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SubjectRe: [PATCH 03/39] x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler
On Thu, Jul 12, 2018 at 01:49:13PM -0700, Andy Lutomirski wrote:
> > On Jul 11, 2018, at 4:29 AM, Joerg Roedel <joro@8bytes.org> wrote:
> > /* Offset from the sysenter stack to tss.sp0 */
> > - DEFINE(TSS_entry_stack, offsetof(struct cpu_entry_area, tss.x86_tss.sp0) -
> > + DEFINE(TSS_entry_stack, offsetof(struct cpu_entry_area, tss.x86_tss.sp1) -
> > offsetofend(struct cpu_entry_area, entry_stack_page.stack));
> >
>
> The code reads differently. Did you perhaps mean TSS_task_stack?

Well, the offset name came from TSS_sysenter_sp0, which was the offset
from the sysenter_sp0 (==sysenter-stack) to the task stack in TSS, now
sysenter_sp0 became entry_stack, because its used for all entry points
and not only sysenter. So with the old convention the naming makes still
sense, no?

> Also, the “top of task stack” is a bit weird on 32-bit due to vm86.
> Can you document *exactly* what goes in sp1?

Will do, thanks for your feedback!


Joerg
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