On Mon, Aug 21, 2006 at 10:29:36PM +0900, Magnus Damm wrote:
> On 8/21/06, Andi Kleen <[email protected]> wrote:
> >
> >>
> >> + /* Reload CS with a value that is within our GDT. We need to do
> >this
> >> + * if we were loaded by a 64 bit bootloader that happened to use a
> >> + * CS that is larger than the GDT limit. This is true if we came
> >here
> >> + * from kexec running under Xen.
> >> + */
> >> + movq %rsp, %rdx
> >> + movq $__KERNEL_DS, %rax
> >> + pushq %rax /* SS */
> >> + pushq %rdx /* RSP */
> >> + movq $__KERNEL_CS, %rax
> >> + movq $cs_reloaded, %rdx
> >> + pushq %rax /* CS */
> >> + pushq %rdx /* RIP */
> >> + lretq
> >
> >Can't you just use a normal far jump? That might be simpler.
>
> I couldn't find a far jump that took a 64-bit address to jump to. But
> I guess that the kernel will be loaded in the lowest 4G regardless so
> I guess 32-bit pointers are ok, right? That will make it simpler for
> sure.
>
Given the idea of relocatable kernel is floating around I would prefer if
we are not bounded by the restriction of loading a kernel in lowest 4G.
Thanks
Vivek
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