Re: ARM setup: How to load from flash?

[Grant Edwards <grante at visi dot com>]

> I'm also wondering how other people handle applications that will be 
> stored on a flash, i.e. how they are linked, how data is moved to RAM 
> etc. That's still for a standalone (no OS) arm-coff application with no 
> and debug monitor support. Some questions:
> 
>   1. Should I use a separate "loader" program, or have the app do the
>      load itself?

Either one.  I've done both in the past. If you've got plenty
of flash, I'd lean towards the separate loader program -- IMO
it's easier to maintain things that way, and I think it's
easier to disaster-recovery stuff into the loader.

>   2. Do I need to move the entire program, or just the data section?

It depends.  I've done it both ways in the past.  Running with
text/const in ROM is convenient, but often slow.  On some
platforms RAM is much, much faster than flash ROM.

>   3. How can I override the default "start" behaviour (if that's what I
>      want)? I tried specifying an alternative entry-point via the
>      linker script, but the start code from crt0.S would still end up
>      first in the output file (at least, it has the lowest address in
>      disassembly output.)

Tell gcc you don't want start files linked in.  IIRC, it's
-nostartfiles.

>   4. What does "entry point" in the context of linker scripts/linker
>      options mean anyway?

It set's the "entry point" field in the ojbect file.  This is
used by things like gdb (set's the initial PC value) and
objcopy sets the "entry-point" record in hex files .

> Does the COFF format know of such a concept,

Yes.  So do ELF and most hex file formats.

> or will it just execute the first instruction found in the file?

Depends.  To what does "it" refer to your question?

Here's a question for you:

Why are you using COFF instead of ELF?

-- 
Grant Edwards
grante@visi.com

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