[coreboot] How does SeaBIOS transition to Linux?

[Peter Stuge]

Haleigh Novak wrote:
> I was wondering if anyone could take a few minutes and explain the
> proccess of how coreboots SeaBIOS payload (or even how coreboot
> itself) transitions into a Linux boot sequence to me?

SeaBIOS does nothing coreboot-specific, but uses the de-facto
standard BIOS method: Master Boot Record

In the MBR there is code installed by the bootloader in use
(LILO/NTLDR/GRUB/SYSLINUX/etc)

See wikipedia.org and osdev.org for all MBR details you may want.

Writing a small assembly program to run out of the MBR is a great
exercise.



When coreboot instead starts a Linux kernel directly (with Linux as
payload) then the key word is: SELF

SELF is Simple ELF, and when cbfstool adds a kernel payload to
coreboot.rom it also adds a small stub code at the entry point,
which sets up the data structure in memory which Linux requirs to
boot on x86, before jumping to the kernel entry point.


//Peter