Re: [PATCH] Enable reset attack mitigation

From: Matthew Garrett
Date: Sat Aug 05 2017 - 17:41:32 EST

On Sat, Aug 5, 2017 at 10:34 AM, Lukas Wunner <lukas@xxxxxxxxx> wrote:
> Just an innocent question from a bystander, what's the downside of
> unconditionally requesting that memory be overwritten? Does it
> prolong reboot noticeably?

Yes, it's just to avoid stalling reboot for as long as it takes to clear RAM.

> I've also wondered why you've chosen to put this in a separate file
> rather than the existing secureboot.c, my naive understanding is that
> TPM and SecureBoot is related but I'm not an expert on this. It would
> allow you to reuse the existing get_efi_var() macro.

It's not related to Secure Boot (systems can have TPMs but not Secure
Boot, and vice versa), the spec is managed by a different body (TCG
rather than UEFI), and there'll be more TPM-related code for the boot
stub in future.