> What effect would this same hack have on the intended target if the x86 > system being targeted was running as a guest under z/VM? Wouldn't the ill > effects be reduced by the wall between virtual guests inherent with z/VM?
It would be unlikely to be effective, IMHO, because it would need to be two level; at the Intel emulation layer and at the z/VM layer, and in a properly secured z/VM system with virtual machines running as class G machines, it'd be really, really hard to compromise CP without doing something very invasive via another vector (eg, compromising a privileged id with access to real storage). There's also an awful lot of hardware isolation that isn't present in the Intel space that you'd have to bypass to get into somebody else's address space. If you were smart about using the multiple address space capability of the Z processor (as CP does), then you'd also have hardware protection working for you as well, and that would take some doing to get around. Not impossible, but darn hard. -- db
