linux-kernel - [PATCH 09/46] perf data: Explicitly set byte order for integer types

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Date:	Fri, 26 Feb 2016 09:31:57 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	Alexei Starovoitov <ast@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	Jiri Olsa <jolsa@...nel.org>, Li Zefan <lizefan@...wei.com>,
	"Peter Zijlstra" <peterz@...radead.org>, <pi3orama@....com>,
	Wang Nan <wangnan0@...wei.com>, <linux-kernel@...r.kernel.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jérémie Galarneau 
	<jeremie.galarneau@...icios.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH 09/46] perf data: Explicitly set byte order for integer types

After babeltrace commit 5cec03e402aa ("ir: copy variants and
sequences when setting a field path"), 'perf data convert' gets
incorrect result if there's bpf output data. For example:

 # perf data convert --to-ctf ./out.ctf
 # babeltrace ./out.ctf
 [10:44:31.186045346] (+?.?????????) evt: { cpu_id = 0 }, { perf_ip = 0xFFFFFFFF810E7DD1, perf_tid = 23819, perf_pid = 23819, perf_id = 518, raw_len = 3, raw_data = [ [0] = 0xC028E32F, [1] = 0x815D0100, [2] = 0x1000000 ] }
 [10:44:31.286101003] (+0.100055657) evt: { cpu_id = 0 }, { perf_ip = 0xFFFFFFFF8105B609, perf_tid = 23819, perf_pid = 23819, perf_id = 518, raw_len = 3, raw_data = [ [0] = 0x35D9F1EB, [1] = 0x15D81, [2] = 0x2 ] }

The expected result of the first sample should be:

 raw_data = [ [0] = 0x2FE328C0, [1] = 0x15D81, [2] = 0x1 ] }

however, 'perf data convert' output big endian value to resuling CTF
file.

The reason is a internal change (or a bug?) of babeltrace.

Before this patch, at the first add_bpf_output_values(), byte order of
all integer type is uncertain (is 0, neither 1234 (le) nor 4321 (be)).
It would be fixed by:

perf_evlist__deliver_sample
 -> process_sample_event
   -> ctf_stream
      ...
      ->bt_ctf_trace_add_stream_class
        ->bt_ctf_field_type_structure_set_byte_order
          ->bt_ctf_field_type_integer_set_byte_order

during creating the stream.

However, the babeltrace commit mentioned above duplicates types in
sequence to prevent potential conflict in following call stack and
link the newly allocated type into the 'raw_data' sequence:

perf_evlist__deliver_sample
 -> process_sample_event
   -> ctf_stream
      ...
      -> bt_ctf_trace_add_stream_class
        -> bt_ctf_stream_class_resolve_types
           ...
           -> bt_ctf_field_type_sequence_copy
             ->bt_ctf_field_type_integer_copy

This happens before byte order setting, so only the newly allocated
type is initialized, the byte order of original type perf choose to
create the first raw_data is still uncertain.

Byte order in CTF output is not related to byte order in perf.data.
Setting it to anything other than BT_CTF_BYTE_ORDER_NATIVE solves this
problem (only BT_CTF_BYTE_ORDER_NATIVE needs to be fixed). To reduce
behavior changing, set byte order according to compiling options.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Brendan Gregg <brendan.d.gregg@...il.com>
Cc: David S. Miller <davem@...emloft.net>
Cc: Jérémie Galarneau <jeremie.galarneau@...icios.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Zefan Li <lizefan@...wei.com>
Cc: pi3orama@....com
---
 tools/perf/util/data-convert-bt.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index 1f608a6..811af89 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -1080,6 +1080,12 @@ static struct bt_ctf_field_type *create_int_type(int size, bool sign, bool hex)
 	    bt_ctf_field_type_integer_set_base(type, BT_CTF_INTEGER_BASE_HEXADECIMAL))
 		goto err;
 
+#if __BYTE_ORDER == __BIG_ENDIAN
+	bt_ctf_field_type_set_byte_order(type, BT_CTF_BYTE_ORDER_BIG_ENDIAN);
+#else
+	bt_ctf_field_type_set_byte_order(type, BT_CTF_BYTE_ORDER_LITTLE_ENDIAN);
+#endif
+
 	pr2("Created type: INTEGER %d-bit %ssigned %s\n",
 	    size, sign ? "un" : "", hex ? "hex" : "");
 	return type;
-- 
1.8.3.4