On 2014/12/10 09:17PM, Michael Ellerman wrote:
> On Tue, 2014-12-09 at 23:04 +0530, Naveen N. Rao wrote:
> > Use symbol table lookups by default if DWARF is not necessary, since
> > powerpc ABIv2 encodes local entry points in the symbol table and the
> > function entry address in DWARF may not be appropriate for kprobes,
> > as described here:
> > https://sourceware.org/bugzilla/show_bug.cgi?id=17638
>
> Needs a better changelog.
Ok. Will add, but to elaborate quickly: DWARF will only include the
entire function in low_pc/entry_pc and high_pc. It can't indicate the
local entry point. Hence, we need to use the symbol table instead of
DWARF on ABIv2.
>
> > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> > index 174c22e..adcdbd2 100644
> > --- a/tools/perf/util/probe-event.c
> > +++ b/tools/perf/util/probe-event.c
> > @@ -2382,6 +2382,14 @@ static int convert_to_probe_trace_events(struct
> > perf_probe_event *pev,
> > }
> > }
> >
> > +#if defined(__powerpc64__) && defined(_CALL_ELF) && _CALL_ELF == 2
> > + if (!perf_probe_event_need_dwarf(pev)) {
> > + ret = find_probe_trace_events_from_map(pev, tevs, max_tevs,
> > target);
> > + if (ret > 0)
> > + return ret; /* Found in symbol table */
> > + }
> > +#endif
>
> And should be in an arch helper, not a big powerpc wart dropped in the middle
> of the generic code.
Sure - will change.
Thanks for the review!
- Naveen
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