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Date: Wed, 10 Apr 2013 11:52:12 +0200
From: Ingo Molnar <mingo@kernel.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>,
        "kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>,
        Ingo Molnar <mingo@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
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        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
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        Marcelo Tosatti <mtosatti@redhat.com>, Alex Shi <alex.shi@intel.com>,
        Borislav Petkov <borislav.petkov@amd.com>,
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        Eric Northup <digitaleric@google.com>
Subject: Re: [kernel-hardening] Re: [PATCH] x86: make IDT read-only
Message-ID: <20130410095212.GE24443@gmail.com>
References: <20130408224328.GA17641@www.outflux.net>
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* H. Peter Anvin <hpa@zytor.com> wrote:

> On 04/09/2013 11:22 AM, Kees Cook wrote:
> > 
> > Can we create a RO fixed per-cpu area?
> > 
> 
> "Fixed" and "percpu" are mutually exclusive...

There's a fixmap area that holds kmap_atomic() percpu mappings:

        FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
        FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,

In a similar fashion we could use a per CPU high-mapped read-only alias as well 
(assuming it fits, memory is pretty tight there).

Thanks,

	Ingo
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