libbpf: add "prog_flags" to bpf_program/bpf_prog_load_attr/bpf_load_program_attr

libbpf doesn't allow passing "prog_flags" during bpf program load in a
couple of load related APIs, "bpf_load_program_xattr", "load_program" and
"bpf_prog_load_xattr".

It makes sense to allow passing "prog_flags" which is useful for
customizing program loading.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/bpf.c

@@ -256,6 +256,7 @@ int bpf_load_program_xattr(const struct bpf_load_program_attr *load_attr,
 	if (load_attr->name)
 		memcpy(attr.prog_name, load_attr->name,
 		       min(strlen(load_attr->name), BPF_OBJ_NAME_LEN - 1));
+	attr.prog_flags = load_attr->prog_flags;
 
 	fd = sys_bpf_prog_load(&attr, sizeof(attr));
 	if (fd >= 0)

tools/lib/bpf/bpf.h

@@ -87,6 +87,7 @@ struct bpf_load_program_attr {
 	const void *line_info;
 	__u32 line_info_cnt;
 	__u32 log_level;
+	__u32 prog_flags;
 };
 
 /* Flags to direct loading requirements */

tools/lib/bpf/libbpf.c

@@ -188,6 +188,7 @@ struct bpf_program {
 	void *line_info;
 	__u32 line_info_rec_size;
 	__u32 line_info_cnt;
+	__u32 prog_flags;
 };
 
 enum libbpf_map_type {
@@ -2076,6 +2077,7 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
 	load_attr.line_info_rec_size = prog->line_info_rec_size;
 	load_attr.line_info_cnt = prog->line_info_cnt;
 	load_attr.log_level = prog->log_level;
+	load_attr.prog_flags = prog->prog_flags;
 	if (!load_attr.insns || !load_attr.insns_cnt)
 		return -EINVAL;
 
@@ -3521,6 +3523,7 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
 						      expected_attach_type);
 
 		prog->log_level = attr->log_level;
+		prog->prog_flags = attr->prog_flags;
 		if (!first_prog)
 			first_prog = prog;
 	}

tools/lib/bpf/libbpf.h

@@ -320,6 +320,7 @@ struct bpf_prog_load_attr {
 	enum bpf_attach_type expected_attach_type;
 	int ifindex;
 	int log_level;
+	int prog_flags;
 };
 
 LIBBPF_API int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,