libbpf: Add ability to get/set per-program load flags

Add bpf_program__flags() API to retrieve prog_flags that will be (or
were) supplied to BPF_PROG_LOAD command.

Also add bpf_program__set_extra_flags() API to allow to set *extra*
flags, in addition to those determined by program's SEC() definition.
Such flags are logically OR'ed with libbpf-derived flags.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211111051758.92283-2-andrii@kernel.org

tools/lib/bpf/libbpf.c

@@ -8262,6 +8262,20 @@ void bpf_program__set_expected_attach_type(struct bpf_program *prog,
 	prog->expected_attach_type = type;
 }
 
+__u32 bpf_program__flags(const struct bpf_program *prog)
+{
+	return prog->prog_flags;
+}
+
+int bpf_program__set_extra_flags(struct bpf_program *prog, __u32 extra_flags)
+{
+	if (prog->obj->loaded)
+		return libbpf_err(-EBUSY);
+
+	prog->prog_flags |= extra_flags;
+	return 0;
+}
+
 #define SEC_DEF(sec_pfx, ptype, atype, flags, ...) {			    \
 	.sec = sec_pfx,							    \
 	.prog_type = BPF_PROG_TYPE_##ptype,				    \

tools/lib/bpf/libbpf.h

@@ -493,6 +493,9 @@ LIBBPF_API void
 bpf_program__set_expected_attach_type(struct bpf_program *prog,
 				      enum bpf_attach_type type);
 
+LIBBPF_API __u32 bpf_program__flags(const struct bpf_program *prog);
+LIBBPF_API int bpf_program__set_extra_flags(struct bpf_program *prog, __u32 extra_flags);
+
 LIBBPF_API int
 bpf_program__set_attach_target(struct bpf_program *prog, int attach_prog_fd,
 			       const char *attach_func_name);

tools/lib/bpf/libbpf.map

@@ -397,8 +397,10 @@ LIBBPF_0.6.0 {
 		bpf_object__prev_program;
 		bpf_prog_load_deprecated;
 		bpf_prog_load;
+		bpf_program__flags;
 		bpf_program__insn_cnt;
 		bpf_program__insns;
+		bpf_program__set_extra_flags;
 		btf__add_btf;
 		btf__add_decl_tag;
 		btf__raw_data;