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Date: Thu, 5 Dec 2019 09:01:50 -0800
From: Thomas Garnier <thgarnie@...omium.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Kristen Carlson Accardi <kristen@...ux.intel.com>, Kees Cook <keescook@...omium.org>,
Andy Lutomirski <luto@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, "the arch/x86 maintainers" <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 04/11] x86/entry/64: Adapt assembly for PIE support
On Thu, Dec 5, 2019 at 1:04 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, Dec 04, 2019 at 04:09:41PM -0800, Thomas Garnier wrote:
>
> > @@ -1625,7 +1627,11 @@ first_nmi:
> > addq $8, (%rsp) /* Fix up RSP */
> > pushfq /* RFLAGS */
> > pushq $__KERNEL_CS /* CS */
> > - pushq $1f /* RIP */
> > + pushq $0 /* Future return address */
>
> We're building an IRET frame, the IRET frame does not have a 'future
> return address' field.
I assumed that's the target RIP after iretq.
>
> > + pushq %rdx /* Save RAX */
>
> fail..
Yes, sorry. I was asked to switch from RAX to RDX and missed the comment.
>
> > + leaq 1f(%rip), %rdx /* RIP */
>
> nonsensical comment
That was the same comment from the push $1f that I changed.
>
> > + movq %rdx, 8(%rsp) /* Put 1f on return address */
> > + popq %rdx /* Restore RAX */
>
> fail..
I will change in next iteration.
>
> > iretq /* continues at repeat_nmi below */
> > UNWIND_HINT_IRET_REGS
> > 1:
> > --
> > 2.24.0.393.g34dc348eaf-goog
> >
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