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Date: Tue, 17 Jul 2018 09:07:25 +0200
From: Joerg Roedel <jroedel@suse.de>
Subject: Re: [PATCH 07/39] x86/entry/32: Enter the kernel via trampoline stack
Message-ID: <20180717070725.paxlewuu4z4qd3cu@suse.de>
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To: Andy Lutomirski <luto@amacapital.net>
Cc: Joerg Roedel <joro@8bytes.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>, X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>, Linus Torvalds <torvalds@linux-foundation.org>, Andy Lutomirski <luto@kernel.org>, Dave Hansen <dave.hansen@intel.com>, Josh Poimboeuf <jpoimboe@redhat.com>, Juergen Gross <jgross@suse.com>, Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Brian Gerst <brgerst@gmail.com>, David Laight <David.Laight@aculab.com>, Denys Vlasenko <dvlasenk@redhat.com>, Eduardo Valentin <eduval@amazon.com>, Greg KH <gregkh@linuxfoundation.org>, Will Deacon <will.deacon@arm.com>, "Liguori, Anthony" <aliguori@amazon.com>, Daniel Gruss <daniel.gruss@iaik.tugraz.at>, Hugh Dickins <hughd@google.com>, Kees Cook <keescook@google.com>, Andrea Arcangeli <aarcange@redhat.com>, Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>, "David H . Gutteridge" <dhgutteridge@sympatico.ca>

On Fri, Jul 13, 2018 at 10:21:39AM -0700, Andy Lutomirski wrote:
> On Fri, Jul 13, 2018 at 3:56 AM, Joerg Roedel <joro@8bytes.org> wrote:
> > Right, I implement a more restrictive check.
> 
> But the check needs to be correct or we'll mess up, right?  I think
> the code will be much more robust and easier to review if you check
> "on the entry stack" instead of ">= the entry stack".  (Or <= -- I can
> never remember how this works in AT&T syntax.)

Yeah, I re-used the check implemented on the NMI entry path, it checks
exactly for the entry-stack range.


Regards,

	Joerg