2b034922 breaks kexec on ARM

[Russell King - ARM Linux]

On Mon, Nov 07, 2011 at 06:51:25PM +0000, Will Deacon wrote:
> Hello,
> 
> I've just finished rebasing and reworking my kexec patches so that they sit
> nicely on top of Russell's recent reset work. The only problem is that
> commit 2b034922 ("ARM: 7098/1: kdump: copy kernel relocation code at the
> kexec prepare stage") is causing kexec to fail.
> 
> The symptoms are that the .init.text section is not loaded as part of the
> new kernel image, so when we try to do the SMP/UP fixups we hit a whole sea
> of poison left there by the previous kernel.
> 
> So my guess is that machine_kexec_prepare *is* too early for preparing the
> reboot_code_buffer and, unless anybody has a good reason not to, I'd like to
> revert the patch causing these problems.

Hmm, having looked at kernel/kexec.c, this patch is clearly wrong.
There are two kernels which can be loaded into kexec - a crash kernel
and a default kernel.  These are kept entirely separately (and the
per-kernel context is stored in 'image').

However, this patch makes machine_kexec_prepare() store into some
_global_ variables, which means if you've loaded a crash kernel
followed by a default kernel, the values for the crash kernel will
be corrupted.

So yes, I think a revert of this patch is the right thing.

I think the only valid thing its doing is moving the copy of the
reboot code earlier, but I don't see the value of moving just that.