Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200428151725.31091-1-joro@8bytes.org> <20200428151725.31091-36-joro@8bytes.org>
 <CAMzpN2gfiBAeCV_1+9ogh42bMMuDW=qdwd7dYp49-=zY3kzBaA@mail.gmail.com> <20200603151857.GC23071@8bytes.org>
In-Reply-To: <20200603151857.GC23071@8bytes.org>
From:   Brian Gerst <brgerst@gmail.com>
Date:   Wed, 3 Jun 2020 13:14:11 -0400
Message-ID: <CAMzpN2j4t7UwOFwSR8gVo-FpAQ_RS5pE1c8JZns3xyUXP3yANQ@mail.gmail.com>
Subject: Re: [PATCH v3 35/75] x86/head/64: Build k/head64.c with -fno-stack-protector
To:     Joerg Roedel <joro@8bytes.org>
Cc:     "the arch/x86 maintainers" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Jiri Slaby <jslaby@suse.cz>,
        Dan Williams <dan.j.williams@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Juergen Gross <jgross@suse.com>,
        Kees Cook <keescook@chromium.org>,
        David Rientjes <rientjes@google.com>,
        Cfir Cohen <cfir@google.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Mike Stunes <mstunes@vmware.com>,
        Joerg Roedel <jroedel@suse.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        kvm list <kvm@vger.kernel.org>,
        Linux Virtualization <virtualization@lists.linux-foundation.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jun 3, 2020 at 11:18 AM Joerg Roedel <joro@8bytes.org> wrote:
>
> On Tue, May 19, 2020 at 09:58:18AM -0400, Brian Gerst wrote:
> > On Tue, Apr 28, 2020 at 11:28 AM Joerg Roedel <joro@8bytes.org> wrote:
>
> > The proper fix would be to initialize MSR_GS_BASE earlier.
>
> That'll mean to initialize it two times during boot, as the first C
> function with stack-protection is called before the kernel switches to
> its high addresses (early_idt_setup call-path). But okay, I can do that.

Good point.  Since this is boot code which isn't subject to stack
smashing attacks, disabling stack protector is probably the simpler
option.

--
Brian Gerst