libbpf: Constify few bpf_program getters

bpf_program__get_type() and bpf_program__get_expected_attach_type() shouldn't
modify given bpf_program, so mark input parameter as const struct bpf_program.
This eliminates unnecessary compilation warnings or explicit casts in user
programs.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210324172941.2609884-1-andrii@kernel.org

tools/lib/bpf/libbpf.c

@@ -8458,7 +8458,7 @@ int bpf_program__nth_fd(const struct bpf_program *prog, int n)
 	return fd;
 }
 
-enum bpf_prog_type bpf_program__get_type(struct bpf_program *prog)
+enum bpf_prog_type bpf_program__get_type(const struct bpf_program *prog)
 {
 	return prog->type;
 }
@@ -8503,7 +8503,7 @@ BPF_PROG_TYPE_FNS(extension, BPF_PROG_TYPE_EXT);
 BPF_PROG_TYPE_FNS(sk_lookup, BPF_PROG_TYPE_SK_LOOKUP);
 
 enum bpf_attach_type
-bpf_program__get_expected_attach_type(struct bpf_program *prog)
+bpf_program__get_expected_attach_type(const struct bpf_program *prog)
 {
 	return prog->expected_attach_type;
 }

tools/lib/bpf/libbpf.h

@@ -361,12 +361,12 @@ LIBBPF_API int bpf_program__set_struct_ops(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_extension(struct bpf_program *prog);
 LIBBPF_API int bpf_program__set_sk_lookup(struct bpf_program *prog);
 
-LIBBPF_API enum bpf_prog_type bpf_program__get_type(struct bpf_program *prog);
+LIBBPF_API enum bpf_prog_type bpf_program__get_type(const struct bpf_program *prog);
 LIBBPF_API void bpf_program__set_type(struct bpf_program *prog,
 				      enum bpf_prog_type type);
 
 LIBBPF_API enum bpf_attach_type
-bpf_program__get_expected_attach_type(struct bpf_program *prog);
+bpf_program__get_expected_attach_type(const struct bpf_program *prog);
 LIBBPF_API void
 bpf_program__set_expected_attach_type(struct bpf_program *prog,
 				      enum bpf_attach_type type);