Messages in this thread | | | Date | Tue, 31 Dec 2013 10:42:47 -0800 | From | "H. Peter Anvin" <> | Subject | Re: Sanitize CPU-state when switching from virtual-8086 mode to other task |
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On 12/30/2013 07:52 AM, halfdog wrote: >> >> Still in VirtualBox? > > Yes, again: after comparing the results from initrd on real hardware > with Vbox, I'm getting to understand the timing problem involved and why > timing in VBox is different: The test program usually OOPSes when > touching FPU multiple times, otherwise, when terminated before second > FPU-interacation, it OOPSes on next invocation, stumbling over invalid > CPU state from prior invocation. With improved code, I can rather > reliably bring CPU into that state, so that next process invoked and > touching FPU/MMX-state is OOPSed. Currently searching SUID-binaries and > running UID=0 daemons, that might show interesting reaction on that > event, but only on DOS level yet, e.g. after running V2 test program > once and then connecting via SSH, this currently kills the ssh daemon > nicely. > > It seems that machine lockup occurs when e.g. switch to idle task > happens at exactly the right moment, which I currently cannot trigger on > real hardware, but still working on that. >
I'm still wondering if this is a VirtualBox-specific problem or if it is something that *could* occur on hardware, or in other virtualization environments (KVM, Xen HVM, Hy-perV, VMware etc.)
-hpa
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