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Tuesday, 04 February 2014 10:20

SUSE develops module to patch running kernel Featured


Enterprise Linux users could soon have a free means of patching running kernels without any downtime if the efforts of the engineers at SUSE bear fruit.

Developers at the company have come up with what they call kGraft; the technology is in the prototype stage and was developed as a research project, according to a post by Vojtech Pavlik, the director of SUSE Labs and the head of kernel development at SUSE.

Pavlik wrote that while there were a couple of technologies that could be used to patch a running kernel without downtime - Ksplice and OpenVZ Checkpointing - the first would never make it upstream because its open source version was never updated.

Ksplice, which was developed by Ksplice Inc under an open source licence until July 2011 when it was bought by Oracle, is used by the company as an incentive to get companies to use Oracle Linux. Prior to being acquired, it was available for the Red Hat, CentOS, Debian, Ubuntu and Fedora Linux distributions.

Pavlik wrote that  the second solution needed some infrastructure and would not be able to apply a patch without a short interruption of service.

"kGraft builds on technologies and ideas that are already present in the kernel: ftrace and its mcount-based reserved space in function headers, the INT3/IPI-NMI patching also used in jumplabels, and RCU-like update of code that does not require stopping the kernel," Pavlik wrote.  

"A kGraft patch is a kernel module and fully relies on the in-kernel module loader to link the new code with the kernel. Thanks to all that, the design can be nicely minimalistic."

Pavlik wrote that while kGraft was, by choice, limited to replacing whole functions and constants they referenced, this would not limit the set of code patches that could be applied significantly.

"kGraft will offer tools to assist in creating the live patch modules, identifying which functions need to be replaced based on a patch, and creating the patch module source code.," he wrote.

A first kGraft release is planned for next month. The release will be under the GPLv3 licence for parts that touch GCC, and under the GPLv2 licence for Linux kernel parts.

"We aim at getting it merged fully into the upstream projects," he wrote.

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Sam Varghese

Sam Varghese has been writing for iTWire since 2006, a year after the site came into existence. For nearly a decade thereafter, he wrote mostly about free and open source software, based on his own use of this genre of software. Since May 2016, he has been writing across many areas of technology. He has been a journalist for nearly 40 years in India (Indian Express and Deccan Herald), the UAE (Khaleej Times) and Australia (Daily Commercial News (now defunct) and The Age). His personal blog is titled Irregular Expression.

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