Re: [PATCH bpf-next v1 2/8] libbpf: tie struct_ops programs to kernel BTF ids, not to local ids

[Eduard Zingerman <eddyz87@gmail.com>]

On Wed, 2024-02-28 at 15:28 -0800, Andrii Nakryiko wrote:
[...]

> > @@ -1134,8 +1134,27 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map)
> > 
> >                         if (mod_btf)
> >                                 prog->attach_btf_obj_fd = mod_btf->fd;
> > -                       prog->attach_btf_id = kern_type_id;
> > -                       prog->expected_attach_type = kern_member_idx;
> > +
> > +                       /* if we haven't yet processed this BPF program, record proper
> > +                        * attach_btf_id and member_idx
> > +                        */
> > +                       if (!prog->attach_btf_id) {
> > +                               prog->attach_btf_id = kern_type_id;
> > +                               prog->expected_attach_type = kern_member_idx;
> > +                       }
> > +
> > +                       /* struct_ops BPF prog can be re-used between multiple
> > +                        * .struct_ops & .struct_ops.link as long as it's the
> > +                        * same struct_ops struct definition and the same
> > +                        * function pointer field
> > +                        */
> > +                       if (prog->attach_btf_id != kern_type_id ||
> > +                           prog->expected_attach_type != kern_member_idx) {
> > +                               pr_warn("struct_ops reloc %s: cannot use prog %s in sec %s with type %u attach_btf_id %u expected_attach_type %u for func ptr %s\n",
> 
> Martin already pointed out s/reloc/init_kern/, but I also find "cannot
> use prog" a bit too unactionable. Maybe "invalid reuse of prog"?
> "reuse" is the key here to point out that this program is used at
> least twice, and that in some incompatible way?

Ok, I'll change the wording.
And split the line despite the coding standards.