Re: [PATCH bpf-next v7 4/8] libbpf: Create a bpf_link in bpf_map__attach_struct_ops().

[Kui-Feng Lee <sinquersw@xxxxxxxxx>]

On 3/17/23 11:44, Martin KaFai Lau wrote:
> On 3/15/23 7:36 PM, Kui-Feng Lee wrote:
> > @@ -11590,31 +11631,32 @@ struct bpf_link 
> > *bpf_map__attach_struct_ops(const struct bpf_map *map)
> >       if (!link)
> >           return libbpf_err_ptr(-EINVAL);
> > -    st_ops = map->st_ops;
> > -    for (i = 0; i < btf_vlen(st_ops->type); i++) {
> > -        struct bpf_program *prog = st_ops->progs[i];
> > -        void *kern_data;
> > -        int prog_fd;
> > +    /* kern_vdata should be prepared during the loading phase. */
> > +    err = bpf_map_update_elem(map->fd, &zero, 
> > map->st_ops->kern_vdata, 0);
> > +    if (err) {
>
> It should not fail for BPF_F_LINK struct_ops when err is EBUSY.
> The struct_ops map can attach, detach, and then attach again.
>
> It needs a test for this case.

Got it!

> > +        free(link);
> > +        return libbpf_err_ptr(err);
> > +    }