From mboxrd@z Thu Jan  1 00:00:00 1970
From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
Date: Tue, 17 Nov 2015 14:38:28 -0500
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To: Andy Lutomirski <luto@amacapital.net>, Andrew Cooper <andrew.cooper3@citrix.com>
Cc: David Vrabel <david.vrabel@citrix.com>, Borislav Petkov <bp@alien8.de>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "H. Peter Anvin" <hpa@zytor.com>, xen-devel <xen-devel@lists.xen.org>
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On 11/17/2015 02:37 PM, Boris Ostrovsky wrote:
> On 11/17/2015 02:16 PM, Andy Lutomirski wrote:
>>>> Looks good to me.  Does Xen have any sysexit/sysret32 equivalent to
>>>> return to 32-bit user mode?  If so, it could be worth trying to wire
>>>> it up by patching the jz instead of the test instruction.
>
> We can actually make patching a little bit more efficient by replacing 
> the test instruction with 'xor %eax,%eax'. That way we won't need any 
> 'nop's.

Nevermind that, we are looking at flags, not register.

-boris