Disable automatic update checks if booting from a removable device.

utils.cc

 // Copyright (c) 2009 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/utils.h"
+
 #include <sys/mount.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+
 #include <algorithm>
+
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/string_util.h"
 #include "chromeos/obsolete_logging.h"
 #include "update_engine/file_writer.h"
 #include "update_engine/omaha_request_params.h"
 #include "update_engine/subprocess.h"
 
 using std::min;
 using std::string;
 using std::vector;
 
 namespace chromeos_update_engine {
@@ skipping 173 matching lines @@
                                                dir_entry_p->d_name));
     }
     TEST_AND_RETURN_FALSE(err == 0);
   }
   // unlink dir
   TEST_AND_RETURN_FALSE_ERRNO((rmdir(path.c_str()) == 0) || (errno == ENOENT));
   return true;
 }
 
 string RootDevice(const string& partition_device) {
-  CHECK(!partition_device.empty());
+  FilePath device_path(partition_device);
+  if (device_path.DirName().value() != "/dev") {
+    return "";
+  }
   string::const_iterator it = --partition_device.end();
   for (; it >= partition_device.begin(); --it) {
     if (!isdigit(*it))
       break;
   }
   // Some devices contain a p before the partitions. For example:
   // /dev/mmc0p4 should be shortened to /dev/mmc0.
   if (*it == 'p')
     --it;
   return string(partition_device.begin(), it + 1);
 }
 
 string PartitionNumber(const string& partition_device) {
   CHECK(!partition_device.empty());
   string::const_iterator it = --partition_device.end();
   for (; it >= partition_device.begin(); --it) {
     if (!isdigit(*it))
       break;
   }
   return string(it + 1, partition_device.end());
 }
 
+string SysfsBlockDevice(const string& device) {
+  FilePath device_path(device);
+  if (device_path.DirName().value() != "/dev") {
+    return "";
+  }
+  return FilePath("/sys/block").Append(device_path.BaseName()).value();
+}
+
+bool IsRemovableDevice(const std::string& device) {
+  string sysfs_block = SysfsBlockDevice(device);
+  string removable;
+  if (sysfs_block.empty() ||
+      !file_util::ReadFileToString(FilePath(sysfs_block).Append("removable"),
+                                   &removable)) {
+    return false;
+  }
+  TrimWhitespaceASCII(removable, TRIM_ALL, &removable);
+  return removable == "1";
+}
+
 std::string ErrnoNumberAsString(int err) {
   char buf[100];
   buf[0] = '\0';
   return strerror_r(err, buf, sizeof(buf));
 }
 
 std::string NormalizePath(const std::string& path, bool strip_trailing_slash) {
   string ret;
   bool last_insert_was_slash = false;
   for (string::const_iterator it = path.begin(); it != path.end(); ++it) {
@@ skipping 170 matching lines @@
   Subprocess::SynchronousExec(command, &rc);
   TEST_AND_RETURN_FALSE(rc == 0);
   return true;
 }
 
 const char* const kStatefulPartition = "/mnt/stateful_partition";
 
 }  // namespace utils
 
 }  // namespace chromeos_update_engine