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Date: Fri, 5 Aug 2011 23:21:53 +0200
From: Andi Kleen <andi@firstfloor.org>
To: Andrew Lutomirski <luto@mit.edu>
Cc: Andi Kleen <andi@firstfloor.org>, "H. Peter Anvin" <hpa@zytor.com>,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        torvalds@linux-foundation.org, lueckintel@yahoo.com,
        kimwooyoung@gmail.com
Subject: Re: New vsyscall emulation breaks JITs
Message-ID: <20110805212153.GL5782@one.firstfloor.org>
References: <20110805200945.GA14014@tassilo.jf.intel.com> <4E3C5154.2050307@zytor.com> <CAObL_7E3yOHtx9N3qd2UXVn+h6tACoNjekRhiMcHrzb=Mu4q8A@mail.gmail.com> <4E3C571C.1070903@zytor.com> <20110805205222.GK5782@one.firstfloor.org> <CAObL_7G2TqBVXvfuh2GPNteYBNoc8_s398KS+jPOPQYAhPHz0Q@mail.gmail.com>
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On Fri, Aug 05, 2011 at 05:00:44PM -0400, Andrew Lutomirski wrote:
> > If anything runtime, but really for me it looks like the vsyscall
> > changes should be only in one of those limited compability paranoia
> > patchkits.
> 
> Switching it in runtime would be a giant mess because user code might

You can always switch at boot time.

But really serious binary incompatibility like this should not be default
(not even talking about the slow down for existing binaries using time())

-Andi