On Thu, Mar 10, 2022 at 4:12 PM Delyan Kratunov <delyank@xxxxxx> wrote:
>
> Currently, libbpf considers a single routine in .text as a program. This
> is particularly confusing when it comes to library objects - a single routine
> meant to be used as an extern will instead be considered a bpf_program.
>
> This patch hides this compatibility behavior behind a libbpf_mode strict
> mode flag.
>
> Signed-off-by: Delyan Kratunov <delyank@xxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 7 +++++++
> tools/lib/bpf/libbpf_legacy.h | 6 ++++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 43161fdd44bb..b6f11ce0d6bc 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -3832,7 +3832,14 @@ static bool prog_is_subprog(const struct bpf_object *obj,
> * .text programs are subprograms (even if they are not called from
> * other programs), because libbpf never explicitly supported mixing
> * SEC()-designated BPF programs and .text entry-point BPF programs.
> + *
> + * In libbpf 1.0 strict mode, we always consider .text
> + * programs to be subprograms.
> */
> +
> + if (libbpf_mode & LIBBPF_STRICT_TEXT_ONLY_SUBPROGRAMS)
> + return prog->sec_idx == obj->efile.text_shndx;
> +
> return prog->sec_idx == obj->efile.text_shndx && obj->nr_programs > 1;
> }
>
> diff --git a/tools/lib/bpf/libbpf_legacy.h b/tools/lib/bpf/libbpf_legacy.h
> index a283cf031665..388384ea97a7 100644
> --- a/tools/lib/bpf/libbpf_legacy.h
> +++ b/tools/lib/bpf/libbpf_legacy.h
> @@ -78,6 +78,12 @@ enum libbpf_strict_mode {
> * in favor of BTF-defined map definitions in SEC(".maps").
> */
> LIBBPF_STRICT_MAP_DEFINITIONS = 0x20,
> + /*
> + * When enabled, always consider routines in the .text section to
> + * be sub-programs. Previously, single routines in the .text section
> + * would be considered a program on their own.
> + */
> + LIBBPF_STRICT_TEXT_ONLY_SUBPROGRAMS = 0x40,
We have LIBBPF_STRICT_SEC_NAME, we can probably just rely on that one.
STRICT_SEC_NAME means (among other things) that there has to be
SEC("abc"), so there can't be BPF program in .text section. We don't
enforce that yet, but that's a separate thing.
>
> __LIBBPF_STRICT_LAST,
> };
> --
> 2.34.1
