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    • Locate Heap in SDRAM

    Posted by tarek bouchkati on 2016-02-10 13:37 Tunisia

    We can also do that without big modifcations in linker script 😀

    by defining the heap start/end in linker miscellaneous flags, ie :

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    -Wl,--defsym=__heap_start=0xD0000000,--defsym=__heap_limit=0xD0800000

    Note: you have to change these values with yours

    and removing heap informations from linker (not necessary but good for your linker lisibility)

    1- remove this line :
    _Min_Heap_Size = 0; /* required amount of heap */
    2- and replace this

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    /* User_heap_stack section, used to check that there is enough RAM left */
  ._user_heap_stack :
  {
    . = ALIGN(8);
    PROVIDE ( end = . );
    PROVIDE ( _end = . );
    . = . + _Min_Heap_Size;
    . = . + _Min_Stack_Size;
    . = ALIGN(8);
  } >RAM

    with the following

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    /* User_stack section, used to check that there is enough RAM left */
  ._user_stack :
  {
    . = ALIGN(8);
    PROVIDE ( end = . );
    PROVIDE ( _end = . );
    . = . + _Min_Stack_Size;
    . = ALIGN(8);
  } >RAM



    Edit: I forgot syscalls modifications 😁

    You have to add syscalls.c to project (you can borrow it from another SystemWorkbench project)
    then replace _sbrk function by the following

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    caddr_t _sbrk(int incr)
{
	extern char __heap_start asm("__heap_start"); /* Defined by the linker. */
	extern char __heap_limit asm("__heap_limit"); /* Defined by the linker. */

	static char *heap_end;
    static char *heap_limit = &__heap_limit;

	char *prev_heap_end;

	if (heap_end == 0)
		heap_end = &__heap_start;

	prev_heap_end = heap_end;
	if (heap_end + incr > heap_limit)
	{
		errno = ENOMEM; // not enough memory
		return (caddr_t) -1;
	}

	heap_end += incr;

	return (caddr_t) prev_heap_end;
}
    Reads: 3192