Add gyp machinery to build with packed ARM relative relocations.

build/android/gyp/pack_arm_relocations.py

Index: build/android/gyp/pack_arm_relocations.py
diff --git a/build/android/gyp/pack_arm_relocations.py b/build/android/gyp/pack_arm_relocations.py
new file mode 100755
index 0000000000000000000000000000000000000000..84df4f109c3a99c6d02001a08b1ebd4b4982679e
--- /dev/null
+++ b/build/android/gyp/pack_arm_relocations.py
@@ -0,0 +1,88 @@
+#!/usr/bin/env python
+#
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+

[rmcilroy, 2014/06/27 11:14:54]

nit - please add a docstring comment here describing the package.

[simonb (inactive), 2014/06/30 16:23:23]

Done.

+import json
+import optparse
+import os
+import shutil
+import sys
+import tempfile
+
+from util import build_utils
+
+

[rmcilroy, 2014/06/27 11:14:54]

nit - single newline here (I believe, though still double newline between
functions)

[simonb (inactive), 2014/06/30 16:23:23]

Done.

+def PackArmLibraryRelocations(android_pack_relocations,
+                              android_objcopy,
+                              library_path,
+                              output_path):
+  if not build_utils.IsTimeStale(output_path, [library_path]):
+    return
+
+  # Copy and add a 'NULL' .android.rel.dyn section for the packing tool.
+  with tempfile.NamedTemporaryFile() as stream:

[rmcilroy, 2014/06/27 11:14:54]

nit - /s/stream/section_contents_tmp

[simonb (inactive), 2014/06/30 16:23:23]

Doesn't seem to offer much benefit.  Let me know if you strongly disagree.

[rmcilroy, 2014/07/01 11:13:02]

To me it makes the code more readable.  "stream.write('NULL')" doesn't convey
much to me, but "section_contents_tmp.write('NULL')" explains to me what it's
doing.  I don't strongly care though.

+    stream.write('NULL')
+    stream.flush()
+    objcopy_command = [android_objcopy,
+                       '--add-section', '.android.rel.dyn=%s' % stream.name,
+                       library_path, output_path]
+    build_utils.CheckOutput(objcopy_command)
+
+  # Pack R_ARM_RELATIVE relocations.
+  pack_command = [android_pack_relocations, output_path]
+  build_utils.CheckOutput(pack_command)
+
+
+def CopyArmLibraryUnchanged(library_path, output_path):
+  if not build_utils.IsTimeStale(output_path, [library_path]):
+    return
+
+  shutil.copy(library_path, output_path)
+
+
+def main():
+  parser = optparse.OptionParser()
+
+  parser.add_option('--enable-packing',
+      help='Pack relocations if true, otherwise plain file copy')

[rmcilroy, 2014/06/27 11:14:54]

Pack relocations if '1', otherwise plain file copy (also maybe just make this a
"choices" type with ['0', '1'] as the choices). 

[simonb (inactive), 2014/06/30 16:23:23]

Done.  Looks better, thanks.

+  parser.add_option('--android-pack-relocations',
+      help='Path to the ARM relocations packer binary')
+  parser.add_option('--android-objcopy',
+      help='Path to the toolchain\'s objcopy binary')
+  parser.add_option('--stripped-libraries-dir',
+      help='Directory for stripped libraries')
+  parser.add_option('--packed-libraries-dir',
+      help='Directory for packed libraries')
+  parser.add_option('--libraries-file',
+      help='Path to json file containing list of libraries')
+  parser.add_option('--stamp', help='Path to touch on success')
+
+  options, _ = parser.parse_args()
+  enable_packing = options.enable_packing.lower() in ['true', 't', 'yes', '1']
+
+  with open(options.libraries_file, 'r') as libfile:
+    libraries = json.load(libfile)
+
+  for library in libraries:
+    library_path = os.path.join(options.stripped_libraries_dir, library)
+    output_path = os.path.join(options.packed_libraries_dir, library)
+
+    if enable_packing and library != 'libchromium_android_linker.so':

[rmcilroy, 2014/06/27 11:14:54]

This hardcoded name is getting sprinkled around the codebase - could we figure
out a way to have it as a gyp variable which is passed to this tool, as well as
being passed to Anton's rezip tool to avoid being hardcoded in both tools?

[simonb (inactive), 2014/06/30 16:23:23]

Done.

+      PackArmLibraryRelocations(options.android_pack_relocations,
+                                options.android_objcopy,
+                                library_path,
+                                output_path)
+    else:
+      CopyArmLibraryUnchanged(library_path, output_path)
+
+
+  if options.stamp:
+    build_utils.Touch(options.stamp)
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())