linux-kernel - Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen

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Message-ID: <564B81DE.90909@oracle.com>
Date:	Tue, 17 Nov 2015 14:37:02 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Andrew Cooper <andrew.cooper3@...rix.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	xen-devel <xen-devel@...ts.xen.org>,
	Borislav Petkov <bp@...en8.de>,
	David Vrabel <david.vrabel@...rix.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [Xen-devel] [PATCH] xen/x86: Adjust stack pointer in xen_sysexit

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.


-boris
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