> You could put a 'jump table' at a fixed location in your bootstrap's
> program space, with each entry jumping to one routine that you may call
> from your application.

Or you can use the MAP file to figure out the function entries and some
Perl/Python scripts to generate a similar function declaration as mentioned
by Isaac. You could then put that script into the tool path so that it will
run automatically every time you compile your application, so it will never
out of sync.

Tamas


On Mon, Jan 19, 2009 at 10:57 AM, Isaac Marino Bavaresco <
isaacbavaresco@yahoo.com.br> wrote:

> Tony Vandiver escreveu:
> > I'm trying to write a custom bootstrap to load in my application code
> > from an SD card.  I want to call file I/O routines located in my
> > bootstrap from my application rather than duplicating the file I/O
> > library functions in the application because it represents about 10% of
> > my code space.  Typically when I compile, I compile and link everything
> > that pertains to a project at the same time, but in this instance, do I
> > need to reference an object file from the bootstrap compilation without
> > compiling it into the application project, and if so, how do I keep it
> > from being relocated by the linker without expressly setting the address
> > of each function?  I'll start reading the compiler reference material
> > now and see how long it will take me to start drooling.
> >
> > Thanks for the help,
> >
> > Tony
> >
>
> You could put a 'jump table' at a fixed location in your bootstrap's
> program space, with each entry jumping to one routine that you may call
> from your application.
>
> The reason for the 'jump table' is to make the entry points fixed, even
> if you change your bootstrap code.
>
> Assuming you are using MPLAB C18 (other Cs may have a slightly different
> syntax, but not much even for other MCUs).
>
> In the bootstrap:
>
> #pragma code JUMPTABLE =3D 0x1f000
>
> void JumpTable( void )
>    {
>    _asm
>    goto mount;
>    goto remove;
>    goto ...
>    _endasm;
>    }
>
> #pragma code
>
> In your application you call the functions this way:
>
> typedef void (*func_type1)( void );   // Pointer to a function that take
> void and return void;
> typedef int (*func_type2)( const char rom * );   // Pointer to a
> function that take a string and return int;
> ....
>
> #define mount() ((func_type1)0x1f000)() /* mount entry point is at
> 0x1f000 */
> #define remove(name) ((func_type2)0x1f004)(name) /* remove entry point
> is at 0x1f004 */
> ....
>
> void main( void )
>    {
>    mount();
>    remove( "backup.bin" );
>    }
>
> Best regards,
>
> Isaac
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