1How to create vmcores for tests 2=============================== 3 41. Boot a FreeBSD VM with as little memory as possible and create a core dump 5 per `FreeBSD Handbook Kernel Debugging Chapter`_. Note that you may need to 6 reboot with more memory after the kernel panic as otherwise savecore(8) may 7 fail. 8 9 For instance, I was able to boot FreeBSD and qemu-system-x86_64 with 128 MiB 10 RAM but had to increase it to 256 MiB for the boot after kernel panic. 11 122. Transfer the kernel image (``/boot/kernel/kernel``) and vmcore 13 (``/var/crash/vmcore.latest``) from the VM. 14 153. Patch libfbsdvmcore using ``libfbsdvmcore-hacks.patch`` and build LLDB 16 against the patched library. 17 184. Patch LLDB using ``lldb-minimize-processes.patch`` and build it. 19 20 WARNING: LLDB will now modify core files in order to make the resulting 21 test vmcores smaller. Make a backup if necessary. 22 235. Do a test run of ``test.script`` in LLDB against the kernel + vmcore:: 24 25 lldb -b -s test.script --core /path/to/core /path/to/kernel 26 27 If everything works fine, the LLDB output should be interspersed with 28 ``%RD`` lines. The vmcore will also be modified to shorten the process 29 list in ``allproc``. 30 316. Open the vmcore in the patched LLDB again and choose interesting threads 32 for testing. Update thread numbers in ``test.script`` if necessary. 33 347. Use the ``copy-sparse.py`` tool to create a sparse version of the vmcore:: 35 36 lldb -b -s test.script --core /path/to/core /path/to/kernel | 37 grep '^% RD' | python copy-sparse.py /path/to/core vmcore.sparse 38 398. Compress the sparse vmcore file using ``bzip2``:: 40 41 bzip2 -9 vmcore.sparse 42 43 44.. _FreeBSD Handbook Kernel Debugging Chapter: 45 https://docs.freebsd.org/en/books/developers-handbook/kerneldebug/ 46