From: Andi Kleen <ak@suse.de>
To: Zachary Amsden <zach@vmware.com>
Subject: Re: [PATCH 19/21] i386 Kprobes semaphore fix
Date: Wed, 9 Nov 2005 14:38:09 +0100
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Cc: virtualization@lists.osdl.org, Andrew Morton <akpm@osdl.org>,
       Chris Wright <chrisw@osdl.org>, Linus Torvalds <torvalds@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       "H. Peter Anvin" <hpa@zytor.com>,
       Zwane Mwaikambo <zwane@arm.linux.org.uk>,
       Martin Bligh <mbligh@mbligh.org>,
       Pratap Subrahmanyam <pratap@vmware.com>,
       Christopher Li <chrisl@vmware.com>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Ingo Molnar <mingo@elte.hu>
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On Tuesday 08 November 2005 14:36, Zachary Amsden wrote:

> One can imagine clever uses for ptrace to do, say user space
> virtualization (since I'm on the topic), or other neat things.  So there
> is nothing really wrong about having the fully correct EIP conversion
> (and here we shouldn't need to worry about races causing some issues
> with strict correctness, since there can be one external control thread).

Well, the code still scaries me a bit, but ok. x86-64 left at least one case 
intentionally out.

> But were kprobes even inteneded for userspace?  There are races here
> that are difficult to close without some heavy machinery, and I would
> rather not put the machinery in place if simplifying the code is the
> right answer.

I believe user space kprobes are being worked on by some IBM India folks yes.

-Andi
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