linux-kernel - Re: [PATCH v2] tools lib traceevent: add checks for returned EVENT

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Date:	Thu, 20 Aug 2015 10:23:25 -0500
From:	Dean Nelson <dnelson@...hat.com>
To:	a.p.zijlstra@...llo.org, mingo@...hat.com, rostedt@...dmis.org,
	acme@...nel.org
Cc:	namhyung@...nel.org, linux-kernel@...r.kernel.org, jolsa@...nel.org
Subject: Re: [PATCH v2] tools lib traceevent: add checks for returned
 EVENT_ERROR type

On 08/10/2015 07:22 AM, 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 ~]#
>
> 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>
> ---
> Changes in v2:
>    - Moved the second hunk's check for EVENT_ERROR to a separate line.

I misunderstood what Namhyung meant by his request that I put the check
on separate lines.

I've posted a v3 that hopefully corrects this misunderstanding. So
consider v2 NAK'd.


>   tools/lib/traceevent/event-parse.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index cc25f05..dafddc6 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 +1943,8 @@ 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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