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Date: Mon, 27 Jun 2016 10:28:12 -0700
From: Linus Torvalds <>
To: Andy Lutomirski <>
Cc: Brian Gerst <>, Andy Lutomirski <>, 
	"the arch/x86 maintainers" <>, Linux Kernel Mailing List <>, 
	linux-arch <>, Borislav Petkov <>, 
	Nadav Amit <>, Kees Cook <>, 
	"" <>, Josh Poimboeuf <>, 
	Jann Horn <>, Heiko Carstens <>
Subject: Re: [PATCH v4 15/29] x86/mm/64: Enable vmapped stacks

On Mon, Jun 27, 2016 at 8:54 AM, Andy Lutomirski <> wrote:
> How about:
>     tsk_stack = (unsigned long)task_stack_page(tsk);
>     if (regs->rsp <= tsk_stack + 7*8 && regs->rsp > tsk_stack - PAGE_SIZE) {

I'm not at all convinced that regs->rsp will be all that reliable
under a double-fault scenario either. I'd be more inclined to trusr
cr2 than the register state.

It's true that double faults can happen for *other* reasons entirely,
and as such it's not clear that %cr2 is reliable either, but since
this is all just about a printout, I'd rather go that way anyway.


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