On Mon, Mar 3, 2025 at 5:58 AM Mykyta Yatsenko
<mykyta.yatsenko5@xxxxxxxxx> wrote:
>
> From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
>
> Introduce bpf_object__prepare API: additional intermediate preparation
> step that performs ELF processing, relocations, prepares final state of
> BPF program instructions (accessible with bpf_program__insns()), creates
> and (potentially) pins maps, and stops short of loading BPF programs.
>
> We anticipate few use cases for this API, such as:
> * Use prepare to initialize bpf_token, without loading freplace
> programs, unlocking possibility to lookup BTF of other programs.
> * Execute prepare to obtain finalized BPF program instructions without
> loading programs, enabling tools like veristat to process one program at
> a time, without incurring cost of ELF parsing and processing.
>
> Signed-off-by: Mykyta Yatsenko <yatsenko@xxxxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 144 +++++++++++++++++++++++++++------------
> tools/lib/bpf/libbpf.h | 13 ++++
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 115 insertions(+), 43 deletions(-)
>
[...]
> + err = bpf_object_prepare_token(obj);
> + err = err ? : bpf_object__probe_loading(obj);
> + err = err ? : bpf_object__load_vmlinux_btf(obj, false);
> + err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
> + err = err ? : bpf_object__sanitize_maps(obj);
> + err = err ? : bpf_object__init_kern_struct_ops_maps(obj);
> + err = err ? : bpf_object_adjust_struct_ops_autoload(obj);
> + err = err ? : bpf_object__relocate(obj, obj->btf_custom_path ? : target_btf_path);
> + err = err ? : bpf_object__sanitize_and_load_btf(obj);
> + err = err ? : bpf_object__create_maps(obj);
> + err = err ? : bpf_object_prepare_progs(obj);
> + obj->state = OBJ_PREPARED;
> +
> + if (err) {
> + bpf_object_unpin(obj);
> + bpf_object_unload(obj);
I think it's best to set obj->state = OBJ_LOADED here to prevent
subsequent bpf_object__load() from trying to do anything (and probably
crashing). I'll add this while applying.
> + return err;
> + }
> + return 0;
> +}
> +
> static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path)
> {
> - int err, i;
> + int err;
>
> if (!obj)
> return libbpf_err(-EINVAL);
[...]
