linux-kernel - Re: [PATCH 1/3] tracing/filters: allow user-input to be integer-like string

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Message-Id: <1239682887.7011.54.camel@tropicana>
Date:	Mon, 13 Apr 2009 23:21:27 -0500
From:	Tom Zanussi <tzanussi@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Li Zefan <lizf@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] tracing/filters: allow user-input to be
 integer-like string

On Tue, 2009-04-14 at 00:29 +0200, Ingo Molnar wrote:
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
> 
> > On Mon, Apr 13, 2009 at 10:38:12AM +0800, Li Zefan wrote:
> > > Suppose we would like to trace all tasks named '123', but this
> > > will fail:
> > >  # echo 'parent_comm == 123' > events/sched/sched_process_fork/filter
> > >  bash: echo: write error: Invalid argument
> > > 
> > > Don't guess the type of the filter pred in filter_parse(), but instead
> > > we check it in filter_add_pred().
> > > 
> > > Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> > > ---
> > >  kernel/trace/trace_events_filter.c |   26 +++++++++++++-------------
> > >  1 files changed, 13 insertions(+), 13 deletions(-)
> > > 
> > > diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> > > index 9f8ecca..a63f965 100644
> > > --- a/kernel/trace/trace_events_filter.c
> > > +++ b/kernel/trace/trace_events_filter.c
> > > @@ -229,6 +229,7 @@ static int is_string_field(const char *type)
> > >  int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
> > >  {
> > >  	struct ftrace_event_field *field;
> > > +	unsigned long long val;
> > >  
> > >  	field = find_event_field(call, pred->field_name);
> > >  	if (!field)
> > > @@ -237,14 +238,14 @@ int filter_add_pred(struct ftrace_event_call *call, struct filter_pred *pred)
> > >  	pred->offset = field->offset;
> > >  
> > >  	if (is_string_field(field->type)) {
> > > -		if (!pred->str_val)
> > > -			return -EINVAL;
> > >  		pred->fn = filter_pred_string;
> > >  		pred->str_len = field->size;
> > >  		return __filter_add_pred(call, pred);
> > >  	} else {
> > > -		if (pred->str_val)
> > > +		if (strict_strtoull(pred->str_val, 0, &val))
> > >  			return -EINVAL;
> > > +		pred->val = val;
> > > +		kfree(pred->str_val);
> > 
> > 
> > And you might also want to do
> > pred->str_val = NULL;
> > Otherwise filter_free_pred() may crash later:
> > 
> > void filter_free_pred(struct filter_pred *pred)
> > {
> > 	if (!pred)
> > 		return;
> > 
> > 	kfree(pred->field_name);
> > 	kfree(pred->str_val);
> > 	kfree(pred);
> > }
> > 
> > 
> > Other than that, it looks good.
> 
> This also conflicts with Tom's rewrite of the filter engine to make 
> it on-the-fly modifiable.
> 
> Li, mind reworking your series against latest -tip? (it has Tom's 
> patch included already)
> 
> Also, it would be nice to hear Tom's opinion about this series as 
> well. I know there's new parsing features planned - if it's better 
> that way then Tom you might want to pick up Li's patches and submit 
> them together with any pending or upcoming changes? We can apply 
> them directly too if that's easier to you.
> 

I had started on the new parser a couple weeks ago, but got sidetracked
by other things.  I'll be getting back to it this week, but until it's
ready it wouldn't hurt for you to pick up Li's patches, and I'll make
any changes I need to in the new code.

What this patch does will be needed by the new code too, so it would be
good to have it, though it might get moved around.  Patch 2 won't hurt
either, though everything in filter_parse() will probably change.  And
patch 3 fixes a bug that needs to be fixed regardless...

Thanks,

Tom

> Thanks,
> 
> 	Ingo

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