Re: [PATCH] trace-cmd record: Fix syntax in make_pid_filter

[Steven Rostedt]

On Fri, 13 Oct 2017 13:57:12 -0400
Will Hawkins <hawki...@borlaugic.com> wrote:

> In older versions of the kernel, event filtering by
> pid does not use the set_event_pid file. Instead,
> ftrace uses a common filter (created in make_pid_filter)
> to filter events based on PID.
> 
> The syntax of the filter generated by this function is
> overly permissive. When filtering by pid, || is used
> where && should be (in certain cases) which means that
> unrelated events are captured.
> 

Thanks for sending this.

> Signed-off-by: Will Hawkins <hawki...@borlaugic.com>
> ---
>  trace-record.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/trace-record.c b/trace-record.c
> index a0b6541..d9c2959 100644
> --- a/trace-record.c
> +++ b/trace-record.c
> @@ -935,14 +935,19 @@ static char *make_pid_filter(char *curr_filter, const 
> char *field)
>       str = filter + curr_len;
>  
>       for (p = filter_pids; p; p = p->next) {
> -             if (p == filter_pids)
> -                     orit = "";
> -             else
> -                     orit = "||";
> -             if (p->exclude)
> +             if (p->exclude) {
>                       match = "!=";
> -             else
> +                     if (p == filter_pids)
> +                             orit = "";
> +                     else
> +                             orit = "&&";
> +             } else {
>                       match = "==";
> +                     if (p == filter_pids)
> +                             orit = "";
> +                     else
> +                             orit = "||";
> +             }

A little nicer way of doing this is:


        if (p->exclude) {
                match = "!=";
                orit = "&&";
        } else {
                match = "==";
                orit = "||";
        }
        if (p == filter_pids)
                orit = "";

Care to send a v2?

-- Steve

>               len = sprintf(str, "%s(%s%s%d)", orit, field, match, p->pid);
>               str += len;
>       }