modules_linux: Add support for builtin kernel modules

[TheAifam5]

Previously, kernel modules names were read from the /proc/modules only which prevented k8s linux distribution with kernel modules builtin into the kernel to pass the validation of required kernel modules by Cilium.

This patch adds support for systems with builtin modules by trying to read the kernel module names from following files additionally:

• /lib/modules/<kernel-version>/modules.builtin
• /usr/lib/modules/<kernel-version>/modules.builtin
• /usr/lib/debug/lib/modules/<kernel-version>/modules.builtin

Fixes: #23863

Add support for builtin kernel modules

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[TheAifam5]

I mistakenly made it as draft. Please publish the PR. I am unable to change the state of this PR. :)

[TheAifam5]

Should I rebase? The one of the pipelines is failing (perhaps due to 0.6 gateway api upgrade).

[pchaigno]

Should I rebase? The one of the pipelines is failing (perhaps due to 0.6 gateway api upgrade).

Yes, please. The ConformanceGatewayAPI failure doesn't look like a flake and seems fixed on master.

[pchaigno]

/test

[gentoo-root]

This patch adds support for systems with builtin modules by trying to read the kernel module names from following files additionally:
/lib/modules//modules.builtin
/usr/lib/modules//modules.builtin
/usr/lib/debug/lib/modules//modules.builtin

IMO, it's more reliable to query subdirectories of /sys/module (which also exist for builtin modules), rather than files on filesystem (which technically don't have to exist). Imagine a hypothetical situation when all modules are builtin, there is no /lib/modules at all, and even the kernel image doesn't have to be on a mounted filesystem. In this case the only way to check what modules are present is to query sysfs.

[TheAifam5]

@gentoo-root

IMO, it's more reliable to query subdirectories of /sys/module

I thought that also. The problem with /sys/module is that only appears when at least has a version or at least one parameter and it is not reliable source due to The conditions of creation in the built-in case are not by design and may be removed in the future.

Since the /lib/modules is getting already mounted due to cilium's btf (findVMLinux function) - I see no problem here.

[NikAleksandrov]

@TheAifam5 could you please squash the last commit into the first? Since it's not merged yet we can just have the
correct code in the original commit.

[TheAifam5]

@NikAleksandrov Understood. I will do it today, around 19-23:00 GMT+1.

[NikAleksandrov]

Looks good to me, but it needs to be rebased on top of latest master.

[pchaigno]

/test

[TheAifam5]

Should I rebase it again?

[pchaigno]

Should I rebase it again?

No. In general it's best not to rebase unless 1) you're going to push a change anyway, or 2) there is a merge conflict, or 3) a maintainer asks you to. When rebasing all tests need to be restarted.

I'll triage CI results now and will rerun or mark ready to merge accordingly.

[pchaigno]

Thanks for fixing this @TheAifam5!

[dedene]

@pchaigno I was hoping this to be in the 1.13.2 release, but it seems to be not. Any idea when this will be released?

[pchaigno]

This will be released in v1.14.0. I've added the backport label given that it fits the backporting criteria and shouldn't cause backport conflicts (that code is rarely touched). So unless the backporter hits issues, it should also be in the next v1.13 release.

[dedene]

Awesome, thanks!

[dedene]

Any idea when there will be another 1.13 release or the 1.14 release?