linux-kernel - [PATCH 02/12] perf bpf: Mute libbpf when '-v' not set

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Date:	Thu,  5 Nov 2015 13:02:12 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Wang Nan <wangnan0@...wei.com>,
	Zefan Li <lizefan@...wei.com>, pi3orama@....com,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 02/12] perf bpf: Mute libbpf when '-v' not set

From: Wang Nan <wangnan0@...wei.com>

According to [1], libbpf should be muted. This patch reset info and
warning message level to ensure libbpf doesn't output anything even
if error happened.

[1] http://lkml.kernel.org/r/20151020151255.GF5119@kernel.org

Committer note:

Before:

Testing it with an incompatible kernel version in the .c file that
generated foo.o:

  [root@zoo ~]# perf record -e /tmp/foo.o sleep 1
  libbpf: load bpf program failed: Invalid argument
  libbpf: -- BEGIN DUMP LOG ---
  libbpf:

  libbpf: -- END LOG --
  libbpf: failed to load program 'fork=_do_fork'
  libbpf: failed to load object '/tmp/foo.o'
  event syntax error: '/tmp/foo.o'
                       \___ Invalid argument: Are you root and runing a CONFIG_BPF_SYSCALL kernel?

  (add -v to see detail)
  Run 'perf list' for a list of valid events

   Usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

      -e, --event <event>   event selector. use 'perf list' to list available events
  [root@zoo ~]#

After:

  [root@zoo ~]# perf record -e /tmp/foo.o sleep 1
  event syntax error: '/tmp/foo.o'
                       \___ Invalid argument: Are you root and runing a CONFIG_BPF_SYSCALL kernel?

  (add -v to see detail)
  Run 'perf list' for a list of valid events

   Usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

      -e, --event <event>   event selector. use 'perf list' to list available events
  [root@zoo ~]#

This, BTW, need fixing to emit a proper message by validating the
version in the foo.o "version" ELF section against the running kernel,
warning the user instead of asking the kernel to load a binary that it
will refuse due to unmatching kernel version.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Zefan Li <lizefan@...wei.com>
Cc: pi3orama@....com
Link: http://lkml.kernel.org/r/1446547486-229499-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/bpf-loader.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index ba6f7526b282..0c5d174245bb 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -26,8 +26,8 @@ static int libbpf_##name(const char *fmt, ...)	\
 	return ret;				\
 }
 
-DEFINE_PRINT_FN(warning, 0)
-DEFINE_PRINT_FN(info, 0)
+DEFINE_PRINT_FN(warning, 1)
+DEFINE_PRINT_FN(info, 1)
 DEFINE_PRINT_FN(debug, 1)
 
 struct bpf_prog_priv {
-- 
2.1.0

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