[PATCH v1 0/6] TIMESTAMP output section command

[Ulf Samuelsson]

Den 2025-10-07 kl. 15:06, skrev Jan Beulich:
> On 07.10.2025 14:58, Ulf Samuelsson wrote:
>> Den 2025-10-07 kl. 14:43, skrev Jan Beulich:
>>> On 07.10.2025 14:39, binutils@emagii.com wrote:
>>>> [PATCH v1 1/6] ld:TIMESTAMP command, ldlex.l
>>>> [PATCH v1 2/6] ld:TIMESTAMP command, ldgram.y
>>>> [PATCH v1 3/6] ld:TIMESTAMP command, ldlang.*
>>>> [PATCH v1 4/6] ld:TIMESTAMP info
>>>> [PATCH v1 5/6] ld:TIMESTAMP ChangeLog
>>>> [PATCH v1 6/6] ld:TIMESTAMP NEWS
>>>>
>>>> ld:TIMESTAMP command
>>>>       
>>>> Add TIMESTAMP command to linker.
>>>>       
>>>> The TIMESTAMP command inserts a QUAD-word entry with the current time
>>>> into the image at the current location.
>>>> The value is the number of seconds since the Epoch,
>>>> 1970-01-01 00:00:00 +0000 (UTC)
>>>>
>>>> The main purpose for the command is for application headers
>>>> in embedded systems which often require a timestamp to be able to
>>>> exactly identify the build.
>>> And those embedded systems all agree on all the field properties? I find
>>> it hard to believe that anything time related can be "general purpose".
>> Each company is likely to have their own definition of the application
>> header
>> So you create a linker command file that will generate a header
>> according to your specification.
>>
>> Many will want to have a timestamp inside the application header so they
>> can use
>> that to ensure that two devices are running exactly the same code.
>>
>> The TIMESTAMP is generated using the "time" function which I assume is
>> what people expect.
>> It is highly unlikely that a company will release or even build two
>> different images that are linked in
>> exactly the same second, so it is enough resolution.
> A lot of assumptions. I can't help the impression that what we want instead
> is a time _value_ (at higher precision) which one can then use in arbitrary
> expressions.
>
> Jan

It is not assumptions. It is based on experience.

A system that allows new versions of the application to be downloaded
needs to verify that the application is bona fide before execution if it
wants to be considered professional.

Do you disagree with this?

If an embedded application has problems, you often want to verify the 
problem
on another identical unit, and you need to ensure that you run the same 
software.

Do you disagree with that?

A timestamp with a one second resolution is in practice a unique 
identifier that shows you
if one image is the same as another. I do not see any use for any higher 
resolution.
The actual value of the timestamp is not important at all.

I fail to see the use of an arbitrary time within the linking process is 
useful
in an expression. Please enlighten me with an example when this would be 
useful.

There is no standard for how a header should look like. That is not an 
assumption.
There may be organisations which has an internal standard.
U-Boot assumes a certain header to boot Linux,
but that is not a valid header for non-Linux systems.
So there is no standard.
Each will need their own linker command file.
-- 

Best Regards
Ulf Samuelsson