OpenSolaris is an operating system.
We're currently evaluating how to boot OpenSolaris via coreboot using the GRUB2 payload.
OpenSolaris has moved to multiboot, so GRUB2 contains all necessary parts, except maybe the filesystem support (ufs compatibility must be checked, zfs doesn't exist yet for grub2).
The instructions on Shudong Zhou's blog don't work anymore, because Sun changed the boot mechanism (again).
what should work (but doesn't for me, yet):
multiboot /platform/i86pc/kernel/unix module /boot/x86.microroot (that filename might be different)
Part of the problem is that the multiboot kernel's header claims that the file is "a.out kludge", but really is ELF (someone probably copy&pasted example code too eagerly). PatrickGeorgi reported it with them, see http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6691145
That still doesn't work, probably because GRUB2 doesn't provide all multiboot tables yet (memory table stuff, etc)
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