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Re: [Xen-devel] [RFC 5/7] WIP:arm64:armds: Build XEN with ARM Compiler 6.6





On 13.11.19 07:50, Julien Grall wrote:
To be honest, I don't think this file should even exist. This looks like a copy 
of xen.lds.S with a different syntax.

And lacking features like symbols definition, current address setup, etc.

Furthermore, the comments from Stefano shows that is going to be hard to 
maintain/check everything has been written correctly.

It will be terribly hard.

So how about trying to abstract xen.lds.S?

I failed to find the common ground for them.
You are very welcomed to suggest that piece of code.


     > +/*
     > + * armlink does not understand shifts in scat file expressions
     > + * so hardcode needed values
     > + */


Please give a pointer to the doc of the armlink in the commit message. So we 
can easily cross-check what's happening.

The best cross-check would be running the compiler. Yet, this particular thing 
is somehow documented [1].

In this case, I don't particularly like the re-definition of the defines 
outside of their header. This is going to make more difficult if we have to 
update them in the future.

I can see a few ways to do it:

  - Avoid using shifts in the definitions
  - Find a way to evaluate the value (maybe similar to asn-offset) before using 
them.

My preference would be the latter but I could be convinced for the former.

The first option is not realistic. I suggested ARM to consider shifts support 
as an improvement for their compiler.
I'd be very happy to adopt the second option. Do you have any code examples or 
hints how to evaluate expressions on the pre-processing stage?

[1] 
https://developer.arm.com/docs/100070/0612/scatter-file-syntax/expression-evaluation-in-scatter-files/expression-rules-in-scatter-files

--
Sincerely,
Andrii Anisov.

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