Re: [PATCH v3 sysctl-next] bpf: move bpf sysctls from kernel/sysctl.c to bpf module

[Luis Chamberlain]

On Fri, Mar 04, 2022 at 12:44:48AM +0100, Daniel Borkmann wrote:
> On 3/2/22 9:39 PM, Luis Chamberlain wrote:
> > On Wed, Mar 02, 2022 at 10:04:12AM +0800, Yan Zhu wrote:
> > > We're moving sysctls out of kernel/sysctl.c as its a mess. We
> > > already moved all filesystem sysctls out. And with time the goal is
> > > to move all sysctls out to their own susbsystem/actual user.
> > > 
> > > kernel/sysctl.c has grown to an insane mess and its easy to run
> > > into conflicts with it. The effort to move them out is part of this.
> > > 
> > > Signed-off-by: Yan Zhu <zhuyan34@xxxxxxxxxx>
> > 
> > Daniel, let me know if this makes more sense now, and if so I can
> > offer take it through sysctl-next to avoid conflicts more sysctl knobs
> > get moved out from kernel/sysctl.c.
> 
> If this is a whole ongoing effort rather than drive-by patch,

It is ongoing effort, but it will take many releases before we tidy
this whole thing up.

> then it's
> fine with me. 

OK great. Thanks for understanding the mess.

> Btw, the patch itself should also drop the linux/bpf.h
> include from kernel/sysctl.c since nothing else is using it after the
> patch.

I'll let Yan deal with that.

> Btw, related to cleanups.. historically, we have a bunch of other knobs
> for BPF under net (in net_core_table), that is:
> 
>   /proc/sys/net/core/bpf_jit_enable
>   /proc/sys/net/core/bpf_jit_harden
>   /proc/sys/net/core/bpf_jit_kallsyms
>   /proc/sys/net/core/bpf_jit_limit
> 
> Would be nice to consolidate all under e.g. /proc/sys/kernel/bpf_* for

Oh the actual "name" / directory location is not changing.
What changes is just where in code you declare them.

> future going forward, and technically, they should be usable also w/o
> net configured into kernel.

That's up to you, and just consider if you have scrupts using these
already. You may need backward compatibility. You don't need networking
to create the net directory for sysctls too. The first sysctl to create
the directory creates it, if its not created, it will be created.

> Is there infra to point the sysctl knobs
> e.g. under net/core/ to kernel/, or best way would be to have single
> struct ctl_table and register for both?

Try proc_symlink().

  Luis