linux-kernel - Re: [PATCH 1/2] x86/xen/pvh: Set up percpu for stack canary in 32-bit kernel entry

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Message-ID: <20231024023328.GA29837@k08j02272.eu95sqa>
Date:   Tue, 24 Oct 2023 10:33:28 +0800
From:   "Hou Wenlong" <houwenlong.hwl@...group.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     linux-kernel@...r.kernel.org, Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "moderated list:XEN HYPERVISOR X86" <xen-devel@...ts.xenproject.org>,
        "open list:X86 PLATFORM DRIVERS - ARCH" 
        <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86/xen/pvh: Set up percpu for stack canary in
 32-bit kernel entry

On Mon, Oct 23, 2023 at 08:02:02PM +0800, Andy Shevchenko wrote:
> On Mon, Oct 23, 2023 at 12:10 PM Hou Wenlong
> <houwenlong.hwl@...group.com> wrote:
> >
> > In a 32-bit SMP kernel, the stack canary is a percpu variable accessed
> > as %fs:__stack_chk_guard. However, the ABI for PVH entry does not
> > specify the %fs register state. It currently works because the initial
> > %fs register is 0x10 for QEMU, which is the same as $PVH_DS_SEL.
> 
> > %However, for added safety, the percpu should be set up explicitly
> > %before calling xen_prepare_pvh(), which accesses the stack canary.
> 
> Stray leading % in two lines above.
>
Oh, sorry for that. It was added by mistake by my editor, and I didn't
carefully review it before sending.
 
Thanks!

> -- 
> With Best Regards,
> Andy Shevchenko