[fuchsia] [packaging] Layout debug symbols for Fuchsia (flutter#13338)

This packages and moves the relevant symbols to the right
locations in root_out_dir, but doesn't upload them to CIPD
yet. That will be done in a following change.

Refer: go/flutter-fuchsia-packaging for more information.

tools/fuchsia/copy_debug_symbols.py

@@ -0,0 +1,121 @@
+#!/usr/bin/env python
+#
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+""" Gather the build_id, prefix_dir, and exec_name given the path to executable
+    also copies to the specified destination.
+
+    The structure of debug symbols is as follows:
+      .build-id/<prefix>/<exec_name>[.debug]
+"""
+
+import argparse
+import json
+import os
+import re
+import shutil
+import subprocess
+import sys
+import time
+
+
+def Touch(fname):
+  with open(fname, 'a'):
+    os.utime(fname, None)
+
+
+def GetBuildIdParts(exec_path, read_elf):
+  file_out = subprocess.check_output(
+      [read_elf, '--hex-dump=.note.gnu.build-id', exec_path])
+  second_line = file_out.splitlines()[-1].split()
+  build_id = second_line[1] + second_line[2]
+  return {
+      'build_id': build_id,
+      'prefix_dir': build_id[:2],
+      'exec_name': build_id[2:]
+  }
+
+
+def main():
+  parser = argparse.ArgumentParser()
+
+  parser.add_argument(
+      '--executable-name',
+      dest='exec_name',
+      action='store',
+      required=True,
+      help='This is the name of the executable that we wish to layout debug symbols for.'
+  )
+  parser.add_argument(
+      '--executable-path',
+      dest='exec_path',
+      action='store',
+      required=True,
+      help='Path to the executable on the filesystem.')
+  parser.add_argument(
+      '--destination-base',
+      dest='dest',
+      action='store',
+      required=True,
+      help='Path to the base directory where the debug symbols are to be laid out.'
+  )
+  parser.add_argument(
+      '--stripped',
+      dest='stripped',
+      action='store_true',
+      default=True,
+      help='Executable at the specified path is stripped.')
+  parser.add_argument(
+      '--unstripped',
+      dest='stripped',
+      action='store_false',
+      help='Executable at the specified path is unstripped.')
+  parser.add_argument(
+      '--read-elf',
+      dest='read_elf',
+      action='store',
+      required=True,
+      help='Path to read-elf executable.')
+
+  args = parser.parse_args()
+  assert os.path.exists(args.exec_path)
+  assert os.path.exists(args.dest)
+  assert os.path.exists(args.read_elf)
+
+  parts = GetBuildIdParts(args.exec_path, args.read_elf)
+  dbg_prefix_base = os.path.join(args.dest, parts['prefix_dir'])
+
+  success = False
+  for _ in range(3):
+    try:
+      if not os.path.exists(dbg_prefix_base):
+        os.makedirs(dbg_prefix_base)
+      success = True
+      break
+    except OSError as error:
+      print 'Failed to create dir %s, error: %s. sleeping...' % (
+          dbg_prefix_base, error)
+      time.sleep(3)
+
+  if not success:
+    print 'Unable to create directory: %s.' % dbg_prefix_base
+    return 1
+
+  dbg_suffix = ''
+  if not args.stripped:
+    dbg_suffix = '.debug'
+  dbg_file_name = '%s%s' % (parts['exec_name'], dbg_suffix)
+  dbg_file_path = os.path.join(dbg_prefix_base, dbg_file_name)
+
+  shutil.copyfile(args.exec_path, dbg_file_path)
+
+  # Note this needs to be in sync with debug_symbols.gni
+  completion_file = os.path.join(args.dest, '.%s_dbg_success' % args.exec_name)
+  Touch(completion_file)
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())

tools/fuchsia/fuchsia_archive.gni

@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("$flutter_root/tools/fuchsia/fuchsia_debug_symbols.gni")
+
 # Creates a Fuchsia archive (.far) file using PM from the Fuchsia SDK.
 template("fuchsia_archive") {
   assert(defined(invoker.binary), "package must define binary")
@@ -72,6 +74,13 @@ template("fuchsia_archive") {
              },
              "json")
 
+  _dbg_symbols_target = "${target_name}_dbg_symbols"
+  fuchsia_debug_symbols(_dbg_symbols_target) {
+    deps = pkg.deps
+    testonly = pkg_testonly
+    binary = invoker.binary
+  }
+
   pkg_dir_deps = pkg.deps + [ ":$cmx_target" ]
 
   action("${target_name}_dir") {
@@ -86,7 +95,10 @@ template("fuchsia_archive") {
 
   action(target_name) {
     script = "$flutter_root/tools/fuchsia/gen_package.py"
-    deps = pkg_dir_deps + [ ":${target_name}_dir" ]
+    deps = pkg_dir_deps + [
+             ":${target_name}_dir",
+             ":${_dbg_symbols_target}",
+           ]
     sources = copy_outputs
 
     inputs = []

tools/fuchsia/fuchsia_debug_symbols.gni

@@ -0,0 +1,74 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# The inputs to this template are 'binary_path' and a boolean 'unstripped'.
+# If 'unstripped' is specified, we append '.debug' to the symbols name.
+template("_copy_debug_symbols") {
+  assert(defined(invoker.binary_path), "'binary_path' needs to be defined.")
+  assert(defined(invoker.unstripped), "'unstripped' needs to be defined.")
+
+  action(target_name) {
+    forward_variables_from(invoker,
+                           [
+                             "deps",
+                             "unstripped",
+                             "binary_path",
+                             "testonly",
+                           ])
+
+    script = "$flutter_root/tools/fuchsia/copy_debug_symbols.py"
+
+    sources = [
+      binary_path,
+    ]
+
+    _dest_base =
+        "${root_out_dir}/flutter-debug-symbols-${target_os}-${target_cpu}"
+
+    args = [
+      "--executable-name",
+      target_name,
+      "--executable-path",
+      rebase_path(binary_path),
+      "--destination-base",
+      rebase_path(_dest_base),
+      "--read-elf",
+      rebase_path("//fuchsia/toolchain/$host_os/bin/llvm-readelf"),
+    ]
+
+    if (unstripped) {
+      args += [ "--unstripped" ]
+    }
+
+    outputs = [
+      "${_dest_base}/.${target_name}_success",
+    ]
+  }
+}
+
+# Takes a binary and generates its debug symbols following
+# the Fuchsia packaging convention.
+template("fuchsia_debug_symbols") {
+  assert(defined(invoker.binary), "'binary' needs to be defined.")
+
+  _copy_debug_symbols("_${target_name}_stripped") {
+    forward_variables_from(invoker, "*")
+    binary_path = rebase_path("${root_out_dir}/$binary")
+    unstripped = false
+  }
+
+  _copy_debug_symbols("_${target_name}_unstripped") {
+    forward_variables_from(invoker, "*")
+    binary_path = "${root_out_dir}/exe.unstripped/$binary"
+    unstripped = true
+  }
+
+  group(target_name) {
+    forward_variables_from(invoker, [ "testonly" ])
+    deps = [
+      ":_${target_name}_stripped",
+      ":_${target_name}_unstripped",
+    ]
+  }
+}