Bug(?) in linux kernel EFI support

[Tony Hoyle <tmh@nodomain.org>]

Hi,

I'm building kernels on an embedded system which uses an odd version of 
EFI (elilo/egrub don't run for example, only its own shipped boot.efi 
that loads a raw vmlinux).  I've been unable to get it to boot with any 
kernel > 2.6.24.7 - as in it doesn't start up far enough to get netconsole.

I've tracked it down to the following commit.  Prior to this commit, it 
boots.. after it, it doesn't:

e429795c68d3001ecae74f6465420c9f043b0ece is first bad commit
commit e429795c68d3001ecae74f6465420c9f043b0ece
Author: Huang, Ying <ying.huang@intel.com>
Date:   Wed Jan 30 13:31:19 2008 +0100

     x86: EFI runtime service support: remove duplicated code from efi_32.c

     This patch removes the duplicated code between efi_32.c and efi.c.

     Signed-off-by: Huang Ying <ying.huang@intel.com>
     Cc: Andi Kleen <ak@suse.de>
     Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
     Signed-off-by: Ingo Molnar <mingo@elte.hu>
     Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

:040000 040000 e6ac42e8fddef99698e5ebb39ed0a3d0c18bf1ac 
1974f788a81cc6ced68ce87345e107e614691831 M	arch
:040000 040000 f7b172e407b45e571eac4612dc799e44e7b24928 
20608b877d79449318d72a31dc202f2341f0fceb M	include

Now I don't really understand the inner workings of EFI (or of the 
kernel for that matter).. I imagine 32bit EFI-only booting is fairly 
unusual and few platforms support it... is there anything that anyone 
can see that could cause a crash in this patch?

I have no ability to see the actual fault - The device has no console 
(the display is hardcoded to show a logo until X boots.. there's an fb 
driver shipped with it that appears to be able to override that but it's 
binary only*.  There's no serial port on the board, only USB & Ethernet 
- so I'm stuck with netconsole basically.  kexec doesn't work (memory 
regions have different names & kexec has hardcoded text searches.. 
patching it with the new names doesn't work either..).

I realise this makes things somewhat harder to debug :p  I call it 
challenging..

Tony

* despite a 'strings' saying GPL in the text.. sigh..