[coreboot] Where is the first instrucion?

Rudolf Marek r.marek at assembler.cz
Sat Jan 9 20:19:36 CET 2016


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.


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