tools/lib/bpf: bpf_program__insns allow to retrieve insns in libbpf

This allows consumers of libbpf to iterate trough the insns
of a program without loading it first directly after the ELF parsing.

Being able to do that is useful to create tooling that can show
the structure of a BPF program using libbpf without having to
parse the ELF separately.

Usage:
  struct bpf_insn *insn;
  insn = bpf_program__insns(prog);

Signed-off-by: Lorenzo Fontana <fontanalorenz@gmail.com>

tools/lib/bpf/libbpf.c

@@ -8908,6 +8908,11 @@ void *bpf_program__priv(const struct bpf_program *prog)
 	return prog ? prog->priv : libbpf_err_ptr(-EINVAL);
 }
 
+struct bpf_insn *bpf_program__insns(const struct bpf_program *prog)
+{
+	return prog ? prog->insns : libbpf_err_ptr(-EINVAL);
+}
+
 void bpf_program__set_ifindex(struct bpf_program *prog, __u32 ifindex)
 {
 	prog->prog_ifindex = ifindex;

tools/lib/bpf/libbpf.h

@@ -195,6 +195,7 @@ typedef void (*bpf_program_clear_priv_t)(struct bpf_program *, void *);
 LIBBPF_API int bpf_program__set_priv(struct bpf_program *prog, void *priv,
 				     bpf_program_clear_priv_t clear_priv);
 
+LIBBPF_API struct bpf_insn *bpf_program__insns(const struct bpf_program *prog);
 LIBBPF_API void *bpf_program__priv(const struct bpf_program *prog);
 LIBBPF_API void bpf_program__set_ifindex(struct bpf_program *prog,
 					 __u32 ifindex);