Booting Linux from coreboot+grub2

Booting Linux from coreboot+grub2

[Patrick Georgi]

Hi,

I just want to report that booting linux from grub2/i386-linuxbios 
doesn't work in my tests.

To solve this, I'd propose to start from the i386-efi loader, which 
(other than the i386-pc loader which is currently used by the linuxbios 
platform) doesn't use the real mode code of linux (which relies on bios 
calls)

In my tests, it mostly works (initrd has issues, but linux boots) when 
stripping all the EFI bits, while replacing all memory allocations with 
simple grub_malloc() calls (and not copy the real mode code at all).

That's probably nothing to rely on, given that the 32bit-boot 
specification of linux gives some "hints" on where things should be 
stored.

Some more capable memory management functions might help reconcile the 
i386-{efi,ieee1275,linuxbios} loaders eventually, such as a generic way 
to request "page aligned memory in the memory range (x,y) of size z", and 
a generic way to get a memory map. Currently that seems to be done as-
needed in the various loaders.


Regards,
Patrick

Re: Booting Linux from coreboot+grub2

[Bean]

On Thu, May 1, 2008 at 10:30 PM, Patrick Georgi <patrick@georgi-clan.de> wrote:
> Hi,
>
>  I just want to report that booting linux from grub2/i386-linuxbios
>  doesn't work in my tests.
>
>  To solve this, I'd propose to start from the i386-efi loader, which
>  (other than the i386-pc loader which is currently used by the linuxbios
>  platform) doesn't use the real mode code of linux (which relies on bios
>  calls)
>
>  In my tests, it mostly works (initrd has issues, but linux boots) when
>  stripping all the EFI bits, while replacing all memory allocations with
>  simple grub_malloc() calls (and not copy the real mode code at all).

I encounter similar problem when writing the linux loader for
i386-ieee1275. The fix is quite simple, besides setting ramdisk_image
and ramdisk_size, you also need to set type_of_loader to a non-zero
value:

lh->type_of_loader = 1;

>  That's probably nothing to rely on, given that the 32bit-boot
>  specification of linux gives some "hints" on where things should be
>  stored.
>
>  Some more capable memory management functions might help reconcile the
>  i386-{efi,ieee1275,linuxbios} loaders eventually, such as a generic way
>  to request "page aligned memory in the memory range (x,y) of size z", and
>  a generic way to get a memory map. Currently that seems to be done as-
>  needed in the various loaders.

That would be nice.

-- 
Bean