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Date: Mon, 15 Aug 2016 10:42:33 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
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        Kees Cook <keescook@chromium.org>,
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        Frederic Weisbecker <fweisbec@gmail.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Nilay Vaish <nilayvaish@gmail.com>
Subject: Re: [PATCH v3 45/51] x86: remove 64-byte gap at end of irq stack
Message-ID: <20160815154233.gquogzg24q3jtcdh@treble>
References: <cover.1471011425.git.jpoimboe@redhat.com>
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On Sun, Aug 14, 2016 at 12:52:40AM -0700, Andy Lutomirski wrote:
> On Fri, Aug 12, 2016 at 7:29 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > There has been a 64-byte gap at the end of the irq stack for at least 12
> > years.  It predates git history, and I can't find any good reason for
> > it.  Remove it.  What's the worst that could happen?
> 
> I can't think of any reason this would matter.
> 
> For that matter, do you have any idea why irq_stack_union is a union
> or why we insist on sticking it at %gs:0?  Sure, the *canary* needs to
> live at a fixed offset (because GCC is daft, sigh), but I don't see
> what that has to do with the rest of the IRQ stack.

Good question.  I have no idea...

-- 
Josh