Merge branch 'change-libbpf-print-api'

Yonghong Song says:

====================
These are patches responding to my comments for
Magnus's patch (https://patchwork.ozlabs.org/patch/1032848/).
The goal is to make pr_* macros available to other C files
than libbpf.c, and to simplify API function libbpf_set_print().

Specifically, Patch #1 used global functions
to facilitate pr_* macros in the header files so they
are available in different C files.
Patch #2 removes the global function libbpf_print_level_available()
which is added in Patch 1.
Patch #3 simplified libbpf_set_print() which takes only one print
function with a debug level argument among others.

Changelogs:
 v3 -> v4:
   . rename libbpf internal header util.h to libbpf_util.h
   . rename libbpf internal function libbpf_debug_print() to libbpf_print()
 v2 -> v3:
   . bailed out earlier in libbpf_debug_print() if __libbpf_pr is NULL
   . added missing LIBBPF_DEBUG level check in libbpf.c __base_pr().
 v1 -> v2:
   . Renamed global function libbpf_dprint() to libbpf_debug_print()
     to be more expressive.
   . Removed libbpf_dprint_level_available() as it is used only
     once in btf.c and we can remove it by optimizing for common cases.
====================
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/lib/bpf/btf.h

@@ -55,11 +55,8 @@ struct btf_ext_header {
 	__u32	line_info_len;
 };
 
-typedef int (*btf_print_fn_t)(const char *, ...)
-	__attribute__((format(printf, 1, 2)));
-
 LIBBPF_API void btf__free(struct btf *btf);
-LIBBPF_API struct btf *btf__new(__u8 *data, __u32 size, btf_print_fn_t err_log);
+LIBBPF_API struct btf *btf__new(__u8 *data, __u32 size);
 LIBBPF_API __s32 btf__find_by_name(const struct btf *btf,
 				   const char *type_name);
 LIBBPF_API const struct btf_type *btf__type_by_id(const struct btf *btf,
@@ -70,7 +67,7 @@ LIBBPF_API int btf__fd(const struct btf *btf);
 LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
 
-struct btf_ext *btf_ext__new(__u8 *data, __u32 size, btf_print_fn_t err_log);
+struct btf_ext *btf_ext__new(__u8 *data, __u32 size);
 void btf_ext__free(struct btf_ext *btf_ext);
 int btf_ext__reloc_func_info(const struct btf *btf,
 			     const struct btf_ext *btf_ext,

tools/lib/bpf/libbpf.c

@@ -42,6 +42,7 @@
 #include "bpf.h"
 #include "btf.h"
 #include "str_error.h"
+#include "libbpf_util.h"
 
 #ifndef EM_BPF
 #define EM_BPF 247
@@ -53,39 +54,39 @@
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
-__printf(1, 2)
-static int __base_pr(const char *format, ...)
+__printf(2, 3)
+static int __base_pr(enum libbpf_print_level level, const char *format, ...)
 {
 	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;
 }
 
-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)
+static __printf(2, 3) libbpf_print_fn_t __libbpf_pr = __base_pr;
 
-#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 fn)
+{
+	__libbpf_pr = fn;
+}
 
-void libbpf_set_print(libbpf_print_fn_t warn,
-		      libbpf_print_fn_t info,
-		      libbpf_print_fn_t debug)
+__printf(2, 3)
+void libbpf_print(enum libbpf_print_level level, const char *format, ...)
 {
-	__pr_warning = warn;
-	__pr_info = info;
-	__pr_debug = debug;
+	va_list args;
+
+	if (!__libbpf_pr)
+		return;
+
+	va_start(args, format);
+	__libbpf_pr(level, format, args);
+	va_end(args);
 }
 
 #define STRERR_BUFSIZE  128
@@ -839,8 +840,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 		else if (strcmp(name, "maps") == 0)
 			obj->efile.maps_shndx = idx;
 		else if (strcmp(name, BTF_ELF_SEC) == 0) {
-			obj->btf = btf__new(data->d_buf, data->d_size,
-					    __pr_debug);
+			obj->btf = btf__new(data->d_buf, data->d_size);
 			if (IS_ERR(obj->btf)) {
 				pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
 					   BTF_ELF_SEC, PTR_ERR(obj->btf));
@@ -915,8 +915,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, int flags)
 				 BTF_EXT_ELF_SEC, BTF_ELF_SEC);
 		} else {
 			obj->btf_ext = btf_ext__new(btf_ext_data->d_buf,
-						    btf_ext_data->d_size,
-						    __pr_debug);
+						    btf_ext_data->d_size);
 			if (IS_ERR(obj->btf_ext)) {
 				pr_warning("Error loading ELF section %s: %ld. Ignored and continue.\n",
 					   BTF_EXT_ELF_SEC,

tools/lib/bpf/libbpf.h

@@ -47,17 +47,17 @@ enum libbpf_errno {
 
 LIBBPF_API int libbpf_strerror(int err, char *buf, size_t size);
 
-/*
- * __printf is defined in include/linux/compiler-gcc.h. However,
- * it would be better if libbpf.h didn't depend on Linux header files.
- * So instead of __printf, here we use gcc attribute directly.
- */
-typedef int (*libbpf_print_fn_t)(const char *, ...)
-	__attribute__((format(printf, 1, 2)));
+enum libbpf_print_level {
+        LIBBPF_WARN,
+        LIBBPF_INFO,
+        LIBBPF_DEBUG,
+};
+
+typedef int (*libbpf_print_fn_t)(enum libbpf_print_level level,
+				 const char *, ...)
+	__attribute__((format(printf, 2, 3)));
 
-LIBBPF_API void libbpf_set_print(libbpf_print_fn_t warn,
-				 libbpf_print_fn_t info,
-				 libbpf_print_fn_t debug);
+LIBBPF_API void libbpf_set_print(libbpf_print_fn_t fn);
 
 /* Hide internal to user */
 struct bpf_object;

tools/lib/bpf/libbpf_util.h

+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+/* Copyright (c) 2019 Facebook */
+
+#ifndef __LIBBPF_LIBBPF_UTIL_H
+#define __LIBBPF_LIBBPF_UTIL_H
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern void libbpf_print(enum libbpf_print_level level,
+			 const char *format, ...)
+	__attribute__((format(printf, 2, 3)));
+
+#define __pr(level, fmt, ...)	\
+do {				\
+	libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__);	\
+} while (0)
+
+#define pr_warning(fmt, ...)	__pr(LIBBPF_WARN, fmt, ##__VA_ARGS__)
+#define pr_info(fmt, ...)	__pr(LIBBPF_INFO, fmt, ##__VA_ARGS__)
+#define pr_debug(fmt, ...)	__pr(LIBBPF_DEBUG, fmt, ##__VA_ARGS__)
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif

tools/lib/bpf/test_libbpf.cpp

@@ -8,11 +8,11 @@
 int main(int argc, char *argv[])
 {
     /* libbpf.h */
-    libbpf_set_print(NULL, NULL, NULL);
+    libbpf_set_print(NULL);
 
     /* bpf.h */
     bpf_prog_get_fd_by_id(0);
 
     /* btf.h */
-    btf__new(NULL, 0, NULL);
+    btf__new(NULL, 0);
 }

tools/perf/util/bpf-loader.c

@@ -24,21 +24,17 @@
 #include "llvm-utils.h"
 #include "c++/clang-c.h"
 
-#define DEFINE_PRINT_FN(name, level) \
-static int libbpf_##name(const char *fmt, ...)	\
-{						\
-	va_list args;				\
-	int ret;				\
-						\
-	va_start(args, fmt);			\
-	ret = veprintf(level, verbose, pr_fmt(fmt), args);\
-	va_end(args);				\
-	return ret;				\
-}
+static int libbpf_perf_print(enum libbpf_print_level level __attribute__((unused)),
+			      const char *fmt, ...)
+{
+	va_list args;
+	int ret;
 
-DEFINE_PRINT_FN(warning, 1)
-DEFINE_PRINT_FN(info, 1)
-DEFINE_PRINT_FN(debug, 1)
+	va_start(args, fmt);
+	ret = veprintf(1, verbose, pr_fmt(fmt), args);
+	va_end(args);
+	return ret;
+}
 
 struct bpf_prog_priv {
 	bool is_tp;
@@ -59,9 +55,7 @@ bpf__prepare_load_buffer(void *obj_buf, size_t obj_buf_sz, const char *name)
 	struct bpf_object *obj;
 
 	if (!libbpf_initialized) {
-		libbpf_set_print(libbpf_warning,
-				 libbpf_info,
-				 libbpf_debug);
+		libbpf_set_print(libbpf_perf_print);
 		libbpf_initialized = true;
 	}
 
@@ -79,9 +73,7 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
 	struct bpf_object *obj;
 
 	if (!libbpf_initialized) {
-		libbpf_set_print(libbpf_warning,
-				 libbpf_info,
-				 libbpf_debug);
+		libbpf_set_print(libbpf_perf_print);
 		libbpf_initialized = true;
 	}
 

tools/testing/selftests/bpf/test_btf.c

@@ -54,8 +54,9 @@ static int count_result(int err)
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
 
-__printf(1, 2)
-static int __base_pr(const char *format, ...)
+__printf(2, 3)
+static int __base_pr(enum libbpf_print_level level __attribute__((unused)),
+		     const char *format, ...)
 {
 	va_list args;
 	int err;
@@ -5650,7 +5651,7 @@ int main(int argc, char **argv)
 		return err;
 
 	if (args.always_log)
-		libbpf_set_print(__base_pr, __base_pr, __base_pr);
+		libbpf_set_print(__base_pr);
 
 	if (args.raw_test)
 		err |= test_raw();

tools/testing/selftests/bpf/test_libbpf_open.c

@@ -34,23 +34,22 @@ static void usage(char *argv[])
 	printf("\n");
 }
 
-#define DEFINE_PRINT_FN(name, enabled) \
-static int libbpf_##name(const char *fmt, ...)  	\
-{							\
-        va_list args;					\
-        int ret;					\
-							\
-        va_start(args, fmt);				\
-	if (enabled) {					\
-		fprintf(stderr, "[" #name "] ");	\
-		ret = vfprintf(stderr, fmt, args);	\
-	}						\
-        va_end(args);					\
-        return ret;					\
+static bool debug = 0;
+static int libbpf_debug_print(enum libbpf_print_level level,
+			      const char *fmt, ...)
+{
+	va_list args;
+	int ret;
+
+	if (level == LIBBPF_DEBUG && !debug)
+		return 0;
+
+	va_start(args, fmt);
+	fprintf(stderr, "[%d] ", level);
+	ret = vfprintf(stderr, fmt, args);
+	va_end(args);
+	return ret;
 }
-DEFINE_PRINT_FN(warning, 1)
-DEFINE_PRINT_FN(info, 1)
-DEFINE_PRINT_FN(debug, 1)
 
 #define EXIT_FAIL_LIBBPF EXIT_FAILURE
 #define EXIT_FAIL_OPTION 2
@@ -120,15 +119,14 @@ int main(int argc, char **argv)
 	int longindex = 0;
 	int opt;
 
-	libbpf_set_print(libbpf_warning, libbpf_info, NULL);
+	libbpf_set_print(libbpf_debug_print);
 
 	/* Parse commands line args */
 	while ((opt = getopt_long(argc, argv, "hDq",
 				  long_options, &longindex)) != -1) {
 		switch (opt) {
 		case 'D':
-			libbpf_set_print(libbpf_warning, libbpf_info,
-					 libbpf_debug);
+			debug = 1;
 			break;
 		case 'q': /* Use in scripting mode */
 			verbose = 0;

tools/testing/selftests/bpf/test_progs.c

@@ -10,6 +10,7 @@
 #include <string.h>
 #include <assert.h>
 #include <stdlib.h>
+#include <stdarg.h>
 #include <time.h>
 
 #include <linux/types.h>
@@ -1783,6 +1784,21 @@ static void test_task_fd_query_tp(void)
 				   "sys_enter_read");
 }
 
+static int libbpf_debug_print(enum libbpf_print_level level,
+			      const char *format, ...)
+{
+	va_list args;
+	int ret;
+
+	if (level == LIBBPF_DEBUG)
+		return 0;
+
+	va_start(args, format);
+	ret = vfprintf(stderr, format, args);
+	va_end(args);
+	return ret;
+}
+
 static void test_reference_tracking()
 {
 	const char *file = "./test_sk_lookup_kern.o";
@@ -1809,9 +1825,9 @@ static void test_reference_tracking()
 
 		/* Expect verifier failure if test name has 'fail' */
 		if (strstr(title, "fail") != NULL) {
-			libbpf_set_print(NULL, NULL, NULL);
+			libbpf_set_print(NULL);
 			err = !bpf_program__load(prog, "GPL", 0);
-			libbpf_set_print(printf, printf, NULL);
+			libbpf_set_print(libbpf_debug_print);
 		} else {
 			err = bpf_program__load(prog, "GPL", 0);
 		}