Re: Generating code to execute from ROM?

[William Gatliff <gatliff at haulpak dot com>]

Jeff:

Check out the AT command in the linker manual.

Basically, it tells ld to load data at a different address than the one located
to, which is exactly what you want.

Here's an example, culled from one of my scripts:

SECTIONS
{
  /* code and constants */
  .text :
  {
    __text_start = .;
    *(.text)
    *(.strings)
     __text_end = .;
  }  > rom

  /* initialized data section
     ld will load this at __text_end in the output file,
     but will actually locate it in ram.  By doing a
     memcpy( &_data_start, &_text_end, (&_data_end - &_data_start);
     during startup, we initialize our nonzero globals . */
  .init : AT (__text_end)
  {
    __data_start = .;
    *(.data)
    __data_end = .;
  } > ram


Cheers!

b.g.


Jeff Mock wrote:

> How do you generate code suitable for execution out of ROM with GCC?  The
> main thing
> is that I need a way to link the addresses for initialized data at one location
> and put the actual initialization data in another location in such a way that
> crt0 can figure out how to copy the initialized data from ROM to RAM.
>
> I suppose there are a lot of ways to do this.  I've seen embedded C compilers
> generate code this way or it can be done by a clever linker, etc.  I can't
> figure out how to do it with GCC...
>
> thanks,
> jeff
>
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--
William A. Gatliff
Senior Design Engineer
Komatsu Mining Systems
To teach is to learn.




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