Messages in this thread | | | Date | Thu, 15 Jan 2015 21:11:05 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH v2 4/4] perf probe: Fix probing kretprobes |
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(2015/01/14 20:18), Namhyung Kim wrote: > The commit dfef99cd0b2c ("perf probe: Use ref_reloc_sym based address > instead of the symbol name") converts kprobes to use ref_reloc_sym > (i.e. _stext) and offset instead of using symbol's name directly. So > on my system, adding do_fork ends up with like below: > > $ sudo perf probe -v --add do_fork%return > probe-definition(0): do_fork%return > symbol:do_fork file:(null) line:0 offset:0 return:1 lazy:(null) > 0 arguments > Looking at the vmlinux_path (7 entries long) > Using /lib/modules/3.17.6-1-ARCH/build/vmlinux for symbols > Could not open debuginfo. Try to use symbols. > Opening /sys/kernel/debug/tracing/kprobe_events write=1 > Added new event: > Writing event: r:probe/do_fork _stext+456136 > Failed to write event: Invalid argument > Error: Failed to add events. Reason: Operation not permitted (Code: -1) > > As you can see, the do_fork was translated to _stext+456136. This was > because to support (local) symbols that have same name. But the > problem is that kretprobe requires to be inserted at function start > point so it simply checks whether it's called with offset 0. And if > not, it'll return with -EINVAL. You can see it with dmesg. > > $ dmesg | tail -1 > [125621.764103] Return probe must be used without offset. > > So we need to use the symbol name instead of ref_reloc_sym in case of > return probes. > > Reported-by: Jiri Olsa <jolsa@redhat.com> > Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Looks good to me!
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Thank you,
> Signed-off-by: Namhyung Kim <namhyung@kernel.org> > --- > tools/perf/util/probe-event.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index b1406d79b271..7c94acc014e9 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -446,7 +446,7 @@ static int post_process_probe_trace_events(struct probe_trace_event *tevs, > } > > for (i = 0; i < ntevs; i++) { > - if (tevs[i].point.address) { > + if (tevs[i].point.address && !tevs[i].point.retprobe) { > tmp = strdup(reloc_sym->name); > if (!tmp) > return -ENOMEM; > @@ -2255,7 +2255,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev, > goto out; > } > > - if (!pev->uprobes) { > + if (!pev->uprobes && !pp->retprobe) { > kmap = map__kmap(map); > reloc_sym = kmap->ref_reloc_sym; > if (!reloc_sym) { >
-- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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