Re: [avr-gcc-list] Reusing code and variables from bootloader in main program

[Stefan Ernst]

Andrey Demenev schrieb:

> link the bootloader with filesystem libraries, and in main
> program have a set of pointers to filesystem library functions in
> .noinit section. When bootloader is started , it upgrades main program
> if necessary, and then initializes the prointers with correct
> addresses and jumps to address zero, starting the main program. Since
> variables are in .noinit, main program would not initialize them,
> preserving the addresses.

Needlessly complicated.
Place a table of jumps to the filesystem functions in the bootloader
section at a fixed address (e.g. at the very end of the Flash).
Then that functions have a (virtual) known fixed address, because you
can simply "call" the table entries in the main program.

> Obviously, main program also needs to know
> addresses of all global variables used by filesystem lib.

Best way is to *not* use any global variables in that functions.
Instead let them operate on structures passed in by pointer.
E.g. like this:

FileStruct file;
open(&file, ...
read(&file, ...