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

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Message-ID: <55C4AC61.2050105@redhat.com>
Date:	Fri, 7 Aug 2015 08:02:25 -0500
From:	Dean Nelson <dnelson@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...hat.com>
Cc:	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

On 08/07/2015 07:16 AM, Namhyung Kim wrote:
> 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

Sure, I've attached it. See my other email in reply to jirka's question
about what kernel I was running on, for some details about where the
sizeof operator comes from.

>
> 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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