > 
> > > Here is the 13th version of rethook x86 port. This is developed for a part
> > > of fprobe series [1] for hooking function return. But since I forgot to send
> > > it to arch maintainers, that caused conflict with IBT and SLS mitigation series.
> > > Now I picked the x86 rethook part and send it to x86 maintainers to be
> > > reviewed.
> > > 
> > > [1] https://lore.kernel.org/all/164735281449.1084943.12438881786173547153.stgit@devnote2/T/#u
> > 
> > As mentioned elsewhere, I have similar (though not identical) concerns
> > to Peter for the arm64 patch, which was equally unreviewed by
> > maintainers, and the overall structure.
> 
> Yes, those should be reviewed by arch maintainers.
> 
> > > Note that this patch is still for the bpf-next since the rethook itself
> > > is on the bpf-next tree. But since this also uses the ANNOTATE_NOENDBR
> > > macro which has been introduced by IBT/ENDBR patch, to build this series
> > > you need to merge the tip/master branch with the bpf-next.
> > > (hopefully, it is rebased soon)
> > 
> > I thought we were going to drop the series from the bpf-next tree so
> > that this could all go through review it had missed thusfar.
> > 
> > Is that still the plan? What's going on?
> 
> Now the arm64 (and other arch) port is reverted from bpf-next.
> I'll send those to you soon.

Ah; thanks for confirming!

> Since bpf-next is focusing on x86 at first, I chose this for review in
> this version. Sorry for confusion.

No problem; I think the confusion is all my own, so nothing to apologise
for! :)

> > > The fprobe itself is for providing the function entry/exit probe
> > > with multiple probe point. The rethook is a sub-feature to hook the
> > > function return as same as kretprobe does. Eventually, I would like
> > > to replace the kretprobe's trampoline with this rethook.
> > 
> > Can we please start by converting each architecture to rethook?
> 
> Yes. As Peter pointed, I'm planning to add a kretprobe patches to use
> rethook if available in that series. let me prepare it.
> 
> > Ideally we'd unify things such that each architecture only needs *one*
> > return trampoline that both ftrace and krpboes can use, which'd be
> > significantly easier to get right and manage.
> 
> Agreed :-)

Great!

Thanks,
Mark.