From: "requiem." <rqm@0xde501a7a.net>
Subject: Fw: Compiling bsd.rd / bsd.update with custom kernel patches?
To: tech@openbsd.org
Date: Wed, 18 Jun 2025 20:06:58 +0100

Dear Tech@,

I have written an e-mail earlier about this to misc@ but it was
suggested this is a better place for this query.

I have an older Macbook that needs some kernel patching in order to
avoid long boot times. (Details here:
https://openbsdonapple.wiki/doku.php?id=misc:acpi_patch) 

I can and successfully have done it before a few times but the problem
is that whenever I need to upgrade the system on -current the bugs
return as non-patched "bsd" and "bsd.rd" / "bsd.upgrade" files get
installed via the normal install process. I would then need to wait out
the long boot on upgrade and first boot, re-patch and install the
kernel in place, etc.

I have been trying to speed up this process by compiling the kernel on
another machine running the same version. However I have not been too
successful so I am asking for some guidance:

Here's what I would hope to achieve:
- on the affected mac, run `sysupgrade -ns && pkg_update -u -Dsnap` and
  not reboot
- compile the patched bsd.rd and bsd.mp on another machine
- swap out the mac's /bsd.upgrade with the patched bsd.rd as well
  as /home/_sysupgrade/bsd.rd and /home/_sysupgrade/bsd.mp
- hopefully then reboot the macbook and boot normally without getting
  stuck for hours due to the acpi firmware bug it has

Here's what I tried:
- on the mac: `sysupgrade -ns`
- on the other machine:
```
# patch < mypatch.diff
# cd /sys/arch/amd64/compile/RAMDISK
# make obj
# make config
# make
# cp obj/bsd.gdb ~/bsd.rd.tocopy
# cd /sys/arch/amd64/compile/GENERIC.MP
# make obj
# make config
# make
# cp obj/bsd.gdb ~/bsd.mp.tocopy
```
- copy over the new `bsd.{rd,mp}.tocopy` to the Macbook over the lan

- on the mac again:
```
# cp ~/bsd.rd.tocopy /bsd.upgrade
# cp ~/bsd.rd.tocopy /home/_sysupgrade/bsd.rd
# cp ~/bsd.mp.tocopy /home/_sysupgrade/bsd.mp
# reboot
```

Here's what happens:

```
upgrade detected: switching to /bsd.upgrade
boot> 
booting sr0a:/bsd.upgrade [...]
fchmod a-x sr0a/bsd.upgrade: failed
entry point at 0x1001000

[machine reboots]
```

What am I doing wrong? How can I compile the ramdisk kernel only?

Thanks,

rqm