Re: [PATCH] x86: entry_32.S: change ESPFIX test to not touch PT_OLDSS(%esp)

From: Linus Torvalds
Date: Mon Mar 09 2015 - 14:16:12 EST


On Mon, Mar 9, 2015 at 11:04 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>
> One option would be to change the NMI entry code to move itself down 8
> bytes if this happens (came from kernel mode or sp == sp0 - 12,
> perhaps).

Hmm. That whole code currently depends on the stack setup being just a
single instruction (the move to esp). And that simplifies things, I'd
like to keep it that way.

I'd *much* rather just keep the 8-byte padding. What was so
problematic with that? It worked. It's been around forever. Removing
it is the bug.

Linus
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