Re: [PATCH bpf-next v4 01/13] bpf: Rename 'early' BTF checking as a preparation phase

On Wed, Aug 5, 2026 at 2:05 PM Kumar Kartikeya Dwivedi <[email protected]> wrote:
>
> BTF processing is split around subprogram discovery. The first phase gets
> program BTF and imports func_info because a BTF-tagged exception callback
> may not be referenced by any instruction. Subprogram discovery needs this
> metadata to find it.
>
> The later phase validates func_info and line_info against the complete
> subprogram table and applies CO-RE relocations. This split breaks a real
> dependency cycle rather than merely running the same checks early.
>
> Rename bpf_check_btf_info_early() and check_btf_func_early() to preparation
> names that reflect this role. Add short call-site comments to make the two
> phases and their responsibilities clear.
>
> No functional change is intended.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>

Reviewed-by: Amery Hung <[email protected]>

> ---
>  include/linux/bpf_verifier.h |  4 ++--
>  kernel/bpf/check_btf.c       | 14 +++++++-------
>  kernel/bpf/verifier.c        |  4 +++-
>  3 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index a2a40caca0a0..a9555d17fd8e 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -1177,8 +1177,8 @@ static inline void bpf_trampoline_unpack_key(u64 key, u32 *obj_id, u32 *btf_id)
>                 *btf_id = key & 0x7FFFFFFF;
>  }
>
> -int bpf_check_btf_info_early(struct bpf_verifier_env *env,
> -                            const union bpf_attr *attr, bpfptr_t uattr);
> +int bpf_prepare_btf_info(struct bpf_verifier_env *env,
> +                        const union bpf_attr *attr, bpfptr_t uattr);
>  int bpf_check_btf_info(struct bpf_verifier_env *env,
>                        const union bpf_attr *attr, bpfptr_t uattr);
>
> diff --git a/kernel/bpf/check_btf.c b/kernel/bpf/check_btf.c
> index 93bebe6fe12e..0e8b3ccc7a5b 100644
> --- a/kernel/bpf/check_btf.c
> +++ b/kernel/bpf/check_btf.c
> @@ -28,9 +28,9 @@ static int check_abnormal_return(struct bpf_verifier_env *env)
>  #define MIN_BPF_FUNCINFO_SIZE  8
>  #define MAX_FUNCINFO_REC_SIZE  252
>
> -static int check_btf_func_early(struct bpf_verifier_env *env,
> -                               const union bpf_attr *attr,
> -                               bpfptr_t uattr)
> +static int prepare_btf_func(struct bpf_verifier_env *env,
> +                           const union bpf_attr *attr,
> +                           bpfptr_t uattr)
>  {
>         u32 krec_size = sizeof(struct bpf_func_info);
>         const struct btf_type *type, *func_proto;
> @@ -407,9 +407,9 @@ static int check_core_relo(struct bpf_verifier_env *env,
>         return err;
>  }
>
> -int bpf_check_btf_info_early(struct bpf_verifier_env *env,
> -                            const union bpf_attr *attr,
> -                            bpfptr_t uattr)
> +int bpf_prepare_btf_info(struct bpf_verifier_env *env,
> +                        const union bpf_attr *attr,
> +                        bpfptr_t uattr)
>  {
>         struct btf *btf;
>         int err;
> @@ -429,7 +429,7 @@ int bpf_check_btf_info_early(struct bpf_verifier_env *env,
>         }
>         env->prog->aux->btf = btf;
>
> -       err = check_btf_func_early(env, attr, uattr);
> +       err = prepare_btf_func(env, attr, uattr);
>         if (err)
>                 return err;
>         return 0;
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index d925197c2e5f..129e50888b90 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -20317,7 +20317,8 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
>                 INIT_LIST_HEAD(&env->explored_states[i]);
>         INIT_LIST_HEAD(&env->free_list);
>
> -       ret = bpf_check_btf_info_early(env, attr, uattr);
> +       /* Prepare BTF and func_info needed to discover all subprograms. */
> +       ret = bpf_prepare_btf_info(env, attr, uattr);
>         if (ret < 0)
>                 goto skip_full_check;
>
> @@ -20329,6 +20330,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
>         if (ret < 0)
>                 goto skip_full_check;
>
> +       /* Validate BTF against the complete subprogram layout and apply CO-RE. */
>         ret = bpf_check_btf_info(env, attr, uattr);
>         if (ret < 0)
>                 goto skip_full_check;
> --
> 2.53.0
>
>