perf probe: Skip if the function address is 0

Skip probes if the entry address of the target function is 0. This can
happen when we're handling C++ debuginfo files.

E.g. without this fix, below case still fail.
----
$ ./perf probe -x /usr/lib64/libstdc++.so.6 -vD is_open
probe-definition(0): is_open
symbol:is_open file:(null) line:0 offset:0 return:0 lazy:(null)
0 arguments
symbol:catch file:(null) line:0 offset:0 return:0 lazy:(null)
symbol:throw file:(null) line:0 offset:0 return:0 lazy:(null)
symbol:rethrow file:(null) line:0 offset:0 return:0 lazy:(null)
Open Debuginfo file: /usr/lib/debug/usr/lib64/libstdc++.so.6.0.22.debug
Try to find probe point from debuginfo.
Matched function: is_open [295df]
found inline addr: 0x8ca80
Probe point found: is_open+0
found inline addr: 0x8ca70
Probe point found: is_open+0
found inline addr: 0x8ca60
Probe point found: is_open+0
Matched function: is_open [6527f]
Matched function: is_open [9fe8a]
Probe point found: is_open+0
Matched function: is_open [19710b]
found inline addr: 0xecca9
Probe point found: stdio_filebuf+57
found inline addr: 0x0
Probe point found: swap+0
Matched function: is_open [19fc9d]
Probe point found: is_open+0
Found 7 probe_trace_events.
p:probe_libstdc++/is_open /usr/lib64/libstdc++.so.6.0.22:0x8ca80
p:probe_libstdc++/is_open_1 /usr/lib64/libstdc++.so.6.0.22:0x8ca70
p:probe_libstdc++/is_open_2 /usr/lib64/libstdc++.so.6.0.22:0x8ca60
p:probe_libstdc++/is_open_3 /usr/lib64/libstdc++.so.6.0.22:0xb0ad0
p:probe_libstdc++/is_open_4 /usr/lib64/libstdc++.so.6.0.22:0xecca9
Failed to synthesize probe trace event.
Error: Failed to add events. Reason: Invalid argument (Code: -22)
----
This is because some instances have entry_pc == 0 (see 19710b and
19fc9d). With this fix, those are skipped.

----
$ ./perf probe -x /usr/lib64/libstdc++.so.6 -D is_open
p:probe_libstdc++/is_open /usr/lib64/libstdc++.so.6.0.22:0x8ca80
p:probe_libstdc++/is_open_1 /usr/lib64/libstdc++.so.6.0.22:0x8ca70
p:probe_libstdc++/is_open_2 /usr/lib64/libstdc++.so.6.0.22:0x8ca60
p:probe_libstdc++/is_open_3 /usr/lib64/libstdc++.so.6.0.22:0xb0ad0
p:probe_libstdc++/is_open_4 /usr/lib64/libstdc++.so.6.0.22:0xecca9
----

Signed-off-by: Masami Hiramatsu <[e-mail]>
Tested-by: Arnaldo Carvalho de Melo <[e-mail]>
Tested-by: Jiri Olsa <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Link: http://lkml.kernel.org/r/147464490707.29804.14277897643725143867.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/probe-finder.c

···
 				   dwarf_diename(in_die));
 			return -ENOENT;
 		}
+		if (addr == 0) {
+			pr_debug("%s has no valid entry address. skipped.\n",
+				 dwarf_diename(in_die));
+			return -ENOENT;
+		}
 		pf->addr = addr;
 		pf->addr += pp->offset;
 		pr_debug("found inline addr: 0x%jx\n",
···
 	} else if (die_is_func_instance(sp_die)) {
 		/* Instances always have the entry address */
 		dwarf_entrypc(sp_die, &pf->addr);
+		/* But in some case the entry address is 0 */
+		if (pf->addr == 0) {
+			pr_debug("%s has no entry PC. Skipped\n",
+				 dwarf_diename(sp_die));
+			param->retval = 0;
 		/* Real function */
-		if (pp->lazy_line)
+		} else if (pp->lazy_line)
 			param->retval = find_probe_point_lazy(sp_die, pf);
 		else {
 			skip_prologue(sp_die, pf);