[FEATURE] Enable userspace verifier by default

[yunwei37]

Is your feature request related to a problem? Please describe.

The PREVAIL should be enable by default, and:

• Add runtime option to bypass the userspace verifier
• Add prompt to let user using kernel verifier when the userspace verifer is not pass

Describe the solution you'd like

[Officeyutong]

Note that ebpf-verifier lacks a lot of features, enabling it may cause a lot of confusion

[yunwei37]

Yes. So when there is error occur in userspace verifier, we should treat it as a warning.

If the error is due to unsupport features, there should be a warning and default operation is just continue, and tell user how to use kernel verifier if they want.
If the error sounds like a realy bug, it should block it but also tell user how to bypass it or use the kernel verifier.

We maybe can have 3 mode:

• BPFTIME_VERIFY_STRICT: all verifier wanring are errors, you should pass either kernel or userspace verifier.
• BPFTIME_VERIFY_WARNING: userspace verifier are warning, kernel verifier are error.
• BPFTIME_NO_VERIFY: no verify.

[Officeyutong]

Yes. So when there is error occur in userspace verifier, we should treat it as a warning.

If the error is due to unsupport features, there should be a warning and default operation is just continue, and tell user how to use kernel verifier if they want. If the error sounds like a realy bug, it should block it but also tell user how to bypass it or use the kernel verifier.

We maybe can have 3 mode:

• BPFTIME_VERIFY_STRICT: all verifier wanring are errors, you should pass either kernel or userspace verifier.
• BPFTIME_VERIFY_WARNING: userspace verifier are warning, kernel verifier are error.
• BPFTIME_NO_VERIFY: no verify.

But we even don't know which features are supported by ebpf-verifier, making it hard to distinguish whether it's a lack of feature or bug

[yunwei37]

Ok, so maybe just 3 levels? The default level is verify warning

[Officeyutong]

Ok, so maybe just 3 levels? The default level is verify warning

Agree