2 files changed, 52 insertions, 0 deletions

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index c08d6bca1c22..6f0c13a1fb3c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7,8 +7,48 @@
  */
 
 #include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <string.h>
 #include <unistd.h>
 #include <asm/unistd.h>
 #include <linux/bpf.h>
 
 #include "libbpf.h"
+
+#define __printf(a, b)  __attribute__((format(printf, a, b)))
+
+__printf(1, 2)
+static int __base_pr(const char *format, ...)
+{
+        va_list args;
+        int err;
+
+        va_start(args, format);
+        err = vfprintf(stderr, format, args);
+        va_end(args);
+        return err;
+}
+
+static __printf(1, 2) libbpf_print_fn_t __pr_warning = __base_pr;
+static __printf(1, 2) libbpf_print_fn_t __pr_info = __base_pr;
+static __printf(1, 2) libbpf_print_fn_t __pr_debug;
+
+#define __pr(func, fmt, ...)    \
+do {                            \
+        if ((func))             \
+                (func)("libbpf: " fmt, ##__VA_ARGS__); \
+} while (0)
+
+#define pr_warning(fmt, ...)    __pr(__pr_warning, fmt, ##__VA_ARGS__)
+#define pr_info(fmt, ...)       __pr(__pr_info, fmt, ##__VA_ARGS__)
+#define pr_debug(fmt, ...)      __pr(__pr_debug, fmt, ##__VA_ARGS__)
+
+void libbpf_set_print(libbpf_print_fn_t warn,
+                      libbpf_print_fn_t info,
+                      libbpf_print_fn_t debug)
+{
+        __pr_warning = warn;
+        __pr_info = info;
+        __pr_debug = debug;
+}
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index a6f46d908097..8d1eebafa958 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -8,4 +8,16 @@
 #ifndef __BPF_LIBBPF_H
 #define __BPF_LIBBPF_H
 
+/*
+ * In include/linux/compiler-gcc.h, __printf is defined. However
+ * it should be better if libbpf.h doesn't depend on Linux header file.
+ * So instead of __printf, here we use gcc attribute directly.
+ */
+typedef int (*libbpf_print_fn_t)(const char *, ...)
+        __attribute__((format(printf, 1, 2)));
+
+void libbpf_set_print(libbpf_print_fn_t warn,
+                      libbpf_print_fn_t info,
+                      libbpf_print_fn_t debug);
+
 #endif