Tool fixes for new kernels #2136
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Kernel 5.16 contains commit:
torvalds/linux@be6bfe3
which renamed some of the functions that the bio* tools attach to.
tcpdrop.bt attaches to kprobe:tcp_drop which is likely inlined on newer kernels and cannot be replaced by anything else. The script will not work on such kernels.
Many of the tools rely on kprobes and internal kernel structs which are not stable. This means that tools may break with newer kernel versions and bpftrace syntax does not always allow to support all kernels within a single script. This introduces a new directory tools/old/ which will contain versions of tools for older kernels. Since the container images used in CI may require some of the old tool versions, this also introduces a new env variable TOOLS_TEST_OLDVERSION which makes tools-parsing-test.sh use old versions of chosen tools.
Since Linux 5.12, accessing gendisk from struct bio requires an extra field access. tools/mdflush.bt now contains the new version while the old version (for Linux <= 5.12) is moved to tools/old.
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Provides fixes to several tools that got broken with newer kernels. Resolves #2128.
List of changes:
tools/olddirectory which contains versions of scripts for older kernels that cannot be easily maintained as a single script.mdflush.btis split into 2 versions. Resolves mdflush.bt not working on newer kernels #1896.tcpdrop.btthat it can stop working on newer kernels (not replacable). Resolves tcpdrop.bt not working on newer kernels #1895.bio*.bttools as they were renamed in kernel. This is an example of a single script covering multiple kernel versions (it'll print always print a warning about a missing probe, though). Together with tools: Make tools rely on BTF instead of header files. #1823 resolves all bio*.bt tools stop working from kernel 5.16 #2127.Checklist
man/adoc/bpftrace.adocand if needed indocs/reference_guide.mdCHANGELOG.md