Re: [PATCH 0/3] Fix duplicated VAR and secinfo

On Tue, 2025-02-11 at 16:49 -0800, Stephen Brennan wrote:

[...]

> I've gone ahead and tested this by building & booting a kernel with these
> changes, and the kernel patch series at [1]. The result exhibited no BPF
> varidation errors, and the drgn BTF branch[2] is working perfectly with it!

I tried out this patch-set:
- applied it to pahole;
- applied [1] to kernel;
- configured kernel as in [2] to run BPF selftests.

With this all done none of BPF selftests could be run.
E.g. doing './test_progs -vvv -n 1' gets me the following error:

  libbpf: Error in bpf_object__probe_loading(): -EINVAL. Couldn't load trivial BPF program. Make sure your kernel supports BPF (CONFIG_BPF_SYSCALL=y) and/or that RLIMIT_MEMLOCK is set to big enough value.

If libbpf is hacked to print verifier log for
bpf_object__probe_loading, the log looks as follows:

  in-kernel BTF is malformed
  processed 0 insns (limit 1000000) max_states_per_insn 0 total_states 0 peak_states 0 mark_read 0

BTF is broken in some nasty way, as nothing is printed to dmesg,
even if I add some printk's inside bpf_get_btf_vmlinux().
All I can see is that 'btf_vmlinux' is set to 0xffffffffffffffea very
early in the boot process.

[1] https://lore.kernel.org/bpf/[email protected]/
[2] https://gist.github.com/eddyz87/5282db54255b81eed731b955dc5ea690