Re: [PATCH sched_ext/for-6.15 v3 3/5] sched_ext: Add scx_kfunc_ids_ops_context_sensitive for unified filtering of context-sensitive SCX kfuncs

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

On Thu, Feb 27, 2025 at 1:32 PM Tejun Heo <tj@xxxxxxxxxx> wrote:
>
> Hello,
>
> On Thu, Feb 27, 2025 at 09:23:20PM +0000, Juntong Deng wrote:
> > > > + if (prog->type == BPF_PROG_TYPE_STRUCT_OPS &&
> > > > +     prog->aux->st_ops != &bpf_sched_ext_ops)
> > > > +         return 0;
> > >
> > > Why can't other struct_ops progs call scx_kfunc_ids_unlocked kfuncs?
> > >
> >
> > Return 0 means allowed. So kfuncs in scx_kfunc_ids_unlocked can be
> > called by other struct_ops programs.
>
> Hmm... would that mean a non-sched_ext bpf prog would be able to call e.g.
> scx_bpf_dsq_insert()?

Not as far as I can tell.
scx_kfunc_ids_unlocked[] doesn't include scx_bpf_dsq_insert.
It's part of scx_kfunc_ids_enqueue_dispatch[].

So this bit in patch 3 enables it:
+       if ((flags & SCX_OPS_KF_ENQUEUE) &&
+           btf_id_set8_contains(&scx_kfunc_ids_enqueue_dispatch, kfunc_id))

and in patch 2:
+       [SCX_OP_IDX(enqueue)]                   = SCX_OPS_KF_ENQUEUE,

So scx_bpf_dsq_insert() kfunc can only be called out
of enqueue() sched-ext hook.

So the restriction is still the same. afaict.