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Increasing Automation in the Backporting of Linux Drivers Using Coccinelle

Luis R. Rodriguez, Suse Labs Julia Lawall, Inria/LIP6/UPMC/Sorbonne University

Software is continually evolving, to fix bugs and add new features. Industry users, however, often value stability, and thus are not always able to update their code base to the latest versions. This raises the need to selectively backport new features to older software versions. Traditionally, backporting has been done by cluttering the backported code with preprocessor directives, to replace behaviors that are unsupported in an earlier version by appropriate workarounds. This approach however involves writing a lot of error-prone backporting code, and results in implementations that are hard to read and maintain. We consider this issue in the context of the Linux kernel, for which older versions are in wide use. We present a new backporting strategy that relies on the use of a compatability library and on code that is automatically generated using the program transformation tool Coccinelle. This approach reduces the amount of code that must be manually written, and thus can help the Linux kernel backporting effort scale.