The PTI path does this:
...
SWITCH_TO_KERNEL_CR3 scratch_reg=%rsp
/* Load the top of the task stack into RSP */
movq CPU_ENTRY_AREA_tss + TSS_sp1 + CPU_ENTRY_AREA, %rsp
And the non-PTI entry path does this:
...
movq %rsp, PER_CPU_VAR(rsp_scratch)
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
Both "mov ___, %rsp" instructions have the kernel %GS value in place and
both are running on a good kernel CR3. Does anybody remember why we
don't use cpu_current_top_of_stack in the PTI-on case?
I'm wondering if it was because we, at some point, did the mov ...,
%rsp before CR3 was good. But it doesn't look like we do that now, so
should we maybe make both copies do:
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
for consistency?
