perf callchain: Do not report zero address in unwind

We are not interested in zero addresses in callchain, do not report
them.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Jean Pihet <jean.pihet@linaro.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1389098853-14466-8-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/unwind.c

@@ -563,7 +563,7 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 		unw_word_t ip;
 
 		unw_get_reg(&c, UNW_REG_IP, &ip);
-		ret = entry(ip, ui->thread, ui->machine, cb, arg);
+		ret = ip ? entry(ip, ui->thread, ui->machine, cb, arg) : 0;
 	}
 
 	unw_destroy_addr_space(addr_space);