Hardware Bugs? Don't Fence Me In

Bugs in the hardware? Never happens, right? While in fact, hardware bugs probably happen more than you'd like to think. Certainly more than CPU designers would like to think. In the meantime, processors are growing more and more complex--the Intel Core 2 Duo has 291 million transistors--which means the chance of hardware bugs becomes greater and greater.

Of course, knowing that bugs can creep into hardware, CPU vendors do what they can to identify and simulate all possible configurations that might trigger bugs. Still, it is impossible to simulate every scenario, which is where the bugs come in. To keep bugs out, researchers at the University of Michigan are proposing a "virtual fence" that prevents a processor from operating in untested configurations. The technique keeps tabs of all tested configurations, and loads that information onto a "semantic guardian"--a monitor added to each processor that assumes all untested configurations are potential bugs. The semantic guardian lets the processor work only within its virtual fence by switching the processor into a slower safe mode when the processor encounters an untested configuration.

"If you consider all the possible configurations of the processor, only a tiny fraction of them is verified. But that tiny portion accounts for the configurations that occur 99.9 percent of the time," says Valeria Bertacco, who, along with Ilya Wagner, authored Engineering Trust with Semantic Guardians.

And, according to independent security researcher Kris Kaspersky, semantic guardians could also be a safeguard against exploiting hardware design bugs to gain control of other computers. "Semantic guardians would stop these security attackers dead in their tracks, since the processor would no longer be able to execute the buggy configurations that they were planning to exploit," explains Ilya Wagner.

-- Jonathan Erickson
jerickson@ddj.com

Posted by Jon Erickson at 12:15 PM  Permalink