[MIR]: Include dwarves-dfsg-hwe package into Bionic and Focal

[Rafael David Tinoco]

This is a follow-on request of bug:

HWE kernels should support eBPF CO-RE
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1926330

[Availability]

- Package is already available in all Ubuntu versions.
- This is a backported version (Impish) to Bionic and Focal

[Rationale]

- Current package dwarves-dfsg is old in Ubuntu Bionic and Focal.
- HWE kernel compilation needs recent "pahole" binary to encode BTF[1] information.
- After talking to SRU team members, updating dwarves-dfsg seemed risky.
- Creating a new package containing only the new "pahole" tool binary is the best option.
- Kernel HWE compilations will need to use this package, so it has to be in main repository (as kernels builds depend on main only).

[Security]

- This package is already stable and exists in Ubuntu.

[Quality assurance]

- This package is already stable and exists in Ubuntu.

[Dependencies]

- Same dependencies as dwarves-dfsg package (already satisfied).

[Standards compliance]

- This package is already stable and exists in Ubuntu.

[Maintenance]

- SRUs for dwarves-dfsg package within Impish should be applied to this package as well.

[Background information]

Bug: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1926330 contains more information about why this is needed.

I have been maintaining BTFHUB (https://github.com/aquasecurity/btfhub) in order to generate BTF files to each existing Ubuntu kernel but I feel that a simple change, like adding a recent pahole tool to the main archive in Bionic and Focal, is enough to resolve a VERY BIG problem for eBPF applications to run in HWE kernels in those Ubuntu versions.

A very complete explanation on why BTF is needed for eBPF to be portable among different kernels currently exists at: https://github.com/aquasecurity/btfhub/tree/main/tools.

Projects that would already benefit from this change:

- Microsoft: Sysmon Tools for Linux
- Microsoft: Inspektor Gadge
- Elastic: They're working together with us upstream
- Aqua Security: libbpfgo & tracee-ebpf
- All BCC libbpf-tools

and many more.

----
[1] https://www.kernel.org/doc/html/latest/bpf/btf.html

[Rafael David Tinoco (rafaeldtinoco)]

The proposed package is at:

https://launchpad.net/~rafaeldtinoco/+archive/ubuntu/pahole-btf

[Rafael David Tinoco (rafaeldtinoco)]

After this MIR, the kernel HWE source code will have to use "pahole-btf" tool to do the BTF encoding in the HWE kernel builds from then on.

[Dimitri John Ledkov (xnox)]

NAK

we have backported dwarves-dfsg to bionic and up with support for pahole which is now in use by kernel builds to enable CONFIG_DEBUG_INFO_BTF in them.

The backports were done in https://bugs.launchpad.net/ubuntu/+source/dwarves-dfsg/+bug/1912811

Why do we need pahole-btf? Given that dwarves-dfsg got backported to bionic+ at 1.21 version now?

[Rafael David Tinoco (rafaeldtinoco)]

We don't, like we've spoken on IRC. Thanks a lot for the information. I missed the SRUs and I'm very glad they were done.