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

[Stephen Brennan <stephen.s.brennan@oracle.com>]

Eduard Zingerman <eddyz87@gmail.com> writes:

> 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/20250207012045.2129841-1-stephen.s.brennan@oracle.com/
> [2] https://gist.github.com/eddyz87/5282db54255b81eed731b955dc5ea690

Thank you for the testing (and the review). I haven't yet been able to
reproduce this. But I see you're using clang. I'll spend the morning
building & running selftests with clang to see whether that is the
issue.

Thanks,
Stephen