Use chain-loading for Linux nacl_helper

chrome/nacl/nacl_helper_bootstrap_munge_phdr.py

+#!/usr/bin/python
+# Copyright (c) 2011 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.
+#
+# This takes three command-line arguments:
+#       MUNGE-PHDR-PROGRAM      file name of program built from
+#                               nacl_helper_bootstrap_munge_phdr.c
+#       INFILE                  raw linked ELF file name
+#       OUTFILE                 output file name
+#
+# We just run the MUNGE-PHDR-PROGRAM on a copy of INFILE.
+# That modifies the file in place.  Then we move it to OUTFILE.
+#
+# We only have this wrapper script because nacl_helper_bootstrap_munge_phdr.c
+# wants to modify a file in place (and it would be a much longer and more
+# fragile program if it created a fresh ELF output file instead).
+
+import shutil
+import subprocess
+import sys
+
+
+def Main(argv):
+  if len(argv) != 4:
+    print 'Usage: %s MUNGE-PHDR-PROGRAM INFILE OUTFILE' % argv[0]
+    sys.exit(1)
+  [prog, munger, infile, outfile] = argv
+  tmpfile = outfile + '.tmp'
+  shutil.copy(infile, tmpfile)
+  segment_num = '1'
+  subprocess.check_call([munger, tmpfile, segment_num])
+  shutil.move(tmpfile, outfile)
+
+if __name__ == '__main__':
+  Main(sys.argv)