sync with bpf-next

Sync with the following bug fix:
  commit a8a1f7d09cfc7e18874786c7634c9e71384fcd4e (HEAD -> bpf-next2, bpf-next/master)
  Author: Stanislav Fomichev <sdf@google.com>
  Date:   Mon Feb 4 16:20:55 2019 -0800

    libbpf: fix libbpf_print

    With the recent print rework we now have the following problem:
    pr_{warning,info,debug} expand to __pr which calls libbpf_print.
    libbpf_print does va_start and calls __libbpf_pr with va_list argument.
    In __base_pr we again do va_start. Because the next argument is a
    va_list, we don't get correct pointer to the argument (and print noting
    in my case, I don't know why it doesn't crash tbh).

    ......

    Signed-off-by: Stanislav Fomichev <sdf@google.com>

Signed-off-by: Yonghong Song <yhs@fb.com>

src/libbpf.c

@@ -54,22 +54,16 @@
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
-__printf(2, 3)
-static int __base_pr(enum libbpf_print_level level, const char *format, ...)
+static int __base_pr(enum libbpf_print_level level, const char *format,
+		     va_list args)
 {
-	va_list args;
-	int err;
-
 	if (level == LIBBPF_DEBUG)
 		return 0;
 
-	va_start(args, format);
-	err = vfprintf(stderr, format, args);
-	va_end(args);
-	return err;
+	return vfprintf(stderr, format, args);
 }
 
-static __printf(2, 3) libbpf_print_fn_t __libbpf_pr = __base_pr;
+static libbpf_print_fn_t __libbpf_pr = __base_pr;
 
 void libbpf_set_print(libbpf_print_fn_t fn)
 {

src/libbpf.h

@@ -54,8 +54,7 @@ enum libbpf_print_level {
 };
 
 typedef int (*libbpf_print_fn_t)(enum libbpf_print_level level,
-				 const char *, ...)
-	__attribute__((format(printf, 2, 3)));
+				 const char *, va_list ap);
 
 LIBBPF_API void libbpf_set_print(libbpf_print_fn_t fn);