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Date:      Mon, 10 Dec 2012 03:12:08 -0500
From:      Zaphod Beeblebrox <zbeeble@gmail.com>
To:        Aryeh Friedman <aryeh.friedman@gmail.com>
Cc:        FreeBSD Mailing List <freebsd-hackers@freebsd.org>
Subject:   Re: using FreeBSD to create a completely new OS
Message-ID:  <CACpH0MfdRsjx-xCOPyh2zQJ2cJvAj%2BatkwTrPHnutrKZ79vqSA@mail.gmail.com>
In-Reply-To: <CAGBxaXmRdc166NwG%2B38jM5F1vEgxtiu-52-P4q8GeR5mbfH80A@mail.gmail.com>
References:  <CAGBxaX=y9yLBymKX8Psmer0sPFWCgAFy3gs%2BtgU7waQt2g6hKA@mail.gmail.com> <CACpH0Mfj77ccSOeeoaQfYtvXAWB_=gsJMKK7WoFckj%2BdJotggw@mail.gmail.com> <CAGBxaXmRdc166NwG%2B38jM5F1vEgxtiu-52-P4q8GeR5mbfH80A@mail.gmail.com>

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On Mon, Dec 10, 2012 at 2:56 AM, Aryeh Friedman
<aryeh.friedman@gmail.com> wrote:
> On Mon, Dec 10, 2012 at 2:38 AM, Zaphod Beeblebrox <zbeeble@gmail.com> wrote:

> I know (about the list not being google) and have seen the formats for
> MBR's (even wrote a few by hand) the question was how to extract it
> from the virtual HDD (see above).... namely is I have a prototype MBR
> that should be made I want to check if it was actually written to the
> virtual HDD correctly

The simplest thing I can think of is to attach said virtual disk to a
FreeBSD guest and use dd.  Sure ... I'm pretty sure the virtual disk
you're using is documented, but follow the path of least resistance.

> From my initial research there is almost nothing that depends on
> actual ASM except for a very small number of things that create the
> environment needed to run the equiv of the JVM (no garbage collection
> at this level) natively on an x86.   My guess the total amount of ASM
> needed is less then a thousand instructions (99% are macro's mostly
> for performance reasons).   The other 1% is just to get the protected
> mode and the native JVM loaded and started.

If you mean swtch.s here, I suppose you're interpreting what I said rightly.

> Note when I say JVM I actually mean a collection of VM's that model
> real HW (not some abstract HW like the sun JVM does) and if the VM
> just happens to be identical to the native HW then it skips the
> emulation part of the VM (i.e. direct execution on the actual HW).
> The first such VM I am planning is x86 (64-bit).  Namely if your
> running on a PC then it runs natively but on anything else it runs on
> a VM identical to a PC.

Note that this pretty much makes java pretty much worthless.  I say
that carefully as the seemingly "good" thing that makes the extra
effort in java "worth it" is the guarantee against the halting problem
that makes the security madness possible.  If your "vm" is i386, you
can't offer that guarantee.  The JVM is very specially crafted for
this purpose.



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