Update default linux config to support ftrace, for bpf tracing, fixes #8637

[dalehamel]

This should fix #8637

My goal here is to be able to use minikube with bpftrace / bcc.

In order to do this, they need to be able to list the available filter functions.

Prior to this change, /sys/kernel/debug/tracing/available_filter_functions does not exist. After this change, the file exists. I have not been able to verify end-to-end that everything works yet, but this is a good start.

These changes should be safe to merge, as all of the Linux kernel tracing features must be explicitly be enabled by a user. Almost all production systems should have these flags enabled anyways, so it's quite clear that they do not harm performance on their own.

As a side note, while preparing this PR, i believe I've found evidence that the linux config has been edited directly by users, or is otherwise somehow out of sync with the machine-generated config. I created #9394 to remedy this.

[k8s-ci-robot]

Hi @dalehamel. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: dalehamel
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[minikube-bot]

Can one of the admins verify this patch?

[dalehamel]

Looks like bpftrace is happy after this change:

$ curl https://raw.githubusercontent.com/iovisor/bpftrace/master/scripts/check_kernel_features.sh | bash -
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   859  100   859    0     0   7953      0 --:--:-- --:--:-- --:--:--  7953
All required features present!

[dalehamel]

ISO build on CI seems broken?

[dalehamel]

Started a draft PR #9395 to see why the ISO build is failing

[tstromberg]

LGTM.