Name packed relocations section appropriately for arm64.

build/android/gyp/pack_arm_relocations.py

 #!/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.
 
 """Pack ARM relative relocations in a library (or copy unchanged).
 
 If --enable-packing and --configuration-name=='Release', invoke the
-relocation_packer tool to pack the .rel.dyn section in the given library
-files.  This step is inserted after the libraries are stripped.  Packing
-adds a new .android.rel.dyn section to the file and reduces the size of
-.rel.dyn accordingly.
+relocation_packer tool to pack the .rel.dyn or .rela.dyn section in the given
+library files.  This step is inserted after the libraries are stripped.
+Packing adds a new .android.rel.dyn or .android.rela.dyn section to the file
+and reduces the size of .rel.dyn or .rela.dyn accordingly.
 
 Currently packing only understands ARM32 shared libraries.  For all other
 architectures --enable-packing should be set to zero.  In this case the
 script copies files verbatim, with no attempt to pack relative relocations.
 
 Any library listed in --exclude-packing-list is also copied verbatim,
 irrespective of any --enable-packing setting.  Typically this would be
 'libchromium_android_linker.so'.
 """
 
 import optparse
 import os
 import shlex
 import shutil
 import sys
 import tempfile
 
 from util import build_utils
 
 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.
+  # 32-bit libraries will contain .rel.dyn, and 64-bit ones .rela.dyn.
+  # Select an appropriate name for the section we add.
+  # From elf.h, e_ident[EI_CLASS (4)] == ELFCLASS32 (1) or ELFCLASS64 (2).
+  with open(library_path) as stream:
+    elfclass = ord(stream.read(5)[-1])
+  if elfclass == 2:
+    new_section = '.android.rela.dyn'
+  else:
+    new_section = '.android.rel.dyn'

[rmcilroy, 2014/10/07 14:02:39]

This seems a bit hacky to work out if it's 32 or 64.  Could we just pass this in
as an argument instead and use the target_arch variable in gyp to decide on what
name to pass to the too instead?

[simonb (inactive), 2014/10/07 15:34:20]

Done.  Updated version in patch set 2.  PTAL, thanks.

+
+  # Copy and add a 'NULL' packed relocations section for the packing tool.
   with tempfile.NamedTemporaryFile() as stream:
     stream.write('NULL')
     stream.flush()
     objcopy_command = [android_objcopy,
-                       '--add-section', '.android.rel.dyn=%s' % stream.name,
+                       '--add-section', '%s=%s' % (new_section, 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]):
@@ skipping 50 matching lines @@
       CopyArmLibraryUnchanged(library_path, output_path)
 
   if options.stamp:
     build_utils.Touch(options.stamp)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))