linux-kernel - Re: [PATCH 2/3] perf: collect BPF metadata from existing BPF programs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aEC9UqkKeEj4on3M@google.com>
Date: Wed, 4 Jun 2025 14:40:34 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Blake Jones <blakejones@...gle.com>, Song Liu <song@...nel.org>,
	Jiri Olsa <jolsa@...nel.org>
Cc: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Chun-Tse Shao <ctshao@...gle.com>,
	Zhongqiu Han <quic_zhonhan@...cinc.com>,
	James Clark <james.clark@...aro.org>,
	Charlie Jenkins <charlie@...osinc.com>,
	Andi Kleen <ak@...ux.intel.com>, Dmitry Vyukov <dvyukov@...gle.com>,
	Leo Yan <leo.yan@....com>, Yujie Liu <yujie.liu@...el.com>,
	Graham Woodward <graham.woodward@....com>,
	Yicong Yang <yangyicong@...ilicon.com>,
	Ben Gainey <ben.gainey@....com>, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 2/3] perf: collect BPF metadata from existing BPF programs

On Tue, Jun 03, 2025 at 03:29:35PM -0700, Blake Jones wrote:
> On Tue, Jun 3, 2025 at 3:10 PM Namhyung Kim <namhyung@...nel.org> wrote:
> > > Hmmm. Is that documented and tested anywhere? Offhand it sounds like an
> > > implementation detail that I wouldn't feel great about depending on -
> > > certainly not without a strong guarantee that it wouldn't change.
> >
> > Good point.  Maybe BPF folks have some idea?
> >
> > Anyway the current code generates them together in a function.
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/events/core.c?h=v6.15#n9825
> 
> It certainly does, yeah. But I don't want to have that become another
> instance of https://www.hyrumslaw.com/.

Thanks for sharing this.

I'm curious about the semantics of the KSYMBOL and BPF_EVENT.  And I
feel like there should be a connection between them.

Song and Jiri, what do you think?

Thanks,
Namhyung

> 
> > > Can you say more about why the duplicated records concern you?
> >
> > More data means more chance to lost something.  I don't expect this is
> > gonna be a practical concern but in general we should pursue less data.
> 
> That makes sense. In this case, it will only show up for BPF programs that
> define "bpf_metadata_" variables (which is already an opt-in action), and
> the number of variables a given program defines is likely to be quite small.
> So I think the cost of the marginal increase in data generated is outweighed
> by the usability and reliability benefits of being able to match these events
> 1:1 with the KSYMBOL events. If this proves to be a problem in practice,
> it can be revisited.
> 
> Blake