After a three-year hiatus, the Live Patching Microconference is back for 2023.

Accomplishments post 2019 Microconference:

• API enhancements: Livepatch pre/post (un)patch callback system state change tracking was added in v5.5. The new API enhances the safety of cumulative livepatch upgrades [v5.5]
• KLP-relocations: To facilitate module_disable_ro() removal, arch-specific livepatch .klp.arg sections were deprecated. Special arch section KLP-relocations (like x86 jump labels) are still supported for vmlinux cases, and are now applied at the same time as normal relocations. [v5.8]
• Documentation: Practical information on how to implement reliable stacktraces needed by the livepatching consistency model was added [v5.12]
• Architecture: Implemented Power32 support [v5.18]
• KLP-relocations: To support target module reloading, clear KLP-relocations in livepatch modules when their target module is unloaded. This satisfies a module loader sanity check when resolving relocations on the next target module load (x86_64 only) [v6.3]

Discussion Topics

The following topics have been proposed:

• Shadow variables are considered a livepatching power-feature that can require careful management, especially across livepatch up and downgrades. Is garbage collection or a refactoring of callbacks a  better approach to manage these resources?
• klp-relocations were originally introduced to resolve livepatch / kernel and module symbol scoping issues. Recent security features like CET and IBT suggest another use case and renewed interest in having an in-tree klp-relocation build support. Is a simple conversion utility sufficient, or does said tool require greater features?
• The livepatching kselftests consist of test scripts under tools/testing/selftests and associated livepatch module code in lib/. Consolidating these under the former offers better flexibility in templating the livepatch modules as well as the benefits of building them out-of-tree.  Are there any outstanding blockers to implement these changes?
• arm64 support is moving forward on several fronts: toolchain, reliable stack unwinding, user space, etc.  The Toolchains MC plans to address topics like CFG in ELF and handling of noinstr functions.  What issues remain in livepatching and the kernel at large to fully support arm64?
• Rust looks to be a hot topic at this year’s LPC.  Its impact on kernel livepatching is relatively open ended as Rust code has only recently been merged in small parts.  That said, which features, problems, patchsets should we be paying attention to as we all learn more about this newly supported kernel language?

These potential discussion topics were selected from on-going livepatching mailing list threads, but additional livepatching related topics are welcome for consideration as well. For ideas on what makes for an ideal Microconference topic, checkout this post.