[PATCH -tip v2 5/8] perf-probe: Retry to find given address fromoffline dwarf

[Masami Hiramatsu]

Retry to find the given address from offline dwarfs too.

On the KASLR enabled kernel, the kernel text section is
loaded with random offset, and debuginfo__new_online_kernel
tries to map the debuginfo with that offset. However,
perf's map object tries to make a non-randomized ummapped
address. This leads to fail looking up the appropriate
debuginfo from that address.

To solve this issue, we retry to use offline dwarfs if
possible.

Without this change;

  # ./perf probe -l
    probe:t_show         (on _stext+901288 with m v)
    probe:t_show_1       (on _stext+939624 with m v t)
    probe:t_show_2       (on _stext+980296 with m v fmt)
    probe:t_show_3       (on _stext+1014392 with m v file)

With this change;

  # ./perf probe -l
    probe:t_show         (on t_show@linux-3/kernel/trace/ftrace.c with m v)
    probe:t_show_1       (on t_show@linux-3/kernel/trace/trace.c with m v t)
    probe:t_show_2       (on t_show@kernel/trace/trace_printk.c with m v fmt)
    probe:t_show_3       (on t_show@kernel/trace/trace_events.c with m v file)

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
---
 tools/perf/util/probe-event.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 120954b..b35f047 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -272,6 +272,8 @@ static int kprobe_convert_to_perf_probe(struct probe_trace_point *tp,
 			 tp->offset, addr);
 
 		dinfo = debuginfo__new_online_kernel(addr);
+		if (!dinfo)	/* For kaslr kernel */
+			dinfo = open_debuginfo(tp->module);
 		if (dinfo) {
 			ret = debuginfo__find_probe_point(dinfo,
 						 (unsigned long)addr, pp);


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