Support sd_mod being compiled as module

[p12tic]

Currently trying to use zolspinup on a system where sd_mod module is compiled as a module fails with the following error:

bpf: sd_resume_runtime is not found in vmlinux BTF
...
Exception: Failed to load BPF program b'kfunc__vmlinux__sd_resume_runtime': No such file or directory

This is because when the target function is in a module, the eBPF program must use MODULE_KFUNC_PROBE instead of KFUNC_PROBE.

This commit adds support for both cases by checking whether sd_mod is loaded as a module and if yes, using MODULE_KFUNC_PROBE-based eBPF program.

sd_mod is compiled as a module in popular Linux distributions by default, such as on Debian Bookworm and Trixie (BLK_DEV_SD=m).

[geppi]

Could you please elaborate a little on the issue that this PR is supposed to fix?

[p12tic]

@geppi I am sorry for producing poor PR and commit description the first time. I've now updated both to include full information about what the problem was.

Please let me know if I could improve them more.

[p12tic]

@geppi Just a friendly ping :-)

[geppi]

Sorry, I'm currently a little bit swamped. It's not forgotten.

[geppi]

This would be a nice improvement.
However, in this form the PR does create a large diff for a small change in the BPF program strings.
I would prefer a diff that highlights what really had to be changed to implement the improvement.

[geppi]

The conditional replace operation on the strings could be directly performed in the start_monitor method in the above if/else statement like

    )
else:
    if self.__is_sd_mod_module:
        eBPF_program = ZpoolRpmManager.eBPF_resume_monitor.replace('KFUNC_PROBE(', 'MODULE_KFUNC_PROBE(sd_mod, ')
    else:
        eBPF_program = ZpoolRpmManager.eBPF_resume_monitor

Also adding a log message in the init method that tells when the module was detected would be nice.