Add "kern_guid=%U" to the secure boot kernel command-line template.

Add "kern_guid=%U" to the secure boot kernel command-line template.

With the newest Chrome OS BIOS and bootstub, this will be expanded to the
booted kernel partition's UniqueGuid, so that the kernel device can be
determined with certainty, since the BIOS and kernel may enumerate drives
differently.

You can identify the booted kernel partition at runtime with something like
this:

  sudo cgpt find -1 -u \
    $(cat /proc/cmdline | sed 's/.*kern_guid=\([0-9a-f-]\+\).*/\1/')

[gauravsh, 2010-07-23 01:46:29]

lgtm

[Bill Richardson, 2010-07-23 01:47:43]

Testing:

This is a multiple-repository change set. All three of these
changes must have landed before any changes will be visible:

  http://codereview.chromium.org/3056014/show
  http://codereview.chromium.org/2832078/show
  http://codereview.chromium.org/3035020/show

AND a Chrome OS BIOS that incorporates CL 3056014 must also
be used.

If all that has happened, boot the device, log in, switch to
a console, and run

  cat /proc/cmdline

You should see a term something like this (the actual
numbers will be different):

  kern_guid=af208ed8-788f-6841-b250-8654755089a3


That GUID should correspond to the kernel partition, which
you can display using the cgpt tool. For example,

  sudo cgpt show /dev/sda

Of course, you'll want to replace /dev/sda with the actual
root device (which you can find by running "rootdev").


If the kern_guid numbers are all zeros or a simple '%U' or
is not present at all, not all changes have landed (or
something is broken).