Re: [PATCH 3/3] bootm: add initial FIT support

From: Yegor Yefremov <yegorslists@googlemail.com>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Sascha Hauer <sha@pengutronix.de>,
	barebox <barebox@lists.infradead.org>,
	kernel@pengutronix.de
Subject: Re: [PATCH 3/3] bootm: add initial FIT support
Date: Tue, 5 Jan 2016 14:05:28 +0100	[thread overview]
Message-ID: <CAGm1_kuAijx2ZqpJ7aSyLZvSoYDv306QyvtsSA8pRCpFrWM+3Q@mail.gmail.com> (raw)
In-Reply-To: <568BAF11.4090009@pengutronix.de>

On Tue, Jan 5, 2016 at 12:54 PM, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
> On 01/05/2016 11:40 AM, Yegor Yefremov wrote:
>> On Tue, Jan 5, 2016 at 11:32 AM, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
>>> On 01/05/2016 11:28 AM, Yegor Yefremov wrote:
>>>> Hi Marc,
>>>>
>>>> thanks for reposting the patches.
>>>>
>>>> On Tue, Jan 5, 2016 at 9:11 AM, Marc Kleine-Budde <mkl@pengutronix.de> wrote:
>>>>> From: Jan Luebbe <jlu@pengutronix.de>
>>>>>
>>>>> This implementation is inspired by U-Boot's FIT support. Instead of
>>>>> using libfdt (which does not exist in barebox), configuration signatures
>>>>> are verified by using a simplified DT parser based on barebox's own
>>>>> code.
>>>>>
>>>>> Currently, only signed configurations with hashed images are supported,
>>>>> as the other variants are less useful for verified boot. Compatible FIT
>>>>> images can be created using U-Boot's mkimage tool.
>>>>
>>>> What about unsigned images?
>>>
>>> That's not our use case. We use plain zImages instead.
>>
>> The solution would be to introduce an option like in U-Boot?
>>
>> CONFIG_FIT_SIGNATURE:
>>
>> This option enables signature verification of FIT uImages,
>> using a hash signed and verified using RSA. If
>> CONFIG_SHA_PROG_HW_ACCEL is defined, i.e support for progressive
>> hashing is available using hardware, RSA library will use it.
>> See doc/uImage.FIT/signature.txt for more details.
>
> Technically possible, but I'm not sure what are the benefits of using
> fit images, if you don't need signatures. barebox implements
> freedesktop.org's bootspec and this is IMHO the way to go.

For me FIT is just a way to have a kernel and a bunch of device tree
blobs in one file. Signed or not signed is an option for me. Just like
U-Boot implements it. This is user responsibility.

In my use case I just read device ID from EEPROM, load my
kernel-fit.itb and select needed DTB via this ID. This way I have only
one SD card image, that can be run on more, than 10 different devices
using the same core module.

>>>> I also get: unsupported algo crc32
>>>> Is it intended to be supported?
>>>
>>> Not for our usecase - feel free to add crc32 support.
>>
>> OK.
>>
>> But what about FIT configuration selection syntax?
>
> What's this?

Have you seen my comments to this patch regarding
fit_open_configuration() routine?

http://lists.infradead.org/pipermail/barebox/2016-January/025718.html

Yegor

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