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README.md

This directory is intended for non-Go support functionality. For example, the eBPF code and supporting Python scripts for bytecode offsets to line number translation.

Testing eBPF code on different kernel version

Via the following commands, you can run the eBPF loading tests on kernel version 4.9.198, 4.19.81 or 5.4.5 respectively.

$ ./run-tests.sh 4.9.198
$ ./run-tests.sh 4.19.81
$ ./run-tests.sh 5.4.5

The script loads the provided eBPF code into the kernel in a virtual environment so that it does not affect your local environment.

Requirements

The tests are built on top of the following dependencies. Make sure you have them installed beforehand.

  • qemu-system-x86
  • statically linked busybox

Building a Custom Kernel Image

Kernel images can be build with the script provided in ci-kernels. This directory contains also the basic configuration settings needed to enable eBPF features for the kernel image.

Test a Custom Kernel Image

By default run-tests.sh takes only the kernel version as argument. The script looks for the kernel image with the specified version in ci-kernels. As an alternative one can provide a directory to look for this kernel image via KERN_DIR.

$ KERN_DIR=my-other-kernels/ ./run-tests.sh 5.4.31

Manually Debugging a Custom Kernel Image

  1. Compile eBPF and Go code
$ make ebpf
$ cd support
$ go test -c -tags integration ./...
  1. Get virtme to run the environment
$ tmp_virtme="$(mktemp -d --suffix=-virtme)"
$ git clone -q https://git.kernel.org/pub/scm/utils/kernel/virtme/virtme.git "${tmp_virtme}"
  1. Start the virtual environment for debugging with gdb:
$ ${tmp_virtme}/virtme-run --kimg  ci-kernels/linux-5.4.31.bz \
    --memory 4096M \
    --pwd \
    --script-sh "mount -t bpf bpf /sys/fs/bpf ; ./support.test -test.v" \
    --qemu-opts -append nokaslr -s
  1. Start gdb in a second shell:
$ cd support
$ gdb
# Attach gdb to the running qemu process in the same directory:
(gdb) target remote localhost:1234
# Load source code:
(gdb) directory ./ci-kernels/_build/linux-5.4.31
# Load symbols for debugging:
(gdb) sym ./ci-kernels/_build/linux-5.4.31/vmlinux
# Set breakpoint at entry of eBPF verifier:
(gdb) break do_check
Breakpoint 1 at 0xffffffff81184460: file kernel/bpf/verifier.c, line 4105.