Research For The Dynamic Behaviors Of Linux Kernel About Safety

For the past few years, especially after the "WenZhou High-Speed Rail Accident", The system safety requirements continue to improve and Safety awareness and demands also reached a new height.These are realized by safety critical system, which reduces the risk of system to an acceptable level. As one of the most popular operating systems, Linux has the potential as a platform for systems critical to safety, and has the broad application prospect.How to cover some potential faults of the kernel which evades the test when use Linux as a platform for safety critical system? How can the developers verify that the system can be upgraded to a new kernel version quickly, or how to point out the places where there are the safety impact when upgrade the kernel version in the safety critical systems? What Safety Integrity Level does the Linux kernel can reach for safety? These questions need deep understanding of the Linux kernel, especially the dynamic behaviors.For this reason, this paper designs and implements a project, SIL4Linux, which can auto traces and records the dynamic behaviors of Linux kernel in a restrictive environment (POSIX). The traced behaviors including system calls, kernel functions execution paths, execution time, the execution times of code block, coverage rate of the kernel functions, and so on. The data from SIL4Linux provides the evidences about diversity of kernel-the diversity of execution path and the randomness of execution time. Based on these evidences, we argue that there is inherent diversity of the Linux kernel. This paper proposes to utilize the inherent diversity to cover some types of faults which could only occur when the system is in a specific state, and covers the random faults and some systematic faults to some extent. What is more, in the restrictive context (POSIX), SIL4Linux can be used to verify that the system can be upgraded to a new kernel version, only when the behaviors recorded by SIL4Linux’s method with new kernel are similar to those with the old kernel version.At last, SIL4Linux is a project for finding out some available methods to ensure the Linux Kernel can achieve SIL4under some restrictive conditions. The data from it might be useful for some semiformal methods, such as FTA. The data used in this paper are published and maintained here: http://sil4Linux.dslab.lzu.edu.cn...