"Huang, Ying" <ying.huang at intel.com> writes:
> On Thu, 2008-05-15 at 11:39 -0700, Eric W. Biederman wrote:
> [...]
>> 2) After we figure out our address read the stack pointer from
>> a fixed location and simply set it. (This is my preference)
>
> Just for confirmation (My English is poor).
>
> Do you mean that kernel A just read the stack top as re-entry point,
> regardless of whether it is return address or argument 1?
What I was thinking was:
In kernel A()
relocate_new_kernel:
...
call *%eax
kexec_jump_back_entry:
/* This code should be PIC so figure out where we are */
call 1f
1:
popl %edi
subl $(1b - relocate_kernel), %edi
/* Setup a safe stack */
leal PAGE_SIZE(%edi), %esp
...
Then in purgatory we can read the address of kexec_jump_back_entry
by examining 0(%esp) and export it in whatever fashion is sane.
However we reach kexec_jump_back_entry we should be fine.
Eric
