linux-kernel - Re: [PATCH] tracing/eprobe: Fix eprobe filter to make a filter correctly

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Date:   Tue, 15 Nov 2022 00:02:33 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Rafael Mendonca <rafaelmendsr@...il.com>
Cc:     Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>
Subject: Re: [PATCH] tracing/eprobe: Fix eprobe filter to make a filter
 correctly

On Mon, 14 Nov 2022 11:24:32 -0300
Rafael Mendonca <rafaelmendsr@...il.com> wrote:

> On Sat, Nov 12, 2022 at 02:41:04PM +0900, Masami Hiramatsu (Google) wrote:
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Since the eprobe filter was defined based on the eprobe's trace event
> > itself, it doesn't work correctly. Use the original trace event of
> > the eprobe when making the filter so that the filter works correctly.
> > 
> > Without this fix:
> > 
> >  # echo 'e syscalls/sys_enter_openat \
> > 	flags_rename=$flags:u32 if flags < 1000' >> dynamic_events
> >  # echo 1 > events/eprobes/sys_enter_openat/enable
> > [  114.551550] event trace: Could not enable event sys_enter_openat
> > -bash: echo: write error: Invalid argument
> > 
> > With this fix:
> >  # echo 'e syscalls/sys_enter_openat \
> > 	flags_rename=$flags:u32 if flags < 1000' >> dynamic_events
> >  # echo 1 > events/eprobes/sys_enter_openat/enable
> >  # tail trace
> > cat-241     [000] ...1.   266.498449: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0
> > cat-242     [000] ...1.   266.977640: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0
> > 
> > Fixes: 752be5c5c910 ("tracing/eprobe: Add eprobe filter support")
> > Reported-by: Rafael Mendonca <rafaelmendsr@...il.com>
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > ---
> >  kernel/trace/trace_eprobe.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Hi Masami,
> 
> Tested this on top of v6.1-rc5 and the event filtering seems to be
> working fine now. Tested with multiple events and conditions. Thanks.
> 
> Tested-by: Rafael Mendonca <rafaelmendsr@...il.com>

Thanks a lot!

> 
> > 
> > diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> > index fe4833a7b7b3..1c3096ab2fe7 100644
> > --- a/kernel/trace/trace_eprobe.c
> > +++ b/kernel/trace/trace_eprobe.c
> > @@ -643,7 +643,7 @@ new_eprobe_trigger(struct trace_eprobe *ep, struct trace_event_file *file)
> >  	INIT_LIST_HEAD(&trigger->list);
> >  
> >  	if (ep->filter_str) {
> > -		ret = create_event_filter(file->tr, file->event_call,
> > +		ret = create_event_filter(file->tr, ep->event,
> >  					ep->filter_str, false, &filter);
> >  		if (ret)
> >  			goto error;
> > 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>