[tools] Add sections without symbols into binary_size's treemap.

This makes the cost of especially unwind tables and relocation visible and gets the treemap's total much closer the stripped binary size.

Change-Id: I1123e294b79b83cd709e7dc6e8e89c7a9545ef2c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/423605
Commit-Queue: Ryan Macnak <[email protected]>
Reviewed-by: Brian Quinlan <[email protected]>

Author: rmacnak-google

runtime/tools/binary_size

@@ -71,6 +71,33 @@ const filteredPathComponents = <String>[
   "ProductXARM64",
 ];
 
+const filteredSections = <String>[
+  // Covered by symbols
+  ".data",
+  ".data.rel.ro",
+  ".rodata",
+  ".text",
+
+  // Does not contribute to file size
+  ".bss",
+  ".tbss",
+
+  // Debug info / stripped
+  ".debug_abbrev",
+  ".debug_aranges",
+  ".debug_info",
+  ".debug_line",
+  ".debug_line_str",
+  ".debug_loc",
+  ".debug_loclists",
+  ".debug_macro",
+  ".debug_ranges",
+  ".debug_rnglists",
+  ".debug_str",
+  ".strtab",
+  ".symtab",
+];
+
 var cwd = Directory.current.path;
 String prettyPath(String path) {
   if (path.startsWith(cwd)) {
@@ -174,6 +201,46 @@ analyze(String binaryPath) {
     addToPath(s, path);
   }
 
+  var readExec = "readelf";
+  var readArgs = ["--sections", binaryPath];
+  var readResult = Process.runSync(readExec, readArgs);
+  if (readResult.exitCode != 0) {
+    print("+ ${readExec} ${readArgs.join(' ')}");
+    print(readResult.exitCode);
+    print(readResult.stdout);
+    print(readResult.stderr);
+    exit(1);
+  }
+
+  lines = readResult.stdout.split("\n");
+  var nameRegex = new RegExp("\\[([ 0-9a-f]+)\\] ([_0-9a-zA-Z.]+)");
+  var sizeRegex = new RegExp("([_0-9a-f]+)");
+  var sectionName = null;
+  for (var line in lines) {
+    print(line);
+    var match = nameRegex.firstMatch(line);
+    if (match != null) {
+      sectionName = match[2];
+      continue;
+    }
+    match = sizeRegex.firstMatch(line);
+    if (match != null) {
+      int size = int.parse(match[1]!, radix: 16);
+
+      if (sectionName != null && !filteredSections.contains(sectionName)) {
+        var s = new Symbol();
+        s.name = sectionName;
+        s.type = "section";
+        s.shallowSize = size;
+        addToPath(s, "");
+      }
+
+      sectionName = null;
+      continue;
+    }
+    sectionName = null;
+  }
+
   root.compressTrivialPaths();
   root.computeRetainedSize();