AU: Handle firmware update failure when booted from FW slot B.

postinstall_runner_action.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/postinstall_runner_action.h"
 #include <sys/mount.h>
 #include <stdlib.h>
 #include <vector>
 #include "update_engine/subprocess.h"
 #include "update_engine/utils.h"
@@ skipping 47 matching lines @@
   command.push_back(temp_rootfs_dir_ + kPostinstallScript);
   command.push_back(install_device);
   Subprocess::Get().Exec(command, StaticCompletePostinstall, this);
 }
 
 void PostinstallRunnerAction::CompletePostinstall(int return_code) {
   ScopedActionCompleter completer(processor_, this);
   ScopedTempUnmounter temp_unmounter(temp_rootfs_dir_);
   if (return_code != 0) {
     LOG(ERROR) << "Postinst command failed with code: " << return_code;
+    if (return_code == 2) {
+      // This special return code means that we tried to update firmware,
+      // but couldn't because we booted from FW B, and we need to reboot
+      // to get back to FW A.
+      completer.set_code(kActionCodePostinstallBootedFromFirmwareB);
+    }
     return;
   }
   if (HasOutputPipe()) {
     CHECK(HasInputObject());
     SetOutputObject(GetInputObject());
   }
   completer.set_code(kActionCodeSuccess);
 }
 
 void PostinstallRunnerAction::StaticCompletePostinstall(int return_code,
                                                         const string& output,
                                                         void* p) {
   reinterpret_cast<PostinstallRunnerAction*>(p)->CompletePostinstall(
       return_code);
 }
 
 }  // namespace chromeos_update_engine