[avr-gcc-list] Boot loader issues

[larry barello]

I am implementing a boot-loader for the Xmega.  Actually I have a working
boot-loader, but I had to do some ugly things that I am sure there are
proper ways to do if I were not so ignorant.  

Pointers to FAQ, samples or replies appreciated.  I did find the libc FAQ
and the gnu documentation on this subject.

1. How do I specify a long call from my application to jump into the
boot-loader (which resides at 0x20000).  This is my solution:

        case SMB_GOTO_BOOTLOADER:
                EIND = 1;       // HACK HACK
                ((void (*)(bool bCalled))((BOOT_SECTION_START)/2))(true);
                break;

2. How do I get Studio 6 to not include the C startup files?  I know how
this works with older versions of Winavr but specifying -nostdlib (or
-nostartfiles) doesn't seem to work with studio 6 avr-gcc.  Currently I go
ahead and include gcrt... and accept the huge vector table (which I don't
use).

3. The boot loader C runtime sets RAMPZ=1 but the compiler insists on using
indirect through Z to access I/O so it fails miserably in the boot section.
I solved this problem by wrapping my various I/O routines (init, TWI
handler, etc) with "RAMPZ=0; . RAMPZ=1;" Surely there is a better way.

4. It appears that the boot-loader pushes 116 bytes of stuff into the end of
the APPTABLE section of FLASH.  It is avr-gcc jamming trampolines or
something there?  How do I make that go away?  I don't need the loader and
my applications fighting over that chunk of flash.

Thanks for your patience with my ignorance.  This is the first time I have
broken the 128k barrier.