Open Source Summit Europe 2024

Once in a while, new processor architectures show up -- aarch64, RISC-V, Loongarch, Elbrus -- and more to come. Getting Linux distributions - especially those using binary packages - up on them has traditionally been difficult, but it doesn't have to be. For the new OpenMandriva RISC-V port, we have automated the process in a way that will also work for other new architectures (or even other core changes like spins using a different libc). This talk introduces the pitfalls and the Open Source tools we've used to overcome them.

There is a lot of work around how to achieve good real-time on Linux, but not as much on how to simulate faults such as jitter in the system, deadline misses or other faults. Without this it is difficult to test how your application or entire system copes with these problems.

As part of work with a number of clients, especially in the safety sphere, questions have come up on how to test processes which rely on real-time scheduling. If we have a way of injecting faults we can reliably test error handling and other mitigations. Mitigations such as throttling, restarting or some measured shutdown of services.

We will go through some methods we evaluated for fault injection via both user and kernel space. How existing kernel features can be used and what needs to be done in the way of either configuring or extending kernel features. There will be discussion about how each method works and the comparative merits where overlaps exist.

We hope that this can help to promote thinking and improvements on how the scheduler and particularly real-time scheduling is tested under Linux.

DAMON is a Linux kernel subsystem for efficient data access monitoring that has been integrated into the mainline since v5.15. The subsystem has been further developed into an access-aware system operating engine. In addition, userspace tools for DAMON have been developed to provide a human-friendly interface and additional userspace capabilities. Several major Linux distributions now offer DAMON-enabled kernels and user-space tool packages. Of course, not all use cases for DAMON are known, but the DAMON maintainer has been privileged to hear about some interesting and creative uses of DAMON from several people who primarily use DAMON for memory efficiency in their prototypes, researches, and products. In this talk, we'll give a brief introduction to the practical benefits and unique internal mechanisms that DAMON provides, with live demos of key features. We'll then detail real-world examples of DAMON use in prototypes, researches, and products. Finally, we'll show you how you can join the project community for participating to the development or get help. The rest of the talk will be followed by a Q&A.

The first flexible-array transformation we implemented in the kernel, as part of the Kernel Self-Protection Project, took place back in March 2019. At the time, our work on preventing integer overflows during memory allocations led us to discover an 8-year-old bug. Addressing this bug not only resolved a longstanding issue but also initiated the work of flexible-array transformations across the whole kernel tree. This marked the beginning of a challenging yet rewarding journey to add bounds-checking on trailing arrays in the Linux kernel. Five years have passed since then, and we've come a long way. We have now new Clang and GCC hardening compiler options and attributes, that significantly improve the security of the Linux kernel, particularly in the spatial-safety area. We have new hardening helpers that make traditional methods less prone to error. In general, we have new and safer ways of doing things, which usually require a learning curve, even for seasoned kernel developers. In this talk, we will walk through the most recent challenges and history of our quest to improve spatial safety in the Linux kernel, and with that, get rid of out-of-bounds bugs once and for all.