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Subject: Re: [PATCH v5] x86: make sure IDT is page aligned
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Tue, 16 Jul 2013 13:43:26 -0700
To: Steven Rostedt <rostedt@goodmis.org>, Kees Cook <keescook@chromium.org>
CC: Yinghai Lu <yinghai@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Seiji Aguchi <seiji.aguchi@hds.com>, Fenghua Yu <fenghua.yu@intel.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        PaX Team <pageexec@gmail.com>
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The F00F big just means the IDT must be readonly.

Steven Rostedt <rostedt@goodmis.org> wrote:

>On Tue, 2013-07-16 at 13:28 -0700, Kees Cook wrote:
>> On Tue, Jul 16, 2013 at 1:21 PM, Yinghai Lu <yinghai@kernel.org>
>wrote:
>> > On Tue, Jul 16, 2013 at 11:34 AM, Kees Cook <keescook@chromium.org>
>wrote:
>> >> Since the IDT is referenced from a fixmap, make sure it is page
>aligned.
>> >> Merge with 32-bit one, since it was already aligned to deal with
>F00F
>> >> bug. Since bss is cleared before IDT setup, it can live there.
>This also
>> >> moves the other *_idt_table variables into common locations.
>> >>
>
>> It seemed more correct to me to define all the IDTs the same, but
>> there was no technical reason for that, just one of regularity. I
>only
>> care about keeping the real IDT page aligned. :) I'm fine to do
>> whatever is deemed "correct". :)
>
>I'm actually unfamiliar with the F00F bug (heard of it, but have no
>idea
>what it is). What happens if the F00F bug exists and we switch to an
>IDT
>that's not paged aligned? Is that an issue?
>
>-- Steve

-- 
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