[PATCH] kexec based hibernation: a prototype of kexec multi-stage load
ying.huang at intel.com
Thu May 15 22:56:15 EDT 2008
On Thu, 2008-05-15 at 19:25 -0700, Eric W. Biederman wrote:
> "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()
> call *%eax
> /* This code should be PIC so figure out where we are */
> call 1f
> 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.
I think it is reasonable to enable jumping back and forth more than one
time. So the following should be possible:
1. Jump from A to B (actually jump to purgatory, trigger the boot of B)
2. Jump from B to A
3. Jump from A to B again (jump to the kexec_jump_back_entry of B)
4. Jump from B to A
So it should be possible to get the re-entry point of kernel B in
kexec_jump_back_entry of kernel A too. So I think in
kexec_jump_back_entry, the caller's stack should be checked to get
re-entry point of peer. And the stack state is different depend on where
come from, from relocate_new_kernel() or return.
More information about the kexec