>>> On 15.11.13 at 21:07, David Vrabel <david.vrabel at citrix.com> wrote: > On 15/11/13 15:56, Daniel Kiper wrote: >> Clear unused registers before jumping into an image. This way >> loaded image could not assume that any register has an specific >> info about earlier running Xen hypervisor. However, it also >> does not mean that the image may expect that a given register >> is zeroed. The image MUST assume that every register has a random >> value or in other words it is uninitialized or has undefined state. > > I think this, where the specification (registers undefined) differs from > the implementation (registers zeroed), is the worst option. > > I also think it is more likely for an image to inadvertently rely on a > zero value that whatever junk Xen has left behind. Preventing users to rely on anything would likely make it desirable to put some random value into all unused registers. Jan
