[U-Boot] U-Boot as first bootloader on Exynos platforms

[Simon Glass]

Hi Paul,

On 1 March 2016 at 01:10, Paul Kocialkowski <contact at paulk.fr> wrote:
> Hi,
> Le lundi 29 février 2016 à 19:03 -0700, Simon Glass a écrit :
>> On 29 February 2016 at 03:15, Lukasz Majewski <l.majewski at samsung.com> wrote:
>> > > I was told some time ago that a publicly-available version of the
>> > > Samsung Chromebook 2 (supposedly, the one with an Exynos 5800 SoC)
>> > > allows running unsigned code (the U-Boot SPL) directly after the
>> > > bootrom. Is that correct?
>> > >
>> > > Do you know of any (other) publicly available device with an Exynos
>> > > SoC that doesn't check for the first bootloader's signature, and thus
>> > > could load the U- Boot SPL without any intermediary signed stage on
>> > > storage memory?
>> >
>> > For sure Odroid XU3 needs signed SPL to boot up, so this devel board
>> > will not work for you.
>>
>> You can use snow which is Chromebook 1, or pit / pi which are
>> Chromebook 2. I have not tried its 'BL1' with Odroid XU3 but I doubt
>> it will work.
>
> I know those have U-Boot support, but do any of them work without the
> proprietary and signed on-memory first stage bootloaders?
>
> I was told that at least snow's bootrom checks the signature of the first
> bootloader it loads from memory. Is it the case for all Exynos devices?

I think that is true for all. But in the case of these Chromebooks,
the BL1 does not check the signature of the image it loads, which
breaks the chain. For Chrome OS, this kind of restriction is not
useful, since the user should be able to run their own software on the
platform. I'm really not sure why XU3 cannot do this too.

Regards,
Simon