netdev - Re: [PATCH 3/3] trace: print address if symbol not found

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Message-ID: <20171219002245.GE19604@eros>
Date:   Tue, 19 Dec 2017 11:22:45 +1100
From:   "Tobin C. Harding" <me@...in.cc>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     kernel-hardening@...ts.openwall.com,
        Tycho Andersen <tycho@...ho.ws>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Alexei Starovoitov <ast@...nel.org>,
        linux-kernel@...r.kernel.org,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH 3/3] trace: print address if symbol not found

On Mon, Dec 18, 2017 at 06:51:43PM -0500, Steven Rostedt wrote:
> On Tue, 19 Dec 2017 08:16:14 +1100
> "Tobin C. Harding" <me@...in.cc> wrote:
> 
> > > >  #endif /* _LINUX_KERNEL_TRACE_H */
> > > > diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> > > > index 1e1558c99d56..3e28522a76f4 100644
> > > > --- a/kernel/trace/trace_events_hist.c
> > > > +++ b/kernel/trace/trace_events_hist.c
> > > > @@ -982,7 +982,7 @@ static void hist_trigger_stacktrace_print(struct seq_file *m,
> > > >  			return;
> > > >  
> > > >  		seq_printf(m, "%*c", 1 + spaces, ' ');
> > > > -		sprint_symbol(str, stacktrace_entries[i]);
> > > > +		trace_sprint_symbol_addr(str, stacktrace_entries[i]);  
> > > 
> 
> > 
> > If you have the time to give me some brief pointers on how I should go
> > about testing this I'd love to test it before the next version. I know
> > very little about ftrace.
> 
> For hitting the histogram stacktrace trigger (this code path), make
> sure you have CONFIG_HIST_TRIGGERS enabled. And then do:
> 
>  # cd /sys/kernel/debug/tracing
>  # echo 'hist:keys=common_pid.execname,stacktrace:vals=prev_state' > \
>      events/sched/sched_switch/trigger
>  # cat events/sched/sched_switch/hist
> 
> For the "sym" part, you can do (from the same directory):
> 
>  # echo 'hist:keys=call_site.sym:vals=bytes_req' > \
>      events/kmem/kmalloc/trigger
>  # cat events/kmem/kmalloc/hist
> 
> 
> And for sym-offset:
> 
>  # echo 'hist:keys=call_site.sym-offset:vals=bytes_req' > \
>     events/kmem/kmalloc/trigger
>  # cat events/kmem/kmalloc/hist
> 
> -- Steve

Thanks, you're the man