Re: 2001-05-27 patch against 2.4.5

From: Crispin Cowan (crispinat_private)
Date: Wed May 30 2001 - 13:46:21 PDT

  • Next message: Greg KH: "Re: 2001-05-27 patch against 2.4.5"

    Valdis.Kletnieksat_private wrote:
    > On Wed, 30 May 2001 00:14:41 -0300, Bruj0 said:
    > > No no, you didnt got it, its a linux kernel in all ways from boot
    > > to halt, running in top of other. So you can test boot stuff without a
    > > serial link :) and not to mention rebooting everytime it oopses.
    > Off topic, but... ;)   This same exact logic was wny IBM programmers
    > developed CP/67, which eventually evolved into the VM operating system....
    Actually, that is very much on-topic.  Virtual machines are a classic method
    of security containment.  As Valdis says, IBM's VM system is the classic
    progenitor of self-virtualizing machines.  With a virtualized machine, you
    cna run multiple instances of the OS as processes, creating a very effective
    security confinement mechanism for un-trusted services.
    The big catch is the cost.  Some CPU architectures (the 360 mainframe of old,
    and the contemporary Alpha) can self-virtualize, i.e. all CPU features work
    in such a way that a program running in non-privileged mode cannot tell that
    it is in non-privileged mode.  Some other processors (the x86, and the
    Itanium) are not self-virtualizing:  one has to employ expensive software
    tricks to create a virtual environment.
    VMWare is such a software trick:  they trap privileged instructions, and
    emulate them in software.  This is why user-mode apps run at speed in VMWare
    environments, but system code slows down.  VMWare exists because the x86
    instruction set architecture does not allow for virtual processors.  This is
    forgivable: who knew in 1980 that people would want to run virtually emulated
    operating systems on this little chip 25 years after it was designed?
    What is tragic is that the Itanium does not support self-virtualization.  It
    is unclear whether this was negligance (Intel just didn't care enough) or if
    it was capricious (Intel doesn't *want* you to be able to run virtual
    processors; buy more chips) but according to a heresay report from a friend,
    it was at least a conscious decision.  So at least VMWare has job security
    for the future :-)
    In LSM land: I can imagine someone wanting to make a LSM module that does
    essentially what VMWare does.  Anyone from VMWare, Plex86, or User Mode Linux
    on this list care to comment?
    Crispin Cowan, Ph.D.
    Chief Scientist, WireX Communications, Inc.
    Security Hardened Linux Distribution:
    Available for purchase:
    linux-security-module mailing list

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