Re: [PATCH v3 25/33] tracing: Allow whitespace to surround hist trigger filter

[Namhyung Kim]

Hi Tom,

On Wed, Oct 04, 2017 at 02:05:17PM -0500, Tom Zanussi wrote:
> Hi Steve,
> 
> On Wed, 2017-10-04 at 14:11 -0400, Steven Rostedt wrote:
> > On Fri, 22 Sep 2017 15:00:05 -0500
> > Tom Zanussi <tom.zanu...@linux.intel.com> wrote:
> > 
> > > The existing code only allows for one space before and after the 'if'
> > > specifying the filter for a hist trigger.  Add code to make that more
> > > permissive as far as whitespace goes.  Specifically, we want to allow
> > > spaces in the trigger itself now that we have additional syntax
> > > (onmatch/onmax) where spaces are more natural e.g. spaces after commas
> > > in param lists.
> > > 
> > > Signed-off-by: Tom Zanussi <tom.zanu...@linux.intel.com>
> > > ---
> > >  kernel/trace/trace_events_hist.c | 24 +++++++++++++++++++-----
> > >  1 file changed, 19 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/kernel/trace/trace_events_hist.c 
> > > b/kernel/trace/trace_events_hist.c
> > > index ba42fe2..431f2b2 100644
> > > --- a/kernel/trace/trace_events_hist.c
> > > +++ b/kernel/trace/trace_events_hist.c
> > > @@ -4857,7 +4857,7 @@ static int event_hist_trigger_func(struct 
> > > event_command *cmd_ops,
> > >   struct synth_event *se;
> > >   const char *se_name;
> > >   bool remove = false;
> > > - char *trigger;
> > > + char *trigger, *p;
> > >   int ret = 0;
> > >  
> > >   if (!param)
> > > @@ -4866,10 +4866,23 @@ static int event_hist_trigger_func(struct 
> > > event_command *cmd_ops,
> > >   if (glob[0] == '!')
> > >           remove = true;
> > >  
> > > - /* separate the trigger from the filter (k:v [if filter]) */
> > > - trigger = strsep(&param, " \t");
> > > - if (!trigger)
> > > -         return -EINVAL;
> > > + /*
> > > +  * separate the trigger from the filter (k:v [if filter])
> > > +  * allowing for whitespace in the trigger
> > > +  */
> > > + trigger = param;
> > > + p = strstr(param, " if");
> > > + if (!p)
> > > +         p = strstr(param, "\tif");
> > > + if (p) {
> > > +         if (p == trigger)
> > > +                 return -EINVAL;
> > > +         param = p + 1;
> > > +         param = strstrip(param);
> > > +         *p = '\0';
> > > +         trigger = strstrip(trigger);
> > > + } else
> > > +         param = NULL;
> > 
> > I think you forgot to update this:
> > 
> 
> I was going to but on closer inspection realized the simpler form
> wouldn't accomplish the same thing - the problem this is trying to solve
> is to allow bits of whitespace within the trigger (because we now have
> function-like syntax, which should allow whitespace after commas for
> instance) and separating the trigger from the filter ('if').  So we
> explicitly search for 'if' with preceding whitespace, which strsep won't
> accomplish.

What if a field name is started with 'if' (like "ifb")?  I think you
also need to check whitespace after the 'if'.

Thanks,
Namhyung