'Improving the reliability of commodity operating systems'
ABSTRACT:

Despite a decade of research in extensible OS technology, operating system extensions such as device drivers remain a significant cause of system failures. In Windows XP, for example, drivers account for 85\% of recently reported failures.

This work describes Nooks, a new OS subsystem that permits existing kernel extensions to execute safely in commercial operating systems. With Nooks, drivers and other OS extensions can fail and recover {em without} disturbing other system components.

Furthermore, extension writers can benefit from improved reliability {em without modifying existing code} or programming practices.

Instead, Nooks' services isolate an extension within a lightweight protection domain inside the kernel address space. Extensions thus run unchanged in kernel mode but are prevented from corrupting the kernel by both software and hardware mechanisms. Nooks also tracks an extension's use of kernel resources to hasten automatic clean-up during recovery.

To prove the viability of our approach, we implemented Nooks in the Linux operating system and used it to fault-isolate several classes of Linux extensions, including device drivers, file systems, and Internet services. Our results show that Nooks offers a substantial increase in the reliability of operating systems that use extensions, catching and quickly recovering from many faults that would otherwise crash the system. Performance impact ranges from very small to significant, depending on the type of extension.

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