linux-kernel - Re: [PATCH] tools lib traceevent: add checks for returned EVENT

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Date:	Fri, 7 Aug 2015 21:16:27 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Dean Nelson <dnelson@...hat.com>, a.p.zijlstra@...llo.org,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...nel.org>
Subject: Re: [PATCH] tools lib traceevent: add checks for returned EVENT_ERROR type

Hi,

On Fri, Aug 7, 2015 at 7:59 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Mon, Aug 03, 2015 at 01:08:05PM -0400, Dean Nelson wrote:
>> Running the following perf-stat command on an arm64 system produces the
>> following result...
>>
>>   [root@...ch64 ~]# perf stat -e kmem:mm_page_alloc -a sleep 1
>>     Warning: [kmem:mm_page_alloc] function sizeof not defined
>>     Warning: Error: expected type 4 but read 0
>>   Segmentation fault

Oops,


>>   [root@...ch64 ~]#
>
> hum, what kernel are you running on? I dont see that warning
> on my system:
>
> [jolsa@...va perf]$ sudo ./perf stat -e kmem:mm_page_alloc -a sleep 1
>
>  Performance counter stats for 'system wide':
>
>                227      kmem:mm_page_alloc
>
>        1.000762466 seconds time elapsed
>
> Cc-ing Namhyung

Yeah, it seems his kernel has sizeof() somewhere in the event format.
Anyway, it's not good to see a segfault.

Dean, could you share your event format file?

  $ sudo cat /sys/kernel/debug/tracing/events/kmem/mm_page_alloc/format

Thanks,
Namhyung


>
>>
>> The second warning message and SIGSEGV stem from the issue expressed in the
>> first warning message, and are the result of ignoring the EVENT_ERROR type
>> returned back through the call chain.
>>
>> Dealing with the first warning message is beyond the scope of this patch. But
>> the second warning is addressed by this patch's first hunk. And the SIGSEGV is
>> eliminated by its second hunk.
>>
>> Signed-off-by: Dean Nelson <dnelson@...hat.com>
>> ---
>>  tools/lib/traceevent/event-parse.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
>> index cc25f05..72e2933 100644
>> --- a/tools/lib/traceevent/event-parse.c
>> +++ b/tools/lib/traceevent/event-parse.c
>> @@ -1680,6 +1680,9 @@ process_cond(struct event_format *event, struct print_arg *top, char **tok)
>>       type = process_arg(event, left, &token);
>>
>>   again:
>> +     if (type == EVENT_ERROR)
>> +             goto out_free;
>> +
>>       /* Handle other operations in the arguments */
>>       if (type == EVENT_OP && strcmp(token, ":") != 0) {
>>               type = process_op(event, left, &token);
>> @@ -1940,7 +1943,7 @@ process_op(struct event_format *event, struct print_arg *arg, char **tok)
>>
>>               type = process_arg_token(event, right, tok, type);
>>
>> -             if (right->type == PRINT_OP &&
>> +             if (type != EVENT_ERROR && right->type == PRINT_OP &&
>>                   get_op_prio(arg->op.op) < get_op_prio(right->op.op)) {
>>                       struct print_arg tmp;
>>
--
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