Subject: Re: [PATCH v4 bpf-next 05/14] bpf: Remove btf_id helpers resolving

From: Jiri Olsa <[email-masked]>
Date: Sun, 28 Jun 2020 23:20:19 +0200

On Sun, Jun 28, 2020 at 01:59:54PM -0700, Yonghong Song wrote:

SNIP

> > > 
> > > The corresponding BTF_ID definition here is:
> > >    BTF_ID_LIST(bpf_skb_output_btf_ids)
> > >    BTF_ID(struct, sk_buff)
> > > 
> > > The bpf helper writer needs to ensure proper declarations
> > > of BTF_IDs like the above matching helpers definition.
> > > Support we have arg1 and arg3 as BTF_ID. then the list
> > > definition may be
> > > 
> > >    BTF_ID_LIST(bpf_skb_output_btf_ids)
> > >    BTF_ID(struct, sk_buff)
> > >    BTF_ID(struct, __unused)
> > >    BTF_ID(struct, task_struct)
> > > 
> > > This probably okay, I guess.
> > 
> > right, AFAIK we don't have such case yet, but would be good
> > to be ready and have something like
> > 
> >    BTF_ID(struct, __unused)
> > 
> > maybe adding new type for that will be better:
> > 
> >    BTF_ID(none, unused)
> 
> Maybe we can have a separate macro BTF_ID_UNUSED macro
> which simply adds 4 bytes hole in the .btf_ids* section.

right, we don't need symbols for that

jirka