Re: [PATCH bpf-next v5 3/5] bpf: Add helper to detect indirect jump targets

[Xu Kuohai]

On 3/4/2026 1:19 AM, Alexei Starovoitov wrote:

[...]

> > -       for (i = 0; i < insn_cnt; i++, insn++) {
> > +       for (i = 0, j = 0; i < insn_cnt; i++, j++, insn++) {
> > +               env->insn_aux_data[subprog_start + j].final_idx = i;
> >                  if (bpf_pseudo_func(insn)) {
> >                          /* ld_imm64 with an address of bpf subprog is not
> >                           * a user controlled constant. Don't randomize it,
> > @@ -1512,6 +1542,8 @@ struct bpf_prog *bpf_jit_blind_constants(struct bpf_verifier_env *env, struct bp
> >                           */
> >                          insn++;
> >                          i++;
> > +                       j++;
> > +                       env->insn_aux_data[subprog_start + j].final_idx = i;
>
> You're adding final_idx because bpf_jit_blind_constants()
> doesn't call adjust_insn_aux_data() ?

Yes, I added final_idx because insn_aux is not updated here.

> imo that's an ugly workaround. Just call adjust_insn_aux_data().

If we adjust the env->insn_aux_data here, should we also adjust the global
env->prog->insnsi array? I think env->insn_aux_data should remain consistent
with the global env->prog->insnsi array. Since constant blinding only rewrites
the subprog's private instruction array, updating the env->insn_aux_data
causes a mismatch with the global state.

> And in the future please mention such design decisions in the commit log,
> so that reviewers don't need to reverse engineer your thought process.

Sorry for the lack of clarity. I’ll make an effort to clarify things more
clearly in the future.

> pw-bot: cr