ITR: Reliable Technologies for Operating Systems and Operating System Services

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Despite decades of research in extensible operating systemtechnology, extensions such as device drivers remaina significant cause of system failures. In Windows XP, for example,drivers account for 85% of recently reported failures.In this project, the researchers are developing a reliability subsystemfor commodity operating systems. Their approach isto improve OS reliability by isolating the OS from driverfailures. Rather than guaranteeingcomplete fault tolerance through a new (and incompatible) OS ordriver architecture, their goal is to prevent the vast majority ofdriver-caused crashes with little or no change to existingdriver and system code. To achieve this, they isolate drivers withinlightweight protection domains inside the kernel address space.Drivers run largely unchanged in kernel mode, but are preventedfrom corrupting the kernel by both software and hardware means. The systemalso tracks a driver's use of kernel resources to hasten automaticclean-up during recovery.To prove the viability of their approach, they are implementing a systemcalled "Nooks" in the Linux operating system and are using itto fault-isolate several devicedrivers. Their initial results show that Nooks offers a substantial increasein the reliability of operating systems, catching and quicklyrecovering from 99% of the faults that would otherwise crash the system.While Nooks was designed for drivers, their techniques generalize toother kernel extensions as well. The researchers are demonstratingthis by isolating a kernel-mode file system and anin-kernel Internet service.Overall, because Nooks supports existing C-language extensions, runs on acommodity operating system and commodity hardware, and enablesautomated recovery, it represents a substantial step beyond thespecialized architectures and type-safe languages required by previousefforts directed at safe extensibility.