powerpc: adjust FreeBSD kernel backward compatibility list

[alfredo]

Summary

Adjust FreeBSD kernel backward compatibility list

Test Plan

Run "make buildkernel" for the affected targets

[alfredo]

updated after discussion on IRC

[imp]

I'd be sorely tempted to commit the style changes separately.
Also, I thought that we broke powerpc bin-compat with ELFv2. if so, all these lists are way too long :)

[pkubaj]

In D33421#755638, @imp wrote:

Also, I thought that we broke powerpc bin-compat with ELFv2. if so, all these lists are way too long :)

This is about kernel, not userland. While you can't execute binaries built for older releases on newer systems, you can have a new kernel and e.g. old chroot or jail.

[imp]

Makes sense. In that case, I think this is good

[alfredo]

• style change commited with hash 8d1ab5ad8449e6f51f081e261ed6202a0483a595
• removed COMPAT_FREEBSD8 from config files, since it doesn't exist.

[imp]

looking better! Thanks for splitting out the style changes.
Just a couple of bits of feedback for comments.

sys/powerpc/conf/GENERIC64LE

70

I'd add a rust version here, as well as adding it to the other config files for which it's relevant

sys/powerpc/conf/MPC85XXSPE

68

Why don't the last two have the /powerpc binaries?

[alfredo]

sys/powerpc/conf/MPC85XXSPE

68

MPC85XXSPE (powerpcspe) was introduced by FreeBSD 12 according to arch(7), so originally I'd remove compatibility with 10 and 11.
However, after discussion on powerpc64 IRC channel, we concluded that *FreeBSD/powerpcspe* is able to run any *FreeBSD/powerpc* binary/userland, so COMPAT options should be in sync. I'd like to have something to remember us in the future that compat 6-11 is there for that specific reason, but yeah, text looks misleading.

Should I get rid of text "/powerpc binaries" on all lines and explain the reason as a full line comment before COMPAT_FREEBSD6 instead?

[imp]

sys/powerpc/conf/MPC85XXSPE

68

Should I get rid of text "/powerpc binaries" on all lines and explain the reason as a full line comment before COMPAT_FREEBSD6 instead?

I think that would be better.

[alfredo]

add ports package versions and adjust comments

[pkubaj]

sys/powerpc/conf/MPC85XXSPE also includes COMPAT_43. That should also be removed.

[pkubaj]

Or maybe not, I can see some ARM configs also have this, along with comment [KEEP THIS!].