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From: Christoph Hellwig <hch@infradead.org>
To: Jeremie Le Hen <jeremie.le-hen@epita.fr>
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	from jeremie.le-hen@epita.fr on Mon, Sep 13, 2004 at 07:13:29PM +0200
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Subject: Re: FreeBSD on Xserve?
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On Mon, Sep 13, 2004 at 07:13:29PM +0200, Jeremie Le Hen wrote:
> I would add that the UML patch applied to the hosted kernel source deeply
> modifies the ptrace(2) infrastructure.  All UML processes are in fact
> processes on the host kernel, but the UML kernel ptrace's so that it reroutes
> all invoked syscalls to itself and mmap's processes address space to its
> own one.

That's not ture.  For the ptrace method you describe unmodified host
kernels work.  There's an alternate implementation using multiple address
spaces per process that needs a heavily patched kernel.  (the SKAS patch
you mention below)