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Date: Wed, 19 Jul 2017 18:30:24 -0500
From: Josh Poimboeuf <jpoimboe@...hat.com>
To: Kees Cook <keescook@...omium.org>
Cc: Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>,
Christoph Hellwig <hch@...radead.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jann Horn <jannh@...gle.com>, Eric Biggers <ebiggers3@...il.com>,
Elena Reshetova <elena.reshetova@...el.com>,
Hans Liljestrand <ishkamiel@...il.com>,
Greg KH <gregkh@...uxfoundation.org>,
Alexey Dobriyan <adobriyan@...il.com>,
"Serge E. Hallyn" <serge@...lyn.com>, arozansk@...hat.com,
Davidlohr Bueso <dave@...olabs.net>,
Manfred Spraul <manfred@...orfullife.com>,
"axboe@...nel.dk" <axboe@...nel.dk>,
James Bottomley <James.Bottomley@...senpartnership.com>,
"x86@...nel.org" <x86@...nel.org>, Arnd Bergmann <arnd@...db.de>,
"David S. Miller" <davem@...emloft.net>,
Rik van Riel <riel@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v6 2/2] x86/refcount: Implement fast refcount overflow
protection
On Wed, Jul 19, 2017 at 04:12:37PM -0700, Kees Cook wrote:
> On Wed, Jul 19, 2017 at 12:37 PM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> > +#define ASM_UNREACHABLE \
> > + "999: .pushsection .discard.unreachable\n\t" \
> > + ".long 999b - .\n\t" \
> > + ".popsection\n\t"
>
> Will this end up running into the same bug fixed with
> 3d1e236022cc1426b0834565995ddee2ca231cee and the __LINE__ macro? I
> could tell under which conditions gcc would do this kind of merging...
I hope not, but objtool should complain about it if it does.
We could involve the __LINE__ macro, or some other way to make the
labels unique, but that might complicate the code a bit, so we can delay
doing that unless necessary.
--
Josh
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