How to dynamically compute space for LMA of .data section in ld script?

[Ian Lance Taylor]

"Jeffi Edward.J" <j.jeffi@yahoo.co.in> writes:

> Ian Lance Taylor-3 wrote:
>> 
>> "Jeffi Edward.J" <j.jeffi@yahoo.co.in> writes:
>> 
>>>   __sw_data_start = __code_end ;
>>>   __sw_data_end = __sw_data_start + 1000; /* using constant size 1000 may
>>> leave hole or cause inadequate space (overlapping)for LMA of .data */
>> 
>> __sw_data_end = __sw_data_start + SIZEOF(.data);
> 
> Thanks for the reply Ian.
> I tried SIZEOF(.data) too. The GNU linker again reports error since the
> .data section has not been defined at the calculation point. i.e again its a
> forward reference.
>
> Have I missed something in my script so that SIZEOF() is not working? Please
> suggest.

Hmmm.  That surprises me.  But I would have to dig into the
implementation so see why that is happening.  I assume that you are
using a reasonable recent version of the linker?

If that doesn't work then I suppose I don't know if there is a good
way to leave a hole the exact size of the .data section.  Usually
people don't care about that since the .data section comes at the end.
Actually it comes at the end for you, too.  I guess the reason you
care is that you want to have the writable version of .data
immediately follow the read-only version in the address space.  Most
people don't do that because the ROM and RAM are at different
addresses anyhow.

You may need to use a two-phase link.  Do a normal link to get the
size of the .data section, and then generate a linker script to do the
link you want.

Ian