diff --git a/util/mach/mig.py b/util/mach/mig.py
new file mode 100755
index 00000000..2d248854
--- /dev/null
+++ b/util/mach/mig.py
@@ -0,0 +1,123 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+# Copyright 2014 The Crashpad Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import re
+import subprocess
+import sys
+
+def FixUserImplementation(implementation):
+  """Rewrites a MIG-generated user implementation (.c) file.
+
+  Rewrites the file at |implementation| by adding “__attribute__((unused))” to
+  the definition of any structure typedefed as “__Reply” by searching for the
+  pattern unique to those structure definitions. These structures are in fact
+  unused in the user implementation file, and this will trigger a
+  -Wunused-local-typedefs warning in gcc unless removed or marked with the
+  “unused” attribute.
+  """
+
+  file = open(implementation, 'r+')
+  contents = file.read()
+
+  pattern = re.compile('^(\t} __Reply);$', re.MULTILINE)
+  contents = pattern.sub(r'\1 __attribute__((unused));', contents)
+
+  file.seek(0)
+  file.truncate()
+  file.write(contents)
+  file.close()
+
+def FixServerImplementation(implementation):
+  """Rewrites a MIG-generated server implementation (.c) file.
+
+  Rewrites the file at |implementation| by replacing “mig_internal” with
+  “mig_external” on functions that begin with “__MIG_check__”. This makes these
+  functions available to other callers outside this file from a linkage
+  perspective. It then returns, as a list of lines, declarations that can be
+  added to a header file, so that other files that include that header file will
+  have access to these declarations from a compilation perspective.
+  """
+
+  file = open(implementation, 'r+')
+  contents = file.read()
+
+  # Find interesting declarations.
+  declaration_pattern = \
+      re.compile('^mig_internal (kern_return_t __MIG_check__.*)$',
+                 re.MULTILINE)
+  declarations = declaration_pattern.findall(contents)
+
+  # Remove “__attribute__((__unused__))” from the declarations, and call them
+  # “mig_external” or “extern” depending on whether “mig_external” is defined.
+  attribute_pattern = re.compile(r'__attribute__\(\(__unused__\)\) ')
+  declarations = ['#ifdef mig_external\nmig_external\n#else\nextern\n#endif\n' +
+                  attribute_pattern.sub('', x) +
+                  ';\n' for x in declarations]
+
+  # Rewrite the declarations in this file as “mig_external”.
+  contents = declaration_pattern.sub(r'mig_external \1', contents);
+
+  file.seek(0)
+  file.truncate()
+  file.write(contents)
+  file.close()
+  return declarations
+
+def FixHeader(header, declarations=[]):
+  """Rewrites a MIG-generated header (.h) file.
+
+  Rewrites the file at |header| by placing it inside an “extern "C"” block, so
+  that it declares things properly when included by a C++ compilation unit.
+  |declarations| can be a list of additional declarations to place inside the
+  “extern "C"” block after the original contents of |header|.
+  """
+
+  file = open(header, 'r+')
+  contents = file.read()
+  declarations_text = ''.join(declarations)
+  contents = '''\
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+%s
+%s
+#ifdef __cplusplus
+}
+#endif
+''' % (contents, declarations_text)
+  file.seek(0)
+  file.truncate()
+  file.write(contents)
+  file.close()
+
+def main(args):
+  assert len(args) == 5
+  (defs_file, user_c, server_c, user_h, server_h) = args
+  subprocess.check_call(['mig',
+                         '-user', user_c,
+                         '-server', server_c,
+                         '-header', user_h,
+                         '-sheader', server_h,
+                         defs_file])
+  FixUserImplementation(user_c)
+  server_declarations = FixServerImplementation(server_c)
+  FixHeader(user_h)
+  FixHeader(server_h, server_declarations)
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))
diff --git a/util/util.gyp b/util/util.gyp
index 660e2a6d..951a7a77 100644
--- a/util/util.gyp
+++ b/util/util.gyp
@@ -81,6 +81,42 @@
         'stdlib/strnlen.cc',
         'stdlib/strnlen.h',
       ],
+      'actions': [
+        {
+          'action_name': 'mig exc.defs',
+          'inputs': [
+            'mach/mig.py',
+            '$(SDKROOT)/usr/include/mach/exc.defs',
+          ],
+          'outputs': [
+            '<(INTERMEDIATE_DIR)/util/mach/excUser.c',
+            '<(INTERMEDIATE_DIR)/util/mach/excServer.c',
+            '<(INTERMEDIATE_DIR)/util/mach/exc.h',
+            '<(INTERMEDIATE_DIR)/util/mach/excServer.h',
+          ],
+          'action': [
+            'python', '<@(_inputs)', '<@(_outputs)'
+          ],
+          'process_outputs_as_sources': 1,
+        },
+        {
+          'action_name': 'mig mach_exc.defs',
+          'inputs': [
+            'mach/mig.py',
+            '$(SDKROOT)/usr/include/mach/mach_exc.defs',
+          ],
+          'outputs': [
+            '<(INTERMEDIATE_DIR)/util/mach/mach_excUser.c',
+            '<(INTERMEDIATE_DIR)/util/mach/mach_excServer.c',
+            '<(INTERMEDIATE_DIR)/util/mach/mach_exc.h',
+            '<(INTERMEDIATE_DIR)/util/mach/mach_excServer.h',
+          ],
+          'action': [
+            'python', '<@(_inputs)', '<@(_outputs)'
+          ],
+          'process_outputs_as_sources': 1,
+        },
+      ],
     },
     {
       'target_name': 'util_test_lib',