How to put stack and heap in different memroy sections

Well the example .LD files do have this stupid nonsense where they use '. = . + _Min_Stack_Size;' and then use '_estack = 0x2004C000; /* end of RAM */' to set some absolute and unrelated value.

You could put this in your own region

. = . + _Min_Stack_Size;

_estack = .; /* top of stack, descends downward, and predecrements */

Or the quick-and-dirty way would be to describe the _estack value you want, and then removing the memory you want it to use from that visible to the linker in the MEMORY { } descriptions.

You'd also need to fix the _sbrk allocator (syscalls.c) that assumes the heap extends between the top of statics thru bottom of stack, again entirely ignoring _Min_Heap_Size

Code like this will choke if the memory region used for the Stack is below the Heap

sbrk

Increase program data space.

Malloc and related functions depend on this

*/

caddr_t _sbrk(int incr) {
 extern char _ebss; // Defined by the linker

 static char *heap_end;

 char *prev_heap_end;
 if (heap_end == 0) {

 heap_end = &_ebss;

 }

 prev_heap_end = heap_end;
char * stack = (char*) __get_MSP();

 if (heap_end + incr > stack)

 {

 _write (STDERR_FILENO, 'Heap and stack collision
', 25);

 errno = ENOMEM;

 return (caddr_t) -1;

 //abort ();

 }
 heap_end += incr;

 return (caddr_t) prev_heap_end;
}

Well here is a thought:

Split the DTCMRAM into two regions with the upper most region for heap_stack.  Then use the MPU to separate the upper most region into two sections one for stack and one heap.  That way if either heap or stack overrun an exception fault is thrown.