[coreboot] About Paging, Realmode and what is going on

[Philipp Stanner]

Am Samstag, den 02.09.2017, 12:36 +0000 schrieb Peter Stuge:
> 
> Sure, but a payload can. SeaBIOS aims to provide a complete BIOS with
> all neccessary interrupt services for legacy compatibility.

Once coreboot jumped into SeaBIOS-code the latter is responsible for
providing the right interface for interrupt services.

I guess it doesn't matter very much in the end who switches the CPU to
Real Mode. My point is that coreboot's bios calls can't be called
because they don't exist ^^



> 
> That depends. A *payload* can not assume interrupt services, but a
> bootloader (e.g. in MBR) can very well assume interrupt services, 
> especially since MBR is a BIOS paradigm.

Every payload built for and with coreboot won't try to call interrupts.

> 
> > And you can't use the 32-Bit-Instructionset anymore, can you?
> 
> That's orthogonal. You can use 32-bit instructions in 16-bit mode and
> vice versa. The 0x66 and 0x67 opcode prefixes can be used to set an
> instruction mode for a single instruction.

But in the beginning of this thread on 02 Aug Ron Minnich wrote that
coreboot switches to PM, because: 

"And we want the 32-bit instruction set."

P.