Fallback mechanism

Introduction

The fallback mecanism permits to have 2 different romstage,ramstage,payload in the same images under a different prefix. The switch between both can be governed by an nvram configuration parameter.

Howto

• build the coreboot image as usual, it will produce an image in build/coreboot.rom
• After the first build run:

make menuconfig

• Optionally change the payload.
• Go in

General setup  --->

• Change:

(fallback) CBFS prefix to use

To:

(normal) CBFS prefix to use

• Go back to the main menu and select:

Architecture (x86)  --->

select the following option:

[*] Update existing coreboot.rom image

Exit and save and rebuild...

The image will then have fallback and normal:

Name                           Offset     Type         Size
cmos_layout.bin                0x0        cmos_layout  1776
pci1002,9710.rom               0x740      optionrom    60928
fallback/romstage              0xf580     stage        92823
fallback/coreboot_ram          0x26080    stage        66639
fallback/payload               0x36540    payload      54976
config                         0x43c40    raw          4455
normal/romstage                0x44e00    stage        92823
normal/coreboot_ram            0x5b8c0    stage        68820
normal/payload                 0x6c600    payload      159949
(empty)                        0x93700    null         442136