Re: AW: AW: [avr-gcc-list] Using current avr-gcc for target ATmega2561

[Bernard Fouché]

Haase Bjoern (PT-BEU/EMT) * wrote:

> At which address does the bootloader code end up?
>
>  
Always at the end of the flash... from 4 to 32 pages of 256 bytes 
reserved from the end.

Now one may need more than 8K bytes of program size for a complex 
bootloader and so extend its size downward from the end the memory, by 
adding one or more sections. One would not expect to have also data 
already at the beginning of the memory or somewhere in the middle. We 
have done that at my company at least to be able to store debugging code 
while testing a bootloader (for instance by storing printf just under 
the bootloader). Also when a bootloader works, it will usually copy 
everything from a feeding point into the MCU memory. Having to manage a 
'bootloader jump stub section' somewhere and not scratch it will be 
difficult.

In the bootloader case, the jump stubs lose its meaning since if the 
stubs are moved in the bootloader section, then we are already jumping 
from and to an upper section address.

I did not follow all the exchanges about the different solutions, but 
the 4 bytes alignment seem to me the cleanest one since one will loose 
at most 2 bytes per defined function and there is no difference in code 
production between application and bootloader section. Now I have no 
idea about the required work in gcc.

 Bernard