perf libdw: Check for mmaps also in MAP__VARIABLE tree

We've seen cases (softice) where DWARF unwinder went through non
executable mmaps, which we need to lookup in MAP__VARIABLE tree.
Reported-and-Tested-by: Noel Grandin <noelgrandin@gmail.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1452158050-28061-6-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/unwind-libdw.c

@@ -95,6 +95,16 @@ static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 
 	thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
 			      MAP__FUNCTION, addr, &al);
+	if (!al.map) {
+		/*
+		 * We've seen cases (softice) where DWARF unwinder went
+		 * through non executable mmaps, which we need to lookup
+		 * in MAP__VARIABLE tree.
+		 */
+		thread__find_addr_map(ui->thread, PERF_RECORD_MISC_USER,
+				      MAP__VARIABLE, addr, &al);
+	}
+
 	if (!al.map) {
 		pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 		return -1;