[grokdump] Include -z flag to make objdump disassemble all-zero sections

tools/disasm.py

 #!/usr/bin/env python
 #
 # Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 20 matching lines @@
 import re
 import subprocess
 import tempfile
 
 
 # Avoid using the slow (google-specific) wrapper around objdump.
 OBJDUMP_BIN = "/usr/bin/objdump"
 if not os.path.exists(OBJDUMP_BIN):
   OBJDUMP_BIN = "objdump"
 
-
-_COMMON_DISASM_OPTIONS = ["-M", "intel-mnemonic", "-C"]
+# -M intel-mnemonic selects Intel syntax.
+# -C demangles.
+# -z disables skipping over sections of zeroes.
+_COMMON_DISASM_OPTIONS = ["-M", "intel-mnemonic", "-C", "-z"]
 
 _DISASM_HEADER_RE = re.compile(r"[a-f0-9]+\s+<.*:$")
 _DISASM_LINE_RE = re.compile(r"\s*([a-f0-9]+):\s*(\S.*)")
 
 # Keys must match constants in Logger::LogCodeInfo.
 _ARCH_MAP = {
   "ia32": "-m i386",
   "x64": "-m i386 -M x86-64",
   "arm": "-m arm",  # Not supported by our objdump build.
   "mips": "-m mips",  # Not supported by our objdump build.
@@ skipping 34 matching lines @@
       break
   if tmp_name:
     os.unlink(tmp_name)
   split_lines = []
   for line in lines[header_line + 1:]:
     match = _DISASM_LINE_RE.match(line)
     if match:
       line_address = int(match.group(1), 16)
       split_lines.append((line_address, match.group(2)))
   return split_lines