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

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Date:   Mon, 14 Nov 2022 11:24:32 -0300
From:   Rafael Mendonca <rafaelmendsr@...il.com>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
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 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>

> 
> 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;
>