Re: [RFC 2/2] x86_64: expand kernel stack to 16K

Linus Torvalds
2014-05-30T15:41:06Z

On Fri, May 30, 2014 at 8:25 AM, H. Peter Anvin <hpa@zytor.com> wrote:
>
> If we removed struct thread_info from the stack allocation then one
> could do a guard page below the stack. Of course, we'd have to use IST
> for #PF in that case, which makes it a non-production option.

We could just have the guard page in between the stack and the
thread_info, take a double fault, and then just map it back in on
double fault.

That would give us 8kB of "normal" stack, with a very loud fault - and
then an extra 7kB or so of stack (whatever the size of thread-info is)
- after the first time it traps.

That said, it's still likely a non-production option due to the page
table games we'd have to play at fork/clone time.

Linus