From: Andrii Nakryiko <andriin@fb.com>
Date: Sat, 27 Jul 2019 20:25:26 -0700
Subject: libbpf: return previous print callback from libbpf_set_print
Patch-mainline: v5.4-rc1
Git-commit: e87fd8bae44c3eaa6205c9c81419e773896dc157
References: bsc#1154353

By returning previously set print callback from libbpf_set_print, it's
possible to restore it, eventually. This is useful when running many
independent test with one default print function, but overriding log
verbosity for particular subset of tests.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 tools/lib/bpf/libbpf.c |    5 ++++-
 tools/lib/bpf/libbpf.h |    2 +-
 2 files changed, 5 insertions(+), 2 deletions(-)

--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -75,9 +75,12 @@ static int __base_pr(enum libbpf_print_l
 
 static libbpf_print_fn_t __libbpf_pr = __base_pr;
 
-void libbpf_set_print(libbpf_print_fn_t fn)
+libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn)
 {
+	libbpf_print_fn_t old_print_fn = __libbpf_pr;
+
 	__libbpf_pr = fn;
+	return old_print_fn;
 }
 
 __printf(2, 3)
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -57,7 +57,7 @@ enum libbpf_print_level {
 typedef int (*libbpf_print_fn_t)(enum libbpf_print_level level,
 				 const char *, va_list ap);
 
-LIBBPF_API void libbpf_set_print(libbpf_print_fn_t fn);
+LIBBPF_API libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn);
 
 /* Hide internal to user */
 struct bpf_object;