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

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Message-ID: <20150807105910.GE8624@krava.brq.redhat.com>
Date:	Fri, 7 Aug 2015 12:59:10 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Dean Nelson <dnelson@...hat.com>
Cc:	a.p.zijlstra@...llo.org, mingo@...hat.com, rostedt@...dmis.org,
	acme@...nel.org, linux-kernel@...r.kernel.org, jolsa@...nel.org,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH] tools lib traceevent: add checks for returned
 EVENT_ERROR type

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
>   [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


jirka

> 
> 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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