linux-kernel - Re: [PATCH v5 32/32] x86/mm: Add support to make use of Secure Memory Encryption

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Date:   Wed, 31 May 2017 11:15:53 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>, linux-arch@...r.kernel.org,
        linux-efi@...r.kernel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org, Rik van Riel <riel@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Toshimitsu Kani <toshi.kani@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Joerg Roedel <joro@...tes.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Larry Woodman <lwoodman@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dave Young <dyoung@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 32/32] x86/mm: Add support to make use of Secure
 Memory Encryption

On Tue, May 30, 2017 at 10:48:27AM -0500, Tom Lendacky wrote:
> I'll look at doing that instead of removing the support for the whole
> file.

Right, so I don't think the stack protector is even ready that early -
we do set it up later:

        /* Set up %gs.
         *
         * The base of %gs always points to the bottom of the irqstack
         * union.  If the stack protector canary is enabled, it is
         * located at %gs:40.  Note that, on SMP, the boot cpu uses
         * init data section till per cpu areas are set up.
         */
        movl    $MSR_GS_BASE,%ecx
        movl    initial_gs(%rip),%eax
        movl    initial_gs+4(%rip),%edx
        wrmsr

so I think marking the function "no-stack-protector" is the only option
right now. We can always look at fixing that later.

-- 
Regards/Gruss,
    Boris.

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