Probe instruction set #26
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Kernel supports few instruction sets [1], and the default one (which is apparently being used at the moment in falco) is going to be the `generic` or `v1`, which has certain limitations and requires workarounds. It's possible to instruct `llc` to search the latest supported instruction set via `-mcpu` parameter, which generally speaking should result in more compact and potentially more performant generated instructions for the same code. For the support table see great blog post [2] about the topic. The gist for the support is: v2: Linux v4.14 [3], LLVM v6.0 [4] v3: Linux v5.1 [5], LLVM [6] [1]: https://www.kernel.org/doc/html/latest/bpf/bpf_devel_QA.html#q-new-bpf-instruction-for-kernel-and-llvm [2]: https://pchaigno.github.io/bpf/2021/10/20/ebpf-instruction-sets.html [3]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=92b31a9af73b3a3fc801899335d6c47966351830 [4]: https://reviews.llvm.org/rL311522 [5]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=092ed0968bb648cd18e8a0430cd0a8a71727315c [6]: https://reviews.llvm.org/rL353384
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This looks really cool. Now that we've got the custom probe, I think these changes should be in https://github.com/stackrox/collector/blob/8ba5dc88a2dd7d948e7308103b336a4369a2de31/kernel-modules/probe/Makefile instead (or we can mirror them here as well) |
Here [1]. I guess it would have to be overridden based on the version we build for though, still need to look at this. |
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Kernel supports few instruction sets [1], and the default one (which is
apparently being used at the moment in falco) is going to be the
genericorv1, which has certain limitations and requiresworkarounds. It's possible to instruct
llcto search the latestsupported instruction set via
-mcpuparameter, which generallyspeaking should result in more compact and potentially more performant
generated instructions for the same code. For the support table see
great blog post [2] about the topic. The gist for the support is:
v2: Linux v4.14 [3], LLVM v6.0 [4]
v3: Linux v5.1 [5], LLVM [6]