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    SubjectRe: [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@tobin.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

    I ran through these as outlined here for the new version (v4). This hits
    the modified code but doesn't test symbol look up failure.

    I also configured kernel with 'Perform a startup test on ftrace' for
    good luck.

    Are you happy with this level of testing?

    thanks,
    Tobin.

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