linux-kernel - Re: [PATCH] tracing: precise log info for kretprobe addr err

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Date:   Wed, 20 Jan 2021 12:24:15 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Jianlin Lv <Jianlin.Lv@....com>, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: precise log info for kretprobe addr err

Hi,

On Tue, 19 Jan 2021 10:41:06 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> Masami,
> 
> Looks fine to me. What do you think?

Agreed. Since register_kretprobe() checks the address by kprobe_on_func_entry(),
if it is not passed, it should always fail to register at last.

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you!

> 
> -- Steve
> 
> 
> On Tue, 19 Jan 2021 23:10:14 +0800
> Jianlin Lv <Jianlin.Lv@....com> wrote:
> 
> > When trying to create kretprobe with the wrong function symbol in tracefs;
> > The error is triggered in the register_trace_kprobe() and recorded as
> > FAIL_REG_PROBE issue,
> > 
> > Example:
> >   $ cd /sys/kernel/debug/tracing
> >   $ echo 'r:myprobe ERROR_SYMBOL_XXX ret=%x0' >> kprobe_events
> >     bash: echo: write error: Invalid argument
> >   $ cat error_log
> >     [142797.347877] trace_kprobe: error: Failed to register probe event
> >     Command: r:myprobe ERROR_SYMBOL_XXX ret=%x0
> >                        ^
> > 
> > This error can be detected in the parameter parsing stage, the effect of
> > applying this patch is as follows:
> > 
> >   $ echo 'r:myprobe ERROR_SYMBOL_XXX ret=%x0' >> kprobe_events
> >     bash: echo: write error: Invalid argument
> >   $ cat error_log
> >     [415.89]trace_kprobe: error: Retprobe address must be an function entry
> >     Command: r:myprobe ERROR_SYMBOL_XXX ret=%x0
> >                        ^
> > 
> > Signed-off-by: Jianlin Lv <Jianlin.Lv@....com>
> > ---
> >  kernel/trace/trace_kprobe.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index e6fba1798771..3dfd1b6711a3 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -830,7 +830,7 @@ static int trace_kprobe_create(int argc, const char *argv[])
> >  			flags |= TPARG_FL_RETURN;
> >  		if (kprobe_on_func_entry(NULL, symbol, offset))
> >  			flags |= TPARG_FL_FENTRY;
> > -		if (offset && is_return && !(flags & TPARG_FL_FENTRY)) {
> > +		if (is_return && !(flags & TPARG_FL_FENTRY)) {
> >  			trace_probe_log_err(0, BAD_RETPROBE);
> >  			goto parse_error;
> >  		}
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>