> On Thu, Nov 23, 2023 at 03:25:33PM +0100, Jiri Olsa wrote:
> > + link->prog->aux->attach_depth--;
>
> should we just set it to 0 ? the number is assigned from tgt_prog, so I think we'll
> endup with wrong up number here after detach (for both tgt_prog or kernel function)
> > + if (tgt_prog) {
> > + /* Bookkeeping for managing the prog attachment chain. */
> > + tgt_prog->aux->follower_cnt++;
> > + prog->aux->attach_depth = tgt_prog->aux->attach_depth + 1;
> > + }
>
> missing cleanup/dec if the next bpf_trampoline_link_prog call fails?
> probably better move that accounting after that call
> > + printf(" attach depth %d", info->attach_depth);
> > +
>
> I think we should print only if the value != 0 like we do for other fields
> > + if (tgt_prog->type == prog->type &&
> > + (prog_extension || prog->aux->follower_cnt > 0)) {
> > + /*
> > + * To avoid potential call chain cycles, prevent attaching programs
> > + * of the same type. The only exception is standalone fentry/fexit
> > + * programs that themselves are not attachment targets.
> > + * That means:
> > + * - Cannot attach followed fentry/fexit to another
> > + * fentry/fexit program.
> > + * - Cannot attach program extension to another extension.
>
> would be great to have tests for this
Agree on all points, thanks. Will post the updated version soon.
