[PATCH 4/4] kbuild: arm: Fix duplicate builds of dtbs

[Andrew F. Davis <afd@ti.com>]

On 5/8/20 11:54 AM, Jan Kiszka wrote:
> On 08.05.20 17:40, Andrew F. Davis wrote:
>> On 5/4/20 8:38 AM, Jan Kiszka wrote:
>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>
>>> Build the secured board dtbs (.dtb_HS) as part of the regular dtb build
>>> on CONFIG_TI_SECURE_DEVICE targets. This avoids rebuilding them,
>>> possibly overwriting artifacts that are in use, as it is done so far.
>>>
>>> In the same run, fix needless rebuilding of the secured spl dtb.
>>>
>>> Fixes: 508369672ca3 ("arm: mach-k3: Add secure device build support")
>>> CC: Andrew F. Davis <afd@ti.com>
>>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>>> ---
>>> ? arch/arm/dts/Makefile???????????? |? 6 ++++--
>>> ? arch/arm/mach-k3/config_secure.mk | 19 ++++++++++++++-----
>>> ? 2 files changed, 18 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
>>> index 2c123bd6da..b68e9c0726 100644
>>> --- a/arch/arm/dts/Makefile
>>> +++ b/arch/arm/dts/Makefile
>>> @@ -1,5 +1,7 @@
>>> ? # SPDX-License-Identifier: GPL-2.0+
>>>
>>> +include $(srctree)/arch/arm/mach-k3/config_secure.mk
>>> +
>>
>>
>> This is hacky, we should not in the top level dts makefile have a
>> dependency on a specific platform configuration file.
>>
>> What about mach-omap/config_secure.mk, etc..
> 
> They don't need those special signing the k3 need. If they did, they
> could be included here as well.
> 


I did everything the same in that file, so I don't see why it wouldn't
need the same treatment. But my point is that this will keep growing,
the fixes should be local to the mk files or everyone who does something
similar will need to add here.


>>
>> The negative of building dtbs twice for HS is very minor compared to the
>> extra complexity this patch adds. It will be much more difficult to
>> clean this up later.
> 
> Overwriting a build artifacts that were already completed and may just
> be in use while doing so is broken. This must be fixed.
> 


Absolutely agree it needs fixed, just not sure this just doesn't add to
the makefile complexity in the wrong way.


> As I wrote, I will add support for injecting public keys into the dtbs,
> and that also revealed this issue.
> 


If I understand right, you are adding the keys into the dtb then signing
them? Why not add them to the dts first, then nothing would need to
change with multiple builds of the dtbs.

Andrew


> Better suggestions welcome.
> 
> Jan