[avr-gcc-list] EEPROM section overlapping bootloader in stuffed mega8

[Louis Beaudoin]

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I'm compiling a project for a mega8 with about 300 bytes in eeprom 
variables and a large bootloader section.  The bootloader is compiled 
separately, but I have a empty function located at the start of the 
bootloader section so I can jump to the bootloader reset vector without 
resetting the microcontroller.  When I compile I get the following error:

c:\WinAVR\bin\..\lib\gcc-lib\avr\3.3.1\..\..\..\..\avr\bin\ld.exe: 
section .eeprom [000017b8 -> 000018f8] overlaps section .bootldr 
[00001800 -> 00001803]

It seems the eeprom variables are temporarily held in the .text section, 
before being moved out to their own address space in EEPROM memory.  The 
.text section is very full, which is the reason for moving some progmem 
constants to the .eeprom section.  The variables in the .eeprom section 
do not end up in Flash .hex file.

Removing the bootloader code allows the project to compile, but then I 
don't have a way to jump to the bootloader section from my normal 
application.  I can't find a good way to jump to the bootloader section 
without having a function located in the bootloader section.

It should be as simple as asm volatile("jmp 0x1800"), but the gcc 
assembler doesn't support the jmp instruction for the mega8 (yes, it is 
part of the mega8's instruction set).  rjmp could work, but I don't know 
how to make it point to address 0x1800, as I don't know the rjmp 
instructions location at compile time.

I'm using WinAVR 20030913 and the sample makefile from WinAVR.

Any thoughts?

Thanks,
Louis Beaudoin

www.embedded-creations.com


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