diff --git a/aos/util/file.h b/aos/util/file.h
index 7c06ece..2d37ec2 100644
--- a/aos/util/file.h
+++ b/aos/util/file.h
@@ -35,8 +35,11 @@
 // runs across.
 void UnlinkRecursive(std::string_view path);
 
+enum class FileOptions { kReadable, kWriteable };
+
 // Maps file from disk into memory
-std::shared_ptr<absl::Span<uint8_t>> MMapFile(const std::string &path);
+std::shared_ptr<absl::Span<uint8_t>> MMapFile(
+    const std::string &path, FileOptions options = FileOptions::kReadable);
 
 }  // namespace util
 }  // namespace aos