Linux Kernel ABI Tracker

Latest revision as of 11:58, 13 November 2013

The Linux kernel is constantly evolving: improved hardware support, optimized various kernel subsystems, etc. As a result, the size of the kernel and the number of its ABI/API interfaces is growing from version to version. Thus, in the course of development, some of the old interfaces are subject to change, which may break the operation of other software components using kernel interfaces: kernel modules, drivers, dynamic testing/trace tools, etc.

For regular automatic analysis of changes in Linux kernel interfaces we have developed the Kernel ABI Tracker. This tool is looking for new versions of the kernel at kernel.org, building them and analyzing API changes using a set of basic tools. For each version of the kernel the tracker creates a so-called ABI dump from its debug-information using the ABI Dumper tool. ABI dump contains information about all public interfaces exported by the kernel: their properties, parameter types and the structure of data types. And then a pair of ABI dumps for two consequent kernel versions are passed to the ABI Compliance Checker tool in order to analyze changes and create the report. This report describes changes in the kernel API interfaces (added and removed symbols, changes in data types, etc.) and divides them by the severity level for applications. In addition to its direct purpose, ABI dumps may also be used for other kinds of analysis by third-party developers and are therefore available for download.

The tracker provides reports on the results of testing defconfig-configuration of all the latest longterm, stable and mainline kernel versions. The home page shows a plot of the number of interfaces depending on the version of the kernel. The results so far obtained for the two architectures: x86 and x86_64. Support for arm architecture is planned in the near future. Also planned testing of other kernel configurations (allyesconfig, etc.).

Basic tools ABI Dumper and ABI Compliance Checker, previously developed in the ROSA laboratory to track ABI changes in C libraries, have required significant improvements to be able to analyze changes in Linux kernel. The problem was in the huge depth of data structures and a big number of kernel interfaces, so both tools required too much cpu time and RAM to operate. As a result, the tools now are faster in the analysis of large input objects.