Re: [PATCH RFC bpf-next 04/10] bpf: Add bpf_core_add_cands() and wire it into bpf_core_apply_relo_insn().

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Fri, Sep 17, 2021 at 2:57 PM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> From: Alexei Starovoitov <ast@kernel.org>
>
> Given BPF program's BTF perform a linear search through kernel BTFs for
> a possible candidate.
> Then wire the result into bpf_core_apply_relo_insn().
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> ---
>  kernel/bpf/btf.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 147 insertions(+), 2 deletions(-)
>

[...]

> +       /* If candidate is not found in vmlinux's BTF then search in module's BTFs */
> +       spin_lock_bh(&btf_idr_lock);
> +       idr_for_each_entry(&btf_idr, mod_btf, id) {
> +               if (!btf_is_module(mod_btf))
> +                       continue;
> +               /* linear search could be slow hence unlock/lock
> +                * the IDR to avoiding holding it for too long
> +                */
> +               btf_get(mod_btf);
> +               spin_unlock_bh(&btf_idr_lock);
> +               err = bpf_core_add_cands(&local_cand, local_essent_len,
> +                                        mod_btf,
> +                                        btf_nr_types(main_btf),
> +                                        cands);
> +               if (err)
> +                       btf_put(mod_btf);
> +               goto err_out;

this couldn't have worked properly for modules, missing {} ?

> +               spin_lock_bh(&btf_idr_lock);
> +               btf_put(mod_btf);
> +       }
> +       spin_unlock_bh(&btf_idr_lock);
> +
> +       return cands;
> +err_out:
> +       bpf_core_free_cands(cands);
> +       return ERR_PTR(err);
> +}
> +

[...]