Re: Linker options for dividing flash

[DJ Delorie <dj at redhat dot com>]

"Kishore, Jonnalagadda \(IE10\)" <Kishore.Jonnalagadda@honeywell.com> writes:
> The problem I have is that each of the three sections is to be built
> independently thus generating 3 elf images. For section one to jump into
> section 2 or 3, I need to fix the entry address of sections 1 and 2 for
> a given board. Suppose I have allocated 64KB for each section, I need to
> inform the linker that the address range for section 1 is 0-64, 65-128
> for section 2 and 129-192 for section 3.

It sounds like there's a couple tips that might help you.

If you look in newlib's sources in src/libgloss/m32c, you'll see my
code for generating linker maps from scripts in Makefiles.  You can
use something like this to generate a set of link maps that differ
only in the start/end address of your flash memory.

To coordinate the jumps to the two boot images, you have two choices:

1. Declare that the starting address is always the beginning of the
   flash block, or some other fixed address.  Use crt0.S and your link
   script to ensure that the start label is in the right place.  The
   easiest spot is at the lowest address in the block, as you just
   tell the linker to link crt0.o first, but the m32c example includes
   a reset vector at the top of memory if you want to do it that way.

2. Use "<target>-nm" to scan the two elf images and parse the actual
   address of the images.  Use the results of that to create a .S
   program that's used to generate the bootstrap block.

I suspect the first is what you want, as you'd want to flash the
bootstrap the minimum number of times (for safety, yes?).