Found the answer in ptrace.h -- the answer is no.  never mind.

Jeff

On 10/24/15, Jeffrey Merkey <jeffmerkey@gmail.com> wrote:
> I am updating the mdb kernel debugger on 4.2.4 and I noticed that
> user_mode_vm has been removed from the kernel sources for detecting
> user space memory addresses for purposes of loading the SS pointer.  I
> am using __KERNEL_DS presently.
>
> old code:
>
> if (user_mode_vm(regs))
> {
>     sf->tSS = regs->ss;
>     sf->tSP = regs->sp;
> } else {
>       sf->tSS = __KERNEL_DS;
>       sf->tSP = kernel_stack_pointer(regs);
> }
>
> is SS always assumed to be __KERNEL_DS in 4.2.4 for userspace stack
> addresses passed by pt_regs?
>
>
> Thanks
>
> Jeff
>