On Tue, Mar 15, 2022 at 3:15 PM Delyan Kratunov <delyank@xxxxxx> wrote:
>
> Currently, libbpf considers a single routine in .text to be 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 the pre-existing
> SEC_NAME strict mode flag.
>
> Signed-off-by: Delyan Kratunov <delyank@xxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 7 +++++++
> tools/lib/bpf/libbpf_legacy.h | 4 +++-
> 2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 43161fdd44bb..aa26163e4ca1 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_SEC_NAME)
> + 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..8d2e632aec79 100644
> --- a/tools/lib/bpf/libbpf_legacy.h
> +++ b/tools/lib/bpf/libbpf_legacy.h
> @@ -53,7 +53,9 @@ enum libbpf_strict_mode {
> * SEC("xdp") and SEC("perf_event").
> *
> * Note, in this mode the program pin path will be based on the
> - * function name instead of section name.
> + * function name instead of section name. Additionally, routines in the
> + * .text section are always considered sub-programs. (Legacy behavior
> + * allows for a single routine in .text to be a program.)
nit: pinning doesn't have much in common with this, so please put the
new text on a separate paragraph
> */
> LIBBPF_STRICT_SEC_NAME = 0x04,
> /*
> --
> 2.34.1
