Dear Maintainers,
I hope this message finds you well.
Attached is the patch containing some of my changes I'm proposing:
0001-boot-Allow-setting-bootorder-from-CMOS-entry.patch
The change allows seabios to load bootorder not only from CBFS but
also from the NVRAM as well, making use of coreboot's cmos.layout.
To prepare testing environment:
- Prepare the coreboot source code with
coreboot-qemu-q35-cmos.layout-test.patch.
Configure coreboot for QEMU Q35 platform. For the payload, you can
select anything (I simply choose SeaBIOS for simplicity), with
secondary payloads of coreinfo and nvramcui. I've attached the
qemu-q35-defconfig to eliminate possible ambiguity.
- Compile a coreboot.rom.
- Prepare the SeaBIOS source code with
0001-boot-Allow-setting-bootorder-from-CMOS-entry.patch, and compile it.
- On the newly compiled coreboot.rom, use cbfstool (which gets
compiled along with the coreboot.rom) to remove fallback/payload, then
add the newly compiled bios.bin.elf as the new fallback/payload.
- Prepare a Linux bootable. In general, any Linux system would do as
long as you can run the required software. I go with Alpine Linux live
disk as its ISO image is only 64MB. Any additional files go in a
secondary disk, including its overlay system. I simply created a 16MB
image using dd command and then formatted it with FAT.
- Compile cbmem and nvramtool from coreboot's util directory. For my
Alpine Linux setup, I need to make sure to compile with musl instead
of glibc (e.g. in an Alpine chroot)
- Include cbmem and nvramtool to the Linux bootable. For my Alpine
setup, I simply have a secondary disk image (also where I put the
overlay).
- For convenience, I'd put everything in the same directory.
To actually test:
- Run QEMU with `qemu-system-x86_64 -enable-kvm -cpu host -M q35 -bios
coreboot-qemu.rom -m 1G <disks>`
- For the QEMU options, serial output can be used as well, however it
tends to break when loading coreinfo & nvramcui. Regardless, it's
useful when all I have to do is debug with cbmem output.
- On the BIOS screen, press Esc to see the menu. Note the disks should
be on top. Boot to the disk.
- Once your Linux system boots on QEMU, login to CLI as root, use
nvramtool to modify the 'bootorder' entry. I myself ran `nvramtool -w
bootorder="/rom@img/coreinfo"` to make it boot coreinfo first thing.
- Reboot the QEMU system (do NOT kill the QEMU), press Esc again and
see that coreinfo now jumps to the top. You can also not press Esc and
see it loads coreinfo. Feel free to replace coreinfo with something
else!
Some todo
- Create a tool to modify bootorder more properly (i.e. loading from
file would be nice, for starters) -- in progress
- Make bootorder a reserved section on cmos.layout to prevent
unintended changes.
- Test on a read hardware, I have a Thinkpad X230 eager to try it
Do let me know if you have any feedback!
Warm regards,
Timothy Kenno Handojo
