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: <CAHp75VeXiOprRDNakewo2iSe==EeLUxfxuPYS3R+ZsY2KDmQBQ@mail.gmail.com>
Date:   Mon, 23 Oct 2023 15:02:02 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Hou Wenlong <houwenlong.hwl@...group.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 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.

-- 
With Best Regards,
Andy Shevchenko