reserving LMA space in linker script

reserving LMA space in linker script

[Darin Johnson]

In a GNU ld script I'd like to have something like the following:

    .text  : { *(.text ... ) } > ram
   
    . = ALIGN(4);
    _data_load = .
    . += SIZEOF(.data);

    ...

    .data  : AT(_data_load)  { *(.data ...) } > ram

However, ld doesn't allow getting the address or size of a section
before it is defined.  This does work in some other linkers though.

The reason I want to do this is to be able to restart the code on
an embedded system without having to download through the
debugger all over again.  This is just like loading the data from
ROM except that the VMA and LMA are both in RAM.

I can solve this by allocating a large enough space, but I don't
want to leave holes in memory.  Is there any other way to get
this sort of thing done?

Thanks,
Darin Johnson

Re: reserving LMA space in linker script

[Nick Clifton]

Hi Darin,

> I can solve this by allocating a large enough space, but I don't
> want to leave holes in memory.  Is there any other way to get
> this sort of thing done?

Does the region for the duplicated .data section have to occur before 
.data in memory ?  If it can occur afterwards then you should be able to 
use your original linker script like this:

     .data : AT(_data_load) { *(.data) } > ram
     . = ALIGN(4);
     _data_load = .
     . += SIZEOF(.data);

Note - you will probably want to define a couple of symbols to hold the 
start and end addresses of your hole.

Cheers
   Nick