[coreboot] C720 swapparoo

Aaron Durbin adurbin at google.com
Wed Jan 29 23:25:15 CET 2014

On Wed, Jan 29, 2014 at 4:16 PM, John Lewis <jlewis at johnlewis.ie> wrote:
> On 29/01/14 22:03, Aaron Durbin wrote:
>>> This is where we reach the crux of the matter - In the stock/shellball
>>> firmware, extracting BOOT_STUB doesn't yield a file which cbfstool in
>>> upstream coreboot or CrOS coreboot can decipher. Looking at the file in
>>> hexedit it appears to be almost identical to a CBFS that is recognised,
>>> but
>>> that's it. I have managed to extract the SVGA binary from the CBFS in the
>>> RW_LEGACY slot, and I've made an educated guess as to where the
>>> system-agent
>>> begins and ends in the unrecognised CBFS (section beginning "LARCHIVE
>>> mrc.bin" or similar with the binary itself following, surrounded by FF's)
>>> copying and pasting it to a file. I would like to know if I am correct in
>>> my
>>> assumptions about extracting that file manually and what size it should
>>> be,
>>> in bytes?
>> That's interesting. It is just a regular 'ol cbfs. The images that
>> shipped with your device is an 8MiB SPI. First 2MiB Duncan covered.
>> The next 5 have nothing to do w/ coreboot proper -- all the extra
>> vboot firmware bits. The last 1MiB is the cbfs.
> Okay, well I extracted the attached file using:
> eval `./fmap_decode bios.bin | grep BOOT_STUB`
> dd if=c720.rom ibs=$((area_offset)) skip=1 | dd bs=$((area_size))
> iflag=fullblock of=c720-coreboot.bin
> and:
> ../coreboot/build/cbfstool c720-coreboot.bin print
> produces:
> c720-coreboot.bin:
> 1024 kB, bootblocksize 3144, romsize 8388608, offset 0x700000
> alignment: 64 bytes
> Name                           Offset     Type         Size
> zippo.

Try cherry-picking this one:


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