[Bug 1087501] Re: Unable to boot unsigned kernel, boot freezes in shim call

[Stéphane Graber]

12:01 <stgraber> ok, so I've got a patched shim that can log into nvram variables, that should make tracking the hang down a bit easier
12:32 <stgraber> and debugged as far as I can without getting any real shim knowledge
12:32 <stgraber> that is, I tracked it down to the exact line where it's hanging
12:33 <stgraber> http://paste.ubuntu.com/5962449/ is what I've been working with
12:33 <stgraber> after boot, I'm getting: 
12:33 <stgraber> verify_buffer: debug 1a
12:34 <stgraber> so it appears it actually hangs on the Print() call in the error case of that first check in verify_buffer
12:34 <stgraber> possibly because grub prevents it from printing anything (as we've seen with your other test build)
12:57 <stgraber> found the issue, though it's pretty scary
12:57 <stgraber> commenting the Print() call makes my laptop boot just fine
12:57 <stgraber> may be related to some console state change triggered by grub or as Colin suggested in #ubuntu-installer, a memory allocation bug in the firmware's implementation of Print()
12:58 <stgraber> anyway, patching the shim not to print stuff to the screen seems like our easiest fix for this mess

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https://bugs.launchpad.net/bugs/1087501

Title:
  Unable to boot unsigned kernel, boot freezes in shim call

Status in “shim” package in Ubuntu:
  Incomplete

Bug description:
  On a Lenovo x230 with secureboot enabled, I can only boot signed
  kernel.

  Initially this was thought to be a grub2 issue but after investigation
  (added debug code in grub and running with debug=all), it was
  determined that the last thing grub does before the freeze is call a
  shim hook.

  The current workaround is to either disable secureboot or use a signed
  kernel.

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