Re: [PATCH] tools lib traceevent: add checks for returned EVENT_ERROR type

Namhyung Kim
2015-08-07T12:16:48Z

Hi,

On Fri, Aug 7, 2015 at 7:59 PM, Jiri Olsa <jolsa@redhat.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@aarch64 ~]# 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@aarch64 ~]#
>
> hum, what kernel are you running on? I dont see that warning
> on my system:
>
> [jolsa@krava 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@redhat.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;
>>