perf callchain: Use debug_frame if eh_frame is unusable

When NO_LIBUNWIND_DEBUG_FRAME=0, use the .debug_frame if the .eh_frame
doesn't contain the approprate unwind tables.
Signed-off-by: Rabin Vincent <rabin.vincent@axis.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rabin Vincent <rabinv@axis.com>
Link: http://lkml.kernel.org/r/1443379079-29133-3-git-send-email-rabin.vincent@axis.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/unwind-libunwind.c

@@ -330,6 +330,7 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 	struct map *map;
 	unw_dyn_info_t di;
 	u64 table_data, segbase, fde_count;
+	int ret = -EINVAL;
 
 	map = find_map(ip, ui);
 	if (!map || !map->dso)
@@ -348,13 +349,14 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 		di.u.rti.table_data = map->start + table_data;
 		di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
 				      / sizeof(unw_word_t);
-		return dwarf_search_unwind_table(as, ip, &di, pi,
+		ret = dwarf_search_unwind_table(as, ip, &di, pi,
 						need_unwind_info, arg);
 	}
 
 #ifndef NO_LIBUNWIND_DEBUG_FRAME
 	/* Check the .debug_frame section for unwinding info */
-	if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
+	if (ret < 0 &&
+	    !read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
 		int fd = dso__data_get_fd(map->dso, ui->machine);
 		int is_exec = elf_is_exec(fd, map->dso->name);
 		unw_word_t base = is_exec ? 0 : map->start;
@@ -370,7 +372,7 @@ find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
 	}
 #endif
 
-	return -EINVAL;
+	return ret;
 }
 
 static int access_fpreg(unw_addr_space_t __maybe_unused as,