Re: PC with coreboot - boot menu locked

Dear Andrea,


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Am 16.02.25 um 18:30 schrieb Andrea Battelli:

> I have an embedded system that I want to reuse but the bios is locked up
> and when I press the f12 key, it shows only a boot option (payload). How
> can I disassemble the bios or rebuild another one?
> 
> Attached is the dump of the rom and the screenshot of the boot menu

It’d be great if you just copied the text output from the payload.

     SeaBIOS (version SageBIOS-20161017_085144-ttyree-dev-gtk-gtech-com)
     Select boot device:

     1. Payload [igt_secure]

Sage Engineering [1] *was* a company offering coreboot development a 
long time ago. No idea, if they upstreamed this board, or how to get the 
source code. What board is it exactly?

Anyway, your attached dump has a coreboot image (CBFS – coreboot file 
system), you can dump with `cbfstool`:

```
$ ~/src/coreboot/util/cbfstool/cbfstool bios_igt_orig.bin print
FMAP REGION: COREBOOT
bios_igt_orig.bin: 16384 kB, bootblocksize 1024, romsize 16777216, 
offset 0xc00000
alignment: 64 bytes, architecture: x86

Name                           Offset     Type           Size   Comp
roothashes                     0xc00000   (unknown)         192 none
fallback/romstage              0xc00100   stage           60241 none
fallback/ramstage              0xc0ecc0   stage           94548 none
fallback/payload               0xc25e80   simple elf      49158 none
bootsplash.jpg                 0xc31ec0   bootsplash      48411 none
etc/boot-menu-wait             0xc3dc40   raw                 8 none
(empty)                        0xc3dc80   null             4888 none
keyupdate                      0xc3efc0   mma              8192 none
(empty)                        0xc41000   null             3992 none
keystore                       0xc41fc0   mrc            131072 none
img/igt_secure                 0xc62000   simple elf      83362 none
vgaroms/videobios.rom          0xc76600   optionrom       65536 none
(empty)                        0xc86640   null            51544 none
bootorder                      0xc92fc0   raw              4096 none
(empty)                        0xc94000   null          2604952 none
cpu_microcode_blob.bin         0xf0ffc0   microcode       38912 none
(empty)                        0xf19800   null           157592 none
mrc.cache                      0xf3ffc0   mrc_cache       65536 none
(empty)                        0xf50000   null            65432 none
fsp.bin                        0xf5ffc0   spd            524288 none
(empty)                        0xfe0000   null            12248 none
bootorder_sata                 0xfe3000   raw              4096 none
bootorder_usb                  0xfe4040   raw              4096 none
bootorder_sec                  0xfe5080   raw              4096 none
(empty)                        0xfe60c0   null               24 none
rootpub                        0xfe6100   fsp              2064 none
(empty)                        0xfe6940   null           103000 none
```

It does not seem to contain the build configuration, but you might be 
able to boot from a USB device. From there you should be able to read 
the logs with `cbmem` and find out the coreboot version and board name. 
Maybe that brings you further.

I have never heard of `igt_secure`. As you can access the dump, you can 
at least build the payload yourself, and replace `fallback/payload` or 
add it under `img/`. Maybe that works. No idea if the keys/hashes verify 
anything from this.

Anyway, the above should get you going.


Kind regards,

Paul


[1]: https://se-eng.com/
[2]:
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