RE: Early microcode signing in secure boot environment - Was: x86,microcode: Use common get_ramdisk_image()

From: Yu, Fenghua
Date: Wed Apr 10 2013 - 13:47:32 EST


> -----Original Message-----
> From: Thomas Renninger [mailto:trenn@xxxxxxx]
> Sent: Wednesday, April 10, 2013 12:41 AM
> Hello,
>
> On Wednesday, April 10, 2013 01:34:33 PM Tang Chen wrote:
> > On 04/05/2013 07:46 AM, Yinghai Lu wrote:
> > > Use common get_ramdisk_image() to get ramdisk start phys address.
> > >
> > > We need this to get correct ramdisk adress for 64bit bzImage that
> > > initrd can be loaded above 4G by kexec-tools.disk_size;
>
> don't know whether this question came up when this feature got
> submitted (if yes a pointer would be appreciated).
>
> Is there a concept how signed microcode can get verified when applied
> early,
> like it is done via firmware loader?
>
> If not, early microcode loading is not really usable in secure boot
> environment, right?

The microcode is cryptographically authenticated by the CPU itself, so there is no security issue related to early microcode loading.

Thanks.

-Fenghua

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