tools: bpftool: refactor argument parsing for prog load

Add a new macro for printing more informative message than straight
usage() when parameters are missing, and use it for prog do_load().
Save the object and pin path argument to variables for clarity.
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/bpf/bpftool/main.h

@@ -50,6 +50,21 @@
 #define NEXT_ARG()	({ argc--; argv++; if (argc < 0) usage(); })
 #define NEXT_ARGP()	({ (*argc)--; (*argv)++; if (*argc < 0) usage(); })
 #define BAD_ARG()	({ p_err("what is '%s'?", *argv); -1; })
+#define GET_ARG()	({ argc--; *argv++; })
+#define REQ_ARGS(cnt)							\
+	({								\
+		int _cnt = (cnt);					\
+		bool _res;						\
+									\
+		if (argc < _cnt) {					\
+			p_err("'%s' needs at least %d arguments, %d found", \
+			      argv[-1], _cnt, argc);			\
+			_res = false;					\
+		} else {						\
+			_res = true;					\
+		}							\
+		_res;							\
+	})
 
 #define ERR_MAX_LEN	1024
 

tools/bpf/bpftool/prog.c

@@ -681,18 +681,21 @@ static int do_pin(int argc, char **argv)
 
 static int do_load(int argc, char **argv)
 {
+	const char *objfile, *pinfile;
 	struct bpf_object *obj;
 	int prog_fd;
 
-	if (argc != 2)
-		usage();
+	if (!REQ_ARGS(2))
+		return -1;
+	objfile = GET_ARG();
+	pinfile = GET_ARG();
 
-	if (bpf_prog_load(argv[0], BPF_PROG_TYPE_UNSPEC, &obj, &prog_fd)) {
+	if (bpf_prog_load(objfile, BPF_PROG_TYPE_UNSPEC, &obj, &prog_fd)) {
 		p_err("failed to load program");
 		return -1;
 	}
 
-	if (do_pin_fd(prog_fd, argv[1]))
+	if (do_pin_fd(prog_fd, pinfile))
 		goto err_close_obj;
 
 	if (json_output)