Added support for external BTF

[havefuncoding1]

1. Introduced new command line argument '--btfpath' to support external BTF so the tool can be used on system without vmlinx. External BTFs are available here.
2. Updated kernel version check for biolatency. Without it, in my environment running 5.10.178 kernel, the exporter runtime fails with 'Invalid argument'. @ntnx-aleksa just wanted to bring this to your awareness since you made initial update in commit 5511eae. Hope changes here don't break anything.

[havefuncoding1]

Hi @bobrik I noticed there is no reviewer automatically assigned to open PRs. Is there a way to get someone to review this? Thanks.

[bobrik]

Introduced new command line argument '--btfpath' to support external BTF so the tool can be used on system without vmlinx.

Do you plan on using this? If it unlocks older kernels, you might want to add some docs into README.md.

Updated kernel version check for biolatency. Without it, in my environment running 5.10.178 kernel, the exporter runtime fails with 'Invalid argument'.

Could you open a separate PR for this?

Is there a way to get someone to review this?

I get notified for everything, but I'm also short on time. I review when I get a chance.

[havefuncoding1]

Thanks a lot @bobrik for reviewing this. Made all changes per your comments and will send a separate PR for kernel version update in biolatency.btf.c.

[bobrik]

I'm still interested in the answer to this:

Do you plan on using this?

[havefuncoding1]

Yes I will have to use it for my target environments. Otherwise, I wouldn't have implemented the solution.

[bobrik]

Please squash the commits into one.

[havefuncoding1]

Done. Thanks a lot for reviewing this @bobrik

[bobrik]

Could you remove protections your master branch in your fork? I have a few small changes that I want to add before merging, but I can't push them:

To github.com:havefuncoding1/ebpf_exporter.git
 ! [remote rejected] havefuncoding1/master -> havefuncoding1/master (permission denied)
error: failed to push some refs to 'github.com:havefuncoding1/ebpf_exporter.git'

[havefuncoding1]

I did a quick search to remove repo protection. The results all points to configure protection rules which I have none. Not sure how to best proceed :(. If you have a pointer, it will be really great. Otherwise, I added you as a collaborator so you can push changes. Can't assign you write access yet as invitation is pending. Another option is to share the changes with me, and I can push them to the PR. I am fine with whichever method you think is most convenient. Apology for lack of github experience.

[bobrik]

Somehow I messed it up, so I opened #323 as a replacement.