Support alternative GPT header signature

In order to dual boot Windows and ChromeOS, Windows must
not find a GPT partition table on the disk. So change
ChromeOS to cope with an alternative signature "CHROMEOS"
instead of the standard "EFI PART"

BUG=chrome-os-partner:6108
TEST=rebuild chromeos, install it,
     run cgpt legacy /dev/sda
     dd if=/dev/sda of=/tmp/x bs=1k
     hexdump -C /tmp/X
     see the string CHROMEOS
BRANCH=link
Signed-off-by: Stefan Reinauer <reinauer@chromium.org>

Change-Id: Ia88eff33b9880bd73a78c1b8e026c1f8298c4557
Reviewed-on: https://gerrit.chromium.org/gerrit/31264
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Ready: Stefan Reinauer <reinauer@chromium.org>
Tested-by: Stefan Reinauer <reinauer@chromium.org>

1 files changed, 67 insertions, 0 deletions

diff --git a/cgpt/cmd_legacy.c b/cgpt/cmd_legacy.c
new file mode 100644
index 00000000..5dad01e3
--- /dev/null
+++ b/cgpt/cmd_legacy.c
@@ -0,0 +1,67 @@
+// Copyright (c) 2012 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 "cgpt.h"
+
+#include <getopt.h>
+#include <string.h>
+
+#include "cgpt_params.h"
+
+static void Usage(void)
+{
+  printf("\nUsage: %s legacy [OPTIONS] DRIVE\n\n"
+         "Switch GPT header signature to \"CHROMEOS\".\n\n"
+         "Options:\n"
+         "  -e           Switch GPT header signature back to \"EFI PART\"\n"
+         "\n", progname);
+}
+
+int cmd_legacy(int argc, char *argv[]) {
+  CgptLegacyParams params;
+  memset(&params, 0, sizeof(params));
+
+  int c;
+  int errorcnt = 0;
+
+  opterr = 0;                     // quiet, you
+  while ((c=getopt(argc, argv, ":he")) != -1)
+  {
+    switch (c)
+    {
+    case 'e':
+      params.efipart = 1;
+      break;
+
+    case 'h':
+      Usage();
+      return CGPT_OK;
+    case '?':
+      Error("unrecognized option: -%c\n", optopt);
+      errorcnt++;
+      break;
+    case ':':
+      Error("missing argument to -%c\n", optopt);
+      errorcnt++;
+      break;
+    default:
+      errorcnt++;
+      break;
+    }
+  }
+  if (errorcnt)
+  {
+    Usage();
+    return CGPT_FAILED;
+  }
+
+  if (optind >= argc) {
+    Usage();
+    return CGPT_FAILED;
+  }
+
+  params.drive_name = argv[optind];
+
+  return cgpt_legacy(&params);
+}