[coreboot] Group demographics

[Aaron Durbin]

On Tue, Mar 28, 2017 at 3:20 PM,  <tturne at codeaurora.org> wrote:
> On 2017-03-24 17:42, Julius Werner wrote:
>>>
>>> * Google's recovery manifest (from linux_recovery.sh) can pull a
>>> recovery image for a specific product, I have yet to find
>>> depthcharge as a payload
>>> * Obviously I haven't pulled all of the recovery images, but have
>>> looked at ~10
>>> * those interested in recovery image,
>>> /usr/sbin/chromeos_firmwareupdate --sb_extract yields a bios.bin
>>> file that cbfstool can parse (i.e. is a coreboot.rom file)
>>
>>
>> All non-x86 Chromebooks that use coreboot also use depthcharge. What
>> exactly do you mean when you say you can't find it? If you parse
>> bios.bin with cbfstool print, you should see a "fallback/payload"
>> file... that is depthcharge. (coreboot always requires the payload to
>> just be called "payload" in CBFS, regardless of what it actually is.)
>> You can extract it and run 'strings' on it to confirm.
>
>
> This was my understanding (Depthcharge being used as payload for all recent
> Chromebooks).
> What led me to question this understanding was:
>  * limited number of libpayload config files in coreboot source tree
>  * chromiumos build tree explicitly setting CONFIG_PAYLOAD="n" for all
> coreboot boards
>  * u-boot.dtb file being present in all bios.bin files I looked at from
> linux_recovery.sh manifest (including Kevin)
>
> As fallback/payload is compressed in bios.bin, I'm not sure what strings
> will provide.
> I did run strings on bios.bin (as well as looking at it in hex editor) and
> found nothing
> explicitly suggesting depthcharge (or u-boot for that matter) was the
> payload.  I made
> assumption u-boot was payload based on presence of u-boot.dtb file in
> bios.bin.

FWIW, you can 'cbfstool extract' the fallback/payload file from an
existing image. It'll write an ELF file that you should be familiar
with for inspection purposes (strings, readelf, objdump, etc).

>
> As has already been explained in this thread the coreboot build within
> chromiumos tree does not include
> building payload, this is a later step.  My work to date has been solely
> within confines of coreboot
> build tree and directly generating depthcharge, etc. so this deferred
> building of the payload came as a surprise.
>
> I welcome pointers to online documentation (either coreboot or chromiumos)
> that more clearly discuss coreboot inclusion within chromiumos build and
> development cycle.
>
> Thanks to all who have contributed to my current level of knowledge and I
> know I am just scratching the surface.
> Cheers,
> T.mike