We have a new userspace live-patch creation tool, LLpatch, paralleling kpatch-build, but without requiring its arch-specific code for ELF analysis and manipulation. We considered extending kpatch-build to a new target architecture (arm64), cluttering its code with details of another architecture’s quirky instruction sequences & relocation modes, and suspected there might be a better way. The LLVM suite already knows these details, and offers llvm-diff, for comparing generated code at the LLVM-IR (internal representation) level, which has access to much more of the code’s _intent_ than kpatch’s create-diff-object is able to infer from ELF-level differences. Building on this, LLpatch adds namespace analysis, further dead/duplicate code elimination, and creation of patch modules compatible with kernel’s livepatch API. Arm64 is supported - testing against a livepatch-capable v5.12 arm64 kernel, using the preliminary reliable-stacktrace work from madvenka@xxxxxxxxxxxxxxxxxxx, LLpatch modules for x86 and arm64 behave identically to the x86 kpatch-build modules, without requiring any additional arch-specific code. On x86, where both tools are available, LLpatch produces smaller patch modules than kpatch, and already correctly handles most of the kpatch test cases, without any arch-specific code. This suggests it can work with any clang-supported kernel architecture. Work is ongoing, collaboration is welcome. See https://github.com/google/LLpatch for further details on the technology and its benefits. Yonghyun Hwang (yonghyun@xxxxxxxxxx freeaion@xxxxxxxxx) Bill Wendling (morbo@xxxxxxxxxx isanbard@xxxxxxxxx) Pete Swain (swine@xxxxxxxxxx swine@xxxxxxxxx)
