[coreboot] Where is the first instrucion?

ron minnich rminnich at gmail.com
Sun Jan 10 19:23:55 CET 2016

One thing I think you'd enjoy doing is building the qemu target, setting up
qemu with gdb, and just watching what happens, instruction by instruction,
as the system boots.


On Sun, Jan 10, 2016 at 3:28 AM Rafael Machado <
rafaelrodrigues.machado at gmail.com> wrote:

> Hi Peter and Rudolf.
> Thanks for the answers and tips. They are realy helpfull !
> I'll take a look.
> Rafael R. Machado
> Em Sáb, 9 de jan de 2016 17:19, Rudolf Marek <r.marek at assembler.cz>
> escreveu:
>> Hi,
>> I guess your question is more general than the coreboot related right?
>> If you have a firmware image dump of the flash (not the file you download
>> from
>> board vendor) then yes, first location to be executed is the instruction
>> located
>> 16 bytes before end of the image.
>> In coreboot see in build/ bootblock_inc.S which also has reset16.inc and
>> entry16.inc which is a real start. Consult the Intel or AMD manual to see
>> the
>> CPU state after reset. The CPU starts in real mode, but CS base is
>> shifted to
>> last 64KB before end of 4GB address space. In general your CPU starts in
>> compatible mode with 8086 manufactured in 1978.
>> Thanks
>> Rudolf
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