Stefan Reinauer <stepan(a)openbios.org> writes:
* Svante Signell <svante.signell(a)telia.com>
I'm currently reading the mailing list
archives on GRUB V2 and LinuxBIOS
development. Can somebody please enlighten me on the interfaces between
the two development projects.
I've only been marginally following grub2 development, but the short
answer is: There are no interfaces at all at the moment. The somewhat
longer answer is: From the LinuxBIOS perspective, this is not a bad
thing, as LinuxBIOS tries to keep it's interfaces as small as possible.
There are only two "transitions" between LinuxBIOS and a "client":
1) LinuxBIOS comes with an ELF loader that can load any static self
contained ELF binary from flash and execute it. This means a single
binary containing all grub parts that are needed to boot an OS
could be packed together with LinuxBIOS and burned to flash. So
far: in theory.
In that case it would be easy to create a GRUB 2 binary which can be
loaded from LinuxBIOS. There are similar binaries to load GRUB 2
using PXE or Multiboot (from GRUB Legacy, for example) already. I
assume it is little work to implement this.
2) There is a mechanism to pass information from
LinuxBIOS to the
outside world called the "LinuxBIOS table". This table contains
internal information about the BIOS, such as the possible CMOS
settings, the RAM map of the machine, etc (there's also E820,
PIRQ, MPTABLE and ACPI).
NOTE: LinuxBIOS does not provide any "legacy bios interrupt callbacks",
so no client can call back into the bios to load stuff from the hard
disk. This means a client has to provide a driver for this that accesses
the hardware, not the BIOS. This is why I wrote "in theory" above.
It's possible to add drivers to GRUB 2. At the moment there are no
drivers there yet, but it surely is possible without too much effort.
I have been working on taking the grub1 frontend and
packing it into FILO
a while ago. So you can use a grub user interface easily with LinuxBIOS
already (with a reduced function set. patches welcome)
It would be nice to have a GRUB 2 payload as well. I plan to add
drivers in the long term, it's required for several ports. So it fits
well within the design and direction of the GRUB 2 project, IMO.
> Is anything tutorial-like written explaining the
> functionality of the (Linux)BIOS (CPU, memory, peripheral
> initialisation, etc) and GRUB (kernel loading, transfer of control
> to kernel etc).
GRUB 2 has loaders, you can find them in loaders/. For every OS a
separate loader is required. I think the sourcecode is quite easy to
understand, but feel free to ask any question you have regarding the
code and its design.