Re: [kernel-hardening] Re: [PATCH] x86: make IDT read-only

[Ingo Molnar]

* H. Peter Anvin <hpa@xxxxxxxxx> 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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