5.1.2. Specifying stack and heap using the
scatter-loading description file
The ARM C library provides alternative implementations of
the function __user_initial_stackheap(), and
can select the correct one for you automatically from information
given in a scatter-loading description file.
To select the two region memory model, define two special
execution regions in your scatter-loading description file named ARM_LIB_HEAP and ARM_LIB_STACK.
Both regions have the EMPTY attribute. This causes
the library to select the non default implementation of __user_initial_stackheap() that
uses the value of the symbols:
Image$$ARM_LIB_STACK$$Base
Image$$ARM_LIB_STACK$$ZI$$Limit
Image$$ARM_LIB_HEAP$$Base
Image$$ARM_LIB_HEAP$$ZI$$Limit
Only one ARM_LIB_STACK or ARM_LIB_HEAP region
can be specified, and you must allocate a size, for example:
ARM_LIB_HEAP 0x20100000 EMPTY 0x100000-0x8000 ; Heap starts at 1MB
; and grows upwards
ARM_LIB_STACK 0x20200000 EMPTY -0x8000 ; Stack space starts at the end
; of the 2MB of RAM
; And grows downwards for 32KB
You can force __user_initial_stackheap() to
use a combined stack/heap region by defining a single execution
region named ARM_LIB_STACKHEAP, with the EMPTY attribute. This
causes __user_initial_stackheap() to use the
value of the symbols Image$$ARM_LIB_STACKHEAP$$Base and Image$$ARM_LIB_STACKHEAP$$ZI$$Limit.
Note
If you re-implement __user_initial_stackheap(),
this overrides all library implementations.
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