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Date:   Tue, 19 May 2020 11:15:26 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Joerg Roedel <jroedel@...e.de>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v3 35/75] x86/head/64: Build k/head64.c with
 -fno-stack-protector

On Tue, Apr 28, 2020 at 05:16:45PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> The code inserted by the stack protector does not work in the early
> boot environment because it uses the GS segment, at least with memory
> encryption enabled.

Can you elaborate on why is that a problem?

The stack cookie is not generated that early yet so it should be
comparing %gs:40 to 0.

Also, it generates the checking code here only with

CONFIG_STACKPROTECTOR_STRONG=y

> Make sure the early code is compiled without this feature enabled.

If so, then this should be with CONFIG_AMD_MEM_ENCRYPT ifdeffery around
it.

-- 
Regards/Gruss,
    Boris.

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