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From: Lorenz Bauer <lmb@cloudflare.com>
To: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com>,
	Luke Nelson <luke.r.nels@gmail.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	kernel-team <kernel-team@cloudflare.com>,
	linux-riscv@lists.infradead.org,
	Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH v2 0/4] Fix up bpf_jit_limit some more
Date: Thu, 14 Oct 2021 15:22:26 +0100	[thread overview]
Message-ID: <CACAyw99FGc_z2zXjrjP=0k3jz0vz2u6ddiGVbzD0zuTcTU4rzg@mail.gmail.com> (raw)
In-Reply-To: <87wnmgg0mf.fsf@cloudflare.com>

On Wed, 13 Oct 2021 at 20:56, Jakub Sitnicki <jakub@cloudflare.com> wrote:
>
> On Tue, Oct 12, 2021 at 03:59 PM CEST, Lorenz Bauer wrote:
> > Some more cleanups around bpf_jit_limit to make it readable via sysctl.
> >
> > Jakub raised the point that a sysctl toggle is UAPI and therefore
> > can't be easily changed later on. I tried to find another place to stick
> > the info, but couldn't find a good one. All the current BPF knobs are in
> > sysctl.
> >
> > There are examples of read only sysctls:
> > $ sudo find /proc/sys -perm 0444 | wc -l
> > 90
> >
> > There are no examples of sysctls with mode 0400 however:
> > $ sudo find /proc/sys -perm 0400 | wc -l
> > 0
> >
> > Thoughts?
>
> I threw this idea out there during LPC already, that it would be cool to
> use BPF iterators for that. Pinned/preloaded iterators were made for
> dumping kernel data on demand after all.
>
> What is missing is a BPF iterator type that would run the program just
> once (there is just one thing to print), and a BPF helper to lookup
> symbol's address.
>
> I thought this would require a bit of work, but actually getting a PoC
> (see below) to work was rather pleasntly straightforward.
>
> Perhaps a bit of a hack but I'd consider it as an alternative.

I spoke to Jakub, I won't have time to work on this myself. So I'll
drop this patch from the series and send a v3 with just the fixes to
bpf_jit_limit.

-- 
Lorenz Bauer  |  Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK

www.cloudflare.com

      reply	other threads:[~2021-10-14 14:22 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-12 13:59 [PATCH v2 0/4] Fix up bpf_jit_limit some more Lorenz Bauer
2021-10-12 13:59 ` [PATCH v2 1/4] bpf: define bpf_jit_alloc_exec_limit for riscv JIT Lorenz Bauer
2021-10-12 13:59 ` [PATCH v2 2/4] bpf: define bpf_jit_alloc_exec_limit for arm64 JIT Lorenz Bauer
2021-10-12 13:59 ` [PATCH v2 3/4] bpf: prevent increasing bpf_jit_limit above max Lorenz Bauer
2021-10-12 13:59 ` [PATCH v2 4/4] bpf: export bpf_jit_current Lorenz Bauer
2021-10-12 16:29   ` Nicolas Dichtel
2021-10-13  8:35     ` Lorenz Bauer
2021-10-13 12:29       ` Nicolas Dichtel
2021-10-13 19:56 ` [PATCH v2 0/4] Fix up bpf_jit_limit some more Jakub Sitnicki
2021-10-14 14:22   ` Lorenz Bauer [this message]

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