[H-GEN] User mode Linux

[Robert Brockway]

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On Fri, 24 Jan 2003, Trent WADDINGTON wrote:

[On UML]

> Always wondered, does it run binaries unmodified?  If so, how does it

Yep, definately.

> redirect the system calls to the kernel process?  I guess it could use a

Traps them somehow and feeds them out (boy thats a non-technical answer :)

> kernel module or something but how does it distinquish the system calls
> from normal processes from the system calls of the UML processes.  Hmm..

The UML kernel can recognise the difference between another process
running on the real box and its virtual processes.  From memory, processes
running in the UML box get seperate process ids, etc.

> which leads me to ask the question: do processes under the UML run as
> seperate processes on the host machine or are they loaded into the
> userspace of the UML kernel process?

As far as I can tell they are loaded into the userspace of the UML kernel
process.  No modifications are made to the host system kernel so I can't
see any trickery going on at that level - it must be a clean approach
which holds the virual processes fully within the address space allocated
to the UML kernel process.

Cheers,
	-Rob

-- Robert Brockway B.Sc. email: robert at timetraveller.org  ICQ: 104781119
   Linux counter project ID #16440 (http://counter.li.org)
   "The earth is but one country and mankind its citizens" -Baha'u'llah


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