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Re: [Xen-devel] [PATCH] x86: make IDT read-only

On Mon, 8 Apr 2013, Kees Cook wrote:

> This makes the IDT unconditionally read-only. This primarily removes
> the IDT from being a target for arbitrary memory write attacks. It has
> an added benefit of also not leaking (via the "sidt" instruction) the
> kernel base offset, if it has been relocated.
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -215,7 +201,6 @@ static void __cpuinit intel_workarounds(struct 
> cpuinfo_x86 *c)
>               c->f00f_bug = 1;
>               if (!f00f_workaround_enabled) {
> -                     trap_init_f00f_bug();
>                       printk(KERN_NOTICE "Intel Pentium with F0 0F bug - 
> workaround enabled.\n");
>                       f00f_workaround_enabled = 1;
>               }

 FWIW the change looks reasonable to me, however given that that it makes 
the arrangement unconditional and there is no longer a workaround to 
enable I think it would make sense to remove the conditional block quoted 
above altogether, along with the f00f_workaround_enabled variable itself 
(alternatively "Intel Pentium with F0 0F bug" alone could be printed 
instead and the name of the variable adjusted to make sense with the new 
meaning -- up to you to decide).


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