# Re: \[PATCH v2 0/4\] Fix up bpf\_jit\_limit some more

- From: Lorenz Bauer \<hidden\>
- Date: 2021-10-14 14:22:45 
- List: netdev
- Page: https://ratatoskr.run/netdev/2021/10/7782492
- Thread: https://ratatoskr.run/linux-riscv/2021/10/7782414/t.md

```text
On Wed, 13 Oct 2021 at 20:56, Jakub Sitnicki [ref] 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
```