kexec: Clearing registers just before jumping into purgatory

[Eric W. Biederman]

Matthew Garrett <mjg59 at srcf.ucam.org> writes:

> On Fri, Oct 11, 2013 at 06:59:41PM +0200, Richard Weinberger wrote:
>> Am 11.10.2013 18:55, schrieb Matthew Garrett:
>> > On Fri, Oct 11, 2013 at 06:47:19PM +0200, Richard Weinberger wrote:
>> > 
>> >> But you still need a magic tool which create you this list.
>> > 
>> > I just read /proc/kallsyms. I'm really not doing anything complicated.
>> > 
>> >> If you have a tool which takes two kernel images and create such
>> >> a delta, fine.
>> > 
>> > Isn't that ksplice?
>> 
>> So, you have a variant of ksplice which is able to kexec?
>
> No, I manually look up some addresses from /proc/kallsyms and then 
> modify them in the second kernel.

An interesting approach I think most of the rest of us would have just
built a module, or rebuilt our kernels.

Now if this is a backwards argument to remove that silly code path it
totally fails because now we know the code has not bit-rotted and
that there are active users.

If you are still pushing the signed-boot agenda I eagerly await your
patches to make all of this work in a sensible way with signed binaries.

Eric