Re: [PATCH] Allow UML kernel to run in a separate host address space

[Jeff Dike <jdike@karaya.com>]

jeremy@goop.org said:
> I suspect Valgrind could use this too at some point.  There hasn't
> been much discussion about it yet, but I think Valgrind may well move
> towards a more complete virtualization in a later round of
> development, and isolating the virtual virtual address space from the
> Valgrind's real virtual address space would be very useful.  (Jeff
> suggested the idea of merging Valgrind and UML at some level, which
> does raise some interesting possibilities.) 

Yes, valgrind already has a pseudo-scheduler, a psuedo-threads library, it
delivers signals by hand, and it wants to run its client in a separate
thread so it can get out of the business of being an LD_PRELOAD shared
library.

This is all stuff that UML has, that UML does right (/me crosses fingers),
and that is usable by Valgrind (and anything else that's interested) with 
some repackaging of UML as a library.

Replacing Valgrind's signal delivery with UML's is a no-brainer.  Replacing
its scheduler and threads library would involve it creating UML processes
by calling UML's do_fork().  Valgrind would need to provide the low-level
switch_to, I think.  There are probably other things that Valgrind would
need to provide, but I see no reason this wouldn't work.

				Jeff