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Groups > linux.kernel > #1202801

[PATCH 02/24] bpf tools: Allow caller to set printing function

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From: Wang Nan <wangnan0@huawei.com>

By libbpf_set_print(), users of libbpf are allowed to register he/she
own debug, info and warning printing functions. Libbpf will use those
functions to print messages. If not provided, default info and warning
printing functions are fprintf(stderr, ...); default debug printing
is NULL.

This API is designed to be used by perf, enables it to register its own
logging functions to make all logs uniform, instead of separated
logging level control.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1435716878-189507-5-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/lib/bpf/libbpf.c | 40 ++++++++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h | 12 ++++++++++++
 2 files changed, 52 insertions(+)

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
-- 
2.1.0

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[GIT PULL 00/24] perf/ebpf lib + llvm/clang building infrastructure Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 05/24] bpf tools: Check endianness and make libbpf fail early Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 01/24] bpf tools: Introduce 'bpf' library and add bpf feature check Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 11/24] bpf tools: Collect relocation sections from SHT_REL sections Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 13/24] bpf tools: Add bpf.c/h for common bpf operations Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 18/24] bpf tools: Introduce accessors for struct bpf_program Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 03/24] bpf tools: Open eBPF object file and do basic validation Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 21/24] perf tools: Call clang to compile C source to object code Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 04/24] bpf tools: Read eBPF object from buffer Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 08/24] bpf tools: Collect map definitions from 'maps' section Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 22/24] perf tools: Auto detecting kernel build directory Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 19/24] bpf tools: Link all bpf objects onto a list Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 15/24] bpf tools: Relocate eBPF programs Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 12/24] bpf tools: Record map accessing instructions for each program Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 06/24] bpf tools: Iterate over ELF sections to collect information Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 24/24] perf tests: Add LLVM test for eBPF on-the-fly compiling Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 17/24] bpf tools: Load eBPF programs in object files into kernel Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 23/24] perf tools: Auto detecting kernel include options Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 10/24] bpf tools: Collect eBPF programs from their own sections Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 16/24] bpf tools: Introduce bpf_load_program() to bpf.c Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 02/24] bpf tools: Allow caller to set printing function Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  [PATCH 20/24] perf tools: Introduce llvm config options Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-08-07 17:00 +0200
  Re: [GIT PULL 00/24] perf/ebpf lib + llvm/clang building  infrastructure Ingo Molnar <mingo@kernel.org> - 2015-08-08 10:10 +0200

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