Running Function from specific memory location

This is a discussion on Running Function from specific memory location within the C Programming forums, part of the General Programming Boards category; Hi, I'll explain what my overall objective is first.. I would like to be able to store small functions/algorithms in ...

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    Running Function from specific memory location

    Hi,
    I'll explain what my overall objective is first..
    I would like to be able to store small functions/algorithms in external flash of a BF561 processor. I will then copy these functions into allocated space of main memory and run.

    My problems are.
    How do I copy a function to a specific memory location? I assume I use malloc to create space then copy the address range.

    The hard part is then executing this function. I have complex ideas of creating a function container within the allocated space, then moving the function to a the space within, then i can call the function container. maybe.

    I've assumed you cannot actually control the program counter. As that would make things simple, if a little dangerous.

    thanks for any help,

    Matt

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    > How do I copy a function to a specific memory location?
    memcpy I guess.

    > I assume I use malloc to create space then copy the address range.
    Or a fixed array somewhere.
    It probably doesn't matter (*) which approach you take.

    The next trick would be finding out the location and size of your functions. Which tools are you using?
    This is anywhere from being pretty easy to being a PITA.


    > The hard part is then executing this function.
    If all your movable code has the same calling convention (ie, C), then the stub to call it would be a short asm function to
    - pop the current stack frame (of the stub function itself)
    - jump to the start of the moved function.
    This means a normal return from the moved function will return to the caller of the stub.


    Oh, and one more thing, when you generate your movable code, you need to specify that it is position independent code (helpful). If you can't generate PIC, then you would have to "link" each function against a known destination address (again, this is messy).


    (*) one place where it might matter is if the processor is a Harvard machine with separate program and data memory. All of the memory you could normally write to would be data.
    Program memory may be writeable, but there's probably some library needed to do it.
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    thanks,

    yeah thats the processor.
    I'll work through your advice tomorrow

    I believe i will eventually have to turn the algorithms into relocatedable object files, then figure out how to execute them.

    Matt

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