Questions regarding ld

[Dan Ciliske]

We are at this moment focused on ARM only. That said, I think this is 
the first time in history I've gone looking for a piece of functionality 
and it was _just_ added.

I guess it's time to work with the build team to look into being on the 
bleeding edge...

Thanks,
- Dan

On 3/18/2020 11:19 AM, Jozef Lawrynowicz wrote:
> Hi,
>
> On Wed, 18 Mar 2020 10:55:38 -0700
> Dan Ciliske <dciliske@netburner.com> wrote:
>
>> I do a lot of work at the bottom of embedded systems and I keep running
>> into the same roadblocks that I'm finally asking about. Since space is
>> often tight in these systems, I was wondering if there are any known
>> approaches that I'm missing to solving some common problems.
>>
>> My questions are:
>>
>> 1. Is it possible to automatically spill across sections if the
>> underlying region fills? If not, is there some way after the fact move
>> part of a Section to another Section that is located in a different Region?
> Assuming that you are talking about moving input sections between output
> sections (and not splitting up input sections into parts), then the recently
> added "non-contiguous memory region" functionality sounds like it handles this
> problem for you. See the documentation on the "--enable-non-contiguous-regions"
> configure option in ld/ld.texi.
>
> If you are not only concerned with ARM, the MSP430 linker has had functionality
> to shuffle input sections named ".either.*" between upper and lower memory
> regions for a while. The --{code,data}-region=either LD option also transforms
> section names which don't have the ".either" prefix (e.g. from libraries) to try
> to get the program to fit in the available space.
>
> Jozef
>
>> 2. With ARM Cortex-M, is there a way to split the ex_tab and exidx
>> tables into two parts such that they are accessible within the 31 bit
>> limit imposed by ARM_PREL31? I am well aware of the complex implications
>> of this question, and realize that this is also partly a question for
>> the GCC lists.
>>
-- 
Dan Ciliske
Principal Architect
NetBurner, Inc.
858-558-0293 x216