diff --git a/bloaty/file_sections.proto b/bloaty/file_sections.proto
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+++ b/bloaty/file_sections.proto
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+// Copyright 2021 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+syntax = "proto2";
+
+package file_sections;
+
+message SectionDescriptior {
+  // Name of the section (e.g. .rodata)
+  optional string name = 1;
+
+  // Size of that section as part of the file.
+  optional uint64 file_size = 2;
+
+  // Size of that section when loaded in memory.
+  optional uint64 vm_size = 3;
+}
+
+message File {
+  // Relative path from $OUT_DIR.
+  optional string path = 1;
+
+  // File sections.
+  repeated SectionDescriptior sections = 2;
+}
+
+message FileSizeMetrics {
+  repeated File files = 1;
+}